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Handover 3g Document Transcript

  • 1. W-Handover and Call Drop Problem Optimization Guide For internal use only2009-10-10 All rights reserved Page 1 of 201Product name Confidentiality levelWCDMA RNP For internal use onlyProduct versionTotal 201 pages3.3W-Handover and Call Drop Problem OptimizationGuide(For internal use only)Prepared by Jiao Anqiang Date 2006-03-16Reviewed by Xie Zhibin, Dong Yan, HuWensu, Wan Liang, YanLin, Ai Hua, Xu Zili, andHua YunlongDateReviewed by Wang Chungui DateApproved by DateHuawei Technologies Co., Ltd.All Rights Reserved
  • 2. W-Handover and Call Drop Problem Optimization Guide For internal use only2009-10-10 All rights reserved Page 2 of 201Revision RecordsDate Version Description Author2005-02-01 2.0Completing V2.0 W-Handover and Call DropProblems.Cai Jianyong,Zang Liang, andJiao Anqiang2006-03-16 3.0According to V3.0 guide requirements,reorganizing and updating V2.0 guide, focusingmore on operability of on-site engineers. All trafficstatistics is from RNC V1.5. The update includes:Updating flow chart for handover problemoptimizationMoving part of call drop due to handover problemto handover optimization partSpecifying operation-related part to be moreapplicable to on-site engineersUpdating RNC traffic statistics indexes to V1.5Integrating traffic statistics analysis to NASTAR ofthe network performance analysisOptimizing some cases, adding new cases, andremoving outdated cases and termsMoving content about handover and call drop to theappendix, and keeping operations related to them inthe bodyAdding explanations to SRB&TRB and RLFAILURE.Jiao Anqiang2006-04-303.1Adding HSDPA-related description HSDPAhandover DT/CQT flow, definitions of trafficstatistics in HSDPA handover, HSDPA handoverproblems. Adding algorithms and flows of HSDPAhandover.Zhang Hao andLi Zhen
  • 3. W-Handover and Call Drop Problem Optimization Guide For internal use only2009-10-10 All rights reserved Page 3 of 201Date Version Description Author2006-10-303.11Adding V17-related handover description as below:Changes in signaling flow for H2D HHOChanges in triggering events of H2D and D2HD2H handover in HSDPA based on traffic andtimersUpdating description of HSDPA serving cell andtraffic statistics of HSDPA-DCH handoverAdding call drop indexes in HSDPA DT/statisticsWang Dekai2007-08-09 3.2 Adding HSUPA-related description. Zhang Hao2008-12-153.3Adding MBMS-related description.Yearly reviewWangDekai /Hu Wensu
  • 4. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page4 , Total201Contents1 Introduction .............................................................................................................................142 Handover and Call Drop Performance Indexes......................................................................162.1 Handover Performance Indexes ......................................................................................162.2 Call Drop Performance Indexes.......................................................................................193 Handover Index Optimization .................................................................................................203.1 DT/CQT Index Optimization Flow.....................................................................................203.1.1 SHO DT Index Optimization Flow...........................................................................203.1.2 HHO CQT Flow .....................................................................................................243.1.3 Inter-RAT Handover CQT Flow..............................................................................273.1.4 DT/CQT Flow for HSDPA Handover ......................................................................293.1.5 DT/CQT Flow for HSUPA Handover ......................................................................323.1.6 SHO Ratio Optimization.........................................................................................323.1.7 MBMS Mobility Optimization ..................................................................................323.2 Traffic Statistics Analysis Flow.........................................................................................343.2.1 Analysis Flow for SHO Traffic Statistics .................................................................353.2.2 Analysis Flow of HHO Traffic statistics...................................................................363.2.3 Traffic Statistics Analysis Flow for Inter-RAT Handover..........................................373.2.4 Traffic Statistics Analysis for HSDPA Handover .....................................................403.2.5 Traffic Statistics Analysis for HSUPA Handover .....................................................413.3 SHO Cost Optimization....................................................................................................434 CDR Index Optimization..........................................................................................................444.1 Definition of Call Drop and Traffic Statistics Indexes ........................................................444.1.1 Definition of DT Call Drop ......................................................................................444.1.2 Descriptions of Traffic Statistics Indexes................................................................444.2 DT/CQT Optimization Flow..............................................................................................454.2.1 Call Drop Cause Analysis ......................................................................................464.2.2 Frequently-adjusted Non-handover Algorithm Parameters......................................484.2.3 Judgment Tree for Call Drop Causes .....................................................................494.3 Traffic Statistics Analysis Flow.........................................................................................504.3.1 Analyzing RNC CDR..............................................................................................514.3.2 Analyzing Causes to Call Drop...............................................................................514.3.3 Check Cells...........................................................................................................524.3.4 Further DT for Relocating Problems.......................................................................524.4 Optimization Flow for Tracing Data..................................................................................524.4.1 Obtaining Single Subscriber Tracing Message .......................................................534.4.2 Obtaining Information about Call Drop Point ..........................................................534.4.3 Analyzing Call Drop due to SRB Reset ..................................................................544.4.4 Analyzing Call Drop due to TRB Reset...................................................................544.4.5 Analyzing Abnormal Call Drop ...............................................................................544.4.6 Performing CQT to Recheck Problems ..................................................................55
  • 5. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page5 , Total2014.5 Optimization Process for MBMS Call Drop.......................................................................555 FAQs Analysis.........................................................................................................................565.1 SHO Problems ................................................................................................................565.1.1 Over High SHO Rate due to Improper SHO Relative Threshold .............................565.1.2 Delayed Handover due to Over Great Intra-frequency Filter Coefficient..................575.1.3 Missing Neighbor Cell............................................................................................585.1.4 Redundant Neighbor Cells.....................................................................................625.1.5 Pilot Pollution.........................................................................................................655.1.6 Turning Corner Effect ............................................................................................715.1.7 Needlepoint Effect .................................................................................................745.1.8 Quick Change of Best server Signal.......................................................................755.2 HHO Problems................................................................................................................775.2.1 Intra-frequency Ping-pong HHO due to Improperly Configured 1D Event Hysteresis775.2.2 Delayed Origination of Inter-frequency Measurement due to Improper Inter-frequencyMeasurement Quantity ..................................................................................................785.3 Inter-RAT Handover Problems.........................................................................................805.3.1 Ping-pong Reselection...........................................................................................805.3.2 PS Inter-RAT Ping-pong Handoff ...........................................................................815.3.3 Failure in handoff from 3G to the 2G network.........................................................825.3.4 Inter-RAT Handover Call Drop ...............................................................................845.4 Call Drop Problems .........................................................................................................915.4.1 Over Weak Coverage ............................................................................................915.4.2 Uplink Interference ................................................................................................925.4.3 Abnormal Equipment .............................................................................................955.5 HSDPA-related Problems................................................................................................975.5.1 HSDPA Handover Problems..................................................................................975.5.2 HSDPA Call Drop ..................................................................................................985.6 HSUPA Problems..........................................................................................................1006 Summary................................................................................................................................1017 Appendix................................................................................................................................1027.1 SRB&TRB Reset ...........................................................................................................1027.1.1 RAB ....................................................................................................................1027.1.2 SRB ....................................................................................................................1037.2 RL FAILURE .................................................................................................................1047.3 SHO Flow......................................................................................................................1097.3.1 Analyzing Signaling Flow for Adding Radio Link...................................................1097.3.2 Analyzing Signaling Flow for Deleting Radio Link.................................................1127.3.3 Analyzing Signaling Flow for Adding and Deleting Radio Link ..............................1137.3.4 SHO Algorithm ....................................................................................................1167.4 Ordinary HHO Flow .......................................................................................................1237.4.1 Ordinary HHO (lur Interface and CELL_DCH State) .............................................1237.4.2 Inter-CN HHO Flow..............................................................................................1257.5 HHO Algorithm ..............................................................................................................1287.5.1 Intra-frequency HHO Algorithm............................................................................1287.5.2 Inter-frequency HHO Algorithm............................................................................1287.6 Concept and Classification of HSDPA Handover............................................................1307.6.1 Concept of HSDPA Handover..............................................................................1307.6.2 Classification of HSDPA Handover ......................................................................1307.6.3 Signaling Flow and Message Analysis of HSDPA Handover.................................1317.6.4 HS-PDSCH Serving Cell Update due to DPCH SHO............................................1327.6.5 HS-PDSCH Serving Cell Update due to DPCH HHO............................................1397.6.6 DPCH Intra-frequency HHO with HS-DSCH Serving Cell Update.........................1407.6.7 DPCH Inter-frequency HHO with HS-DSCH Serving Cell Update.........................141
  • 6. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page6 , Total2017.6.8 Handover Between HSDPA and R99...................................................................1437.6.9 Handover between HSDPA and GPRS................................................................1527.6.10 Direct Retry of HSDPA.......................................................................................1527.6.11 Switch of Channel Type .....................................................................................1547.7 Concept and Classification of HSUPA Handover............................................................1577.7.1 Basic Concepts....................................................................................................1577.7.2 Classification of HSUPA Handover ......................................................................1577.7.3 Signaling Flow and Message Analysis of HSUPA Handover.................................1587.7.4 SHO from a HSUPA Cell to a Non-HSUPA Cell ...................................................1647.7.5 SHO from a Non-HSUPA Cell to a HSUPA Cell ...................................................1697.7.6 Handover Between a HSUPA Cell and a GSM/GPRS Cell ...................................1727.7.7 Direct Retry of HSUPA.........................................................................................1727.7.8 Switch between Channel Types...........................................................................1747.8 Handover from WCDMA to GSM ...................................................................................1757.9 Handover from GSM to WCDMA ...................................................................................1797.10 Handover from WCDMA to GPRS................................................................................1827.11 Handover from GRPS to WCDMA................................................................................1867.12 Parameters of Handover from 3G to 2G Network .........................................................1897.13 Data Configuration for Supporting Bi-directional Roaming and Handover Between WCDMA andGSM/GPRS........................................................................................................................192
  • 7. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page7 , Total201FiguresFigure 3-1 SHO DT data analysis flow................................................................................................ 21Figure 3-2 Optimization flow for HHO CQT......................................................................................... 26Figure 3-3 Inter-RAT handover CQT flow............................................................................................ 28Figure 3-4 DT/CQT flow for HSDPA handover .................................................................................... 31Figure 3-5 Movement of the MBMS UE between PTM cells................................................................ 32Figure 3-6 Analysis flow for handover traffic statistics data.................................................................. 35Figure 3-7 Voce inter-RAT outgoing handover flow ............................................................................. 38Figure 4-1 Flow chart for analyzing call drop ...................................................................................... 46Figure 4-2 Judgment tree for call drop causes.................................................................................... 49Figure 4-3 Flow for analyzing call tracing............................................................................................ 53Figure 5-1 SHO relative threshold ...................................................................................................... 57Figure 5-2 Signaling flow recorded by UE before call drop.................................................................. 58Figure 5-3 Scrambles recorded by UE active set and scanner before call drop ................................... 59Figure 5-4 Scrambles in UE active set before call drop....................................................................... 60Figure 5-5 UE intra-frequency measurement control point before call drop ......................................... 61Figure 5-6 Analyzing signaling of UE intra-frequency measurement control before call drop................ 61Figure 5-7 Confirming missing neighbor cell without information from scanner.................................... 62Figure 5-8 Location relationship of 2G redundant neighbor cells......................................................... 64Figure 5-9 Pilot pollution near Yuxing Rd............................................................................................ 65Figure 5-10 Best ServiceCell near Yuxing Rd. .................................................................................... 65Figure 5-11 The 2nd best ServiceCell near Yuxing Rd. ....................................................................... 66Figure 5-12 The 3rd best ServiceCell near Yuxing Rd......................................................................... 66Figure 5-13 The 4th best ServiceCell near Yuxing Rd......................................................................... 67Figure 5-14 Composition of pilot pollution near Yuxing Rd. ................................................................. 67Figure 5-15 RSSI near Yuxing Rd....................................................................................................... 68Figure 5-16 RSCP of Best ServiceCell near Yuxing Rd....................................................................... 68Figure 5-17 RSCP of SC270 cell near Yuxing Rd................................................................................ 69
  • 8. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page8 , Total201Figure 5-18 Pilot pollution near Yuxing Rd. after optimization.............................................................. 70Figure 5-19 Best ServiceCell near Yuxing Rd. after optimization......................................................... 70Figure 5-20 RSCP of best ServiceCell near Yuxing Rd. after optimization........................................... 71Figure 5-21 RSCP of SC270 cell near Yuxing Rd. after optimization ................................................... 71Figure 5-22 Turning corner effect-signals attenuation ......................................................................... 72Figure 5-23 Turning corner effect-signal attenuation recorded by the UE ............................................ 72Figure 5-24 Turning corner effect-traced signaling recorded by the RNC............................................. 73Figure 5-25 Needle point-signal variance............................................................................................ 74Figure 5-26 Call drop distribution of PS384K intra-frequency hard handover....................................... 75Figure 5-27 Signal distribution of cell152 vs. cell88 (signal fluctuation in handover areas)................... 76Figure 5-28 Reporting 1D event ......................................................................................................... 77Figure 5-29 Increasing hysteresis to reduce frequently reporting of 1D event...................................... 78Figure 5-30 Attenuation relationship of RSCP and Ec/No.................................................................... 79Figure 5-31 Indoor 3G RSCP distribution............................................................................................ 83Figure 5-32 Analyzing weak signals.................................................................................................... 91Figure 5-33 Uplink interference according to RNC signaling ............................................................... 93Figure 5-34 Uplink interference according to UE signaling.................................................................. 93Figure 5-35 Uplink interference information recorded by UE ............................................................... 94Figure 5-36 RTWP variation of the cell 89767..................................................................................... 94Figure 5-37 RTWP variation of the cell 89768..................................................................................... 95Figure 5-38 Pilot information recorded by scanner.............................................................................. 97Figure 7-1 UMTS QoS structure....................................................................................................... 102Figure 7-2 SRB and TRB at user panel............................................................................................. 103Figure 7-3 Signaling flow for adding radio link....................................................................................110Figure 7-4 Signaling flow for deleting radio link..................................................................................112Figure 7-5 SHO signaling flow for adding and deleting radio link........................................................114Figure 7-6 Measurement model.........................................................................................................116Figure 7-7 Example 1A event and trigger delay .................................................................................118Figure 7-8 Periodic report triggered by 1A event................................................................................119Figure 7-9 Example of 1C event....................................................................................................... 120Figure 7-10 Example 1D event......................................................................................................... 121Figure 7-11 Restriction from hysteresis to measurement report......................................................... 121Figure 7-12 Example of 1E event ..................................................................................................... 122Figure 7-13 Example of 1F event ..................................................................................................... 122
  • 9. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page9 , Total201Figure 7-14 Ordinary HHO flow (lur interface and CELL_DCH state) ................................................ 124Figure 7-15 Ordinary inter-CN HHO flow .......................................................................................... 126Figure 7-16 Intra-NodeB synchronization serving cell update............................................................ 133Figure 7-17 Inter-NodeB synchronization serving cell update............................................................ 135Figure 7-18 Inter-NodeB HS-DSCH cell update after radio link is added ........................................... 137Figure 7-19 Inter-NodeB HS-DSCH cell update during HHO (single step method) ............................ 139Figure 7-20 DPCH intra-frequency HHO with HS-DSCH serving cell update..................................... 141Figure 7-21 DPCH inter-frequency HHO with HS-DSCH serving cell update..................................... 142Figure 7-22 handover from HSDPA to R99 ....................................................................................... 143Figure 7-23 Intra-frequency handover from R99 to R5...................................................................... 143Figure 7-24 DPCH SHO with handover from HSDPA to R99 (inter-NodeB)....................................... 145Figure 7-25 DPCH SHO with handover from R99 to HSDPA............................................................. 146Figure 7-26 Inter-NodeB SHO with handover from HSDPA to R99 (V17) .......................................... 147Figure 7-27 Intra-frequency HHO with handover from R5 to R99 ...................................................... 148Figure 7-28 Intra-frequency HHO with handover form R99 to R5 ...................................................... 148Figure 7-29 Intra-frequency HHO with handover from R5 to R99 (V17)............................................. 149Figure 7-30 Inter-frequency HHO from HS-PDSCH to DCH.............................................................. 150Figure 7-31 Inter-frequency HHO from DCH to HS-PDSCH.............................................................. 151Figure 7-32 Handover between HSDPA and GPRS.......................................................................... 152Figure 7-33 Flow for direct retry during setup of a service................................................................. 153Figure 7-34 Direct retry triggered by traffic........................................................................................ 153Figure 7-35 Switch of channel type................................................................................................... 155Figure 7-36 Intra-frequency SHO between two HSUPA cells............................................................. 159Figure 7-37 Signaling for HSUPA cell update triggered by a 1D event............................................... 159Figure 7-38 Signaling for HSUPA cell update triggered by a 1D event (reported by the monitor set).. 160Figure 7-39 Intra-frequency HHO between two HSUPA cells ............................................................ 160Figure 7-40 Signaling for intra-frequency HHO between two HSUPA cells ........................................ 161Figure 7-41 Inter-frequency HHO between two HSUPA cells ............................................................ 161Figure 7-42 Signaling for inter-frequency HHO between two HSUPA cells ........................................ 162Figure 7-43 Inter-RNC HSUPA handover.......................................................................................... 163Figure 7-44 SHO from a HSUPA cell to a non-HSUPA cell................................................................ 165Figure 7-45 Addition of an R99 cell when the service is on the E-DCH.............................................. 166Figure 7-46 Intra-frequency HHO from a HSUPA cell to a non-HSUPA cell ....................................... 167Figure 7-47 Signaling for intra-frequency HHO from a HSUPA cell to a non-HSUPA cell ................... 167
  • 10. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page10 , Total201Figure 7-48 Inter-frequency HHO from a HSUPA cell to a non-HSUPA cell ....................................... 168Figure 7-49 Signaling for inter-frequency HHO from a HSUPA cell to a non-HSUPA cell ................... 169Figure 7-50 SHO from a non-HSUPA cell to a HSUPA cell................................................................ 170Figure 7-51 SHO from a non-HSUPA cell to a HSUPA cell (triggered by a 1B event)......................... 170Figure 7-52 Intra-frequency HHO from a non-HSUPA cell to a HSUPA cell ....................................... 171Figure 7-53 Signaling for intra-frequency HHO from a non-HSUPA cell to a HSUPA cell ................... 171Figure 7-54 Inter-frequency HHO from a non-HSUPA cell to a HSUPA cell ....................................... 172Figure 7-55 Direct retry from an R99 cell to a HSUPA cell................................................................. 173Figure 7-56 Direct retry from a HSUPA cell to an R99 cell................................................................. 173Figure 7-57 Direct retry from a HSUPA cell to another HSUPA cell.................................................... 174Figure 7-58 Switch between HSUPA channel types.......................................................................... 174Figure 7-59 Signaling flow for handover from WCDMA to GSM......................................................... 176Figure 7-60 Tracing signaling of handover from WCDMA to GSM..................................................... 176Figure 7-61 Signaling flow for handover from GSM to WCDMA ........................................................ 179Figure 7-62 Tracing signaling of handover from GSM to WCDMA..................................................... 180Figure 7-63 Flow of handover from WCDMA to GPRS (1)................................................................. 183Figure 7-64 Flow of handover from WCDMA to GPRS (2)................................................................. 183Figure 7-65 Tracing signaling of handover from WCDMA to GPRS................................................... 184Figure 7-66 Signaling flow for handover from GPRS to WCDMA (1) ................................................. 186Figure 7-67 Signaling flow for handover from GPRS to WCDMA (2) ................................................. 187Figure 7-68 Data configuration in the location area cell table ............................................................ 193Figure 7-69 Data configuration of neighbor cell configuration table ................................................... 194Figure 7-70 Configuration table for external 3G cells ........................................................................ 196Figure 7-71 Configuration table for GSM inter-RAT neighbor cells .................................................... 197Figure 7-72 Configuration table for 2G reselection parameters ......................................................... 198Figure 7-73 Parameter configuration table for inter-RAT handover.................................................... 199
  • 11. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page11 , Total201TablesTable 2-1 Handover performance indexes and reference values ......................................................... 16Table 2-2 HSDPA handover performance indexes and reference value............................................... 17Table 2-3 HSUPA handover performance indexes and reference value............................................... 17Table 2-4 CDR index and reference value........................................................................................... 19Table 3-1 SHO failure indexes............................................................................................................ 36Table 3-2 HHO failure indexes............................................................................................................ 36Table 3-3 Traffic statistics indexes of CS inter-RAT handover preparation failure................................. 38Table 3-4 Traffic statistics indexes of PS inter-RAT outgoing handover failure ..................................... 39Table 4-1 Types of CDR indexes......................................................................................................... 45Table 4-2 Thresholds of EcIo and Ec .................................................................................................. 46Table 4-3 Traffic statistics indexes for analyzing causes to call drop.................................................... 51Table 5-1 Relationship between the filter coefficient and the corresponding tracing time...................... 58Table 5-2 2G handover times.............................................................................................................. 63Table 5-3 Best servers and other cells ................................................................................................ 67Table 7-1 Timers and counters related to the synchronization and asynchronization.......................... 104Table 7-2 Timers and counters related to call drop at lub interface .................................................... 107Table 7-3 Flow of serving cell update triggered by different events in SHO........................................ 132Table 7-4 Scenarios of handover between HSDPA and R99 (V17) .................................................... 144Table 7-5 Handover between two HSUPA cells................................................................................. 158Table 7-6 Handover between a HSUPA cell and a non-HSUPA cell ................................................... 163Table 7-7 Parameters of handover from 3G to 2G............................................................................. 190
  • 12. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page12 , Total201W-Handover and Call Drop Problem Optimization GuideKey words:Handover, call drop, and optimizationAbstract:This document, aiming at network optimization of handover success rate and call drop rate, detailsthe specific network operation flow. In addition, it analyzes common problems during networkoptimization.Acronyms and abbreviations:Acronyms and Abbreviations Full SpellingAMR Adaptive MultiRateCHR Call History RecordCDR Call Drop RateDCCC Dynamic Channel Configuration ControlRAN Radio Access NetworkRNP Radio Network PlanningSRB Signaling Radio BearerTRB Traffic Radio BearerSHO Soft HandoverHHO Hard HandoverPCH Physical ChannelCN Core NetworkO&M Operation and maintenanceMNC Mobile Network CodeMCC Mobile Country CodeLAC Location Area CodeCIO Cell Independent OffsetHSUPA High Speed Uplink Packet AccessE-DCH Enhanced uplink Dedicated ChannelE-AGCH E-DCH Absolute Grant Channel
  • 13. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page13 , Total201E-RGCH E-DCH Relative Grant Channel
  • 14. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page14 , Total2011 IntroductionThis document aims to meet the requirements by on-site engineers on solving handover andcall drop problems and making them qualified during network optimization. It describes themethods for evaluating network handover and call drop performance, testing methods,troubleshooting methods, and frequently asked questions (FAQs).The appendix provides fundamental knowledge, principles, related parameters, and dataprocessing tools about handover and call drop. This document serves to network KPIoptimization and operation and maintenance (O&M) and helps engineers to locate and solvehandover and call drop problems.The RRM algorithms and problem implementation in this document are based on V16 RNC. Ifsome RRM algorithms are based on V17 RNC, they will be highlighted. HSUPA is introduced inV18 RNC, so the algorithms related to HSUPA are based on RNC V18. The following sectionsare updated:l Traffic Statistics Analysis for HSDPA Handoverl Handover Between HSDPA and R99l Direct Retry of HSDPAl Switch of Channel TypeActually handover is closely relevant to call drop. Handover failure probably leads to call drop.Therefore handover-caused call drop is arranged in handover success rate optimization part.The CDR optimization includes all related to call drop except handover-caused call drop.This document does not include usage of related tools.This document includes the following 12 chapters:l 1 Introductionl 2 Handover and Call Drop Performance Indexesl 3 Handover Index Optimizationl 4 CDR Index Optimizationl 5 FAQs Analysisl 6 Summaryl 7 Appendix
  • 15. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page15 , Total201The traffic statistics analysis is based on RNC V1.5 counter. It will be updated upon the updateof RNC counters.
  • 16. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page16 , Total2012 Handover and Call Drop Performance Indexes2.1 Handover Performance IndexesAccording to RNA KPI baseline document, Table 2-1 lists the handover performance indexesand reference values.Table 2-1 Handover performance indexes and reference valuesIndex Service Statistics methodReferencevalueSHO success rate CS&PS DT&Stat. 99%Intra-frequency HHOsuccess rateVoice DT&Stat. 90%VP DT&Stat. 85%PS UL64K/DL 64K DT&Stat. 85%PS UL64K/DL 144K DT&Stat. 80%PS UL64K/DL 384K DT&Stat. 75%Inter-frequency HHOsuccess rateVoice DT&Stat. 92%VP DT&Stat. 90%PS UL64K/DL 64K DT&Stat. 90%PS UL64K/DL 144K DT&Stat. 87%PS UL64K/DL 384K DT&Stat. 85%Inter-RAT handoversuccess rateVoice handover out DT&Stat. 95%PS handover out DT&Stat. 92%SHO ratio N/A DT 35%SHO cost N/A Stat. 40%
  • 17. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page17 , Total201Table 2-2 lists the HSDPA handover performance indexes and reference value.Table 2-2 HSDPA handover performance indexes and reference valueIndex Service Reference valueHSDPA-HSDPA intra-frequencyserving cell updatePS (HSDPA) 99%HSDPA-HSDPA inter-frequencyserving cell updatePS (HSDPA) 92%HSDPA-R99 intra-frequency handover PS (HSDPA) 99%HSDPA-R99 inter-frequency handover PS (HSDPA) 90%Success rate of R99-to-HSDPA cellhandoverPS (HSDPA) 85%HSDPA-to-GPRS inter-RAT handover PS (HSDPA) 92%Note: The HSDPA handover KPIs are to be updated after formal issue by WCDMA&GSM PerformanceResearch Department.Table 2-3 HSUPA handover performance indexes and reference valueIndex Service Reference valueSuccess rate of inter-cellSHO in HSUPA (includingadding, replacing, anddeleting)PS (HSUPA) –Success rate of inter-cellSHO serving cell update inHSUPAPS (HSUPA)–Success rate ofDCH-to-E-DCHreconfiguration in SHOmode (including replacingand deleting)PS (HSUPA)–Success rate ofE-DCH-to-DCHreconfiguration in SHOmode (including replacingand deleting)PS(HSUPA)–Success rate of inter-cellintra-frequency HHO inHSUPAPS (HSUPA)–
  • 18. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page18 , Total201Index Service Reference valueSuccess rate ofintra-frequency HHO from aHSUPA cell to anon-HSUPA cellPS (HSUPA)–Success rate ofDCH-to-E-DCHreconfiguration in single-linkmode (the second step ofinter- or intra-frequencyHHO from a non-HSUPAcell to a HSUPA cell)PS (HSUPA)–Success rate of inter-cellinter-frequency HHO inHSUPAPS (HSUPA)–Success rate ofinter-frequency HHO from aHSUPA cell to anon-HSUPA cellPS (HSUPA)–Success rate ofHSUPA-to-GPRS inter-RAThandoverPS (HSUPA) 92%Note:The HSUPA handover KPIs are unavailable and to be updated after formal issue by WCDMA&GSMPerformance Department.Decide the specific value according to project requirements or contract requirements of commercial network
  • 19. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page19 , Total2012.2 Call Drop Performance IndexesTable 2-4 lists the CDR index and reference value.Table 2-4 CDR index and reference valueIndex ServiceStatisticsmethodReferencevalueCDRVoice DT&Stat.&CQT 2%VP DT&Stat.&CQT 2.5%PS planned fullcoverage rateDT&CQT 3%PS (UL DCH fullcoverage rate/DLHSDPA)DT 3%PS Stat. 10%PS (UL HSUPA/DLHSDPA)DT 3%The values listed in Table 2-4 are only for reference. Decide the specific value according toproject requirements or contract requirements of commercial network.The call drop rate of HSDPA is not defined yet, so engineers use call drop rate of PStemporarily.
  • 20. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page20 , Total2013 Handover Index Optimization3.1 DT/CQT Index Optimization FlowDT and CQT are important to network evaluation and optimization. DT/CQT KPIs act asstandards for verifying networks. Overall DT helps to know entire coverage, to locate missingneighbor cells, and to locate cross-cell coverage. HHO and inter-RAT handover are used incoverage solutions for special scenarios, in while CQT is proper.The following sections describe the DT/CQT index optimization flow in terms of SHO, HHO, andinter-RAT handover.3.1.1 SHO DT Index Optimization FlowFigure 3-1 shows the SHO DT data analysis flow.
  • 21. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page21 , Total201Figure 3-1 SHO DT data analysis flowInputting Analysis DataPerform DT. Collect DT data, related signaling tracing, RNC CHR, and RNC MML scripts.Obtaining When and Where the Problem OccursDuring the test, SHO-caused call drop might occur or SHO might fail, so record the location andtime for the problem occurrence. This prepares for further location and analysis.
  • 22. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page22 , Total201Missing Neighbor CellDuring the early optimization, call drop is usually due to missing neighbor cell. Forintra-frequency neighbor cells, use the following methods to confirm intra-frequency missingneighbor cell.l Check the active set Ec/Io recorded by UE before call drop and Best Server Ec/Iorecorded by Scanner. Check whether the Best Server scramble recorded byScanner is in the neighbor cell list of intra-frequency measurement control before calldrop. The cause might be intra-frequency missing neighbor cell if all the followingconditions are met:− The Ec/Io recorded by UE is bad.− The Best Server Ec/Io is good.− No Best Server scramble is in the neighbor cell list of measurement control.l If the UE reconnects to the network immediately after call drop and the scramble ofthe cell that UE camps on is different from that upon call drop, missing neighbor cellis probable. Confirm it by measurement control (search the messages back from calldrop for the latest intra-frequency measurement control message. Check theneighbor cell list of this measurement control message)l UEs might report detected set information. If corresponding scramble information isin the monitor set before call drop, the cause must be missing neighbor cell.Missing neighbor cell causes call drop. Redundant neighbor cells impacts network performanceand increases the consumption of UE intra-frequency measurement. If this problem becomesmore serious, the necessary cells cannot be listed. Therefore pay attention to redundantneighbor cells when analyzing handover problems. For redundant neighbor cells, see 5 .Pilot PollutionPilot pollution is defined as below:l Excessive strong pilots exist at a point, but no one is strong enough to be primarypilot.According to the definition, when setting rules for judging pilot pollution, confirm the followingcontent:l Definition of strong pilotWhether a pilot is strong depends on the absolute strength of the pilot, which ismeasured by RSCP. If the pilot RSCP is greater than a threshold, the pilot is astrong pilot. Namely, AbsoluteRSCPThRSCPCPICH __ >.l Definition of "excessive"When judging whether excessive pilots exist at a point, the pilot number is thejudgment criteria. If the pilot number is more than a threshold, the pilots at a pointare excessive. Namely, NThNumberCPICH >_l Definition of "no best server strong enough"When judging whether a best server strong enough exist, the judgment criteria is therelative strength of multiple pilots. If the strength different of the strongest pilot andthe No.)1( +NThstrong pilot is smaller than a threshold, no best server strongenough exists in the point. Namely,
  • 23. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page23 , Total201llativeRSCPthThst ThRSCPCPICHRSCPCPICH N Re_)1(1 )__( <− +Based on previous descriptions, pilot pollution exists if all the following conditions are met:l The number of pilots satisfying AbsoluteRSCPThRSCPCPICH __ >is morethan NTh.llativeRSCPthThst ThRSCPCPICHRSCPCPICH N Re_)1(1 )__( <− +Set dBmTh AbsoluteRSCP 95_ −= , 3=NTh , and dBTh lativeRSCP 5Re_ = , the judgment standardsfor pilot pollution are:l The number of pilots satisfying dBmRSCPCPICH 95_ −> is larger than 3.ldBRSCPCPICHRSCPCPICH thst 5)__( 41 <−Improper Configuration of SHO Algorithm ParametersSolve the following two problems by adjusting handover algorithm parameters.l Delayed handoverAccording to the signaling flow for CS services, the UE fails to receive active set updatecommand (physical channel reconfiguration command for intra-frequency HHO) due tothe following cause. After UE reports measurement message, the Ec/Io of original cellsignals decreases sharply. When the RNC sends active set update message, the UEpowers off the transmitter due to asynchronization. The UE cannot receive active setupdate message. For PS services, the UE might also fail to receive active set updatemessage or perform TRB reset before handover.Delayed handover might be one of the following:− Turning corner effect: the Ec/Io of original cell decreases sharply and that of thetarget cell increases greatly (an over high value appears)− Needlepoint effect: The Ec/Io of original cell decreases sharply before it increasesand the Ec/Io of target cell increase sharply for a short time.According to the signaling flow, the UE reports the 1a or 1c measurement report ofneighbor cells before call drop. After this the RNC receives the event and sends theactive set update message, which the UE fails to receive.l Ping-pong HandoverPing-pong handover includes the following two forms− The best server changes frequently. Two or more cells alternate to be the best server.The RSCP of the best server is strong. The period for each cell to be the best server isshort.− No primary pilot cell exists. Multiple cells exist with little difference of abnormalRSCP. The Ec/Io for each cell is bad.According to the signaling flow, when a cell is deleted, the 1A event is immediatelyreported. Consequently the UE fails because it cannot receive the active set updatecommand.
  • 24. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page24 , Total201Abnormal EquipmentCheck the alarm console for abnormal alarms. Meanwhile analyze traced message, locate theSHO problem by checking the failure message. For help, contact local customer serviceengineers for confirm abnormal equipment.Reperforming Drive Test and Locating ProblemsIf the problem is not due to previous causes, perform DT again and collect DT data. Supplementdata from problem analysis.Adjustment and ImplementationAfter confirming the cause to the problem, adjust the network by using the following pertinentmethods:l For handover problems caused by pilot pollution, adjust engineering parameters ofan antenna so that a best server forms around the antenna. For handover problemscaused by pilot pollution, adjust engineering parameters of other antennas so thatsignals from other antennas becomes weaker and the number of pilots drops.Construct a new site to cover this area if conditions permit. If the interference is fromtwo sectors of the same NodeB, combine the two cells as one.l For abnormal equipment, consult customer service engineer for abnormal equipmentand transport layer on alarm console. If alarms are present on alarm console,cooperate with customer service engineers.l For call drop caused by delayed handover, adjust antennas to expand the handoverarea, set the handover parameters of 1a event, or increase CIO to enable handoverto occur in advance. The sum of CIO and measured value is used in eventevaluation process. The sum of initially measured value and CIP, as measurementresult, is used to judge intra-frequency handover of UE and acts as cell border inhandover algorithm. The larger the parameter is, the easier the SHO is and UEs inSHO state increases, which consumes resources. If the parameter is small, the SHOis more difficult, which might affects receiving quality.l For needle effect or turning corner effect, setting CIO to 5 dB is proper, but thisincreases handover ratio. For detailed adjustment, see SHO-caused call drop ofFAQs Analysis.l For call drop caused by Ping-pong handover, adjust the antenna to form a bestserver or reduce Ping-pong handover by setting the handover parameter of 1B event,which enables deleting a cell in active set to be more difficult. For details, increasethe 1B event threshold, 1B hysteresis, and 1B delay trigger time.3.1.2 HHO CQT FlowHHO TypesHHO includes the following types:l Intra-frequency HHOThe frequency of the active set cell before HHO is the same as that of the cell after HHO.If the cell does not support SHO, HHO might occur. HHO caters for cross-RNC
  • 25. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page25 , Total201intra-frequency handover without lur interface, limited resources at lur interface, andhandover controlled by PS service rate threshold of handover cell. The 1D event ofintra-frequency measurement events determines intra-frequency HHO.l Inter-frequency HHOThe frequency of the active set cell before HHO is different from that of the cell afterHHO. HHO helps to carry out balanced load between carriers and seamless proceeding.Start compression mode to perform inter-frequency measurement according to UEcapability before inter-frequency HHO. HHO judgment for selecting cell depends onperiod measurement report.l Balanced load HHOIt aims to realize balanced load of different frequencies. Its judgment depends onbalanced load HHO.Inter-frequency coverage usually exists in special scenarios, such as indoor coverage, so CQTare used. The following section details the optimization flow for inter-frequency CQT.Optimization Flow of HHO CQTFigure 3-2 shows the optimization flow for HHO CQT.
  • 26. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page26 , Total201Figure 3-2 Optimization flow for HHO CQTAdjustmentThe optimization flow for HHO is similar with that of SHO and the difference lies in parameteroptimization.Confirming inter-frequency missing neighbor cell is similar to that of intra-frequency. When calldrop occurs, the UE does not measure or report inter-frequency neighbor cells. After call drop,the UE re-camps on the inter-frequency neighbor cell.HHO problems usually refer to delayed handover and Ping-pong handover.Delayed HHO usually occurs outdoor, so call drop occurs when the UE is moving. There arethree solutions:l Increase the threshold for starting compression mode.The compression mode starts before inter-frequency or inter-RAT handover. Measure thequality of inter-frequency or inter-RAT cell by compression mode. Compression modestarts if the CPICH RSCP or Ec/Io meets the conditions. RSCP is usually the triggeringcondition.The parameter "inter-frequency measurement quantity" decides to use CPICH Ec/No orEc/Io as the measurement target for inter-frequency handover. When setting"inter-frequency measurement quantity", check that the cell is at the carrier coverageedge or in the carrier coverage center. If intra-frequency neighbor cells lie in all directionof the cell, the cell is defined as in the carrier coverage center. If no intra-frequency celllies in a direction of the cell, the cell is defined as at the carrier coverage edge.
  • 27. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page27 , Total201In the cell at the carrier coverage edge, when UE moves along the direction where nointra-frequency neighbor cell lies, the CPICH Ec/No changes slowly due to the identicalattenuation rate of CPICH RSCP and interference. According to simulation, whenCPICH RSCP is smaller than the demodulation threshold (–100 dBm or so), the CPICHEc/No can still reach –12 dB or so. Now the inter-frequency handover algorithm basedon CPICH Ec/No is invalid. Therefore, for the cell at the carrier coverage edge, usingCPICH RSCP as inter-frequency measurement quantity to guarantee coverage is moreproper.In the cell in the carrier coverage center, use CPICH RSCP as inter-frequencymeasurement quantity, but CPICH Ec/No can better reflect the actual communicationquality of links and cell load. Therefore use CPICH Ec/No as inter-frequencymeasurement quantity in the carrier coverage center (not the cell at the carrier coverageedge), and RSCP as inter-frequency measurement quantity in the cell at the carriercoverage edge.In compression mode, the quality of target cell (inter-frequency or inter-RAT) is usuallymeasured and obtained. The mobility of MS leads to quality deterioration of the currentcell. Therefore the requirements on starting threshold are: before call drop due to thequality deterioration of the current cell, the signals of the target cell must be measuredand reporting is complete. The stopping threshold must help to prevent compressionmode from starting and stopping frequently.The RNC can distinguish CS services from PS services for inter-frequency measurement.If the RSCP is smaller than –95 dBm, compression mode starts. If the RSCP is greaterthan –90 dBm, compression mode stops. Adjust RSCP accordingly for special scenarios.l Increase the CIO of two inter-frequency cells.l Decrease the target frequency handover trigger threshold of inter-frequencycoverage.For Ping-pong HHO problems, solve them by increasing HHO hysteresis and delay trigger time.The intra-frequency HHO optimization is similar to that of inter-frequency. Decrease thehysteresis and delay trigger time of 1D event according to local radio environment to guaranteetimely handover.3.1.3 Inter-RAT Handover CQT FlowFlow ChatFigure 3-3 shows the inter-RAT handover CQT flow.
  • 28. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page28 , Total201Figure 3-3 Inter-RAT handover CQT flowData ConfigurationInter-RAT handover fails due to incomplete configuration data, so pay attention to the followingdata configuration.l GSM neighbor configuration is complete on RNC. The configuration includes:− Mobile country code (MCC)− Mobile network code (MNC)− Location area code (LAC)− GSM cell identity (CELL ID)− Network color code (NCC)− Base station color code (BCC)− Frequency band indicator (FREQ_BAND)− Frequency number− Cell independent offset (CIO)Guarantee the correctness of the previous data and GSM network.
  • 29. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page29 , Total201l Add location area cell information near 2G MSC to location area cell list of 3G MSC.The format of location area identity (LAI) is MCC + MNC + LAC. Select LAI as LAItype. Select Near VLR area as LAI class and add the corresponding 2G MSC/VLRnumber. The cell GCI format is: MCC + MNC + LAC + CI. Select GCI as LAI type.Select Near VLR area as LAI class and add the corresponding 2G MSC/VLRnumber.l Add data of WCDMA neighbor cells on GSM BSS. The data includes:− Downlink frequency− Primary scramble− Main indicator− MCC− MISSING NEIGHBOR CELL− LAC− RNC ID− CELL IDAccording to the strategies of unilateral handover of inter-RAT handover, if the dataconfiguration is complete, the inter-RAT handover problems are due to delayed handover. Afrequently-used solution is increasing CIO, increasing the threshold for starting and stoppingcompression mode, increasing the threshold to hand over to GSM.CausesThe causes to call drop due to 3G-2G inter-RAT handover are as below:l After the 2G network modifies its configuration data, it does not inform the 3Gnetwork of modification, so the data configured in two networks are inconsistent.l Missing neighbor cell causes call drop.l The signals fluctuate frequently so call drop occurs.l Handset problems causes call drop. For example, the UE fails to hand over back orto report inter-RAT measurement report.l The best cell changes upon Physical channel reconfiguration.l Excessive inter-RAT cell are configured (solve it by optimizing number of neighborcells).l Improperly configured LAC causes call drop (solve it by checking data configuration).3.1.4 DT/CQT Flow for HSDPA HandoverTypeAccording to the difference of handover on DPCH in HSDPA network, the HSDPA handoverincludes:l SHO or softer handover of DPCH, with HS-PDSCH serving cell update
  • 30. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page30 , Total201l Intra-frequency and inter-frequency HHO of DPCH, with HS-PDSCH serving cellupdateAccording to different technologies used in the serving cell before and after handover, HSDPAhandover includes:l Handover in HSDPA systeml Handover between HSDPA and R99 cellsl Handover between HSDPA and GPRS cellsMethodsFor HSDPA service coverage test and mobility-related test (such as HHO on DPCH withHS-PDSCH serving cell update, handover between HSDPA and R99, and inter-RAT handover),perform DT to know the network conditions.For location of HSDPA problems and non-mobility problems, perform CQT (in specified point orsmall area).FlowWhen a problem occurs, check R99 network. If there is similar problem with R99 network, solveit (or, check whether the R99 network causes HSDPA service problems, such as weak coverage,missing neighbor cell. Simplify the flow).Figure 3-4 shows the DT/CQT flow for HSDPA handover.
  • 31. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page31 , Total201Figure 3-4 DT/CQT flow for HSDPA handoverThe problems with handover of HSDPA subscribers are usually caused by the faulty handoverof R99 network, such as missing neighbor cell and improper configuration of handoverparameters. When the R99 network is normal, if the handover of HSDPA subscribers is stillfaulty, the cause might be improper configuration of HSDPA parameters. Engineers can checkthe following aspects:l Whether the HSDPA function of target cell is enabled and the parameters arecorrectly configured. Engineers mainly check the words of cell and whether thepower is adequate, whether the HS-SCCH power is low. These parameters mightnot directly cause call drop in handover, but lead to abnormal handover and loweredthe user experience.l Whether the protection time length of HSDPA handover is proper. Now the baselinevalue is 0s. Set it by running SET HOCOMM.l Whether the threshold for R99 handover is proper. The handover flow for HSDPA isgreatly different from that of R99, so the handover of R99 service may succeed whilethe HSDPA handover may fail. For example, in H2D handover, when the UE reports1b event, it triggers RB reconfiguration in the original cell, reconfigures servicebearer to DCH, and updates the cell in active set. If the signals of the original celldeteriorate quickly now, the reconfiguration fails.l Whether the protection time length of D2H handover is proper. Now the baselinevalue is 2s. Set it by running SET HOCOMM.
  • 32. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page32 , Total2013.1.5 DT/CQT Flow for HSUPA HandoverThe DT/CQT flow for HSUPA handover is similar to that for HSDPA. For details, refer to DT/CQTFlow for HSDPA Handover.For the test of HSUPA service coverage and mobility-related tests (such as the test of successrate of HSUPA serving cell update), perform DT to know the network conditions. For locatingHSUPA problems and the problems unrelated to mobility, perform CQT (in specified spot orarea).3.1.6 SHO Ratio OptimizationThis part is to be supplemented.3.1.7 MBMS Mobility OptimizationCurrently, the radio network controller (RNC) V18 supports only the broadcast mode of themultimedia broadcast multicast service (MBMS); the MBMS user equipment (UE) moves onlybetween point-to-multipoint (PTM) cells.Figure 3-5 Movement of the MBMS UE between PTM cellsThe movement of the MBMS UE between PTM cells is similar to the movement of UEperforming PS services in the CELL-FACH state. The UE performs the handover between cells
  • 33. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page33 , Total201through cell reselection and obtains a gain through soft combining or selective combiningbetween two cells to guarantee the receive quality of the service. The UE first moves to thetarget cell and then sends a CELL UPDATE message to notify the serving radio networkcontroller (SRNC) that the cell where the UE stays is changed. The SRNC returns a CELLUPDATE CONFIRM message. The UE receives an MBMS control message from the MCCH inthe target cell and determines whether the MBMS radio bearer to be established is consistentwith that of the neighboring cell. If they are consistent, the original radio bearer is retained. TheMBMS mobility optimization, which guarantees that the UE obtains better quality of service atthe edge of cells, covers the following aspects:l Optimize cell reselection parameters to guarantee that the UE can be reselected tothe best cell in time.l Guarantee that the power of the FACH in each cell is large enough to meet thecoverage requirement of the MBMS UE at the edge of the cells.l Guarantee that the transmission time difference of the UE between different linksmeets the requirement of soft combing or selective combining*.l Guarantee that the power, codes, transmission, and CE resources of the target cellare not restricted or faulty, and that the MBMS service is successfully established.The UE can simultaneously receive the same MBMS service from two PTM cells and combinethe received MBMS service. The UE supports two combining modes:Soft combining: The transmission time difference between the current cell and the neighboringcell is within (one TTI + 1) timeslots and the TFCI in each transmission time interval (TTI) is thesame.Selective combining: The transmission time difference between the current cell and theneighboring cell is within the reception time window stipulated by the radio link controller (RLC).The SCCPCH is decoded and the transmission blocks are combined in the RLC PDU phase
  • 34. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page34 , Total2013.2 Traffic Statistics Analysis FlowThe traffic statistics data is important to network in terms of information source. In addition, it isthe major index to evaluate network performance.The handover traffic statistics data is includes RNC-oriented data and cell-oriented data. RNC–oriented data reflects the handover performance of entire network, while cell-oriented datahelps to locate problematic cells.The analysis flow for SHO, HHO, inter-RAT handover, and HSDPA handover is similar, but thetraffic statistics indexes are different from them.Figure 3-6 shows the analysis flow for handover traffic statistics data.
  • 35. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page35 , Total201Figure 3-6 Analysis flow for handover traffic statistics data3.2.1 Analysis Flow for SHO Traffic StatisticsThe SHO success rate is defined as below:SHO success rate = SHO successful times/SHO timesAccording to the flow, SHO includes SHO preparation process and SHO air interface process.The SHO preparation process is from handover judgment to RL setup completion. The SHO airinterface process is active set update process.l Check the SHO success rate of entire network and cell in busy hour. If they are notqualified, analyze the problematic cells in details.l Sort the SHO (or softer handover) failure times of the cell by TOP N and locate thecells with TOP N failure times. List the specific indexes of failure causes. If locatingspecific causes from traffic statistics is impossible, analyze the corresponding CHR.Table 3-1 lists the detailed traffic statistics indexes to SHO (or softer handover) failureand analysis.
  • 36. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page36 , Total201Table 3-1 SHO failure indexesFailure causes AnalysisConfiguration nonsupportThe UE thinks the content of active set update for RNC to add/delete linksdoes not support SHO. This scenario seldom exists in commercial networks.SynchronizationreconfigurationnonsupportThe UE feeds back that the SHO (or softer handover) for RNC to add/deletelinks is incompatible with other subsequent processes. The RNCguarantees serial processing upon flow processing. This cause is due to theproblematic UE.Invalid configurationThe UE thinks the content of active set update for RNC to add/delete links isinvalid. This scenario seldom exists in commercial networks.No response from UEThe RNC fails to receive response to active set update command foradding/deleting links. This is a major cause to SHO (or softer handover)failure. It occurs in areas with weak coverage and small handover area. RFoptimization must be performed in the areas.l Perform DT to re-analyze problems. The traffic statistics data provides the trend andpossible problems. Further location and analysis of problems involves DT and CHRto the cell. DT is usually performed on problematic cells and signaling flow at the UEside and of RNC is traced. For details, see 3.1.3 .3.2.2 Analysis Flow of HHO Traffic statisticsThe HHO traffic statistics includes outgoing HHO success rate and incoming HHO success rate:l Outgoing HHO Success Rate = Outgoing HHO Success Times/Outgoing HHOTimesl Incoming HHO Success Rate = Incoming HHO Success Times/Incoming HHOTimesUpon HHO failure, pay attention to indexes related to internal NodeB, between NodeBs, andbetween RNCs.Table 3-2 lists the HHO failure indexes.Table 3-2 HHO failure indexesFailure cause AnalysisHHO preparation failureRadio link setup failure Analyze RL setup failure.Other causes Analyze the problem further based on CHR logs.Internal NodeB/Between NodeBs/Between RNCs HHO failureConfigurationnonsupportThe UE thinks it cannot support the command for outgoing HHO,because it is incompatible with HHO.PCH failure The cause is probably weak coverage and strong interference.SynchronizationreconfigurationnonsupportThe UE feeds back HHO is incompatible with other consequent processesdue to compatibility problems of UE.
  • 37. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page37 , Total201Cell updateCell update occurs upon outgoing HHO. These two processes lead tooutgoing HHO failure.Invalid configurationThe UE thinks the command for outgoing HHO as invalid. This is acompatibility problem of UE.Other causes Analyze the problem further based on CHR logs.3.2.3 Traffic Statistics Analysis Flow for Inter-RAT HandoverThe inter-RAT handover success rate includes voice inter-RAT handover success rate and PSinter-RAT handover success rate.Voice Inter-RAT Outgoing Handover Success Rate = Voice Inter-RAT Outgoing HandoverSuccess Times/Voice Inter-RAT Outgoing Handover Attempt TimesVoice Inter-RAT Outgoing Handover Success Times: when the RNC sends a RELOCATIONREQUIRED message.Voice Inter-RAT Outgoing Handover Attempt Times: during CS inter-RAT outgoing, when theRNC receives an IU RELEASE COMMAND message, with the reason value SuccessfulRelocation, or Normal Release.PS Inter-RAT Outgoing Handover Success Rate = PS Inter-RAT Outgoing Handover SuccessTimes/PS Inter-RAT Outgoing Handover Implementation TimesPS Inter-RAT Outgoing Handover Success Times: the RNC sends a CELL CHANGE ORDERFROM UTRAN message to UE.PS Inter-RAT Outgoing Handover Implementation Times: when the RNC receives an IURELEASE COMMAND message, with the reason value Successful Relocation, or NormalRelease.Voice Inter-RAT Outgoing Handover Success RateThe voice inter-RAT outgoing handover includes handover preparation process andimplementation process.Figure 3-7 shows the voice inter-RAT outgoing handover flow.
  • 38. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page38 , Total201Figure 3-7 Voce inter-RAT outgoing handover flowDuring CS inter-RAT outgoing handover process, when the RNC sends a RELOCATIONREQUIRED message to CN, if the current CS service is AMR voice service, count it as aninter-RAT handover preparation. When the RNC receives the IU RELEASE COMMANDmessage replied by CN, count it as inter-RAT outgoing handover success according to theSRNC cell being used by UE.If CS inter-RAT handover fails, check the failure statistics indexes listed in Table 3-3.Table 3-3 Traffic statistics indexes of CS inter-RAT handover preparation failureFailure cause AnalysisRNC-level inter-RAT outgoing handover preparation failureExpiration ofwaiting for SRNSrelocationcommandThe CN does not respond the corresponding command for handoverpreparation request, because the CN parameter configuration or thecorresponding link connection is problematic. To solve this problem,analyze the causes according to CN and BSS signaling tracing.SRNS relocationcancellationAfter the RNC requests handover preparation, it receives the releasecommand from CN. This includes the following two cases:l The inter-RAT handover request occurs during signaling process likelocation update, so the flow is not complete before location update iscomplete. Finally the CN sends a release message.l The subscribers that are calling hang UE before handover preparation,so the CN sends a release message.The previous two cases, despite incomplete handover, are normal nestingflows.SRNS relocationexpirationIt corresponds to incorrect configuration of CN, so you must analyze thecauses according to CN and BSS signaling tracing.SRNS relocationfailure in targetCN/RNC/systemIt corresponds to incorrect configuration of CN or BSS nonsupport, so youmust analyze the causes according to CN and BSS signaling tracing.
  • 39. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page39 , Total201Unknown targetRNCIt corresponds to incorrect configuration of MSC parameters withoutinformation like LAC of target cell, so you must check the parameterconfiguration. It occurs easily after adjustment of 2G networks.UnavailableresourceIt corresponds to incorrect configuration of MSC parameters or unavailableBSC resources, so you must analyze the causes according to CN and BSSsignaling tracing.Other causes Analyze the causes according to CN and BSS signaling tracing.Cell-level inter-RAT outgoing handover preparation failureSRNS relocationexpirationThe CN parameter configuration or the corresponding link connection isproblematic, so you must analyze the causes according to CN and BSSsignaling tracing.SRNS relocationfailure in targetCN/RNC/systemIt corresponds to incorrect configuration of CN or BSS nonsupport, so youmust analyze the causes according to CN and BSS signaling tracing.SRNS relocationnonsupport intargetCN/RNC/systemThe BSC fails to support some parameters of inter-RAT handover request,so you must analyze the causes according to CN and BSS signalingtracing.Other causes Analyze the causes according to CN and BSS signaling tracing.RNC-level/CELL-level inter-RAT outgoing handover failureConfigurationnonsupportThe UE fails to support the handover command in the network, so the UEis incompatible with the handover command.PCH failureThe 2G signals are weak or the interference is strong so the UE fails toconnect to the network.Other causesAnalyze the problem further according to CHR logs and CN/BSS signalingtracing.PS Inter-RAT Handover Success RateAfter the RNC sends the CELL CHANGE ORDER FROM UTRAN message, the PS inter-RAToutgoing handover fails if it receives the CELL CHANGE ORDER FROM UTRAN FAILUREmessage. You must check the indexes listed in Table 3-4.Table 3-4 Traffic statistics indexes of PS inter-RAT outgoing handover failureFailure cause AnalysisRNC-level/CELL-level PS inter-RAT outgoing handover preparation failureConfigurationnonsupportThe UE fails to support the handover command of the network, becausethe UE is incompatible with the command.PCH failureThe 2G signals are weak or the interference is strong, so the UE fails toaccess the network.Radio networklayer causeThe UE is probably incompatible. The UE detects that the sequencenumber of SNQ in the AUTN message is correct, so the handover fails.The value is synchronization failure.Transport layercauseThe corresponding transport link is abnormal.
  • 40. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page40 , Total201Other causes You must analyze the causes according to CN and BSS signaling tracing.3.2.4 Traffic Statistics Analysis for HSDPA HandoverHSDPA switch includesl H-H (HS-DSCH to HS-DSCH) intra-frequency serving cell updatel H-H inter-frequency serving cell updatel HSDPA-R99 intra-frequency switchl HSDPA-R99 inter-frequency switchl HSDPA-GPRS switchThe traffic statistics indexes are defined as below:l Success rate of H-H intra-frequency serving cell update = (Times of successfulupdate of serving cell)/(attempt times update of serving cell)When the RNC sends UE the PHYSICAL CHANNEL RECONFIGURATION message,if the serving cell is updated, engineers count the attempt times of serving cell in theoriginal serving cell. When the RNC receives the PHYSICAL CHANNEL RECFGCOMPLETE message, if the serving cell changes, the RNC counts the times ofsuccessful update of serving cells in the original serving cell when the UE is in the SHOmode not in the HHO mode.l Success rate of H-H inter-frequency serving cell update = Times of successfuloutgoing inter-frequency HHO from HS-DSCH to HS-DSCH/Times of requestedoutgoing inter-frequency HHO from HS-DSCH to HS-DSCHWhen the RNC sends UE the PHYSICAL CHANNEL RECONFIGURATION message,and the inter-frequency HHO is from HS-DSCH to HS-DSCH, the RNC counts the timesof requested outgoing inter-frequency HHO from HS-DSCH to HS-DSCH. When theRNC receives the PHYSICAL CHANNEL RECFG COMPLETE message from UE, andthe inter-frequency HHO is from HS-DSCH to HS-DSCH, engineers count the times ofsuccessful outgoing inter-frequency HHO from HS-DSCH to HS-DSCH.l Success rate of H-H inter-frequency serving cell update = successful times ofoutgoing inter-frequency HHO from HS-DSCH to HS-DSCH/attempt times HHO fromDCH to HS-DSCH in the cellWhen the RNC sends the UE the PHYSICAL CHANNEL RECONFIGURATIONmessage, if the switch is the inter-frequency HHO from HS-DSCH to HS-DSCH, theRNC counts the successful times of inter-frequency HHO from HS-DSCH to HS-DSCHin the cell.l Success rate of H-to-R99 intra-frequency SHO = successful times of switch fromHS-DSCH to DCH in multi-link mode in the cell/attempt times switch from HS-DSCHto DCH in multi-link mode in the cell.Success rate of R99-to-H intra-frequency SHO = successful times of switch fromDCH to HS-DSCH in multi-link mode in the cell/attempt times switch from DCH toHS-DSCH in multi-link mode in the cell.In the DCCC or RAB MODIFY process, if the RNC decides to switch the channel in thecell, it sends the UE the RF RECONFIGURATION message. According to the channelstate of the UE before and after reconfiguration, the RNC counts the previous indexes inthe HSDPA serving cell.
  • 41. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page41 , Total201l Success rate of H-to-R99 intra-frequency HHO = successful times of outgoingintra-frequency HHO from HS-DSCH to DCH in the cell/attempt times outgoingintra-frequency HHO from HS-DSCH to DCH in the cell.When the RNC sends the UE the PHYSICAL CHANNEL RECONFIGURATIONmessage, if the switch is the intra-frequency switch from HS-DSCH to DCH, the RNCcounts the attempt times of inter-frequency HHO from HS-DSCH to DCH in the cell.When the RNC receives the PHYSICAL CHANNEL RECFG COMPLETE messagefrom the UE, if the switch is the intra-frequency HHO from HS-DSCH to DCH, theRNC counts the successful times of outgoing intra-frequency HHO from HS-DSCH toDCH in the cell.Success rate of H-to-R99 inter-frequency switch updateThe RNC algorithm is unavailable now, so this index is unavailable.l Success rate of H-to-R99 inter-frequency switch update = successful times ofoutgoing HHO from HS-DSCH to DCH in the cell/attempt times outgoinginter-frequency HHO from HS-DSCH to DCH in the cellWhen the RNC sends the UE the PHYSICAL CHANNEL RECONFIGURATIONmessage, if the switch is the inter-frequency switch from HS-DSCH to DCH, the RNCcounts the attempt times inter-frequency HHO from HS-DSCH to DCH in the cell. Whenthe RNC receives the PHYSICAL CHANNEL RECFG COMPLETE message from theUE, if the switch is the inter-frequency HHO from HS-DSCH to DCH, the RNC countsthe successful times of outgoing inter-frequency HHO from HS-DSCH to DCH in thecell.Success rate of R99-to-HThe RNC algorithm is unavailable now, so this index is unavailable.l Success rate of R99-to-H switch = successful times of switch from DCH toHS-DSCH in the cell/attempt times of switch from DCH to HS-DSCH in the cellIn the DCCC or RAB MODIFY process, if the RNC decides to switch the channel in thecell, it sends the UE the RF RECONFIGURATION message. According to the channelstate of the UE before and after reconfiguration, the RNC counts the attempt times ofswitch from DCH to HS-DSCH in the HSDPA serving cell. In the DCCC or RABMODIFY process, if the RNC receives the RB RECONFIGURATION COMEPLTEmessage from UE, and the reconfiguration enables UE to switch from the DCH toHS-DSCH in the same cell, the RNC counts the successful times of switch from DCH toHS-DSCH in the HSDPA serving cell.l Success rate of H-to-GPRS handover updateThe traffic statistics does not include the index, and the index will be supplemented later.The causes to failure and analysis methods will be summarized later.3.2.5 Traffic Statistics Analysis for HSUPA HandoverThe traffic statistics indexes for HSUPA are defined as below:l Success rate of SHO between HSUPA cells (including adding, replacing, anddeleting) = attempt times of active set update/complete times of active set update.l Success rate of SHO serving cell update between HSUPA cells = successful timesof SHO serving cell update/attempt times of SHO serving cell update.
  • 42. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page42 , Total201l Success rate of reconfiguration from DCH to E-DCH in the cell (SHO,intra-frequency HHO, and inter-frequency HHO) = successful times of handover fromDCH to E-DCH/attempt times of handover from DCH to E-DCH.l Success rate of reconfiguration from E-DCH to DCH in the cell (including adding andreplacing) = successful times of handover from E-DCH to DCH in SHOmode/attempt times of handover from E-DCH to DCH in SHO mode.l Success rate of intra-frequency HHO serving cell between HSUPA cells = successfultimes of intra-frequency HHO serving cell between HSUPA cells/attempt times ofintra-frequency HHO serving cell between HSUPA cells.l Success rate of intra-frequency HHO from E-DCH to DCH from a HSUPA cell to anon-HSUPA cell = successful times of intra-frequency HHO from E-DCH toDCH/attempt times of intra-frequency HHO from E-DCH to DCH.l Success rate of inter-frequency HHO serving cell update between HSUPA cells =successful times of inter-frequency HHO serving cell update between HSUPAcells/attempt times of inter-frequency HHO serving cell update between HSUPAcells.l Successful times of inter-frequency HHO from a HSUPA cell to a non-HSUPA cell =successful times of inter-frequency HHO from E-DCH to DCH/request times ofinter-frequency HHO from E-DCH to DCH.
  • 43. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page43 , Total2013.3 SHO Cost OptimizationTo be supplemented.
  • 44. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page44 , Total2014 CDR Index Optimization4.1 Definition of Call Drop and Traffic Statistics Indexes4.1.1 Definition of DT Call DropAccording to the air interface signaling recorded at the UE side, during connection, DT call dropoccurs when the UE receives:l Any BCH message (system information)l The RRC Release message with the release cause Not Normal.l Any of the CC Disconnect, CC Release Complete, CC Release message with therelease cause Not Normal Clearing, Not Normal, or Unspecified.4.1.2 Descriptions of Traffic Statistics IndexesA generalized CDR consists of CN CDR and UTRAN CDR. RNO engineers focus on UTRANCDR, so the following sections focus on KPI index analysis at UTRAN side.The related index at UTRAN side is the number of RAB for each service triggered by RNC. Itconsists of the following two aspects:l After the service is set up, the RNC sends CN the RAB RELEASE REQUESTmessage.l After the service is set up, the RNC sends CN the IU RELEASE REQUESTmessage. Afterwards, it receives the IU RELEASE COMMAND sent by CN.Upon statistics, sort them by specific services. Meanwhile, traffic statistics includes the cause torelease of RAB of each service by RNC.CS CDR is calculated as below:%*SuccessCSRABSetupiggedByRNCCSRabrelTrCDRCS 100_∑∑=PS CDR is calculated as below:
  • 45. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page45 , Total201%*SuccessPSRABSetupiggedByRNCPSRabrelTrCDRPS 100_∑∑=The failure cause indexes are sorted in Table 4-1.Table 4-1 Types of CDR indexesCDR type Cause Corresponding signaling processDue to airinterfaceRF RLC reset and RL FailureExpirationof processtimerRB RECFGExpiration of PHY/TRCH/SHO/ASUHHO failureNot due toairinterfaceHardwarefailureThe transport failure between RNC and NodeB. NCPreports failure.FP synchronization failure.Transportlayer failureALCAP report failureSubscribersarereleased byforce byMMLO&M interventionThe definition of RAN traffic statistics call drop is according to statistics of lu interface signaling,including the times of RNCs originating RAB release request and lu release request. The DTcall drop is defined according to the combination of messages at air interface and fromnon-access lay and cause value. They are inconsistent.4.2 DT/CQT Optimization FlowFigure 4-1 shows flow chart for analyzing call drop.
  • 46. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page46 , Total201Figure 4-1 Flow chart for analyzing call drop4.2.1 Call Drop Cause AnalysisCall drop occurs usually due to handover, which is described in chapter 3 . The followingsections describe the call drop not due to handover.Weak CoverageFor voice services, when CPICH Ec/Io is greater than –14 dB and RSCP is greater than –100dBm (a value measured by scanner outside cars), the call drop is usually not due to weakcoverage. Weak coverage usually refers to weak RSCP.Table 4-2 lists the thresholds of Ec/Io and Ec (from an RNP result of an operator, just forreference).Table 4-2 Thresholds of EcIo and EcServiceBit rate ofserviceDL EbNoEcIothresholdsEc thresholdsCS 12.2 12.2 8.7 –13.3 –103.1
  • 47. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page47 , Total201CS 64 64 5.9 –11.9 –97.8PS 64 64 5.1 –12.7 –98.1PS 128 128 4.5 –13.3 –95.3PS 384 384 4.6 –10.4 –90.6Uplink or downlink DCH power helps to confirm the weak coverage is in uplink or downlink bythe following methods.l If the uplink transmission power reaches the maximum before call drop, the uplinkBLER is weak or NodeB report RL failure according to single subscriber tracingrecorded by RNC, the call drop is probably due to weak uplink coverage.l If the downlink transmission power reaches the maximum before call drop and thedownlink BLER is weak, the call drop is probably due to weak downlink coverage.In a balanced uplink and downlink without uplink or downlink interference, both the uplink anddownlink transmit power will be restricted. You need not to judge whether uplink or downlink isrestricted first. If the uplink and downlink is badly unbalanced, interference probably exists in therestricted direction.A simple and direct method for confirming coverage is to observe the data collected by scanner.If the RSCP and Ec/Io of the best cell is low, the call drop is due to weak coverage.Weak coverage might be due to the following causes:l Lack of NodeBsl Incorrectly configured sectorsl NodeB failure due to power amplifier failureThe over great indoor penetration loss causes weak coverage. Incorrectly configured sectors ordisabling of NodeB will occur, so at the call drop point, the coverage is weak. You mustdistinguish them.InterferenceBoth uplink and downlink interference causes call drop.In downlink, when the active set CPICH RSCP is greater than –85 dBm and the active set Ec/Iois smaller than –13 dB, the call drop is probably due to downlink interference (when thehandover is delayed, the RSCP might be good and Ec/Io might be weak, but the RSCP of Ec/Ioof cells in monitor set are good). If the downlink RTWP is 10 dB greater than the normal value(–107 to –105 dB) and the interference lasts for 2s–3s, call drop might occur. You must payattention to this.Downlink interference usually refers to pilot pollution. When over three cells meets the handoverrequirements in the coverage area, the active set replaces the best cell or the best cell changesdue to fluctuation of signals. When the comprehensive quality of active set is bad (CPICH Ec/Iochanges around –10 dB), handover failure usually causes SRB reset or TRB reset.Uplink interference increases the UE downlink transmit power in connection mode, so the overhigh BLER causes SRB reset, TRB reset, or call drop due to asynchronization. Uplinkinterference might be internal or external. Most of scenario uplink interference is external.Without interference, the uplink and downlink are balanced. Namely, the uplink and downlinktransmit power before call drop will approach the maximum. When downlink interference exists,
  • 48. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page48 , Total201the uplink transmit power is low or BLER is convergent. When the downlink transmit powerreaches the maximum, the downlink BLER is not convergent. It is the same with uplinkinterference. You can use this method to distinguish them.Abnormality AnalysisIf the previous causes are excluded, the call drop might due to problematic equipment. Youneed to check the logs and alarms of equipment for further analysis. The causes might be asbelow:l An abnormal NodeB causes failure of synchronization, so links keeps being addedand deleted.l The UE does not report 1a measurement report so call drop occurs.You need to focus on the call drop due to abnormal testing UE, which occurs easily during CQT.Namely, the data recorded in DT does not contain the information reported by UE for a period.HSPA Call Drop AnalysisFor HSPA call drop analysis, refer to previous causes to R99 call drop.4.2.2 Frequently-adjusted Non-handover Algorithm ParametersThe frequently-adjusted non-handover algorithm parameters in call drop are as below:Maximum Downlink Transmit Power of Radio LinkConfiguring the transmit power of dedicated link to a great value helps to eliminate call droppoints due to weak coverage, but it brings interference. The power of a single subscriber isallowed to be great, so the subscriber might impact other subscribers or lower downlink capacityof system when the subscriber consumes great power at the edge of a cell.The configuration of downlink transmit power is usually provided by link budget. An increase ordecrease of 1–2 dB has little impact on call drop in signal DT, but it can be seen from trafficstatistics indexes. The CDR of some cells is high due to weak coverage, you can increase themaximum transmit power of DCH. The access failure probability of some cells is high due toover high load, you can lower the maximum downlink transmit power of radio link.Maximum Retransmission Times of Signaling and ServicesWhen the BLER of the channel is high, the signaling is reset because the retransmissionreaches the maximum times. A reset of signaling causes call drop. The services using AM modefor service transmission will also retransmit signaling. If the retransmission reaches themaximum times, the signaling is reset. The system configures the maximum reset times. Whenthe reset times reaches the maximum, the system starts to release the service, which causescall drop.The default configuration of system guarantees that burst blocks will not cause abnormal calldrop, and call drop occurs when UE moves to an area with weak coverage and when the resetis time, so the system releases resources. In some scenarios, burst interference or needleeffect exists, so 100% block error occurs during burst interference. If you want have less calldrop, increase the retransmission times improper to resist burst interference.This parameter is configured for RNC.
  • 49. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page49 , Total2014.2.3 Judgment Tree for Call Drop CausesBased on various causes to call drop, the judgment tree for analyzing call drop is as shown inFigure 4-2.Figure 4-2 Judgment tree for call drop causesPreparing DataThe data to be prepared include:l Data files collected by DTl Single subscriber tracing recorded by RNCl CHR recorded by RNCObtaining Call Drop LocationYou need to use special software to process DT data. For example, the software Assistant helpsto obtain call drop time and location, PICH data collected by scanner, information about activeset and monitor set collected by UE, and the signaling flow.
  • 50. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page50 , Total201Analyzing Signal Variation of Best server From ScannerAnalyze the signal variation of best server from scanner.l If the signals of best server are stable, analyze RSCP and Ec/Io.l If the signals of best server fluctuate sharply, you must analyze the quick variation ofbest server signals and the situation without best server. Consequently you cananalyze call drop due to ping-pong handover.Analyzing RSCP and Ec/Io of Best cellObserve the RSCP and Ec/Io of best cell according to scanner.l If both RSCP and Ec/Io are bad, call drop must be due to weak coverage.l If RSCP is normal but Ec/Io is bad (delayed handover is excluded, intra-frequencyneighbor cell interference), call drop must be due to downlink interference.l If both RSCP and Ec/Io are normal,When the cell in UE active set is inconsistent with the best cell according to scanner, calldrop must be due to missing neighbor cell and delayed handover.When the cell in UE active set is consistent with the best cell according to scanner, calldrop must be due to uplink interference or must be abnormal.Re-perform DT to Solve ProblemsA DT might not help to collect all information needed to locate call drop problems, so further DTsare needed. In addition, you can confirm whether the call drop point is random or fixed byfurther DT. You must eliminate fixed call drop points, but you can choose to eliminate randomcall drop points.4.3 Traffic Statistics Analysis FlowWhen analyzing traffic statistics indexes, you need to check RNC call drop indexes and masterthe overall situation of network operation. Meanwhile, you must analyze the cell concern fordetailed call drop indexes. You can obtain call drop of different services and approximatecauses to call drop by using traffic statistics analyzers.To analyze traffic statistics indexes, you must analyze the cells with obviously abnormal indexes.If the KPIs of the cell are good, there must be problems with version, hardware, transport,antenna-feeder, or data. Based on alarms, you can check these aspects.If there are no abnormalities, you can form a list of cells with bad KPIs by classifying sectorcarriers. Analyze traffic statistics indexes of these cells (such as more indexes related, analyzingthe interval between two periods, indexes leading to call drop, and handover indexes), andcheck the causes to call drop based on CHR. When solving problems, you need to focus on oneindex and combine other indexes.When the traffic volume reaches a certain level, the traffic statistics indexes work. For example,a CDR of 50% does not indicate a bad network. Only when the absolute value of call times, callsuccess times, and total times of call drop is meaningful in terms of statistics, the traffic statisticsindexes work.The flow for analyzing traffic statistics is as below.
  • 51. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page51 , Total2014.3.1 Analyzing RNC CDRThe RNC CDR involves the number of RAB of each service triggered by RNC, including twoaspects:l After a service is established successfully, the RNC sends CN the RAB RELEASEREQUEST message.l After a service is established successfully, the RNC sends CN the IU RELEASEREQUEST message, and then receives the IU RELEASE COMMAND message sentby CN.AMR CDR = VS.RAB.Loss.CS.RF.AMR / VS.RAB.SuccEstab.AMR.VP CDR = VS.RAB.Loss.CS.Conv64K / VS.RAB.SuccEstCS.Conv.64.To analyze PS call drop of various rates, you can analyze the following indexes:l VS.RAB.Loss.PS.64K / VS.RAB.SuccEstPS.64l VS.RAB.Loss.PS.128K / VS.RAB.SuccEstPS.128l VS.RAB.Loss.PS.384K / VS.RAB.SuccEstPS.384Based on analysis of previous indexes, you can obtain the performance of various services andrates in the network, as well as SHO/HHO call drop. More important, you can obtain the cellswith bad indexes and periods.4.3.2 Analyzing Causes to Call DropIn traffic statistics analysis, you must analyze the major causes to call drop.Table 4-3 lists the major indexes for analyzing traffic statistics.Table 4-3 Traffic statistics indexes for analyzing causes to call dropFailure cause AnalysisOM interference The O&M tasks cause call drop.Causes due to RABpreemptionHigh-priority preemption causes release of CS links. This kind of call dropoccurs when the load and resources are limited. Performing expansiondepends on the times of occurrence.Causes due to UTRANThe causes due to UTRAN in the cell lead to abnormal release of link. Thiscorresponds to abnormal process, so you must further analyze it based onCHR.Uplink RLC resetUplink RLC reset causes release of links, because the coverage quality(including missing neighbor cell and over mall handover area) is bad.Downlink RLC resetDownlink SRB reset causes release of links, because the coverage quality(including missing neighbor cell and over mall handover area) is bad.Uplink synchronizationfailureUplink synchronization failure causes abnormal release of links. Thecoverage quality (including missing neighbor cell and over mall handoverarea) is bad, so the UE powers off the transmitter abnormally or uplinkdemodulation is asynchronous.
  • 52. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page52 , Total201Downlink synchronizationfailureDownlink synchronization failure causes abnormal release of links. Thecoverage quality (including missing neighbor cell and over mall handoverarea) is bad, so the UE powers off the transmitter abnormally or uplinkdemodulation is asynchronous.No response of UU portThe UE air interface fails to respond the command transmitted by system,because the coverage is bad.Other RF causes It is due to RF causes and the coverage quality is bad.Abnormal AAL2 linkThe RNC detects that AAL2 Path at CS lu interface is abnormal, so thesystem originates an abnormal release. The problem might be due toabnormal transport equipment. Immediate normal release during RBestablishment is counted by statistics as abnormal release as the cause.Abnormal GTPUThe RNC detects the GTPU at PS lu interface is abnormal, so the systemoriginates an abnormal release. The problem is due to equipment failure.Other causes You need to analyze the abnormal call drop based on RNC logs.You can classify the previous indexes Table 4-3 by the classification of previous chapters. Theyfall into air interface causes (RF and flow expiration) and not due to air interface causes(hardware failure, transport failure, and subscribers interference). Therefore you can have anoverall master of network and obtain the major causes impacting the network.4.3.3 Check CellsIf the previous KPIs of the cell are normal, check the alarms. By this, you can exclude thecauses due to abnormal cells.4.3.4 Further DT for Relocating ProblemsAnalyzing traffic statistics indexes helps to expose potential problems. To locate and analyzeproblems, you need to use DT and CHR. For problematic cells, the cell-oriented DT isperformed to trace the signaling flow at UE side and of RNC. For details, see 3.1 .4.4 Optimization Flow for Tracing DataAnalysis traced data includes analyzing single subscriber tracing message and performancemonitoring. Based on the combination of single subscriber message and data at UE siderecorded by data collection tools, you can locate basic call drop problems. For more complexproblems, you need to use CHR and performance monitoring.By single subscriber tracing data, you need to locate and analyze problems concerningcommercial UEs or key subscribers which are not recorded at UE side.Single subscriber tracing involves recording the following information:l Signaling message (lu, lur, lub, and Uu) of single subscriberl Performance tracing of CPICH RSCP and Ec/Iol UE transmit powerl Uplink SIR, SIRTargetl Uplink BLER
  • 53. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page53 , Total201l Downlink code transmit powerl Uplink and downlink traffic and throughput (for data services)Figure 4-3 shows the flow for analyzing call tracing.Figure 4-3 Flow for analyzing call tracing4.4.1 Obtaining Single Subscriber Tracing MessageYou must first trace single subscriber tracing message on RNC or M2000 and then record thecorresponding messages. For detailed tracing methods, see W-Equipment Room OperationsGuide. Usually analyzing call drop problems by message for tracing IMSI is enough.4.4.2 Obtaining Information about Call Drop PointAccording to single subscriber tracing messages, the call drop is defined as:l The RNC originates RAB release (the message is RANAP_RAB_RELEASE_REQ)l The RNC originates IU release (the message is RANAP_IU_RELEASE_REQ)The former corresponds to call drop caused by TRB reset. The latter corresponds to call dropcaused by SRB reset. By searching for the previous two messages, you can obtain the call droptime and the signaling message before call drop for further analysis.
  • 54. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page54 , Total2014.4.3 Analyzing Call Drop due to SRB ResetThe call drop due to SRB reset is that the UE or RNC fails to receive signaling transmitted inconfirmation mode, and consequently SRT reset occurs, so the connection is released. SRBreset occurs probably if the UE fails to receive the following messages in downlink:l Security mode processl Authentication and encryption processl Measurement controll Active set updatel Physical channel reconfigurationl Transport channel reconfigurationl RB resetl Handover command from 3G to 2G (HANDOVER FROM UTRAN COMMAND)Confirm that the UE receives these messages by tracing messages at UE side.SRB reset occurs probably if the UE fails to receive the following messages in uplink:l Measurement reportl Active set update completel Physical channel reconfiguration completel Transport channel reconfiguration completel RB reconfiguration completeConfirm that the UE receives these messages by tracing messaged at RNC side.4.4.4 Analyzing Call Drop due to TRB ResetTRB reset usually occurs in PS services. It seldom occurs in voice and VP services. ConfirmTRB reset by the UE transmit power upon call drop and downlink code transmit power.When only one link exists in active set, uplink asynchronization causes RL failure whichconsequently causes lu release originated by RNC. Downlink asynchronization causes UE topower off transmitter, which consequently causes uplink asynchronization. To judge whetheruplink asynchronization or downlink asynchronization causes release, you must analyze the UEtransmit power before call drop and downlink code transmit power monitored in real-time state.Weak downlink coverage, strong downlink interference or uplink interference causes TRB reset.If the retransmission times of data services are improperly configured, TRB reset occurs beforeSRB reset upon delayed handover. Pay attention to this.4.4.5 Analyzing Abnormal Call DropAbnormal call drop can neither be located from coverage and interference nor be explained byTRB reset or SRB reset. It is caused by abnormal equipment or UE. For example, it might becaused by the following factors:l Abrupt transmission failure
  • 55. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page55 , Total201l Abnormal NodeB equipmentl Abrupt breakdown of UEAnalyze abnormal transmission by analyzing CHR or checking alarms. Confirm that the NodeBequipment is abnormal by querying NodeB state. Locate abnormal UE problems by analyzingdata recorded by UE.4.4.6 Performing CQT to Recheck ProblemsWhen the data is inadequate for locating call drop problems, you must start more detailed datatracing. The best method is to perform CQT at call drop points to recheck problems for furtheranalysis.4.5 Optimization Process for MBMS Call DropCurrently, the RNC V18 or V29 supports only the broadcast mode. In broadcast mode, theMBMS receives a control message from the MCCH to establish the MBMS service and radiobearer, without signaling interaction with the RNC. Therefore, we can substitute the MBMSsession drop rate for the MBMS call drop rate. The MBMS session drop rate is defined asfollows:MBMS session drop rate = number of MBMS session drop times/total number of successes ofMBMS-on-demand x 100%Number of MBMS session drop times: One MBMS session drop time is counted once theMBMS service is exceptionally interrupted or the UE is in the buffering state for more than oneminute.Total number of successes of MBMS on demand: Total number of successes ofMBMS-on-demand originated by the UE.You can see from the terminal interface whether the MBMS service is exceptionally interrupted,and you need to use the drive test software to observe whether the UE is the buffering state formore than one minute. Currently, the software tool used for this purpose is Qualcomm drive testsoftware QXDM.The possible causes for a high MBMS deactivation rate are as follows: The network coverage ispoor. The RSCP and Ec/Io in the position where the UE is located are both low. In addition, ablock error rate (BLER) of the FACH of the MBMS service also exists.The cell is in the preliminary congestion state and the channel power of the MBMS service isreset to the minimum; or the cell is in the over-congestion state and the MBMS service with alower priority is released by force. The channel power can, however, be automatically recoveredto the maximum or the service can be re-established through periodic detection.The UE is at the edge of the cells, and the neighboring cells are not configured for the cell inwhich the UE is located. As a result, the UE is unable to obtain a gain through soft combining orselective combining.Run the DSP CELLMBMSSERVICE command to query the status of the current MBMS service.If the MBMS service is not established successfully, the failure cause is displayed.You can improve the coverage rate by optimizing the RF, adding NodeBs, or adjusting theantennas. If the coverage does not improve, increase the maximum power of the MBMS trafficchannel. If a neighboring cell is not configured, configure it.
  • 56. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page56 , Total2015 FAQs Analysis5.1 SHO Problems5.1.1 Over High SHO Rate due to Improper SHO Relative ThresholdDescriptionThe SHO rate in traffic statistics indexes is over high. More than two cells exist in active setmost of the time during DT and are in SHO state.AnalysisAnalyze the relative threshold of 1A and 1B event, namely, reporting range.Figure 5-1 shows the SHO relative threshold
  • 57. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page57 , Total201Figure 5-1 SHO relative thresholdEvent-triggeredreportPCPICH 3PCPICH 1PCPICH 2PeriodicreportPeriodicreportReportingrangeReportingterminatedAccording to Figure 5-1, the greater the reporting range is, the more easily a neighbor cell islisted into active set and the more difficult it is deleted from active set. This causes over highSHO rate.A general method is to configure the threshold of 1A and 1B different. Configure the threshold of1A event small (such as 3 dB) and keep the threshold of 1B threshold the same (5 dB). In thisway, the cells with bad quality cannot be listed into active set easily and the cells with goodquality can be listed into active set. Therefore the SHO rate is lowered based on normal SHO.5.1.2 Delayed Handover due to Over Great Intra-frequency Filter CoefficientDescriptionSHO hysteresis is serious in DT: though the signals of a neighbor cell are strong, the cell can belisted into active set after a long time. If the DT car moves quickly, call drop occurs due todelayed handover.AnalysisLayer 3 filter reduces the impact by frequently-fluctuating signals and avoids ping-ponghandover.The filter of measurement values is calculated as below:nnn MaFaF ⋅+⋅−= −1)1(Wherein,Fn: the measurement resulted update after filter is processed.Fn-1: the measurement result of last point after filter is processed.Mn: the latest measurement value received in physical layer.
  • 58. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page58 , Total201a = (1/2)(k/2). The k is from Filter coefficient, namely, FilterCoef. If K = 0 and a = 1, there is nolayer 3 filter.The filter coefficient ranges from 0 to 6 (integers). The greater it is, the stronger the capability ofsmoothing burr is and the weaker the capability of tracing signals is. You must make a balance.According to simulation, Table 5-1 lists the relationship between the filter coefficient and thecorresponding tracing time.Table 5-1 Relationship between the filter coefficient and the corresponding tracing timeFilter coefficient 0 1 2 3 4 5 6 7 8 9 11Intra-frequencytracing time (s)0.2 0.4 0.6 1 1.4 2 3 4.2 6 8.4 17The distance between sites in dense urban areas is short and the handover time is short, soyou must reduce the tracing time, namely, the filter coefficient. The value 2 is usually proper forfilter coefficient of layer 3.5.1.3 Missing Neighbor CellDescriptionThe call drop point is related to signaling flow before call drop.Figure 5-2 shows the signaling flow recorded by UE before call drop.Figure 5-2 Signaling flow recorded by UE before call drop
  • 59. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page59 , Total201AnalysisCheck the pilot test data from UE and scanner at call drop points. Figure 5-3 shows thescrambles recorded by UE active set and scanner before call drop. In Figure 5-3, themeasurement result of UE active set and canner is inconsistent and the SC 170 of scannerdoes not exist in UE active set.Figure 5-3 Scrambles recorded by UE active set and scanner before call dropThe cause might be missing neighbor cell or delayed handover. Check scrambles in UE activeset. Figure 5-4 shows the scrambles in UE active set before call drop. No SC 170 cell exists inUE monitor set, because this is possibly due to missing neighbor cell.
  • 60. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page60 , Total201Figure 5-4 Scrambles in UE active set before call dropContinue to check the neighbor cell list sent by RNC to UE before call drop, as shown in Figure5-5 and Figure 5-6. According to the latest measurement control before call drop, no SC 170exists in the neighbor cell list, because the call drop is due to missing neighbor cell of SC 6 andSC 170.
  • 61. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page61 , Total201Figure 5-5 UE intra-frequency measurement control point before call dropFigure 5-6 Analyzing signaling of UE intra-frequency measurement control before call dropIf only the UE recorded information during test, without scanner information, confirm that calldrop is due to missing neighbor cell by using the following method, as shown in Figure 5-7:
  • 62. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page62 , Total201l Confirm the scrambles of all cells in active set and the scrambles of cells in monitorset measured by UE before call drop.l Compare the scramble information of the cell where the UE camps on afterreselection after call drop and the scrambles in UE active set and monitor set beforecall drop.If the former scramble is not in the scramble list of active set and monitor set beforecall drop, the call drop is probably due to missing neighbor cell.l Check the neighbor cell list.This applies for solving call drop due to missing neighbor cell on site.Figure 5-7 Confirming missing neighbor cell without information from scannerSolutionAdd neighbor cells. Because the RNC updates measurement control according to the best cellwhich is obtainable by searching for intra-frequency measurement report with 1D event beforemeasurement control is sent. Usually they are configured to bi-directional neighbor cells.5.1.4 Redundant Neighbor CellsAccording to the protocol, the maximum number of neighbor cell is 32 and the host cell is alsoincluded in these cells, so the actual intra-frequency neighbor cell is 31 at most. Theintra-frequency neighbor cells of S subject are based on data of 2G neighbor cells. In the denseurban areas, the densely-located sites and combine make the intra-frequency neighbor cell listlarge. If the intra-frequency neighbor cells reach or exceed 31, a necessary neighbor cell foundduring optimization fails to be listed as an inter-frequency neighbor cell. For this, you mustdelete some redundant neighbor cells.You must be cautious to delete abundant neighbor cells. Deleting necessary neighbor cellsleads to call drop. Following the principles below:
  • 63. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page63 , Total201l Before deleting neighbor cells, check the revision record of neighbor cells. Checkthat the cells to be deleted are not the ones that were added during previous DT andoptimization.l After deleting neighbor cells, perform comprehensive test, including DT and CQT inimportant indoor spots. From this, you can check the variation of traffic statisticsresult of the corresponding cells. The traffic statistics result includes setup successrate, CDR, and handover success rate. Ensure there is no abnormality. Otherwiserestore the configuration.If no reliable 3G handover times can serve as judgment at the network construction stage, youcan estimate the handover probability by using the handover times of 2G neighbor cells.Table 5-2 lists the 2G handover times.Table 5-2 2G handover timesAssist_GSM_HO_CountSERVCELL NCELL HOCOUNT12531 10121 41712531 10161 326212531 10162 207012531 10301 38112531 10321 26512531 12061 912531 12101 96112531 12111 1612531 12251 212531 12291 412531 12292 012531 12330 108212531 12391 106312531 12451 1701912531 12532 1603012531 12540 7412531 12591 92612531 12592 2099412531 14051 212531 14072 212531 14091 21112531 14111 1
  • 64. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page64 , Total20112531 14460 32112531 56361 1612531 56362 012531 56820 012531 56910 206Search for the neighbor cells with few handover times and even no handovers, such as cell12531–12292. Figure 5-8 shows the location relationship of 2G redundant neighbor cells.Figure 5-8 Location relationship of 2G redundant neighbor cellsAccording to Figure 5-8, multiple NodeBs are located between the cell 12531 and the cell 12292,so the handover probability is small. Therefore, delete the neighbor cell relationship.The judgment principles based on 2G statistics might have mistakes, so you must confirm thatno call drop occurs after deleting the neighbor cell relationship.After network launch, the handover times in traffic statistics according to statistics reflects thereal handovers, so deleting abundant neighbor cells by using the handover times in trafficstatistics according to statistics is more reliable. You need to register the traffic statistics tasks oftwo cells on traffic statistics console of RNC.
  • 65. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page65 , Total2015.1.5 Pilot PollutionDescription and Analysisl Locating pilot pollution pointFigure 5-9 shows the pilot pollution point near Yuxing Rd. SC270 cell is planned tocover the area with pilot pollution.Figure 5-9 Pilot pollution near Yuxing Rd.l Analyzing signal distribution of cells near pilot pollution pointFigure 5-10 Best ServiceCell near Yuxing Rd.
  • 66. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page66 , Total201Figure 5-11 The 2nd best ServiceCell near Yuxing Rd.Figure 5-12 The 3rd best ServiceCell near Yuxing Rd.
  • 67. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page67 , Total201Figure 5-13 The 4th best ServiceCell near Yuxing Rd.Figure 5-14 Composition of pilot pollution near Yuxing Rd.From Figure 5-10, Figure 5-11, Figure 5-12, Figure 5-13, and Figure 5-14, though SC20cell is planned to cover the area, but the best ServiceCell is as listed in Table 5-3.Table 5-3 Best servers and other cellsBest ServiceCell Primary Others1stbest ServiceCell SC220 SC260 and SC2702nd best ServiceCell SC270 SC260, SC220, and SC2003rdbest ServiceCell SC200 SC270 and SC2604thbest ServiceCell SC200 SC270 and SC260l Analyzing RSSI distribution near pilot pollution point.Figure 5-15 shows the RSSI near Yuxing Rd..
  • 68. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page68 , Total201Figure 5-15 RSSI near Yuxing Rd.Figure 5-16 shows the RSCP of Best ServiceCell near Yuxing Rd..Figure 5-16 RSCP of Best ServiceCell near Yuxing Rd.As shown in Figure 5-15, the RSSI of the areas with pilot pollution is not large, about–100 dBm to –90 dBm. As shown in Figure 5-16, the RSCP of Best ServiceCell isbetween –105 dBm to –100 dBm. The pilot pollution of the area is caused by no strongpilot, so you can solve the problem by strengthening a strong pilot.l Analyzing RSCP Distribution of Related CellsFigure 5-17 shows the RSCP of SC270 cell near Yuxing Rd.
  • 69. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page69 , Total201Figure 5-17 RSCP of SC270 cell near Yuxing Rd.The SC270 cell is planned to cover the area. Figure 5-17 shows RSCP of RSCPdistribution of SC270 cell. The signals from SC270 cell are weak in the area with pilotpollution.SolutionAccording to on-site survey, the residential area is densely distributed by 6-floor or 7-floorbuildings. The test route fails to cover the major streets, and is performed in narrow streets withbuildings around, so the signals are blocked. The suggestion is to adjust the azimuth of SC270cell from 150° to 130° and the down tilt from 5° to 3°. This enhances the coverage of SC270cell.After analysis of DT data, the expected result after adjustment is that the coverage area bySC270 cell increases and the coverage is enhanced.Figure 5-18 shows the pilot pollution near Yuxing Rd. after optimization.
  • 70. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page70 , Total201Figure 5-18 Pilot pollution near Yuxing Rd. after optimizationFigure 5-19 shows the best ServiceCell near Yuxing Rd. after optimization.Figure 5-19 Best ServiceCell near Yuxing Rd. after optimizationFigure 5-20 shows the RSCP of best ServiceCell near Yuxing Rd. after optimization.
  • 71. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page71 , Total201Figure 5-20 RSCP of best ServiceCell near Yuxing Rd. after optimizationFigure 5-21 shows the RSCP of SC270 cell near Yuxing Rd. after optimization.Figure 5-21 RSCP of SC270 cell near Yuxing Rd. after optimizationAccording to the DT data, the pilot pollution near Yuxing Rd. after optimization is eliminated, thesignals from SC270 cell after optimization are stronger, and the SC270 becomes the bestServiceCell. This complies with the expected result.5.1.6 Turning Corner EffectDescription and AnalysisThe turning corner effect exists in the following situation:The signals of original cell attenuates sharply, and the signals of target cell increases sharply, sothe UE cannot receive the active set update messages, and consequently call drop occurs.The variance of Ec/Io is shown in Figure 5-22 (the interval between two points is 0.5s).
  • 72. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page72 , Total201Figure 5-22 Turning corner effect-signals attenuationcell56 vs cell041-30-20-100timeEcNocell56cell041According to Figure 5-22, the signals of original cell attenuate 10 dB sharply within 1s, and thesignals of target cell increase 10 dB. If the signals are weak before attenuation, and 1a event isconfigured to easily-triggered state, the measurement report is sent according to tracedsignaling of the UE, and the RNC receives the measurement report according to signalingtraced by the RNC.When the RNC sends the active set update message, the UE cannot receive it due to weaksignals of original cell, so the signaling is reset, and call drop occurs. If 1a event is slowlytriggered (such as configuring great hysteresis or triggering time), TRB reset occurs before theUE sends the measurement report.Figure 5-23 shows an example of turning corner effect.Figure 5-23 Turning corner effect-signal attenuation recorded by the UEAccording to Figure 5-23, before turning corner, the signals of active set scramble 104 and 168attenuate to smaller than –17 dB, but that of 208 is strong (–8 dB). According to the signalingtraced by the RNC, and the UE reports the 1a event of the cell of scramble 208, and sends the
  • 73. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page73 , Total201active set update message. The UE does not receive the completion message, so the call dropoccurs, as shown in Figure 5-24.Figure 5-24 Turning corner effect-traced signaling recorded by the RNCSolutionTo solve turning corner effect problems, do as follows:l Configure 1a event parameter of a cell to enable handover to be triggered moreeasily.If you lower the triggering time to 200ms, you can reduce hysteresis. You mustconfigure the triggering time for a specified cell, because the change of theparameter might lead to easily occurrence of handover between the cell and othercells without turning corner effect, or frequent ping-pong handover.l Configure the CIO between two cells with turning corner effect to add the target cellmore easily. The CIO only affects the handover between two cells, with less impact,however, it impacts handover. The configuration leads to an increase of handoverratio.l Adjust antenna to enable the antenna of target cell cover the turning corner. Thishelps avoid fast variance of signals, and avoid call drop. Actually experiences helpjudge whether the adjustment of engineering parameters can cover the turningcorner, so using this method is difficult.Based on previous analysis, the first method prevails. If it fails, use the second method. If thesecond method fails, use the third method (the third method is the best solution, especially inareas where you can adjust antenna easily).
  • 74. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page74 , Total2015.1.7 Needlepoint EffectDescription and AnalysisThe needlepoint effect is that affected by the strong signals of target cell in a short time, theoriginal cell attenuates sharply, and then increase. The variance of Ec/Io is shown in Figure 5-25(the interval between two points is 0.5s).Figure 5-25 Needle point-signal varianceThe needlepoint effect cause call drop in the following situations:l If the needlepoint lasts for a short period, unable to meet the handover conditionsand to affect call drop, it will lead to deterioration of quality of service (QoS), such asover great BLER exists in downlink.l If handover occurs in the target cell, and the signals of the original cell is over weak,so the UE cannot receive active set update messages, and consequently call dropoccurs.l If the needlepoint lasts for a short period, and the handover conditions are difficult tomeet, so the signaling or service RB reset occurs due to weak downlink signalsbefore handover. Finally, call drop occurs.l If the target cell completes handover, and becomes a cell in the active set, call dropoccurs because the cell can exit the active set before completing a handover withthe needlepoint disappearing quickly.Compared with turning corner effect, the needlepoint effect is more risky due to two handovers,and failure of one of the two causes call drop. The needlepoint lasts for a short period, so calldrop may not occur if QoS is lowered (for example, configure a greater retransmission times).The turning corner effect causes an absolute call drop because the signals of original cell willnot recover after turning corner.Observe the needlepoint effect by scramble distribution diagram of the best cell recorded byScanner. If two antennas cover two streets respectively, at the crossing point, needlepoint effectoccurs easily.Figure 5-26 shows the call drop distribution of PS384K intra-frequency hard handover (it is thebest cell). Wherein, call drop point drop4, drop5, drop6, drop7, drop15, and drop16 are causedby needlepoint effect.
  • 75. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page75 , Total201Figure 5-26 Call drop distribution of PS384K intra-frequency hard handoverSolutionTo solve problems caused by needlepoint effect, you can refer to the solution to turning cornereffect. The key to adjust antenna is not to enable original signals attenuate sharply and not toenable target signals increase sharply. In addition, you can increase the retransmission times toresist to attenuation of signals so that CDR is lowered.5.1.8 Quick Change of Best server SignalDescriptionFigure 5-27 shows signal distribution of cell52 vs. cell88 (signal fluctuation in handover areas).
  • 76. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page76 , Total201Figure 5-27 Signal distribution of cell152 vs. cell88 (signal fluctuation in handover areas)After the UE hands over from cell 152 to cell 88, the signals of cell 152 are stronger than that ofcell 88. In Figure 5-27, after the signals of cell 152 keep weaker than that of cell 88, the signalsof cell 152 become stronger than that of cell 88 for continuous 2s.AnalysisWhen the UE hands over from cell 152 to cell 88, and the signals of cell 152 become better thanthat of cell 88. This is similar to the needlepoint effect in 5.1.7 . Therefore quick change of bestserver signals causes the same handover failures as the needlepoint effect causes, as follows:l Ho Req SRB Resetl Ho Failurel TRB ResetTo sole the problem, optimize RF engineering parameters and 1D event parameters to avoidping-pong handover.
  • 77. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page77 , Total2015.2 HHO Problems5.2.1 Intra-frequency Ping-pong HHO due to Improperly Configured 1D EventHysteresisDescriptionThe UE keeps performing intra-frequency HHO at the cell border, so the call quality declinesand even call drop occurs.AnalysisReporting the 1D event triggers the inter-frequency HHO. The 1D event is reported when thebest cell changes, as shown in Figure 5-28.Figure 5-28 Reporting 1D eventThe UE is at the border of two cells, so the signals from the two cells are equivalently strong.Signal fluctuation easily causes ping-pong handover to best cells. Frequent report 1D eventtriggers inter-frequency HHO.To avoid intra-frequency ping-pong HHO caused by 1D event triggered by frequent fluctuation ofsignals if the channels are similar, you can increase the hysteresis, as shown in Figure 5-29.
  • 78. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page78 , Total201Figure 5-29 Increasing hysteresis to reduce frequently reporting of 1D eventAccording to Figure 5-29, the second times does not reach the hysteresis, so reporting 1Devent is not triggered.5.2.2 Delayed Origination of Inter-frequency Measurement due to ImproperInter-frequency Measurement QuantityDescriptionWhen the UE moves to an inter-frequency cell, it fails to start compression mode to startinter-frequency measurement. It camps on the inter-frequency cell after disconnection.AnalysisThe cell mentioned previously is configured as the carrier central cell after querying cellconfiguration. Namely, the 2D event, 2F event, and inter-frequency measurement all take Ec/Noas measurement quantity.The measured value of pilot Ec/No depends on the following two aspects:l CPICH RSCP strengthl Downlink interferenceThe downlink interference in the WCDMA network includes the interference from downlinksignals of intra-frequency cells (the host cell and neighbor cells) and the background noise.Wherein, the downlink interference strength of intra-frequency cells is impacted by path loss andslow attenuation. It is similar to the attenuation that UE receives useful signals (such as CPICHRSCP).At the coverage edge of a carrier, when UE moves from the current cell to another cell, theCPICH RSCP attenuates at the same speed as the attenuation of interference (the backgroundnoise is not impacted by path loss, so the CPICH RSCP attenuates a little faster thaninterference attenuates. However, the difference between the two speeds is close (dependingon the strength of background noise). Therefore the UE receives the signals the CPICH Ec/Io of
  • 79. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page79 , Total201which changes slowly. According to the simulation and on-site test, When the CPICH RSCP isabout –110 dBm, the CPICH Ec/Io can reach about –12 dB.Figure 5-30 Attenuation relationship of RSCP and Ec/NoIf you take Ec/Io as the measurement quantity for 2D event, the 2D event will be triggeredbefore call drop. Therefore adopting Ec/Io as the measurement quantity for 2D event will nottrigger 2D event upon call drop of UE, so the inter-frequency measurement will not be started.In this case, configure the cell to carrier coverage edge cell and take RSCP as themeasurement quantity for 2D/2F event so that inter-frequency measurement is originated intime.
  • 80. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page80 , Total2015.3 Inter-RAT Handover Problems5.3.1 Ping-pong ReselectionDescriptionIn part of the office building of a commercial deployment, the UMTS-GSM dual-mode MSperforms frequent ping-pong reselection of cells between 3G and the 2G network in the idlestate. “2G” and “3G” flag are displayed in the screen of Siemens U15 and Moto A835 MSs.“WCP” and “GCP” are displayed in the screen of the Qualcomm test MS frequently. Thereselection from the 3G network to the 2G network takes 1min on average. The reselection fromthe 2G network to the 3G network takes 1–2 minutes on average. During the testing, thelocation of the MS and the circumstance keep fixed.AnalysisThe reselection from the 3G network to the 2G network is as follows:l When the pilot signal quality Ec/Io in 3G cells minus Qqualmin is less than theinter-RAT measurement start threshold SsearchRAT, the UE started to measure the2G neighbor cell.l When the quality of signal in 2G neighbor cells satisfies the cell reselection criteriaand lasts for Treselection, the UE selects 2G cells.3G RSCP is below –90 dBm at the borders of 3G network. However the 2G RSCP ranges from–60 dBm to –70 dBm with signals of good quality. Therefore, once the UE starts to measure the2G neighbor cells and the signal in the cell fails to be better in Treselection, the UE reselects the2G cells.The key parameter in reselection from the 3G network to the 2G network in test is SsearchRAT.The rational configuration of the reselection delay timing parameter Treselection helps solveping-pong reselection.The reselection from the 2G network to the 3G network is as follows:l When the signal strength of 2G serving cell satisfies the inter-RAT start thresholdQsearch_I, the 3G neighbor cells are measured. From optimized 3G strategy, thecurrent configuration is 7 (always start).l When the signal strength RSCP of the 3G cell minus the current RLA_C (theaverage signal strength in 2G serving and non-serving cells) is greater thanFDD_Qoffest, and it lasts 5s, the 3G cell can serve as the target cell to be reselected.The current FDD_Qoffset is 7 (always reselect 3G cells).l When the signal quality Ec/Io of the 3G cell is greater than or equal to FDD_Qminthreshold, the 3G cell can serve as the target cell to be reselected.l In the cells that satisfy the previous conditions, the UE select the cell of best qualityas the target cell to be reselected.Therefore, the key parameter in from the 2G network to 3G is FDD_Qmin. The defaultconfiguration is –12 dB.
  • 81. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page81 , Total201SolutionsIn network optimization, the operator can take the following adjustment:l The operator increases the interval between SsearchRAT and FDD_Qmin.According to the default parameters, if 3G CPICH Ec/Io is greater than –12 dB in theGSM system, the UE reselects the 3G network. If 3G CPICH Ec/Io is less than orequal to –14 dB, the UE reselects the GSM network from 3G network. In the currentparameters configuration, the signal fluctuation of 3G CPICH Ec/Io decides thefrequency of cell reselection. If the signal fluctuation is over 1 dB, the ping-pongreselection occurs. In field test of 3G cells, if Ec/Io is less than –14 dB, the UE dropsoff the network easily, so the SsearchRAT cannot be less, and FDD_Qmin can beincreased. The value range of FDD_Qmin is over small, so it can be only set to itsmaximum value –13 dB. Since the protocol of September 2003, the value range ofFDD_Qmin is increased through CR GP-032221 (see 5.2 for details). If the UE isupdated according to GP-032221, the FDD_Qmin is increases completely. IfFDD_Qmin is set to –8 dB, compared with the start measurement threshold –14 dBof reselection from the 3G network to 2G network, FDD_Qmin has a space of 6 dB.In this way, the ping-pong reselection caused by signal fluctuation is less likely.l Treselection is increased. If the default configuration is 1s, the Treselection can beset to 5s. In this way, the reselection between the 3G network and the 2G network isreduced.5.3.2 PS Inter-RAT Ping-pong HandoffDescriptionThe UE performing PS domain services hands off between the 3G network and the 2G network.AnalysisFor inter-RAT handoff of CS and PS, the services for CS and PS are different in handoffbetween the 2G network and the 3G network.l In CS service, after handoff from the 3G network to the 2G network and after releaseof services in the 2G network, the UE reside again in the 3G cell through reselectionfrom the 2G network to the 3G network or reselection of PLMN.l In PS service, after the reselection from the 3G network to the 2G network started bythe network, the UE re-accesses the 2G network. In services transmission, the UEperforming PS services may return to the 3G network through reselection betweenthe 2G network and the 3G network. According to the analysis of 3.1 , in thereselection of the cells performing PS domain services from the 2G network to 3Gnetwork, the actual working factor is the configuration of FDD_Qmin (measuringEc/Io). If Ec/Io is greater than FDD_Qmin, the UE reselects 3G network. Whether theUE has handed off from the 3G network to the 2G network is judged throughmeasuring RSCP in condition of the cell as a border cell. Measuring RSCP cannotassure that Ec/Io is greater than FDD_Qmin, so no mechanism can avoid ping-ponghandoff.The solutions lie in as follows:l The measurement target of 2G and the 3G network is unified. If this cannot beperformed, the following method is adopted.
  • 82. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page82 , Total201l The start parameters in compression mode and reselection threshold from the 2Gnetwork to the 3G network is adjusted.Solutionsl Unification of measurement target in the 3G network and the 2G networkWhen there are more than one 3G cells, the change of Ec/Io indicates the change of3G cell quality. If the cell property is configured as “carrier center cell” and themeasurement target in 2D event is Ec/Io, the measurement target between 3G andthe 2G network is Ec/Io. The default parameter of 2D/2F with the measurementtarget Ec/Io is –24 dB. The parameter can be adjusted to –12/–10 dB to avoidping-pong handoff.In addition, the new 3GPP TS 05.08 protocol defines the RSCP (FDD_RSCP) thatcan measure the 3G network in reselection from the 2G network to the 3G network.Now only Ec/Io can be tested. The adjustment fits the 3G cells the cell property ofwhich is “carrier border cell”. However many current NEs does not support this.l Adjustment of start parameters in compression mode and reselection threshold from2G to 3G networkThe adjustment fits the 3G cells the property of which is “carrier border cell”. Only 3GEc/Io can be measured in reselection from the 2G network to 3G network. Thestart/stop threshold in compression mode can be lowered to –105/–100 dBm.5.3.3 Failure in handoff from 3G to the 2G networkDescriptionIn the office building of a commercial deployment, when the UE originates a call in areascovered by the 3G network and moves towards the areas covered by the 2G network, the calldrops easily. The call succeeds one or two times every ten times.AnalysisThe 2G neighbor cells configuration of the 3G network cells that cover the office building in theWCDMA network parameters is examined. The 2G cells that cover office building need to beconfirmed in the 2G neighbor cells list. UMTS outdoor macrocells are used to perform 3Gcoverage in the office building, the test route is switched by passing two iron doors. After theoperator opens the door, enters, and closes the door, the signal attenuates sharply. Figure 5-31shows the UMTS signal distribution observed by a scanner.The signal attenuates sharply, so the handoff is not performed in time, and then the call drops.The key solution is to adjust the inter-RAT switching parameters. This leads to an earlier andfaster handoff.The operator does as follows:l Change the cell independent offset (CIO) in the GSM neighbor cell from 0 dB to 5 dB.The UE hands off to the GSM cell more easily. Call still drops in test.l Change 2D RSCP Threshold from –95 dBm to –85 dBm to –75 dBm. The inter-RATmeasurement starts earlier. Call still drops in test.l Change GSM RSSI from –90 dBm to –95 dBm. The UE hands off to GSM cells moreeasily. Call still drops in test.
  • 83. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page83 , Total201l Change 2D Trigger Time from 640ms to 320ms to 0ms. The inter-RAT measurementstarts more easily. Call still drops in test. Change the parameter back to 640ms.l Change the cell location property from “carrier border” to “carrier center” (theassociated measurement changes from RSCP to Ec/Io). Change 2D Ec/Io Thresholdfrom –24 dB to –10 dB. Call still drops in test.l Change Inter RAT handover trigger time from 5000ms to 2000ms. The UE performsinter-RAT more quickly. Call drop is improved.l Recover the parameter changed in Step 5 as it was.l Change Inter RAT handover trigger time from 2000ms to 1000ms. The UE performsinter-RAT handoff more quickly. Call drop is solved.The adjustment results in that the change to the parameter Inter RAT handover trigger time isthe most effective to complete inter-RAT handoff.Figure 5-31 Indoor 3G RSCP distributionSolutionsThe operator checks as follows:l Check that 2G neighbor cells are validly configured.l Reduce TimeToTrigForVerify (TimeToTrigForNonVerify needs no change. Thecurrent protocol defines that the UE needs not to report on NonVerify) to make UEhand off to the 2G network more quickly.l Increase GSM CIO. This increases the possibility of handoff to the 2G network, butincreases the coverage of the 2G network and reduces the coverage of 3G,therefore this step need consideration.
  • 84. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page84 , Total201l Increase the GSM RSSI handoff threshold. This increases the coverage of the 2Gnetwork, but reduces the coverage of 3G network, therefore this step needsconsideration.Increase 2D/2F threshold in compression mode to start compression mode earlier.5.3.4 Inter-RAT Handover Call DropMissing Neighbor CellConfirm the call drop due to missing neighbor cell by 3G cell information displayed on M testingcell. You must check whether the neighbor cells are missing in the following situations:l The signals of 3G cell are weak.l Ec is smaller than –110 dBm.l Ec/Io is smaller than –10 dB.l A 2G testing UE detects that the 2G signals of indoor DAS are strongl The UE starts compression mode for measurementl The UE does not sent the measurement report of 2G neighbor cells.The following are two examples.l Example 1:14:24:17(12): According to RB Setup, the UE accesses the network by PSC 417.14:25:36(02): The UE does not report 2D measurement report until call drop. The RNCdoes not send measurement control report.Conform that no inter-RAT neighbor cells are configured by examining parameters. Ifthe cells are added, call drop problems are solved.l Example 2:16:38:18(18): The UE reports 1D event of cell 273, and cell 273 becomes the best cell.However, the BCCH 538 indoor 2G cell is not configured as an inter-RAT neighbor cellof cell 273.16:38:40(20): The UE keeps sending measurement reports, but detects that the signals ofother GSM neighbor cells are weak. Therefore the RNC does not start handover, andthen call drop occurs.The cell of PSC273 and PSC 264 alternate to be the best server. Indoor GSM neighborcells are configured as the inter-RAT neighbor cells of the cell of PSC264, but the cell ofPSC273 is not configured with any neighbor cells. When the UE enters indoor, the cellof PSC273 becomes the best server, so call drop occurs. After indoor GSM neighborcells are configured as the inter-RAT neighbor cells of the cell of PSC273, no call dropoccurs.Abundant Inter-RAT Neighbor CellsAccording to the signaling, the phenomena of excessive inter-RAT neighbor cells are as follows:
  • 85. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page85 , Total201After the RNC sends Physical channel reconfiguration and inter-RAT measurement controlmessages, the UE keeps sending the measurement report of Nonverified until call drop.In S subject, for convenient configuration of parameters, the original 2G neighbor cellinformation is used to configure inter-RAT neighbor cells. All the inter-RAT cells are configuredas the neighbor cells of 3G cells. Inter-RAT cell offset is configured to enable the UE to handover to the target cell and to disable the UE to hand over to the undesired cell.If excessive neighbor cells are configured, the UE must spend more time on inter-RATmeasurement. The measurement internal of UE is limited, excessive neighbor cells delay UE tomeasure available neighbor cells, so call drop occurs.Example :11:30:11(92): The RNC sends measurement control messages (23 inter-RAT neighborcells)11:32:22(61): The UE keeps reporting to BSIC Nonverified cell until 2 minutes beforecall drop.Configure the inter-RAT neighbor cells to the needed four neighbor cells, the MotoA835hands over successfully.Improper Configuration of LACConfirm improper configuration of LAC by signaling. The CN replies the No ResourceAvailable messages, so examining data configuration before test is necessary. In addition, ifthe mobile switching center (MSC) fails in assigning related resources, such as inter-MSC trunkresources, the T resource to MGW, control table resource, the CN might reply the No ResourceAvailable messages.Example :10:53:23(29): The RNC sends the Relocation Require message due to the No ResourceAvailable message.10:53:23(71): The CN replies the Relocation Failure message due to the No ResourceAvailable message.The RNC keeps sending Relocation Require message due to No Resource Availablemessage until call drop, and is rejected. The actual LAC is 21000. After adjustment, theUE succeeds in handover.No Measurement Report by UEIf the UE does not send measurement report, the UE performs the same as when the neighborcells are missing. The phenomena are as follows:l The signals of 3G cell is weakl Ec is smaller than –110 dBm.l Ec/Io smaller than –10 dB.l A 2G testing UE detects that the 2G signals of indoor DAS are strongl The UE does not hand over.Check the signaling to confirm whether the UE send measurement report messages. If youcompare it with terminals of other types, confirming the problem is easier and more accurate.
  • 86. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page86 , Total201Example :l Moto A835 handset:16:38:05(99): The UE sends 2D measurement reports.16:38:06(06): The RNC sends Physical channel reconfiguration (active sets containsPSC46, PSC492, and PSC36)16:38:07(19): The RNC receives Physical channel reconfiguration completion, and thensends measurement control messages.16:38:08(75): The cell of PSC 492 reports 1D and becomes the best server. It sends newmeasurement control messages after 1.5s.16:39:19(73): The system does not receive the UE inter-RAT measurement report beforecall drop.l Qualcomm 6250 handset16:38:42(16): The UE sends 2D measurement reports.16:38:42(49): The RNC sends Physical channel reconfiguration (active set containsPSC46 and PSC492)16:38:43(43): The RNC receives Physical channel reconfiguration completion message,and it sends measurement control messages.16:38:47(74): The UE report BCCH 847 BSIC Verified, and the level is –67 dBm.16:38:48(88): The RNC sends HO CMD message, so the handover succeeds.In the test of handover between outdoor 3G to indoor 2G DAS, the Moto A835 handset does notsend inter-RAT the measurement report for multiple times. The IOT engineers think that theversion of out handset is not updated, and they recommend updating handset version.Delayed HandoverAccording to signaling of the RNC, a normal inter-RAT handover takes 5s. The following are thetime needed by the RNC, longer than that on UE. If the walking speed is 3 km/h, it takes 4–5meters. The time depends on different scenes.16:21:06(30): The UE sends the 2D measurement report.16:21:06(37): The RNC sends the Physical channel reconfiguration message.16:21:07(46): The UE sends the Physical channel reconfiguration completion message.16:21:09(72): The UE sends the inter-RAT measurement reports.16:21:10(48): The system sends the UE HO FROM UTRAN CMD GSM message.16:21:11(11): The RNC sends the Iu interface Release Command message.When the UE moves outdoor to indoor with the 3G signals fluctuating sharply, call drop occursdue to delayed handover. According to the signaling, the phenomena of delayed handover areas follows:l During the handover process, the RNC originates lu Release because:− The NodeB reports RL Failure.− The NodeB does not report RL failure, but SRB reset occurs.
  • 87. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page87 , Total201l The CN originates lu Release command, due to treloccomplete expire.l Other situations: 3G signaling is normal, but actually the call drops. You can onlyknow whether the UE confronts call drop problems by checking the UE call droprecorded in test.Example 1:l Moto handset:15:26:27(87): The RNC sends Physical channel reconfiguration (active set containsPSC201 and PSC16).15:26:30(30): The UE report BCCH 844 BSIC Nonverified, and the level is –87 dBm.15:26:31(26): The UE report BCCH 844 BSIC verified, and the level is –88 dBm.15:26:32(13): The RNC sends the HO CMD message.15:26:34(25): The UE sends inter-RAT measurement reports, but does not hand over.This is because the UE does not receive HO CMD sent by the RNC, or the UE fails inaccessing the 2G network. The CN sends lu Release due to treloccomplete expire(normally successful relocation causes lu Release, and the UE succeeds in accessing the2G network).l Qualcomm handset in the same test period:15:26:27(43): The RNC sends Physical channel reconfiguration (active set containsPSC201 and PSC16).15:26:30(90): The UE report BCCH 844 BSIC verified, and the level is –79 dBm.15:26:32(13): The RNC sends HO CMD, and the handover succeeds.Here is the entrance to parking yard of Taigu Shopping Hall. Before call drop, the Moto handsetindexes as follows:l Ec is smaller than –110 dBm.l Ec/Io is small than –15 dB.In addition, according to comparison of two terminals, they are different in measuring GSM level(Qualcomm 6250 uses an external antenna, while Moto A835 uses a built-in camera). Thisaffects the inter-RAT measurement.Example 2:l Moto handset:17:08:59(61): The UE sends 2D measurement reports, and the RNC sends Physicalchannel reconfiguration.17:09:00(78): The RNC receives Physical channel reconfiguration completion, and sendsmeasurement control messages.17:09:04(35): The NodeB is out of synchronization, so call drop occurs, and nointer-RAT the measurement report is sent.17:09:20(89): The RNC originates Iu Release due to Radio Connection with UE lost.l Qualcomm handset in the same test period:17:08:59(29): The UE sends 2D measurement reports, and the RNC sends Physicalchannel reconfiguration.
  • 88. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page88 , Total20117:09:00(33): The RNC receives Physical channel reconfiguration completion, and sendsmeasurement control messages.17:07:58(81): The RNC receives the measurement report from UE, BCCH 853, and thelevel is –61dBm.17:08:00(25): The RNC sends HO CMD.17:08:00(90): The CN sends Iu Release Command (successful relocation).Actually, call drop occurs during handover.Now the starting threshold of compression mode is as high as –95 dBm. Do not change it toavoid impact on other parts of the network so that the handover occurs earlier.Change of Best Cell in Physical Channel ReconfigurationAccording to the test result, if the best cell changes, the handover is delayed, so call dropoccurs in the following situations:l Between RNC sending Physical channel reconfiguration and receiving Physicalchannel reconfiguration completion sent by UE (about 1s).l After Physical channel reconfiguration process is complete.Example 1:14:06:18(75): The best server PSC201 report 2D event (meanwhile, PSC16 is in theactive set).14:06:18(82): The RNC sends Physical channel reconfiguration.14:06:18(95): The UE reports 1D event of PSC16 cell.14:06:19(95): The RNC receives Physical channel reconfiguration completion from UE,and it sends inter-RAT measurement control message of PSC201 cell, and inter-frequency and intra-frequency measurement control of PSC16 cell.14:06:20(94): The UTRAN sends 1B event to the UE to delete PSC 201.14:06:21(45): The RNC sends inter-RAT measurement control to the cell of PSC16 (3sdelay compared with 1D event).14:06:22(83): The UE reports the GSM cell 852 (BSIC Verify) according to the newmeasurement control, and the RSSI is –79 dBm. The RNC does not process the report (toprevent UE from handing over to incorrect cell, the RNC must process UE measurementreport 3s after sending new measurement control)14:06:28(94): NodeB is out of synchronization, so call drop occurs.Example 2: Qualcomm handset:14:53:08(63): The UE sends 2D measurement reports, and the RNC sends Physicalchannel reconfiguration (the cell 144 is the best server)14:53:09(67): The RNC receives Physical channel reconfiguration completion, and sendsmeasurement control messages.14:53:16(58): The UE sends 1D measurement reports, and cell 137 becomes the bestserver. Therefore the RNC sends the measurement control messages of best server 137,including inter-RAT neighbor cells (the neighbor cell list is different from that of cell144)
  • 89. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page89 , Total20114:53:16(62): The RNC does not receive the measurement report from UE, and ensuresthat the cell ID is in the list of neighbor cells of cell 144. The RNC does not process thereports14:53:19(99): The RNC originates Iu Release.If different interRATCellID is used in inter-RAT measurement control, will the RNC avoid thisproblem?UE Hand Back FailureOther abnormalities in handover might cause handover failure.Example :14:07:37(38): The UE reports BCCH the measurement report of cell 852, NonverifiedBSIC.14:07:38(38): The TimeToTrigger of Nonverified is 1s, and after 1s, the RNC sendsRelocation to CN.14:07:38(38): The UE sends BCCH the measurement reports of cell 852, verified BSIC.14:07:38(74): The CN replies that Relocation Prepare fails (no radio resources).14:07:38(78): The UE sends the measurement report before failure, so the RNC againoriginates Relocation to CN.14:07:40(12): The CN replies Relocation to RNC, and RNC sends HO CMD to UE.14:07:40(79): However, the UE replies HO FAIL.Late, the UE keeps deleting cell 201 which is the best server, so the RNC does not process therequest. The 3G signals are weak, so call drop occurs.Delayed Starting of Compression Model Description:The UE cannot hand over from the 3G network to the 2G network smoothly. In details,the UE originates a call in 3G coverage areas or uses PS services, and then enters 2Gcoverage areas. However, it fails in handing over to 2G networks, so call drop occurs.Analyze the signaling process at RNC side, and check the causes to handover failure.The causes include:− The network side fails in receiving 2D report from UE, so compression mode is notstarted. Consequently 2G cells are not measured, and then asynchronization orSRB/TRB reset cause call drop.− The network side receives 2D report, but compression mode is not started. The reasonis that the network side sends a PHY_CH_RECFG message, but the UE fails insending ACK message or PHY_CH_RECFG_CMP, so SRB is reset, and call dropoccurs.− The network side receives Verified measurement reports. After it sends UE thehandover messages, the UE fails in receiving it, so call drop occurs (also for otherreasons).
  • 90. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page90 , Total201The above cases are due to delayed starting of compression mode, so the quality ofsignals of the original cell becomes weak. Therefore subsequent starting compressionmode and handover process cannot proceed normally.l Analysis:Starting compression mode is affected by 2D event configuration of ID2 measurementcontrol sent by the network side. You can enable 2D event to be reported more quicklyby the following methods:− Increasing the threshold of 2D event− Reducing hysteresis− Reducing delayed triggering timeNow the back system can configure different starting threshold of inter-RATcompression mode for signaling, CS and PS services.
  • 91. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page91 , Total2015.4 Call Drop Problems5.4.1 Over Weak CoverageDescription and AnalysisFigure 5-32 shows the call drop due to coverage problems.Figure 5-32 Analyzing weak signalsFigure 5-32 describes the following indexes:l Scrambles, Ec/Io, and RSCP of cells in active set before call dropl Scrambles and Ec/Io of cells in monitor setl Transmit power of UE, BLER of transport channel, and call drop timeThe DT data analysis software Analyzer provides the previous data.According to the data before call drop, the Ec/Io of active set is smaller than –15 dB and theRSCP is close or smaller than –110 dBm, so the call drop must be due to downlink weakcoverage. After call drop, the UE camps on the cell of SC 232 the quality of which is bad, so thecall drop must not be due to missing neighbor cell.According to the Figure 5-32, the transmit power of UE approaches 21 dBm and the downlinkBLER before call drop reaches 100% (due to the comprehensive effect by inner loop and outerloop, the downlink code transmit power reaches the maximum. Confirm this by using the data
  • 92. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page92 , Total201for tracing the performance of RNC). According to previous analysis, the uplink and downlinkare balanced. To sum up, the call drop is due to bad coverage.SolutionTo solve coverage problems, you must adjust engineering parameters of antennas or constructnew sites.5.4.2 Uplink InterferenceDescription and AnalysisUplink interference leads to unbalanced uplink and downlink, so call drop occurs.Figure 5-33 shows the uplink interference according to RNC signaling.
  • 93. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page93 , Total201Figure 5-33 Uplink interference according to RNC signalingAccording to Figure 5-33, the RNC sends a CC Connect message, but the UE does notrespond to the CC Connect message. This causes the call drop.Figure 5-34 Uplink interference according to UE signalingThe UE receives the CC connect message sent by RNC and then replies with CC connectAcknowledge message which the RNC fails to receive.The following paragraphs describe the signals before and after call drop.Figure 5-35 shows the uplink interference information recorded by UE.
  • 94. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page94 , Total201Figure 5-35 Uplink interference information recorded by UEFrom the UE side, the downlink PCICH Ec and Ec/Io are good, but the uplink transmit powerapproaches the maximum. Therefore it is probably an uplink problem.Interference:The problematic site is the site 90640. The cells involve the cell 24231 and 24232. The RTWPof the cell fluctuates sharply.Figure 5-36 RTWP variation of the cell 89767
  • 95. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page95 , Total201Figure 5-37 RTWP variation of the cell 89768SolutionLocate the sources of interference t solve uplink interference problems.5.4.3 Abnormal EquipmentSummarizing call drop problems due to abnormal equipment is difficult. Generally abnormal CN,RNC, NodeB, and UE will lead to call drop. Some call drop problems can be further analyzedand located only in research and development (R&D) environment. The following paragraphsdescribed the call drops that occurred before. You can refer to them.Abnormal Uplink Synchronization of NodeBAccording to the test, at a fixed spot (at the corner under an overhead), call drop occurs in thetest car when it passes the spot every time. Each call drop occurs in the cell of SC 160. The calldrop location is special, so the call drop is probably due to turning corner effect. Based onrepeated DT, a conclusion forms that call drop occurs within 5s when the signals measured byscanner in the cell are from only one cell (SC 160).According to signaling flow, the cell of SC 160 keeps being added because the UE reports themeasurement. It also keeps being deleted because the NodeB is asynchronous, so the link isdeleted 5s after expiration of timer. At the same time, the access to the cell also fails. Strangelythe downlink signals of the cell is normal (because the cell can measure the pilot signals andsend a report), but the uplink is problematic. The NodeB logs and alarms involve no prompts.After reset of board one by one, the problem is solved.Abnormal UEl Failure to report 1a event by UECall drop occurs easily with a version of Qualcomm 6250 during test. According tothe analysis of data, the Ec/Io and RSCP recorded by scanner are good upon everycall drop. The signals of the active set recorded are weak, but there are cells withqualified signals. According to the signaling flow, the UE does not send the 1a event
  • 96. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page96 , Total201measurement report of the cell in monitor set, so finally call drop occurs. After theUE is updated, the problem is solved.l Missing of messages recorded by UEWhen Moto A835 records signaling messages, it loses some signaling before calldrop easily. This leads to incorrect judgment of call drop problems. The signalingbefore call drop is key for analyzing call drop. If it is missing, you must analyze calldrop problems based on the combination of messages form UE and informationabout RNC.l Abnormal Moto handset due to continuous CQTAfter tens of or hundreds of CQTs, the calling or called Moto handset is likely toconfront problems, so calls fail. After reset of the handset, it becomes normal. Thereis another problem. When the handset is called, it does not ring and consequentlycall drop occurs. However, the screen displays an unanswered call. To avoid this,reset the handset after continuous CQT.l Failure to hand over from the 3G network to the 2G networkThe 3G signals received by a Sony-Ericsson handset attenuate slowly at the subwayentrance and finally no signals are received. The 2G signals are received at thesubway entrance and inside subways. Therefore, the handset fails to hand over tothe 2G network. The Moto handset and Nokia handset can succeed in handover.The handover failure is probably due to excessive 2G neighbor cells are configured.After excessive 2G neighbor cells are deleted and only one 2G neighbor cell is kept,the Sony-Ericsson handset succeeds in handover. When two 2G neighbor cells withthe same frequency and different BSIC exists, the handset will stop handoverbecause it is not specified with the BSIC and the target 2G neighbor cell when it issending the measurement report.
  • 97. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page97 , Total2015.5 HSDPA-related Problems5.5.1 HSDPA Handover ProblemsA connected HSDPA subscriber uses the following channels:l HS-PDSCHl HS-SCCHl HS-DPCCHl DPCH as associated channel.When the R99 subscribers have handover problems, the HSDPA subscribers cannot smoothlyhand over. Therefore, when the HSDPA subscribers fail to hand over, engineers need to checkR99 handover. If R99 subscribers have handover problems, solve the problems as previouslymentioned. The call drop problems currently in test is usually caused by R99 problems.ADCH SHO with Serving Cell UpdateWhen SHO occurs on the associated DCH, the HS-DSCH serving cell is updated. This istriggered by reporting 1D event by UE. If now the SHO on the associated DCH is faulty, calldrop occurs with HSDPA subscribers. The causes is as mentioned in 5.1The following paragraphs describe a case: missing neighbor cell causes handover onassociated DCH fails, and this consequently causes call drop of HSDPA subscribers.l Description and AnalysisBefore call drop, the cell of SC 11 serves HSDPA subscribers.Figure 5-38 shows the pilot information recorded by scanner.Figure 5-38 Pilot information recorded by scannerThe active set does not list the cells of SC 25 and SC 26. After call drop, the UE campson the cell of SC 26. Meanwhile, the quality of signals from the cell of SC 11 declinessharply.According to previous description, the call drop is probably due to missing neighbor cell.For detailed analysis, see 5.1 .
  • 98. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page98 , Total201l SolutionTo solve the problem, add the corresponding neighbor cell.ADCH HHO with Serving Cell Updatel Call drops due to ping-pong handover.While the HHO occurs on ADCH, the HS-PDSCH serving cell is updated.When the HHO occurs on ADCH:− If the 1D event is improperly configured, intra-frequency ping-pong HHO occurs onADCH, and the HS-PDSCH serving cell is frequently updated. This leads to declineof QoS, and even call drop.− If the 2D/2F and handover threshold is improperly configured, ping-pong handoveroccurs, and consequently QoS declines.Handover between HS-PDSCH and DPCHRelated causes are to be supplemented.Handover between HSDPA and GPRSFor the handover between HSDPA and GPRS, refer to 5.3.4 .5.5.2 HSDPA Call DropWeak CoverageAfter HSDPA technology is used, the downlink load of cell increases. This has some impact oncoverage radius of cell. If the load of original R99 cell is light, the coverage scope decreasessharply after HSDPA technology is used. Pay attention to cell coverage and call drop problemscaused by decrement of handover areas after R99 network is upgraded to HSDPA network.HS-DPCCH is used in uplink of HSDPA, so the HSDPA UE consumes more power than R99 UE,and consequently, the HSDPA UE at the cell edge reaches the maximum transmit power morequickly than R99 UE at the cell edge. This is uplink power restriction.The maximum transmit power of some R99 UEs and HSDPA UEs are the same, 24 dBm.l Description and analysisIn test, before call drop the Ec/Io of active set before call drop is below –15 dB, and theRSCP is below –110 dBm. After call drop, the UE camps on a new cell, where the Ec/Iois also above –15 dB and RSCP is above –110 dBm. The transmit power of UE beforecall drop approaches 24 dBm (terminal is data card E620), so the problems is caused byweak coverage.l SolutionTo solve the problem, adjust engineering parameters or construct sites.
  • 99. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page99 , Total201Call Drop due to Improper Configuration of ParametersThe call drops due to strong uplink interference if all the following conditions are met:l The power of HS-DPCCH is over highl The uplink admission threshold is lowl There are excessive subscribersThe signaling flow for HSDPA service handover is more complex than that of R99 servicehandover. In some occasions, the handover parameters are differently configured for these twonetworks. For example, in turning corner, the UE is required to respond messages from UTRANmore quickly; in ping-pong handover areas, the protection time is longer.Abnormal Call DropThe early versions of HUAWEI E620 are faulty in inter-frequency handover. After reporting 2Devent, the UE responds measurement control failure, so the call drops due to handover failure.
  • 100. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page100 , Total2015.6 HSUPA ProblemsTo be supplemented.
  • 101. W-Handover and Call Drop Problem Optimization Guide For internal use only2008-12-22 All rights reserved Page101 , Total2016 SummaryBased on related guides to handover and call drop, this guide is complete. It focuses onoperability by on-site engineers. In addition, it describes operation steps in details for the actualhandover and call drop problems in forms of flow chart.The fundamental knowledge and preparation knowledge are placed in the appendix. Operationsare in the body.V3.1 supplements HSDPA knowledge, including:l DT/CQT flow for HSDPA handoverl Definition of traffic statistics indexes for HSDPA handoverl HSDPA handover problemsl Algorithm and flow for HSPDA handoverThe traffic statistics of HSDPA is to be supplemented. HSDPA networks are not commerciallyused in a large scale, so more cases will be supplemented.The SHO ratio analysis will be supplemented after enough RNO experienced are collected.
  • 102. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 102 of 2017 Appendix7.1 SRB&TRB Reset7.1.1 RABRAB is the carrier at the subscriber plane. It is used in transmitting voice, data, and multimediaservices between UE and CN. The RAB assignment is originated by CN. It is a function of RNC.RB is ratio bearer between SRNC and UE. It includes layer 2 and above. It is the serviceprovided to layer 2.Figure 7-1 shows the UMTS QoS structure. It provides the part that RAN and RB play in theUMTS network.Figure 7-1 UMTS QoS structure
  • 103. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 103 of 2017.1.2 SRBThe SRB carries the signaling at U-Net interface. The TRB carries the services at the Uuinterface and it is the radio bearer at the user plane.Figure 7-2 shows the structure of SRB and TRB at the user plane.Figure 7-2 SRB and TRB at user panelThe SRB and TRB carriers signaling and services as blow:l SRB0 for all messages sent on CCCH (needless of configuration)l SRB1 for all messages sent on the DCCH that uses unconfirmed RLCl SRB2 for all messages sent on the DCCH that uses confirmed RLC (excluding initialdirect transfer and uplink/downlink direct transfer)l SRB3/SRB4 for confirming downlink and uplink direct transfer messages of RLCtransferred on DCCHl TRB in the AM mode for carrying PS servicesl TRB in the UM mode for carrying CS servicesThe SRB reset involves the SRB in the AM mode. The AM mode uses theconfirmation-retransmission method. The sender will perform polling to check periodically thatthe receiver has received the PDU with a method. After sending PDU, the sender sends apolling frame and waits for the ACK frame from the receiver. If the waiting timer expires and thesender fails to receive the ACK frame, it keeps sending PDU. If it still fails to receive the ACKframe after sending for maximum retransmitting times, it triggers RLC AM entity reset ordiscards the PDU to be sent. Discarding PCU is not configured now and only triggering RLC AMentity occurs. This is the RB reset.During RLC AM entity reset, the sender sends a RESET frame to the receiver and waits forRESET ACK frame. If the timer expires, the sender will resend the frame. After sending formaximum retransmission times, the sender will report "unreasonable error" to a high layer andstop resending. SRB leads to triggering the release process at signaling plane. TRB leads totriggering the release process at user.
  • 104. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 104 of 2017.2 RL FAILUREWhen a cell sets up a new radio link, there is a process for uplink and downlink synchronization.After UE succeeds in uplink synchronization, it powers on the transmitter, and then the NodeBperforms uplink synchronization. If the NodeB succeeds in synchronization, it sends the RNC anRL RESTORE message. If it fails, it sends the RNC the RL FAILURE message. When the RNCreceives the RL FAILURE message or fails to receive RL RESTORE message, it releases theresources related to the radio link. If the active set uses only one radio link, the RNC thenoriginates the release at signaling plane.Table 7-1 lists the timers and counters related to the synchronization and asynchronization.Table 7-1 Timers and counters related to the synchronization and asynchronizationParameterIDParameterNameDescriptionT302 Timer 302Value range: D100, D200, D400, D600, D800, D1000, D1200,D1400, D1600, D1800, D2000, D3000, D4000, D6000, andD8000Actual value range: 100, 200, 400, 600, 800, 1000, 1200,1400, 1600, 1800, 2000, 3000, 4000, 6000, and 8000Physical unit: msContent: When the UE sends CELL UPDATE/URA UPDATEmessages, start timer T302. When the UE receives CELLUPDATE CONFIRM/URA UPDATE CONFIRM messages,stop time T302.When T302 expires,If V302 ≤ N302, the UE resends CELL UPDATE/URAUPDATE messages.If not, the UE enters idle mode.Recommended value: D2000N302Constant302Value range: 0–7Content: This parameter indicates the maximumretransmission times of sending CELL UPDATE/URAUPDATE messages. The default value is 3.Recommended value: 3
  • 105. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 105 of 201T312 Timer 312Value range: 1–15Physical unit: sContent: When the UE starts DCH, start T312. When the UEdetects 312 continuous synchronization indicators, stop T312.When T312 expires, the DCH connection fails. The defaultvalue is 1.Recommended value: 1N312Constant312Value range: D1, D2, D4, D10, D20, D50, D100, D200, D400,D600, D800, and D1000Actual value range: 1, 2, 4, 10, 20, 50, 100, 200, 400, 600,800, and 1000Physical unit: noneContent: It indicates the maximum times continuoussynchronization indicators received from L1. The default valueis 1.Recommended value: D1T313 Timer 313Value range: 1–15Physical unit: sContent: When the UE detects from L1 continuous N313asynchronization indicators, start T313. When the UE detectsfrom L1 continuous N315 asynchronization indicators, stopT313. When T313 expires, the radio link fails. The defaultvalue is 3.Recommended value: 3N313Constant313Value range: D1, D2, D4, D10, D20, D50, D100, and D200Actual value range: 1, 2, 4, 10, 20, 50, 100, and 200Physical unit: noneContent: It indicates the maximum times continuoussynchronization indicators received from L1. The default valueis 20.Recommended value: D50
  • 106. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 106 of 201T314 Timer 314Value range: D0, D2, D4, D6, D8, D12, D16, and D20Actual value range: 0, 2, 4, 6, 8, 12, 16, and 20Physical unit: noneContent: When the principle of radio link failure is met, and theradio bearer only related to T314 exists, start T314. When thecell update is complete, stop T314. The default value is 12.When the UE of CELL_DCH fails in radio links, start T314 (orT315), and send CELL UPDATE messages. Before T314 (orT315) corresponding to services expires, if the radio linkreconfiguration configured by CELL UPDATE CONFIRMmessage fails, resend CELL UPDATE messages toreconfigure the radio link (related to T302 and N302). Basedon this, configure T314 > T302 × N302.When T314 expires, the service RB of corresponding timers isdeleted.Recommended value: D20T315 Timer 315Value range: D0, D10, D30, D60, D180, D600, D1200, andD1800Actual value range: 0, 10, 30, 60, 180, 600, 1200, and 1800Physical unit: sContent: When the principle of radio link failure is met, and theradio bearer only related to T315 exists, start T315. When thecell update is complete, stop T314. The default value is 180.When the UE of CELL_DCH fails in radio links, start T315 (orT314), and send CELL UPDATE messages. Before T315 (orT314) corresponding to services expires, if the radio linkreconfiguration configured by CELL UPDATE CONFIRMmessage fails, resend CELL UPDATE messages toreconfigure the radio link (related to T302 and N302). Basedon this, configure T315 > T302 × N302.When T315 expires, the service RB of corresponding timers isdeleted.Recommended value: D30N315Constant315Value range: D1, D2, D4, D10, D20, D50, D100, D200, D400,D600, D800, and D1000Actual value range: 1, 2, 4, 10, 20, 50, 100, 200, 400, 600,800, and 1000Physical unit: sContent: It indicates the maximum times continuoussynchronization indicators received from L1. The default valueis 1.Recommended value: D1
  • 107. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 107 of 201Table 7-2 lists the timers and counters related to call drop at lub interface.Table 7-2 Timers and counters related to call drop at lub interfaceParameter ID Parameter Name DescriptionNINSYNCINDTimes ofcontinuoussynchronizationindicatorValue range: 1–256Actual value range: 1–256Physical unit: noneContent: The value indicates the times ofcontinuous synchronization indicators needed bythe timer to trigger radio link recovery process.The radio link set keeps in initial state until theNodeB receives NINSYNCIND continuoussynchronization indicator. Now the NodeB triggersradio link recovery process, and radio link set issynchronized. When the radio link recoveryprocess is triggered, the radio link set is insynchronization state.Recommended value: 5NOUTSYNCINDTimes ofcontinuousasynchronizationindicatorValue range: 1–256Actual value range: 1–256Physical unit: noneContent: The value indicates the times ofcontinuous asynchronization indicators needed bythe timer to trigger radio link failure process. Whenthe radio link set keeps in synchronization state,after the NodeB receives NINSYNCINDcontinuous failure indicators, start radio link failuretimer. After receiving continuous NINSYNCINDsynchronization indicators, the NodeB must stopand reset radio link failure timer. If the radio linkfailure timer expires, the NodeB triggers radio linkfailure process, and indicate the radio link setswhich are in asynchronization state.Recommended value: 5
  • 108. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 108 of 201TRLFAILURERadio link failuretimer periodValue range: 0–255Actual value range: 0–25.5, and the step is 0.1Physical unit: sContent: The value indicates the timer period ofradio link failure. When the radio link set keeps insynchronization state, after the NodeB receivesNINSYNCIND continuous failure indicators, startradio link failure timer. After receiving continuousNINSYNCIND synchronization indicators, theNodeB must stop and reset radio link failure timer.If the radio link failure timer expires, the NodeBtriggers radio link failure process, and indicate theradio link sets which are in asynchronization state.Recommended value: 50
  • 109. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 109 of 2017.3 SHO FlowYou can analyze SHO-related signaling flow by three typical flows. The three flows includeadding radio link, deleting radio link, and combination of adding and deleting radio links. SHO isvalid for FDD mode. The following three flows are SHO with lur signaling. The SHO flow underthe same RNC is simpler, which deletes the parts between SRNC and DRNC. The followingthree cases are typical. The actual signaling flow depends on the actual situation.7.3.1 Analyzing Signaling Flow for Adding Radio LinkThe conditions of SHO signaling flow for adding radio link are:l The UE has one or more radio links with SRNC.l The UE sets up a new radio link through new NodeB and new RNC.The UE can set up only one link with UTRAN, so there is no macro diversitycombination/splitting.Signaling Flow for Adding Radio LinkFigure 7-3 shows the signaling flow for adding radio link.
  • 110. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 110 of 201Figure 7-3 Signaling flow for adding radio linkSteps of Signaling Flow for Adding Radio LinkThe signaling flow proceeds as below:l The SRNC decides to set up a new radio link and the new cell to which the linkbelongs is under the control of another RNC (DRNC). The SRNC sends DRNC aRadio Link Setup Request message, and requires DRNC to prepare thecorresponding radio resources. The new radio link is the first link set up between UEand DRNC, so a new lur signaling connection is required. The lur signalingconnection carries UE-related RNSAP signaling.The Radio Link Setup Request message includes parameters as below:− Cell ID
  • 111. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 111 of 201− TFS− TFCS− Frequency− Uplink Scramblel According to radio resources, the DRNC judge whether the requested radio resourcecan be met. If yes, the DRNC send the NBAP message, namely, Radio Link SetupRequest, to NodeB to which the DRNC belongs. After this, the NodeB starts toreceive messages in uplink.The Radio Link Setup Request message includes parameters as below:− Cell ID− TFS− TFCS− Frequencyl The NodeB allocates radio resources as required. If it succeeds, the NodeB reportsan NBAP message, namely, the Radio Link Setup Response message, to DRNC.The Radio Link Setup Response message includes two parameters: signalingtermination and transport layer addressing information (AAL2 addressing, AAL2bound ID for data transmission and bearer)l The DRNC sends the Radio Link Setup Response message to SRNC throughRNSAP.The Radio Link Setup Response message includes two parameters: transport layeraddressing information (AAL2 addressing, AAL2 bound ID for transmitting andcarrying data) and information about adjacent cells.l The SRNC starts lur/lub data transmission and bearer through the ALCAP protocol.The request includes AAL2 bound ID for binding lub data transmission and bearer,and DCH.l or 7) The NodeB and SRNC set up synchronization of data transmission and bearerby exchanging the corresponding DCH FP frame Downlink Synchronization andUplink Synchronization. The NodeB starts downlink transmission.l The SRNC sends UE the Active Set Update message on DCCH. The messageincludes content on adding radio link.The parameters include:− Update type− Cell ID− Downlink scramble− Power control information− Adjacent cellsl The UE configures the corresponding parameters according to RRC signaling. Itsends SRNC the RRC message, namely, Active Set Update Complete message.
  • 112. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 112 of 2017.3.2 Analyzing Signaling Flow for Deleting Radio LinkThe conditions of SHO signaling flow for deleting radio link are:l The UE has one or more radio links with SRNC.l Delete the link connecting UE and SRNC through DRNC.Signaling Flow for Deleting Radio LinkFigure 7-4 shows the signaling flow for deleting radio link.Figure 7-4 Signaling flow for deleting radio linkSteps of Signaling Flow for Deleting Radio LinkThe signaling flow for deleting radio link proceeds as below:
  • 113. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 113 of 201l The SRNC decides to delete a radio link. The SRNC sends UE the Active SetUpdate message on DCCH. This message includes the content about deleting radiolink.The parameters include update type and cell ID.l The UE deactivates the downlink receiver of radio link to be deleted and sendsSRNC the Active Set Update Complete message.l The SRNC sends the Radio Link Deletion Request to DRNC on through.The parameters include cell ID and transport layer addressing information.l The DRNC sends NodeB the NBAP message, namely, the Radio Link DeletionRequest message. The NodeB stops receiving and sending.The parameters include cell ID and transport layer addressing information.l The NodeB deactivates radio resources and sends DRNC the NBAP message,namely, the Radio Link Deletion Response message.l The SRNC starts releasing lur/lub data bearer through the ALCAP protocol.7.3.3 Analyzing Signaling Flow for Adding and Deleting Radio LinkThe conditions of SHO signaling flow for adding and deleting radio link are:l The UE has one or more radio links with SRNC.l The UE sets up a new radio link through new NodeB and new RNC.l Delete the previous link connecting UE and SRNC through the NodeB which belongsto SRNC.The UE can set up only one link with UTRAN, so there is no macro diversitycombination/splitting.SHO Signaling Flow for Adding and Deleting Radio LinkFigure 7-5 shows the SHO signaling flow for adding and deleting radio link.
  • 114. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 114 of 201Figure 7-5 SHO signaling flow for adding and deleting radio link7. Uplink SynchronisationRNSAP RNSAP1. Radio Link SetupRequestStart TXdescriptionRNSAP RNSAP4. Radio Link SetupResponseNBAP NBAP2. Radio Link Setup RequestNBAP NBAP3. Radio Link Setup ResponseStart RXdescriptionDecision to setupnew RL andrelease old RLNBAP10. Radio Link Deletion RequestNBAP NBAP11. Radio Link Release ResponseStop RX and TX12. ALCAP Iub Data Transport Bearer ReleaseRRCRRC9. DCCH : Active Set Update CompleteRRCRRC8. DCCH : Active Set Update Command[Radio Link Addition & Deletion]NBAPUE Node BDrift RNSNode BServing RNSDriftRNCServingRNCALCAP Iur Bearer Setup5. ALCAP Iub Data Transport Bearer SetupDCH-FPDCH-FPDCH-FPDCH-FP6. Downlink SynchronisationSteps of SHO signaling Flow for Adding and Deleting Radio LinkThe SHO signaling flow for adding and deleting radio link proceeds as below:l The SRNC decides to set up a new radio link and the new cell to which the linkbelongs is under the control of another RNC (DRNC). The SRNC sends DRNC aRadio Link Setup Request message, and requires DRNC to prepare the
  • 115. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 115 of 201corresponding radio resources. The new radio link is the first link set up between UEand DRNC, so a new lur signaling connection is required. The lur signalingconnection carries UE-related RNSAP signaling.The Radio Link Setup Request message includes parameters as below:− Cell ID− TFS− TFCS− Frequency− Uplink Scramblel According to radio resources, the DRNC judge whether the requested radio resourcecan be met. If yes, the DRNC send the NBAP message, namely, Radio Link SetupRequest, to NodeB to which the DRNC belongs. After this, the NodeB starts toreceive messages in uplink.The Radio Link Setup Request message includes parameters as below:− Cell ID− TFS− TFCS− Frequencyl The NodeB allocates radio resources as required. If it succeeds, the NodeB reportsan NBAP message, namely, the Radio Link Setup Response message, to DRNC.The Radio Link Setup Response message includes two parameters: signalingtermination and transport layer addressing information (AAL2 addressing, AAL2bound ID for data transmission and bearer)l The DRNC sends the Radio Link Setup Response message to SRNC throughRNSAP.The Radio Link Setup Response message includes two parameters: transport layeraddressing information (AAL2 addressing, AAL2 bound ID for transmitting andcarrying data) and information about adjacent cells.l The SRNC starts lur/lub data transmission and bearer through the ALCAP protocol.The request includes AAL2 bound ID for binding lub data transmission and bearer,and DCH.l or 7) The NodeB and SRNC set up synchronization of data transmission and bearerby exchanging the corresponding DCH FP frame Downlink Synchronization andUplink Synchronization. The NodeB starts downlink transmission.l The SRNC sends UE the Active Set Update message on DCCH. The messageincludes content on adding and removing radio link.The parameters include:− Update type− Cell ID− Downlink scramble− Power control information− Adjacent cells
  • 116. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 116 of 201l The UE configures the corresponding parameters according to RRC signaling,deactivates the downlink receiver of the link to be deleted, actives the downlinkreceiver to be added, and sends SRNC the Active Set Update Complete message.l The SRNC sends NodeB the NBAP message, namely, the Radio Link DeletionRequest message. The NodeB stops receiving and sending.The parameters include cell ID and transport layer addressing information.l The NodeB deactivates radio resources and sends SRNC the NBAP message,namely, the Radio Link Deletion Response message.l The SRNC starts releasing lur/lub data bearer thought the ALCAP protocol.7.3.4 SHO AlgorithmIntra-frequency Measurement ModelWhen the UE is in CELL_DCH connection mode (for example, voice talk starts), the RNC sendsthe MEASUREMENT CONTROL command to command UE to measure and report events (theevent threshold, hysteresis, delay trigger time are included in signaling). When the best cell isupdated (including occurrence of intra-frequency HHO and inter-frequency HHO), themeasurement control of 1X (including 1A, 1B, 1C, and 1D) event must be updated.Figure 7-6 shows the WCDMA measurement model according to protocol 25.302.Figure 7-6 Measurement modelLayer 1filteringLayer 3filtering Evaluationof reportingcriteriaA DB CCparameters parametersIn Figure 7-6,l Point A is the direct measurement result of physical layer.l Point B is the filtered measurement result at physical layer and it is also themeasurement result provided to upper layer from physical layer.l Point C is the measurement result for event judgment after upper layer filtering.l FilterCoef is filtering factor of measured values and weights the measurement resultsof physical layer at different points. It is used in event report and period report. Thefiltering of measured values is calculated as below:nnn MaFaF ⋅+⋅−= −1)1(Wherein,− Fn: filtered updated measurement result
  • 117. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 117 of 201− Fn-1: filtered previous measurement result at last point− Mn: the latest measured value received from physical layer− α = 1/2(k/2). The k is from Filter coefficient, namely, the handover parameterFilterCoef. FilterCoef is configured in intra-frequency, inter-frequency, and inter-RAThandover measurement. When α is 1 (accordingly k = 0), there is no layer 3 filtering.From previous measurement model, the filtering occurs before event judgment andmeasurement report. In addition, the measured values in cell Measurement results andMeasurement results on RACH of UEs report are filtered. The layer 3 filtering controlled bynetwork layer caters for measurement event judgment and measurement report only. The cellreselection when UE is in the idle mode and connection mode does not support layer 3 filtercontrolled by network layer.Intra-frequency Measurement EventsIn the measurement control message, the UTRAN indicates the events to trigger measurementreport. The intra-frequency measurement report events are marked by "1X".1. 1A event: a Primary Pilot Channel Is in Reporting RangeIn the measurement report mechanism domain, the network requires UE to report the 1A event(for example, the UE enters the Cell_DCH state), the UE sends the measurement report when aprimary pilot channel enters the reporting range. According to protocols, for 1A event, the UEcan report multiple cells of trigger event in a measurement report. The cells are included in thelist of trigger event. The UE sorts the cells good to bad in terms of quality (CPICH Ec/No). If lessthan 3 cells are listed in the active set, the network judges to add links. If the active set is full ofcells, no operation is performed.When the measured value meets the following formula, the UE judges that a primary pilotchannel is in the reporting range.The path loss is:),2/(10)1(1010 11aBestNiiNew HRLogMWMLogWLogMA−+⋅⋅−+⋅⋅≤⋅ ∑=For other measurement values:),2/(10)1(1010 11aBestNiiNew HRLogMWMLogWLogMA−−⋅⋅−+⋅⋅≥⋅ ∑=In the previous formulas:l MNew is the measurement result of cells in the reporting range.l Mi is the measurement result of cells in the active set.l NA is the number of cells in the active set.l MBest is the measured value of the best cell in the active set.l W is the weighting factor.l R is the reporting range, with signal strength as an example. It is equal to the signalstrength of the best cell in the active set minus a value.l H1a is the hysteresis of 1A event.
  • 118. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 118 of 201A parameter TIME-TO-TRIGGER is used to reduce the signalling flow for measurementreport. After the primary pilot enters the reporting range and remains for a specifiedperiod, the UE triggers measurement report. The parameter is also used in other events.Figure 7-7 shows the 1A event and trigger delay.Figure 7-7 Example 1A event and trigger delayReportingevent 1AMeasurementquantityTimeTime-to-triggerP CPICH 1ReportingrangeP CPICH 2P CPICH 3Usually, if the 1A event is triggered, the UE sends a measure report to UTRAN. The UTRANsends an Active Set Update message for updating active set. Probably No response is receivedafter UE sends measurement report (for example, due to limited capacity). The UE changesfrom sending event-triggered report to periodic report. The measure report contains theinformation about the cells in the active set and cells in the monitored set in reporting range.Only when the cell is successfully listed in the active set and leaves the reporting range will UEstop sending periodic reports.
  • 119. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 119 of 201Figure 7-8 Periodic report triggered by 1A eventEvent-triggeredreportPCPICH 3PCPICH 1PCPICH 2PeriodicreportPeriodicreportReportingrangeReportingterminated2. 1B Event: a Primary Pilot Channel Leaves the Reporting RangeWhen the following formulas are met, the UE judges that a primary pilot channel leaves thereporting range. For 1B event and for event-triggered cells,l If more than one links are in the active set, the UE judges to delete the links.l If only one links is in the active set, the UE performs no operation.The path loss is:),2/(10)1(1010 11aBestNiiOld HRLogMWMLogWLogMA++⋅⋅−+⋅⋅≥⋅ ∑=For Other measure values:),2/(10)1(1010 11bBestNiiOld HRLogMWMLogWLogMA+−⋅⋅−+⋅⋅≤⋅ ∑=In the previous formulas:l MOld is the measurement result of cells in the reporting range.l Mi is the measurement result of cells in the active set.l NA is the number of cells in the active set.l MBest is the measured value of the best cell in the active set.l W is the weighting factor.l R is the reporting range.l H1a is the hysteresis of 1B event.If multiple cells meet the reporting conditions at the same time, and reach the trigger delay, theUE sorts the cells in terms of measured value and then reports them.
  • 120. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 120 of 2013. 1C Event: a Non-active Set Primary Pilot ChannelFigure 7-9 shows the 1C event.Figure 7-9 Example of 1C eventIn Figure 7-9, the cells where the PCPICH 1, PCPICH 2, and PCPICH 3 serve are in the activeset but the cell where PCPICH 4 serves is not in the active set. If the cells in the active setreach or exceeds the replacement threshold of active set, the event is used for replacing badcells in the active set.When the 1C event is triggered, the UE reports the replacing cell and the cell to be replaced inthe event trigger list. The UE also sort the reported cells good to bad in terms of quality (CPICHEc/No). After the RNC receives the 1C event trigger list reported by UE, it replaces the cell to bereplaced with the replacing cell in the active set.
  • 121. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 121 of 2014. 1D Event: the Best Cell ChangesFigure 7-10 Example 1D eventWhen channels have little difference, the 1D event might be triggered due to fluctuating signals.This leads to unnecessary increase of signaling flow at the air interface. The hysteresis valuehelps to avoid this, as shown in Figure 7-11.Figure 7-11 Restriction from hysteresis to measurement reportThe second time fails to reach the hysteresis condition, so no 1D event report is triggered. Thisparameter also applied in other events.According to protocols, the 1D event can report only one triggered cell which can be in activeset or monitored set. Therefore the cells in the monitored set must be added to the active set. Ifthe active set is full, the system deletes a cell that is not the best cell. Consequently the systemadds the best cell to the active set. Finally the system marks the cell as the best cell.
  • 122. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 122 of 2015. 1E Event: a Measured Value of Primary Pilot Channel Exceeds theAbsolute ThresholdFigure 7-12 shows an example of 1E event.Figure 7-12 Example of 1E eventThe 1E event triggers measurement report of the cells not monitored when the UE fails toreceive the neighbor cell table.6. 1F Event: the Measured Value of Primary Pilot Channel Is Lowerthan the Absolute Threshold ValueFigure 7-13 shows an example event.Figure 7-13 Example of 1F event
  • 123. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 123 of 2017.4 Ordinary HHO Flow7.4.1 Ordinary HHO (lur Interface and CELL_DCH State)The following HHO flow is based on the lur interface when the UE is in the CELL_DCH state.Ordinary HHO (lur Interface and CELL_DCH State)Figure 7-14 shows the ordinary HHO flow (lur interface and CELL_DCH state).
  • 124. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 124 of 201Figure 7-14 Ordinary HHO flow (lur interface and CELL_DCH state)Signaling Flow AnalysisThe signaling flow proceeds as below:l The SRNC sends the Radio Link Setup Request message to request radio link setup.The parameters include target RNC identity, s-RNTI, cell ID, TFS, and TFCS.l The target RNC allocates RNTI and radio resources for RRC connection and radiolinks. In addition, it sends the NBAP message, namely, the Radio Link SetupRequest message to the target NodeB.The parameters include cell ID, TFS, TFCS, frequency, uplink scramble, powercontrol, and so on.
  • 125. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 125 of 201l The target NodeB allocates radio link resources, starts physical-layer receiver, andsends the target NodeB the Radio Link Setup Response message.The parameters include signaling termination and transport layer addressing for lubdata transmission and bearer.l The target RNC starts setting up lub data transmission and bearer according toALCAP protocol. The request contains that the AAL2 bound ID is for binding lub datatransmission and bearer, as well as transport channel DCH. The NodeB confirms therequest.l When the target RNC completes preparations, it sends SRNC the Radio Link SetupResponse message.l The SRNC starts setting up lub data transmission and bearer according to ALCAPprotocol. The request contains that the AAL2 bound ID is for binding lub datatransmission and bearer, as well as transport channel DCH. The RNC confirms therequest.l The SRNC send UE the Physical Channel Reconfiguration message.l When the UE switches from using the original link to using the new one, the originalNodeB detects that the original link fails in synchronization. Then the original NodeBsends the NBAP message, namely, the Radio Link Failure Indication message to thesource RNC.l The SRNC sends the original SRNC the RNSAP message, namely, the Radio LinkFailure Indication.l When the UE completes setting up RRC connection with target RNC and the relatedradio resources are allocated, the UE sends SRNC the RRC message, namely, thePhysical Channel Reconfiguration Complete message.l The SRNC sends source RNC the RNSAP message, the Radio Link DeletionRequest message. This requires the RNC to release the corresponding resourcesused by original link.l The source RNC sends original NodeB the NBAP message, the Radio Link DeletionRequest message.The parameters include cell ID and transport layer addressing information.l The source NodeB releases radio resources used by original link and sends sourceRNC the NBAP message, the Radio Link Deletion Response message.l The source RNC starts releasing lur data transmission and bearer according to theALCAP protocol.l When the source RNC completes releasing lur data transmission and bearer, itsends SRNC the RNSAP message, the Radio Link Deletion Response message.l The SRNC starts releasing lur data transmission and bearer according to the ALCAPprotocol. The request includes AAL2 bound ID for binding lur data transmission andbearer and the transport channel DCH. The release request is confirmed by thetarget RNC.7.4.2 Inter-CN HHO FlowFigure 7-15 shows the inter-CN (between core networks) HHO flow.
  • 126. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 126 of 201Figure 7-15 Ordinary inter-CN HHO flowSG SN2. Relocation RequiredRAN A P RAN A PRA NA P RA N AP3. Relocation RequestRA N AP RA N A P9. Relocation RequestA ckn owledgeRAN A P RA NA P1. Relocation RequiredUE RNCSourceRN CT argetM SC /SG SNRA NA P RA NA P4. Relocation RequestRAN A P RA NA P10. Relocation RequestA ckn owledgeRA N A P RA N A P11. Relocation Com m andRA NA P12. Relocation Com m an dRAN A PRA NA P RA N A P14. RelocationD etectRRC13. D CC H : Ph ysical Ch ann el Recon figuration N ote 1RRC5. A L CA P Iu DataT ran sport Bearer SetupN ode BS ourceNode BTa rg etN BA P N BA P6. Radio Lin k S etu p RequestN BAP NBA P7. Radio Link S etup Respon se8. A LC A P Iu b D ata T ran sport Bearer SetupRA NA P RA N A P18. RelocationC om pleteRRC RRC17. D CC H : Ph ysical Ch ann el Recon figuration Com plete Note 1RA NA PRA NA P15. Relocation D etectRA N AP RA N AP19. Relocation Com pleteRAN A P20. Iu Release C om m an dRA NA PN BAP N BAP1 6. Radio Lin k Failure In dicationRA N AP21 . Iu Release Com m an dRA N AP22. AL CA P Iu D ata T ran sport BearerReleaseRAN A P23. Iu Release Com pleteRA N A PRA N AP24. Iu Release C om pleteRAN A PSG SN /M SCThe ordinary inter-CN HHO flow proceeds as below:l or 2) The SRNC sends the Relocation required message to the nodes of the sourceCN and the target CN.l or 4) After the CN makes necessary preparations, it sends the Relocation Requiredmessage to the target RNC to allocating the corresponding resources.l The transmission and bearer at the lur interface is set up at the target RNC and CN.l or 7) or 8) The target RNC allocates RNTI and radio resources for RRC connectionand radio links, and then sends target NodeB the NBAP message, the Radio LinkSetup Request message. The target NodeB allocates radio link resources startsphysical layer receiver, and sends target RNC the NBAP message, the Radio Link
  • 127. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 127 of 201Setup Response message.The parameters include cell ID, TFS, TFCS, frequency, uplink scramble, powercontrol, and so on.l or 10) When the RNC completes preparations, the RNC sends CN the RelocationRequired Acknowledge message.l or 12) The CN completes preparations and sends SRNC the Relocation Commandmessage.l The SRNC sends UE the RRC message, the Physical Channel Reconfigurationmessage.l or 15) or 16) When the target RNC detects UE, it sends two nodes of CN theRelocation Detect message. When the UE switches from using the original radio linkto the new one, the source NodeB sends source RNC the Radio Link FailureIndication message upon detection of RL error by source NodeB.l When the UE completes setting up RRC connection with target RNC and thecorresponding radio resources are allocated, it sends target RNC the RRC message,the Physical Channel Reconfiguration Complete message.l or 19) After the UE succeeds in handing over to the target RNC and is allocated withresources, the RNC sends all CNs the Relocation Complete message.l or 21) The CN sends SRNC the Lu Release Command message.l The lu transmission and bearer between the original RNC and CN is released.l or 24) The original RNC sends CN the Lu Release Complete message for confirmingrelease.
  • 128. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 128 of 2017.5 HHO Algorithm7.5.1 Intra-frequency HHO AlgorithmThe intra-frequency HHO occurs in the following two situations:l The intra-frequency neighbor cells belong to different RNCs, but no lur interface isbetween the RNCs.l The handover of high-speed PS Best Effort service which exceeds the speedthreshold. The reason is that SHO takes excessive forward capacity.The 1D event is a judgment evidence for the intra-frequency HHO, namely, the triggering cell of1D event is the target cell for handover.7.5.2 Inter-frequency HHO AlgorithmFundamental ConceptsThe cell at the carrier coverage edge refers to the cell covered by a carrier in the mostperipheral areas. The cell features that no intra-frequency neighbor cells are present in adirection of the cell.The cells in the carrier center area are the rest cells. The cell features that intra-frequencyneighbor cells are present in all directions of the cell.In the cell at the carrier coverage edge, when the UE moves towards the direction with nointra-frequency neighbor cells, the CPICH Ec/No fluctuates slowly due to the same attenuatingspeed of CPICH RSCP and interference. According to simulation, when the CPICH RSCP islower than the demodulation threshold (–110 dBm), the CPICH Ec/No can reach about –12 dB.Now the inter-frequency handover algorithm based on CPICH Ec/No measurement is invalid.Therefore, using CPICH RSCP as inter-frequency measurement quantity is more proper andvalid for cells at the carrier coverage edge.The CPICH RSCP might serve as inter-frequency measurement quantity for cells in the carriercenter area, but the CPICH Ec/No is better to reflect the actual communication quality of linksand cell load.Starting/Stopping Inter-frequency MeasurementThe inter-frequency measurement might use the compression mode which impacts the linkquality and system capacity, so starting the inter-frequency measurement is not recommended.The inter-frequency measurement in only recommended if needed. Reporting 2D and 2F eventsdetermines starting/stopping inter-frequency measurement on V1.2 RNCs.When the UE enters the CELL_DCH state or the best cell changes, if the inter-frequencyhandover algorithm switch is enabled and the best cell is present in the list of inter-frequencyneighbor cells, the measurement of 2D and 2F events is configured. The absolute threshold for2D and 2F events is the staring/stopping inter-frequency measurement. The CPICH Ec/No orRSCP measurement quantity and threshold is respectively used according to the positionproperty (as previously mentioned, there are carrier coverage center and carrier coverage edge)of the best cell in the active set:
  • 129. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 129 of 201l If the quality of measurement quantity is worse than the starting threshold, the 2Devent is reported and then the periodic inter-frequency measurement is startedthrough judgment.l If the quality of active set is higher than the stopping threshold, the 2F event istriggered and inter-frequency measurement is stopped.Inter-frequency HHO JudgmentNow the inter-frequency measurement is reported periodically. The inter-frequency handoverjudgment on RNCs uses the absolute threshold judgment method based on cell property.According to the different cell properties (cell at the carrier coverage edge or in the carriercoverage center), the handover judgment uses different physical measurement quantity (CPICHRSCP and CPICH Ec/No) and handover threshold.If the measurement quantity keeps greater than the absolute threshold and hysteresis untiltrigger delay, the reported cell becomes the target handover cell. After this, according to theinter-frequency measurement result, the RNC carries out inter-frequency HHO threshold.& Note:No dedicated control strategy in compression mode is available, so it is recommended that theinter-frequency handover caters for the compulsory handover caused by in continuous coverageby carrier. Now you can only consider starting compression mode at the carrier coverage edge.In the carrier coverage center, forbid the compression mode from starting by configuringparameters (set the absolute threshold of 2D event to the minimum value) and forbidinter-frequency HHO.
  • 130. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 130 of 2017.6 Concept and Classification of HSDPA Handover7.6.1 Concept of HSDPA HandoverFor a subscriber, if an RAB is mapped on the HS-DSCH of a cell, the cell becomes theHS-DSCH serving cell for the subscriber, and the radio link of the cell is the HS-DSCH servingradio link.As the signals of HSDPA serving cell are weaker and weaker, the network switches the serviceto a HSDPA cell with better signals, namely, the update of HSDPA serving cell. For the handoverof HSDPA subscribers, HS-DSCH serving cell update describes HS-DSCH handover, andhandover describes DCH handover.If other cells do not support HSDPA, the system switches the service to R99 cells. An RAB ismapped on the HS-DSCH of a cell only, so SHO is unavailable on HS-PDSCH bearing HSDPA,but available on associated DCH. The HS-PDSCH does not support SHO, so the major impacton mobility management (MM) after use of HSDPA is as below:l How to select and change the serving cell of HS-DSCHl How to obtain best performance of data transmission.Without violating the coverage handover rules, engineers must give priority to theHSDPA-supported cells for a service. For example, if multiple radio links are present for SHO,and only partial cells support HSDPA, the HSDPA service can be used in the non-superior cells.If the subscriber only for service that is carried on HSDPA, the RNC enable the UE to camps onHSDPA-supporting cell by direct retry and blind handover.7.6.2 Classification of HSDPA HandoverBy Different Handover Types on Associated DPCHAccording to different handover on the associated DPCH in HSDPA network, the HSDPAhandover includes the following types:l Update the serving cell of HS-PDSCH in active setl Update the serving cell of HS-PDSCH by SHO or softer handover on DPCHl Update the serving cell of HS-PDSCH by HHO on DPCHBy Different Technologies Used in Serving Cell before and after HandoverBy different technologies used in serving cell before and after handover, the HSDPA handoverincludes the following types:l Handover in HSDPA systeml Handover between HSDPA and R99l Handover between HSDPA and GRPS
  • 131. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 131 of 201By Location of Cells for HSDPA HandoverBy location of cells for HSDPA handover, the HSDPA handover includes the following types:l Handover under the same NodeBl Handover under different NodeBs of the same RNCl Handover under different RNCs7.6.3 Signaling Flow and Message Analysis of HSDPA HandoverDuring mobility procedures of HSDPA, the UE is connected to a cell by HS-DSCH, so theconnection is different from DCH SHO. In CELL_DCH state, the move from source HS-DSCHcell to target HS-DSCH cell is decided according to measurement reports of UE and otherinformation at network side.A typical handover proceeds as below:l Measurement controll Measurement reportl Handover judgmentl Handover implementationl New measurement controlThe serving cell update of HSDPA subscribers is with DCH handover.When the serving cell is updated,l The DPCH configuration and active set remains;l Or the DPCH is set up, released, and reconfigured;l Or the active set upon SHO is updated.At measurement control and measurement report stage, the handover messages for HSDPAare similar to these of R99 and R4.The signaling related to HSDPA in HSDPA handover includes:During NBAP:l Radio Link Setupl Synchronized Radio Link Reconfiguration Preparationl Physical Shared Channel Reconfigurationl Synchronized Radio Link Reconfiguration Commitl Bearer Re-arrangementl Radio Link Parameter UpdateAt UU interface:l RADIO BEARER SETUPl RADIO BEARER RECONFIGURATION
  • 132. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 132 of 201l RADIO BEARER RELEASEl TRANSPORT CHANNEL RECONFIGURATIONl PHYSICAL CHANNEL RECONFIGURATION7.6.4 HS-PDSCH Serving Cell Update due to DPCH SHODescriptionWhen the HS-PDSCH serving cell is updated due to DPCH SHO, the UE reports the followingevents listed in Table 7-3. The system will respond accordingly.Table 7-3 Flow of serving cell update triggered by different events in SHOEvent Action1D event, the best server is listed inactive setChange the radio link ID by reconfiguring radiolink1B event, the HS-DSCH serving cellis to be deletedUpdate the serving cell in active set, andperform DCH SHO to delete the cellcorresponding to 1B event1C event, the current HS-DSCHserving cell is the worst cell in activesetUpdate the HS-DSCH in active set to supportthe best server of HS-DSCH, and then replacethe cellThe best server to trigger 1D eventis not listed in active set, and theactive set is not fullPerform DPCH SHO to add radio link, andupdate the HS-DSCH serving cell in active setThe best server to trigger 1D eventis not listed in active set, and theactive set is full. The serving cell isnot the worst cellPerform DCH SHO to replace radio link, andupdate the serving cell in active set1D event, the active set is full, thecell to be replaced is the serving cellReplace the second worst cell in active set, andupdate the serving cellHS-DSCH Serving Cell Update (intra-NodeB) upon Fixed Active Set of UEFigure 7-16 shows the intra-NodeB synchronization serving cell update.
  • 133. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 133 of 201Figure 7-16 Intra-NodeB synchronization serving cell updateDCCH: MEASUREMENTREPORTCPHY-Measurement-INDUE-RRC UE-RLC UE-MAC UE-L1 NodeB-L1 SRNC-MAC SRNC-RLC SRNC-RRCUu Iub/IurCPHY-RL-Modify-REQCPHY-RL-Modify-CNFCPHY-RL-Modify-REQServingHS-DSCHcellchange decisionDCCH: PHYSICAL CHANNELRECONFIGURATIONStart tx/rx for HS-DSCHin target HS-DSCHcell,stoptx/rxfor HS-DSCHinsource HS-DSCHcellat the given activationtimeDCCH: PHYSICALCHANNEL RECONFIGURATIONCOMPLETENode B-MACMeasurementReportingcriteriafulfilledSRNC-L1(NBAP/RNSAP: RL Reconfiguration Prepare)(NBAP/RNSAP: RL ReconfigurationReady)CPHY-RL-Commit-REQ(NBAP/RNSAP: RL ReconfigurationCommit)The update process is based on the following conditions:l The DPCH and active set are fixed.l Assume that the parameters like transport channel and radio bearer are fixed.The update does not involve MAC layer, so the entity of MAC-hs needs no reconfiguration.The intra-NodeB synchronization serving cell is updated as below:l When the SRNC decides to update the HS-DSCH serving cell, it sends DRNC theRADIO LINK RECONFIGURATION PREPARE message. The message contains theidentity of target HS-DSCH serving cell.l The DRNC commands NodeB to perform synchronized radio link reconfiguration.The NodeB must reconfigure the resource transition from source HS-DSCH radiolink to target HS-DSCH radio link. The message contains the necessary informationabout setting up HS-DSCH link in target HS-DSCH cell, like UE ID.l The serving NodeB sends the RADIO LINK RECONFIGURATION READY message.l The DRNC sends SRNC the RADIO LINK RECONFIGURATION READY message.The message contains the following information:− HS-SCCH set information− Scramble of target SCCH cell− UE ID of HS-DSCH
  • 134. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 134 of 201l The SRNC sends DRNC the RADIO LINK RECONFIGURATION COMMIT message.The message contains the activation time of SRNC in CFN.l The DRNC sends the serving NodeB the RADIO LINK RECONFIGURATIONCOMMIT message. The message contains its activation time. At the activation time,the NodeB commands the source HS-DSCH cell to stop sending HS-DSCH data toUE. The target HS-DSCH cell sends UE the HS-DSCH data.l The SRNC sends UE the PHYSICAL CHANNEL RECONFIGURATION message.The message contains the following information:− Activation time− MAC-HS RESET indicator− Link ID of the serving HS-DSCH− HS-SCCH set indicator− UE ID of HS-DSCHl In the specified activation time, the UE resets HS-DSCH. It stops receivingHS-DSCH data from the source HS-DSCH cell, and starts receiving HS-DSCH datafrom target HS-DSCH cell. The UE responds SRNC the PHYSICAL CHANNELRECONFIGURATION COMPLETE message.HS-DSCH Serving Cell Update (inter-NodeB) upon Fixed Active Set of UEFigure 7-17 shows the inter-NodeB synchronization serving cell update.
  • 135. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 135 of 201Figure 7-17 Inter-NodeB synchronization serving cell updateUu IubUE SRNCSourceHS-DSCHNodeB DRNC1. RNSAP: RLRECONFIGURATIONPREPARE6. RNSAP: RLRECONFIGURATIONREADY5. NBAP: RLRECONFIGURATIONREADY4. NBAP: RLRECONFIGURATIONPREPARE9. RRC: PHYSICALCHANNELRECONFIGURATION7. RNSAP: RL RECONFIGURATIONCOMMIT8. NBAP: RLRECONFIGURATIONCOMMIT2. NBAP: RLRECONFIGURATIONPREPARE3. NBAP: RLRECONFIGURATIONREADY10. RRC: PHYSICAL CHANNELRECONFIGURATIONCOMPLETEIurALCAP IubDataTransport Bearer setup(HS-DSCH)ALCAPIur DataTransport Bearersetup(HS-DSCH)ALCAP IubDataTransportBearer release(HS-DSCH)ALCAP Iur DataTransport Bearer release(HS-DSCH)Target HS-DSCHNodeBThe update process is based on that the DPCH and active set are fixed.The inter-NodeB synchronization serving cell is updated as below:l a) After SRNC decides to update HS-DSCH cell, it sends DRNC the RADIO LINKRECONFIGURATION PREPARE message. The message contains the identity ofHS-DSCH target cell.l The DRNC sends the source NodeB the RADIO LINK RECONFIGURATIONPREPARE message.l The NodeB responds RADIO LINK RECONFIGURATION READY message. Themessage contains the indicator of RESET MAC-hs after reconfiguration.l The source NodeB responds the RADIO LINK RECONFIGURATION PREPARE tothe target NodeB. The message indicates NodeB to perform synchronized radio linkreconfiguration, namely, to add resource to target HS-DSCH radio link. Themessage contains necessary information to set up HS-DSCH resource in target cell,like UE ID.l The target NodeB responds RADIO LINK RECONFIGURATION READY message.l The DRNC responds RADIO LINK RECONFIGURATION READY message toSRNC. The message contains the following information:− HS-SCCH set information− Scramble of target HS-SCCH cell− UE ID of HS-DSCH
  • 136. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 136 of 201l After setting up the HS-DSCH transport bearer to the target NodeB, the SRNCsends the RADIO LINK RECONFIGURATION COMMIT to DRNC, including theactivation time of SRNC in CRN.l The DRNC sends the RADIO LINK RECONFIGURATION COMMIT message to thesource NodeB and target NodeB. The message contains its activation time. In theactivation time, the source NodeB stops and target NodeB starts sending HS-DSCHdata.l The SRNC sends UE the PHYSICAL CHANNEL RECONFIGURATION message toUE. The message contains the following information:− Activation time− MAC-hs RESET indicator− Link ID of the serving HS-DSCH− HS-SCCH set indicator− UE ID of HS-DSCHl In the specified activation time, the UE resets MAC-hs. It stops receiving theHS-DSCH data from the source HS-DSCH cell, and starts receiving the data fromtarget HS-DSCH cell. It responds the PHYSICAL CHANNEL RECONFIGURATIONCOMPLETE message to SRNC. The HS-DSCH transport bearer to source NodeB isreleased.The signaling is in the attachment below (the corresponding RNC version isV100R005C01B061):INTER_NODEB(ok).tmfDPCH SHO with HS-DSCH Serving Cell UpdateFigure 7-18 shows the inter-NodeB HS-DSCH cell update after radio link is added.
  • 137. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 137 of 201Figure 7-18 Inter-NodeB HS-DSCH cell update after radio link is addedUu IubUE SRNCSource Node BDRNC7. RNSAP: RL RECONFIGURATIONREQUEST12. RNSAP: RL RECONFIGURATION READY11. NBAP: RL RECONFIGURATION READY10. NBAP: RL RECONFIGURATIONREQUEST15. RRC: PHYSICAL CHANNEL RECONFIGURATION13. RNSAP: RL RECONFIGURATION COMMIT14. NBAP: RL RECONFIGURATION COMMIT8. NBAP: RL RECONFIGURATIONREQUEST9. NBAP: RL RECONFIGURATION READY16. RRC: PHYSICAL CHANNEL RECONFIGURATION COMPLETEIurALCAP Iub Data Transport Bearer setup(HS-DSCH)ALCAP Iur Data Transport Bearer setup(HS-DSCH)ALCAP Iub Data TransportBearer release (HS-DSCH)ALCAP Iur Data Transport Bearer release(HS-DSCH)Target Node B1. RNSAP: RL ADDITION REQUEST4. RNSAP: RL ADDITION RESPONSE3. NBAP: RL SETUP RESPONSE2. NBAP: RL SETUP REQUESTALCAP Iub Data Transport Bearer setup(DCH)ALCAP Iur Data Transport Bearer setup(DCH)5. RRC: ACTIVE SET UPDATE6. RRC: ACTIVE SET UPDATE COMPLETESetting a newly-added radio link to HS-DSCH radio link involves two steps:l Add a new link to active setl The HS-DSCH transmits to the new radio linkAfter radio link is added, the inter-NodeB HS-DSCH cell is updated as below:l The SRNC decides to add new radio link. The radio link will be the HS-DSCH link.The SRNC sends DRNC the RADIO LINK ADDITION REQUEST message. Themessage indicates DRNC to set up a radio link without HS-DSCH resource.l The DRNC allocates resources for the new radio link. It sends the RADIO LINKSETUP REQUEST message to the target NodeB. The message contains theinformation to set up DPCH. It indicates the target NodeB to set up new radio link.l The target NodeB allocates resources. It receives information at the physical layer ofthe new DPCH. It responds the RADIO LINK SETUP RESPONSE message.l The DRNC responds the RADIO LINK SETUP RESPONSE message to SRNC. TheDCH transport bearer is set up.
  • 138. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 138 of 201l The SRNC sends UE the ACTIVE SET UPDATE message. The message containsthe new radio link ID.l The UE adds the new radio link to active set, and then responds the ACTIVE SETUPDATE COMPLETE message to SRNC.l The SRNC sends the RADIO LINK RECONFIGURATION REQUEST message toDRNC. The message indicates the target HS-DSCH cell.l Assume that the target HS-DSCH and source HS-DSCH are controlled by differentNodeBs. The DRNC sends the RADIO LINK RECONFIGURATION message tosource NodeB. The message indicates NodeB to perform synchronized radio linkreconfiguration, excluding the resource of original HS-DSCH radio link.l The source NodeB responds the RADIO LINK RECONFIGURATION READYmessage to DRNC.l The DRNC sends the RADIO LINK RECONFIGURATION REQUEST message totarget NodeB. The message indicates target NodeB to perform synchronized radiolink reconfiguration to allocate resources to target HS-DSCH link.l The target NodeB responds the RADIO LINK RECONFIGURATION READYmessage.l The DRNC sends the RADIO LINK RECONFIGURATION READY message toSRNC. The message contains the following information:− HS-SCCH set information− Scramble of target HS-SCCH cell− UE ID of HS-DSCHl The HS-DSCH transport bearer to target NodeB is set up. The SRNC sends theRADIO LINK RECONFIGURATION COMMIT message to DRNC. The messagecontain the activation time in CFN.l The DRNC sends the RADIO LINK RECONFIGURATION COMMIT message to thesource NodeB and the target NodeB. In the specified activation time, the sourceNodeB stops sending HS-DSCH information to UE, and then the target NodeB startssending HS-DSCH information to the UE.l The SRNC sends the PHYSICAL CHANNEL RECONFIGURATION message to UE.The message contains the following information:− Activation time− MAC-hs RESET indicator− Link ID of the HS-DSCH− HS-SCCH code set− UE ID of HS-DSCHl In the specified time, the UE resets MAC-hs. It stops receiving HS-DSCH data fromsource HS-DSCH cell, and starts receiving HS-DSCH data from target HS-DSCHcell. The UE responds the PHYSICAL CHANNEL RECONFIGURATIONCOMPLETE message to SRNC. The transport bearer to source NodeB is released.
  • 139. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 139 of 2017.6.5 HS-PDSCH Serving Cell Update due to DPCH HHODescriptionThe combination of HHO and HS-PDSCH serving cell update is simple. Namely, they occursimultaneously.The intra- and inter-NodeB HHO with serving cell update have the same process. New radio linkis set up in new cell with HS-DSCH. Consequently, the physical channel is reconfigured, and oldlink is deleted.Handover FlowFigure 7-19 shows the inter-NodeB HS-DSCH cell update during HHO (single step method).Figure 7-19 Inter-NodeB HS-DSCH cell update during HHO (single step method)Uu IubUE SRNCSource Node B IurTarget Node B1. RNSAP: RL SETUP REQUEST4. RNSAP: RL SETUP RESPONSE3. NBAP: RL SETUP RESPONSE2. NBAP: RL SETUP REQUESTALCAP Iub Data Transport Bearer setup(DCH + HS-DSCH)ALCAP Iur Data Transport Bearer setup(DCH + HS-DSCH)5. RRC: PHYSICAL CHANNEL RECONFIGURATION6. RRC: PHYSICAL CHANNEL RECONFIGURATION COMPLETETargetDRNCALCAP Iub Data TransportBearer release (DCH + HS-DSCH)ALCAP Iur Data Transport Bearer release(DCH + HS-DSCH)7. RNSAP: RL DELETION REQUEST10. RNSAP: RL DELETION RESPONSE8. NBAP: RL DELETION REQUEST9. NBAP: RL DELETION RESPONSESourceDRNCThe inter-NodeB HS-DSCH cell during HHO (single step method) is updated as below:l The SRNC decides to perform HHO and update HS-DSCH cell. It sends the RADIOLINK SETUP REQUEST message to target DRNC. The message indicates thetarget cell for HHO and the information to set up HS-DSCH resource in targetHS-DSCH cell.l The DRNC allocates resources for new radio link. It sends the RADIO LINK SETUPREQUEST message to target NodeB. The message contains the information to setup DPCH and that to set up HS-DSCH.l The target NodeB allocates resources to set up DPCH link. It starts receiving datafrom physical layer. It responds the RADIO LINK SETUP RESPONSE message. The
  • 140. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 140 of 201message contains the information about HS-SCCH code set, and HS-DSCH flowcontrol.l The DRNC responds the RADIO LINK SETUP RESPONSE message to SRNC. TheDCH and DSCH transport bearer is set up at lub and lur interface. The messagecontains the following information:− HS-SCCH code set− HS-DSCH flow control− UE IDl The SRNC sends UE the PHYSICAL CHANNEL RECONFIGURATION message.The message contains the following information:− Activation time− DPCH of target cell− MAC-hs RESET indicator− Link ID of the HS-DSCH− HS-SCCH code set− UE ID of HS-DSCHl In the specified time, the UE deletes the current active set, and sets up DPCH link totarget cell, RESET MAC-hs, and after it synchronize with target cell at the physicallayer, it starts receiving and sending DPCH data, and receiving HS-DSCH data oftarget cell. The UE responds the PHYSICAL CHANNEL RECONFIGURATIONCOMPLETE message to SRNC.l The SRNC sends the RADIO LINK DELETION REQUEST message to sourceDRNC. The message indicates the cell to be deleted.l The target DRNC sends the RADIO LINK DELETION REQUEST message to sourceNodeB.l The source NodeB releases original radio link resource, and responds the RADIOLINK DELETION RESPONSE message to source DRNC.l The source DRNC responds RADIO LINK DELETION RESPONSE message toSRNC. The DCH and HS-DSCH transport bearer resource to source NodeB arereleased.7.6.6 DPCH Intra-frequency HHO with HS-DSCH Serving Cell UpdateFigure 7-20 shows the signaling when DPCH intra-frequency HHO with HS-DSCH serving cellupdate.
  • 141. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 141 of 201Figure 7-20 DPCH intra-frequency HHO with HS-DSCH serving cell updateThe flows for intra-frequency HHO and HS-PDSCH serving cell update are simple. They occursimultaneously. After the UE reports 1D event, the physical channel reconfiguration triggers theHHO of DPCH and HS-DSCH serving cell update.The following attachment includes the signaling, according to V100R005C01B061).INTER_NODEB(ok).tmf7.6.7 DPCH Inter-frequency HHO with HS-DSCH Serving Cell UpdateFigure 7-21 shows the DPCH inter-frequency HHO with HS-DSCH serving cell update.
  • 142. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 142 of 201Figure 7-21 DPCH inter-frequency HHO with HS-DSCH serving cell updateIn Figure 7-21,l Message 98: the UE sends RNC the 2D measurement report.l Messages 99–105: the UE and NodeB starts compression mode.l Messages 112–143: the UE sends the measurement report. The report meets theHHO threshold. The flow for physical channel reconfiguration occurs. HHO iscomplete. The HS-PDSCH serving cell is updated.The following attachment contains the signaling, according to V100R005C01B061.HSDPA_INTER_FREQ_HHO_WITH_TRAFFIC_OK_UE.tmf
  • 143. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 143 of 2017.6.8 Handover Between HSDPA and R99DescriptionWhen the UE moves from a HSDPA cell to an R99 cell, the service that is born on HS-DSCHchannel is remapped on DCH to guarantee the continuity of service. The HS-DSCH set inHSDPA cell is deleted.Figure 7-22 shows the handover from HSDPA to R99.Figure 7-22 handover from HSDPA to R99The Case 1 is intra-frequency handover from R5 to R99. The Case 2 is inter-frequencyhandover from R5 to R99.When a UE moves from an R99 cell to a HSDPA cell, if the original DCH bears packet dataservice, an HS-DSCH is set up in the link between UE and HSDPA cell, and the data service isremapped on the new HS-DSCH. This helps provide more qualified services for data services.Figure 7-23 shows the intra-frequency handover from R99 to R5.Figure 7-23 Intra-frequency handover from R99 to R5The strategy for handover between HSDPA and R99 in V17 differs from that in V15 and V16. Ifboth an R99 cell and a HSDPA cell are available in the active set of the UE, the UE decides thatthe service is borne over the HS-DSCH or over the DCH depending on whether the best cellsupports HSDPA or not.In V17, four scenarios of handover between HSDPA and R99 exist as listed in Table 7-4.
  • 144. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 144 of 201Table 7-4 Scenarios of handover between HSDPA and R99 (V17)No. Scenario RNC Processing1If the UE moves to an R99 cell froma HSDPA cell:A 1D event occurs and the new bestcell does not support HSDPA.A 1B or 1C event occurs and thenew best cell does not supportHSDPA.The RNC hands over the HSDPAlink of the UE to the DPCH channelof the R99 cell.2The UE moves to an R99 cell ofanother frequency from a HSDPAcell, then an inter-frequency HHOoccurs.The RNC hands over the UE to theDPCH channel of the R99 cellthrough HHO.3The UE moves to a HSDPA cellfrom an R99 cell:A 1D event occurs and the new bestcell supports HSDPA.A 1B or 1C event occurs and thenew best cell supports HSDPA.If the service of the UE is fit for theHS-PDSCH and the updated bestcell supports HSDPA, the RNCswitches the related service to theHS-PDSCH.4The UE moves to a HSDPA cell ofanother frequency from an R99 cell,then an inter-frequency HHO occurs.The RNC hands over the UE to theHSDPA cell through HHO. After aperiod of time (as specified by therelated timer), the RNC sets up therelated service over the HS-PDSC ifthe service of the UE is fit for theHS-PDSCHH.Intra-frequency SHO Between HSDPA Cell and R99 CellFigure 7-24 shows DPCH SHO with handover from HSDPA to R99 (inter-NodeB).
  • 145. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 145 of 201Figure 7-24 DPCH SHO with handover from HSDPA to R99 (inter-NodeB)The meanings of messages shown in Figure 7-24 are as below:l Message 19: the UE sends the 1A measurement report to RNC. The report indicatesthat the signals from R99 cell are stronger than the signals required by threshold.Therefore the R99 cell requires being added to active set.l Messages 20, 21, and 22: the RNC sets up a radio link to NodeB.l Messages 23–26: the RNC sends UE the active set update message, and theassociated DCH can receive the message in two RLs. After the UE receives themessage, it sends the active set update complete message, which the RNC canreceive in two RLs.l Messages 27 and 28: the network sends UE a new measurement control message,updated measurement parameters, and neighbor cell list.l Messages 29 and 30: the RNC informs NodeB of perform dedicated measurement innew link.
  • 146. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 146 of 201l Messages 31 and 32: the R99 cell is listed in active set, so the HS-PDSCHparameters need changing. RL is reconfigured, and HS-PDSCH parameters arechanged.l Message 33: the physical channel is reconfigured, and physical parameters ofHSPDA are changed.l Message 40: the UE sends 1D measurement report, and the R99 cell becomes thebest server. Now the HS-PDSCH serving cell remains the same.l Message 44: the UE sends 1B measurement report.l Message 50: the RB is reconfigured, and the service is reconfigured fromHS-PDSCH to DCH.l Messages 56–60: the RL of original HS-PDSCH is deleted from active set.Figure 7-25 shows the DPCH SHO with handover from R99 to HSDPA.Figure 7-25 DPCH SHO with handover from R99 to HSDPAIn Figure 7-25, in the handover from R99 to R5 HSDPA, after the UE reports 1A event, it firstadds the RL of HS-PDSCH, and then reconfigures the service born on DCH to HS-PDSCH.The following attachment contains the previous signaling, according to V100R005C01B061.
  • 147. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 147 of 201SHO_R5toR99&R99toR5(OK)_Inter_NodeB.tmfFigure 7-26 Inter-NodeB SHO with handover from HSDPA to R99 (V17)In V17, the signaling flow for SHO from HSDPA to R99 is as follows:l The UE accesses a HSDPA cell.− The UE reports a 1A event of the R99 cell (message 18), and the R99 cell is added tothe active set.− The UE reports a 1D event of the R99 cell (message 26), and the R99 changes intothe best cell.− The RNC hands over the UE from the HSDPA cell to the R99 cell (message 34).In V17, the signaling flow for SHO from R99 to HSDPA is similar to that for SHO from HSDPA toR99:l The UE accesses an R99 cell.− The UE reports a 1A event of the HSDPA cell, and the HDSPA cell is added to theactive set.− The UE reports a 1D event of the HDSPA cell, and the HSDPA cell changes into thebest cell.− The RNC hands over the UE from the R99 cell to the HSDPA cell.The following attachment contains the signaling for handover from HSDPA to R99, according toV17C01B060.
  • 148. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 148 of 201RNC_2006-10-30-09-59-11_H2D SHO.rarIntra-frequency HHO Between HS-PDSCH Cell and R99 CellFigure 7-27 shows the intra-frequency HHO with handover from R5 to R99 (intra-NodeB).Figure 7-27 Intra-frequency HHO with handover from R5 to R99The meanings of messages are as below:l Message 31: the UE reports 1A event, requiring network side to add the link for R99cell.l Message 32: the network side prohibits SHO and neglects 1A event. The UE reports1D event.l Message 35: after RB reconfiguration, the born service is configured fromHS-PDSCH to DCH of the current cell.l Messages 39–44: R99 HHO occurs, the UE hands over to a new cell.Figure 7-30 shows the intra-frequency HHO with handover form R99 to R5 (intra-NodeB).Figure 7-28 Intra-frequency HHO with handover form R99 to R5Intra-frequency HHO occurs on DPCH while the handover from R99 to R5 occurs. Theintra-frequency HHO of R99 occurs, and then the service is reconfigured from DCH toHS-PDSCH in the new HSDPA cell.
  • 149. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 149 of 201The following attachment contains the signaling, according to V100R005C01B061.HHO_R5ToR99(OK)and R99toR5_Intra_NodeB.tmfFigure 7-29 Intra-frequency HHO with handover from R5 to R99 (V17)In V17, the signaling flow for intra-frequency HHO from HSDPA to R99 is as follows:l The UE accesses a HSDPA cell.− The UE reports a 1A event of the R99 cell (messages 18 to 22). The RNC does notperform any processing because the SHO is not supported.− The UE reports a 1D event of the R99 cell (message 23), and the R99 cell changesinto the best cell.− The RNC hands over the UE from the HSDPA cell to the R99 cell through HHO (line34).This step differs from that in the earlier versions. In earlier versions, the RNCre-allocates the service from HSDPA to R99, and then hands over the service toanother R99 cell through intra-frequency HHO.The signaling flow for intra-frequency HHO from R99 to HSDPA in V17 is the same as that inthe earlier versions.The following attachment contains the preceding signaling, according to V17C01B060.RNC_2006-10-30-10-41-35_H2D intraHHO.rarInter-frequency HHO Between HS-PDSCH and R99Figure 7-30 shows the inter-frequency HHO from HS-PDSCH to DCH.
  • 150. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 150 of 201Figure 7-30 Inter-frequency HHO from HS-PDSCH to DCHThe meanings of previous messages are as below:l Message 20: the UE reports 2D measurement report to RNC.l Messages 21–27: the UE and NodeB start compression mode.l Messages 28–35: the UE sends measurement report.l Message 36–66: the UE sends measurement report. The report indicates that theinter-frequency HHO threshold is met. The UE reconfigures the service to be born onR99 DCH in RB reconfiguration, and then R99 HHO occurs.Figure 7-31 shows the inter-frequency HHO from DCH to HS-PDSCH.
  • 151. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 151 of 201Figure 7-31 Inter-frequency HHO from DCH to HS-PDSCHThe meanings of previous message are as below:l Message 76: the UE sends 2D measurement report to RNC.l Messages 77–83: the UE and NodeB starts compression mode.l Messages 84–91: the UE sends measurement report.l Messages 92–121: the UE sends measurement report, and the inter-frequency HHOthreshold is met. The inter-frequency HHO occurs. The service is born on HS-DSCHin RB reconfiguration in target cell, and the inter-frequency HHO from DCH toHS-PDSCH is complete.The following attachment contains the signaling, according to V100R005C01B061.IFHO H-R OK(R170H180).tmf
  • 152. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 152 of 201In the signaling flow for inter-frequency HHO from HSDPA to R99 in V17, only the HHO from aHSDPA cell to an R99 cell differs from that in the earlier version. In earlier versions, the RNCre-allocates the service from HSDPA to R99, and then hands over the service to another R99cell through intra-frequency HHO. In V17, the handover from the HSDPA cell to the R99 cellcompletes in one step.The signaling flow for inter-frequency HHO from R99 to HSDPA in V17 is the same as that inthe earlier versions.The signaling is to be implemented.7.6.9 Handover between HSDPA and GPRSThe handover between HSDPA and GPRS is similar to that of R99. For details, see theAppendix 5.Figure 7-32 shows the handover between HSDPA and GRPS.Figure 7-32 Handover between HSDPA and GPRShsdpa-2G.tmf7.6.10 Direct Retry of HSDPAIn V16, direct retry of HSDPA includes the following two types:Inter-frequency direct retry of HSDPA during setup of a serviceWhen the R99 cells and HSDPA cells cover the same geographic area, the system allocates alldata services to the HS-DSCH of HSDPA cells. When the UEs originate to access the networkfrom R99 or HSDPA cells, it can share the HSDPA resource of HSDPA cells however it is anR99 UE or a HSDPA UE. Thus, it can use resource better.
  • 153. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 153 of 201Figure 7-33 Flow for direct retry during setup of a serviceInter-frequency direct retry triggered by 4A eventsWhen an R99 cell and a HSDPA cell cover the same geographic area, the system allocates thedata traffic to the HS-DSCH of the HSDPA cell through direct retry if a 4A event occurs due toincrease of data traffic of the UE in the R99 cell.In this case, the R99 cell shares HSDPA resources with the HSDPA cell. Thus, the resourcesare better used.Figure 7-34 Direct retry triggered by trafficIn V17, the following types of inter-frequency direct retry of HSDPA are available:l Inter-frequency direct retry of HSDPA during setup of a service− Scenario 1An R99 cell overlaps with an inter-frequency R5 cell with the same coverage. If theUE that supports HSDPA originates a request for setup of a service that is fit for
  • 154. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 154 of 201HSDPA in the R99 cell, the service is sent to the R5 cell through direct retry duringRAB setup.− Scenario 2An R5 cell has an inter-frequency R99 cell with the same coverage.If the UE that supports HSDPA originates a request for setup of a service that HSDPAcannot bear in the R5 cell, or the UE that does not support HSDPA originates arequest for setup of a service on HSDPA in the R5 cell, the request is sent to the R99cell through direct retry during RAB setup.The service setup here must be the first service setup of the UE or the existing services areover the FACH. Thus, the new service does not impact the existing services.l Inter-frequency direct retry in the case admission rejectionSuppose an R5 has an inter-frequency R5 cell with the same coverage. The UE thatsupports HSDPA originates a request for setup of a service that is fit for HSDPA ororiginates an RAB reconfiguration request (channel type) in an R5 cell. If the request isrejected by the local cell, the request is sent to the other R5 cell through aninter-frequency direct retry.l Inter-frequency direct retry triggered by 4A eventsThe current service that is fit for the HS-DSCH is over the DCH for some reason (suchas admission rejection), the UE supports HSDPA but the best cell does not. Aninter-frequency R5 cell with the same coverage is available. In this case, the systemre-allocates the service from the DCH to the HS-DSCH in the inter-frequency R5 cellwith the same coverage if the data traffic of the UE increases (the RNC receives a 4Aevent measurement report).l Inter-frequency direct retry triggered by a timerThe current service that is fit for the HS-DSCH is over the DCH for some reason (suchas admission rejection), the UE supports HSDPA but the best cell does not. Aninter-frequency R5 cell with the same coverage is available. In this case, the systemre-allocates the service from the DCH to the HS-DSCH in the inter-frequency R5 cellwith the same coverage if the channel type fit for service mapping has conflicted withthe type of the current serving channel for a period of time (as specified by the HSDPAdirect retry timer).To set the expiry time of the timer, run the command SETCOIFTIMER:HRetryTimerLen=5000;.The signaling is to be supplemented.7.6.11 Switch of Channel TypeWhen the HSDPA is used, a new state appears compared with R99, the CELL_DCH state onHS-DSCH.The switch of channel type between HS-DSCH and FACH/DCH includes:l HS-DSCH <-> FACHl HS-DSCH <-> DCH
  • 155. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 155 of 201Figure 7-35 shows the switch of channel type.Figure 7-35 Switch of channel typeHS-DSCH <-> FACHThe UE with HSDPA channel uses DPCH resource of certain bandwidth. If all services ofHSDPA UE are BE services, the all service (including the service on DCH and HS-DSCH) arewithout data transmission for a long time, the system triggers state transition to reduceconsumption of DPCH resource. Therefore, the UE transits from CELL_DCH (HS-DSCH) stateto CELL_FACH state.Whereas, the data service is more active (the network receives the 4a event of servicemeasurement quantity), the UE is triggered to switch from CELL_FACH state to HS-DSCH.The attachment below contains the signaling.H2F and F2H(OK).tmfHS-DSCH <-> DCHIn V16, the handover between HS-DSCH and DCH might occur in any of the following cases:l One cause to handover between HS-DSCH and DCH is coverage. This caseincludes that UE moves from an R99 cell to a HSDPA cell or from a HSDPA cell to aR99 cell.If the service set up by UE fits for HS-DSCH, the RNC triggers switch of channel type after theHSDPA cell is added to actives set of UE. The RNC reallocate the data service to HS-DSCH.This is due to mobility of UE.l D2H channel type switch triggered by traffic− Scenario 1: A 4A event triggers switch between D2H channel types in a cell.The current service that is suitable for the HS-DSCH is over the DCH for somereason (such as admission rejection). Both the UE and the best cell support HSDPA.The rate of the service on the current DCH is lower than 384 Kbps. In this case, thesystem re-allocates the service from the DCH to the HS-DSCH in the best cell if thedata traffic of the UE increases (the RNC receives a 4A event measurement report).− Scenario 2: A 4A event triggers D2H switch between two cells at differentfrequencies but with the same coverage. See 7.6.10 .
  • 156. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 156 of 201In V17, the switch between HS-DSCH and DCH might occur in any of the following cases:l The reason for handover between HS-DSCH and DCH is coverage. This caseincludes that the UE moves from an R99 cell to a HSDPA cell or from a HSDPA cellto a R99 cell.l D2H channel type switch triggered by traffic− Scenario 1: A 4A event triggers D2H channel type switch in a cell.The current service that is fit for the HS-DSCH is over the DCH for some reason(such as admission rejection). Both the UE and the best cell support HSDPA. The rateof the service on the current DCH is lower than 384 Kbps. In this case, the systemre-allocates the service from the DCH to the HS-DSCH in the best cell if the datatraffic of the UE increases (the RNC receives a 4A event measurement report).− Scenario 2: A 4A event triggers D2H switch between two cells at differentfrequencies but with the same coverage. See 7.6.10 .If the rate of service on the current DCH equals to 384 Kbps, no 4A event occurs. In this case, atimer is needed to trigger the D2H switch.The following attachment contains D2H switch signaling, according to V17C01B060:RNC_2006-10-30-11-31-49_based on trafficrarl D2H channel type switch triggered by a timer− Scenario 1: The timer triggers D2H switch in a cell.The current service that is suitable for the HS-DSCH is over the DCH for somereason (such as admission rejection). Both the UE and the best cell support HSDPA.In this case, the system re-configures the service from the DCH to the HS-DSCH inthe best cell if the channel type fit for service mapping has conflicted with the type ofthe current serving channel for a period of time (as specified by the HSDPA directretry timer).− Scenario 2: The timer triggers D2H switch in the case of inter-frequency direct retry.See 7.6.10 .To set the expiry time of the timer, run the command SETCOIFTIMER:HRetryTimerLen=5000;.The following attachment contains signaling in the case that the timer triggers D2H switch in acell, according to V17C01B060:RNC_2006-10-30-11-11-05_based on timer D2H.rar
  • 157. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 157 of 2017.7 Concept and Classification of HSUPA Handover7.7.1 Basic ConceptsIf the HSUPA is used, the following two types of links may coexist between a subscriber and thenetwork:l HSUPA link: Each UE can have only one HSUPA link with the network. Differentfrom the HSDPA, the HSUPA supports SHO. The HSUPA handover requiresmanagement of the HSUPA serving cell.l DPCH link: The handover functions supported by the DPCH link are the same asthose supported by the R99 system, including SHO, HHO, and handover betweensystemsHSUPA Serving CellThe E-DCH active set has three types of RL:l Serving E-DCH Cell: The UE receives AG scheduling from the serving E-DCH cell.l Serving E-DCH RLS: It refers to a cell set that contains at least the serving E-DCHcell. The UE can receive serving RGCH from such cells and perform softercombination. That is, the cells in the serving E-DCH RLS and the serving E-DCH cellbelong to the same NodeB.l Non-Serving RL: It means cells that belong to the E-DCH active set but to theserving E-DCH RLS. The UE can receive RGCH from these cells.The UE can receive the AGCH message from only one cell. This cell is the serving cell of theHSUPA. According to the protocol, the HSUPA serving cell and HSDPA serving cell for asubscriber must be the same one. If the best cell in the active set changes due to changes ofthe radio environment, the serving cell changes. That is, the serving cell is updated.HSUPA Channel Selection Policyl If all cells in the active set support the HSUPA, the E-DCH bears the uplink services.In other cases, the DCH bears the uplink services.l If all cells in the active set belong to the SRNC, the E-DCH bears the uplink services.In other cases, the DCH bears the uplink services (The lur interface in phase 1 of theproduct does not support the HSUPA).For these reasons, if a new cell added to the active set does not support the HSUPA or the newcell belongs to the DRNC, the channel type changes from the E-DCH to the DCH. In somecases, the channel type changes from the the DCH to the E-DCH.7.7.2 Classification of HSUPA HandoverThe HSUPA handover includes the following types:l Handover between two HSUPA cells
  • 158. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 158 of 201l Handover between a HSUPA cell and a non-HSUPA celll Handover between a HSUPA cell and a GSM/GPRS cell7.7.3 Signaling Flow and Message Analysis of HSUPA HandoverHandover Between Two HSUPA CellsThe handover between two HSUPA cells includes three scenarios as listed in Table 7-5.Table 7-5 Handover between two HSUPA cellsNo. Scenario Rules1Intra-frequency SHO between twoHSUPA cellsA 1A, 1B, 1C, or 1D event occurs.No non-HSUPA cell exists in the activeset before and after the active set isupdated.The RNC updates the active setbased on the measurement report.If the best cell changes, the RNCupdates the HSUPA serving cellby re-configuring the physicalchannel.2Intra-frequency HHO between twoHSUPA cellsA 1D event occurs.The intra-frequency HHO iscomplete through reconfigurationof the physical channel.3Inter-frequency HHO between twoHSUPA cellsA 2D event occurs and the compressedmode is enabled. The handover alsomight be triggered by a 2B event or aperiodic measurement report.The UE reports a 2D event to startthe compression mode andperform inter-frequencymeasurement. If the target cellallows the HSUPA access, theRNC allocates the UE to the targetHSUPA cell by re-configuring thephysical channel.Intra-frequency SHO Between Two HSUPA CellsThe UE moves from Cell 1 to Cell 2. Cell 2 and Cell 1 are adjacent cells at the same frequency.All cells in the active set support the HSUPA. Another HSUPA cell becomes the best cell as theUE moves, so a 1D event occurs. The RNC updates the HSUPA serving cell, and the HSUPAlink of the UE is handed over to Cell 2 from Cell 1.
  • 159. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 159 of 201Figure 7-36 Intra-frequency SHO between two HSUPA cellsFigure 7-37 shows the related signaling.Figure 7-37 Signaling for HSUPA cell update triggered by a 1D eventIf the monitor set reports a 1D event, the HSUPA serving cell also is updated. For example, theservice is over the E-DCH in HSUPA 1 that works as the serving cell. The signals of HSUPA 2 inthe monitor set become stronger. In this case, the UE reports a 1D event and the RNC adds
  • 160. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 160 of 201HSUPA 2 to the active set. At last, the RNC updates the serving cell is updated byre-configuring the physical channel. Figure 7-38 shows the related signaling:Figure 7-38 Signaling for HSUPA cell update triggered by a 1D event (reported by the monitorset)Intra-frequency HHO Between Two HSUPA CellsThe UE moves from Cell 1 to Cell 2. Cell 2 and Cell 1 are adjacent cells at the same frequency.The signals of the current HSUPA serving cell (Cell 1) become weak and those of Cell 2become stronger as the UE moves. In this case, a 1D event occurs. The RNC re-configures thephysical channel to finish the intra-frequency HHO.Figure 7-39 Intra-frequency HHO between two HSUPA cells
  • 161. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 161 of 201Figure 7-40 shows the related signaling:Figure 7-40 Signaling for intra-frequency HHO between two HSUPA cellsInter-frequency HHO Between Two HSUPA CellsThe UE moves from Cell 1 to Cell 2. Cell 2 and Cell 1 are adjacent cells at different frequencies.The signals of the current HSUPA serving cell (Cell 1) become weak and those of Cell 2become stronger as the UE moves. In this case, a 2D event occurs. The UE starts thecompression mode and performs inter-frequency measurement. If the target cell meets thehandover requirements and the E-DCH allows the service setup, the RNC allocates the UE fromCell 1 to Cell 2 by re-configuring the physical channel and sets up the HSUPA link of the UE onthe E-DCH of Cell 2.Figure 7-41 Inter-frequency HHO between two HSUPA cellsFigure 7-42 shows the related signaling:
  • 162. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 162 of 201Figure 7-42 Signaling for inter-frequency HHO between two HSUPA cellsInter-RNC HSUPA HandoverHSUPA Phase 1 does not support HSUPA handover between lur interfaces. If a DRNC cell isadded to the active set, the service must be allocated to the DCH from the E-DCH. After themigration, all cells in the active set belong to the SRNC. In this case, the service is allocated tothe E-DCH from the DCH, provided all cells in the active set support the HSUPA. Figure 7-43shows the inter-RNC HSUPA handover:
  • 163. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 163 of 201Figure 7-43 Inter-RNC HSUPA handoverHandover Between a HSUPA Cell and a Non-HSUPA CellIn the initial stage of use of the HSUPA, usually it is hard to implement continuous coverage ofHSUPA cells. In this case, handover between a HSUPA cell and a non-HSUPA cell occurs whenthe UE moves. The handover between a HSUPA cell and a non-HSUPA cell includes sixscenarios as listed in Table 7-6.Table 7-6 Handover between a HSUPA cell and a non-HSUPA cellNo. Scenario Rules1SHO from a HSUPA cell to anon-HSUPA cellA 1A, 1C, or 1D event occurs.The RNC updates the active set basedon the measurement report, and thenallocates the service from the E-DCH tothe DCH through RB reconfiguration.2Intra-frequency HHO from aHSUPA cell to a non-HSUPA cellA 1D event occurs.The RNC allocates the service from theE-DCH to the DCH through RBreconfiguration.3Inter-frequency HHO from aHSUPA cell to a non-HSUPA cellA 2b event occurs. The handoveralso might be triggered by aperiodic measurement report.The UE reports a 2D event to start thecompression mode and performinter-frequency measurement. If thetarget cell meets the handoverrequirements and its DCH allows servicesetup, the RNC allocates the servicefrom the E-DCH to the DCH through RBreconfiguration.
  • 164. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 164 of 2014SHO from a non-HSUPA cell to aHSUPA cellA 1B or 1C event occurs.The RNC updates the active set basedon the measurement report. If all cells inthe updated active set support theHSUPA, the channel mapping policydetermines whether the service isallocated to the E-DCH through RBreconfiguration.5Intra-frequency HHO from anon-HSUPA cell to a HSUPA cellA 1D event occurs.The intra-frequency HHO of the DCH iscomplete through reconfiguration of thephysical channel. If the target cell allowsthe HSUPA access, the RNC allocatesthe service to the E-DCH through RBreconfiguration.6Inter-frequency HHO from anon-HSUPA cell to a HSUPA cellA 2b event occurs. The handoveralso might be triggered by aperiodic measurement report.The UE reports a 2D event to start thecompression mode and performinter-frequency measurement. If thetarget cell meets the handoverrequirements, the handover is completethrough the following two steps:The intra-frequency HHO of the DCH iscomplete through reconfiguration of thephysical channel.If the target cell allows the HSUPAaccess, the RNC allocates the service tothe E-DCH through RB reconfiguration.7.7.4 SHO from a HSUPA Cell to a Non-HSUPA CellCell 2 and Cell 1 are adjacent cells at the same frequency. If signals of Cell 2 become strongenough to trigger a 1A or 1C event as the UE moves, the RNC adds Cell 2 to the active set. Inthis case, non-HSUPA cells exist in the active set. The RNC allocates the service from theE-DCH to the DCH through RB reconfiguration according to the HSUPA channel selectionpolicy.
  • 165. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 165 of 201Figure 7-44 SHO from a HSUPA cell to a non-HSUPA cellFigure 7-45 shows the handover signaling:
  • 166. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 166 of 201Figure 7-45 Addition of an R99 cell when the service is on the E-DCHIntra-frequency HHO from a HSUPA Cell to a Non-HSUPA CellThe UE moves from Cell 1 to Cell 2. Cell 2 and Cell 1 are adjacent cells at the same frequency.If signals of Cell 2 become stronger as the UE moves, the UE reports a 1D event. In this case,the RNC allocates the service to the DCH from the E-DCH through RB reconfiguration (Theintra-frequency HHO from a HSUPA cell to an R99 cell is complete in one step).
  • 167. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 167 of 201Figure 7-46 Intra-frequency HHO from a HSUPA cell to a non-HSUPA cellFigure 7-47 shows the related signaling:Figure 7-47 Signaling for intra-frequency HHO from a HSUPA cell to a non-HSUPA cellInter-frequency HHO from a HSUPA Cell to a Non-HSUPA CellThe UE moves from Cell 1 to Cell 2. Cell 2 and Cell 1 are adjacent cells at different frequencies.If a 2D event occurs as the UE moves, the UE starts the compression mode and performs theinter-frequency measurement. If the target cell meets the handover requirements, the RNChands over the UE from Cell 1 to Cell 2 (HHO) through RB reconfiguration.
  • 168. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 168 of 201Figure 7-48 Inter-frequency HHO from a HSUPA cell to a non-HSUPA cellFigure 7-49 shows the related signaling:
  • 169. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 169 of 201Figure 7-49 Signaling for inter-frequency HHO from a HSUPA cell to a non-HSUPA cell7.7.5 SHO from a Non-HSUPA Cell to a HSUPA CellThe UE moves from Cell 1 to Cell 2. Cell 2 and Cell 1 are adjacent cells at the same frequency.The DPCH of Cell 1 bears the BE service of the UE. If signals of Cell 1 become weak enough totrigger a 1B event as the UE moves, the UE reports the 1B event. In this case, the RNC deleteCell 1 from the active set. All cells in the updated active set support the HSUPA. If the service isfit for the E-DCH, the RNC allocates the service from the DCH to the E-DCH through RBreconfiguration.
  • 170. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 170 of 201Figure 7-50 SHO from a non-HSUPA cell to a HSUPA cellFigure 7-51 shows the related signaling:Figure 7-51 SHO from a non-HSUPA cell to a HSUPA cell (triggered by a 1B event)Intra-frequency HHO from a Non-HSUPA Cell to a HSUPA CellThe UE moves from Cell 1 to Cell 2. Cell 2 and Cell 1 are adjacent cells at the same frequency.If signals of Cell 2 become strong enough as the UE moves, the UE reports a 1D event. At first,the intra-frequency HHO of the DCH is competed through reconfiguration of the physicalchannel. The target cell then determines whether the service can be set up on the E-DCH if theservice is fit for the E-DCH. If the E-DCH of the target cell allows setup of the service, the RNCallocates the service to the E-DCH through RB reconfiguration (The intra-frequency HHO froman R99 cell to a HSUPA cell is complete through two steps: Carry out intra-frequency HHO from
  • 171. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 171 of 201a DCH to another DCH, and then perform RB reconfiguration from the DCH to the E-DCH in theHSUPA cell).Figure 7-52 Intra-frequency HHO from a non-HSUPA cell to a HSUPA cellFigure 7-53 shows the related signaling:Figure 7-53 Signaling for intra-frequency HHO from a non-HSUPA cell to a HSUPA cellInter-frequency HHO from a Non-HSUPA Cell to a HSUPA CellThe UE moves from Cell 1 to Cell 2. Cell 2 and Cell 1 are adjacent cells at different frequencies.The UE is connected to the DPCH of Cell 1. If signals of Cell 2 become strong enough as theUE moves, a 2D event occurs and the UE starts the compression mode. If the target cell meetsthe handover requirements, the inter-frequency HHO of the DCH is complete. The target cellthen determines whether the service can be set up on the E-DCH if the service is fit for the
  • 172. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 172 of 201E-DCH. If the E-DCH of the target cell allows setup of the service, the RNC allocates theservice to the E-DCH through RB reconfiguration.Figure 7-54 Inter-frequency HHO from a non-HSUPA cell to a HSUPA cellThe signaling is to be supplemented.7.7.6 Handover Between a HSUPA Cell and a GSM/GPRS CellThe handover between different systems is caused by coverage or service. The use of theHSUPA does not impact triggering conditions and decision of the handover between differentsystems. Thus, the handover between a HSUPA cell and a GPRS cell is similar to that betweenan R99 cell and a GPRS cell.The signaling flow is as follows:l The UE starts the compression mode.l The UE measures the GPRS cell.l The RNC carries out handover from a HSUPA cell to a GPRS cell based on themeasurement report from the UE.For details, see the related section earlier in this document.7.7.7 Direct Retry of HSUPAThe direct retry of the HSUPA can balance load between an R99 cell and a HSUPA cell atdifferent frequencies or between different HSUPA cells. Direct retry of the HSUPA includes thefollowing three scenarios:l Direct retry from an R99 cell to a HSUPA celll Direct retry from a HSUPA cell to an R99 celll Direct retry from a HSUPA cell to another HSUPA cell
  • 173. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 173 of 201Direct Retry from an R99 Cell to a HSUPA CellAn R99 cell and a HSUPA cell are at different frequencies but with the same coverage. Directretry from an R99 cell to a HSUPA cell might occur in any of the following cases:l In the R99 cell, the UE originates a service that is fit for the E-DCH.l The traffic of the UE that is over the FACH in the R99 cell increases and the serviceis fit for the E-DCH.l A service that should have been set up over the E-DCH according to the servicemapping rules is over the DCH of the R99 cell. The system periodically checks theservices that conflict with the bearer policy and attempts to retry the services to theE-DCH.The system periodic measurement uses the HSDPA retry timer (ms). The related MML is SETCOIFTIMER.Figure 7-55 Direct retry from an R99 cell to a HSUPA cellDirect Retry from a HSUPA Cell to an R99 CellDirect retry from a HSUPA cell to an R99 cell might occur if the UE requests for setup of the CSservice in the HSUPA cell.Figure 7-56 Direct retry from a HSUPA cell to an R99 cellDirect Retry from a HSUPA Cell to another HSUPA CellDirect retry between two HSUPA cells at different frequencies but with the same coverage mightoccur in any of the following cases:l The HSUPA UE’s request for setup of the PS service is rejected by the HSUPA cell.
  • 174. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 174 of 201l The switch from the FACH to the E-DCH in the case of traffic increase is rejected bythe HSUPA cell.l The switch from the DCH to the E-DCH is rejected by the HSUPA cell.Figure 7-57 Direct retry from a HSUPA cell to another HSUPA cell7.7.8 Switch between Channel TypesAfter the HSUPA is used, a channel state is added: the CELL_DCH state of the E-DCH. TheHSUPA related switch between channel types involves switch between the CELL_FACH andthe CELL_DCH (DCH).The direct retry algorithm might trigger switch between the CELL_FACH and the CELL_DCH(DCH). In addition, a timer for periodic measurement is available in the system. Once the timerexpires, the system checks whether the current bearer mode conflicts with the bearer policy. If aconflict exists, the system triggers switch between channel types.Traffic triggers switch between the CELL_DCH (E-DCH) and the CELL_FACH. Measurementreports (4A) sent by the UE trigger switch from the CELL_FACH to the CELL_DCH. The internalmeasurement of the RNC triggers switch from the CELL_DCH(E-DCH) and the CELL_FACH(According to the current protocol, the UE measurement report does not support measurementof the E-DCH).Figure 7-58 Switch between HSUPA channel types
  • 175. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 175 of 2017.8 Handover from WCDMA to GSMIf the UE performs inter-RAT handover for CS domain services, the flow for CS domainhandover from WCDMA to GSM is followed.Description to Typical Handover Flow from WCDMA to GSMThe typical handover flow includes stages as below:Measurement control > measurement report > handover judgment > handover implementation.l During the measurement control stage, the network informs UE of parameters to bemeasured by sending the measurement control message.l During the measurement report stage, the UE sends the measurement controlmessage to the network.l During the handover judgment stage, the network decides to handover accordingmeasurement report.l During handover implementation, the UE and network follow the signaling flow andrespond according to signaling.When dual-mode UE moves at the edge of WCDMA system and might perform inter-RAThandover, the WCDMA RNC informs UE of starting inter-RAT measurement. After the UEperforms inter-frequency measurement and reports measurement result, the RNC judgeswhether to start signaling flow for inter-frequency handover according to measurement result.The WCDMA system uses code division multiple access (CDMA) technology for access, so theconnected UE in all time works with a specified frequency. When the dual-mode UE needs toperform inter-RAT measurement and keeps a conversation, it and the WCDMA system mightstart compression mode (if the UE has a transceiver, the starting compression mode iscompulsory. If the UE has two transceivers, the UE can test GSM cells without startingcompression mode).Flows of Handover from WCDMA to GSMFigure 7-59 shows the signaling flow for handover from WCDMA to GSM.
  • 176. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 176 of 201Figure 7-59 Signaling flow for handover from WCDMA to GSMFigure 7-60 shows the tracing signaling of handover from WCDMA to GSMFigure 7-60 Tracing signaling of handover from WCDMA to GSMSignaling Flow at UTRAN SideThe signaling flow at UTRAN side proceeds as below:l When the UE moves outwards at the edge of a cell in the WCDMA network and theconditions for report 2D event meet the RNC configuration, the UE sends ameasurement report of occurrence of 2D event. This report indicates that the signalsat the serving frequency in the WCDMA network are weak and other frequencies orsignals of other systems are required.
  • 177. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 177 of 201l The RNC starts compression mode to perform inter-frequency and inter-RATmeasurement. The RNC sends the RL RECONFIG PREPARE message to NodeB toprepare for starting compression mode. The message contains the samplingsequence of compression mode and related parameters of sampling sequence ofcompression mode, including TGSN, TGL, TGD, TGPL, compression mode method,downlink compression frame type, and power control parameters in compressionmode.l After the NodeB prepares resources, it sends the RL RECONFIG READY messageto the RNC.l The RNC sends PHYSICAL CHANNEL RECONFIG message to UE and prepare forstarting compression mode. This includes the activation time, the samplingsequence of compression mode and related parameters of sampling sequence ofcompression mode. The parameters include TGCFN, TGMP, TGSN, TGL, TGD,TGPL, RPP, ITP, compression mode method, downlink compression frame type,and power control parameters in compression mode.l After the RNC confirmed that the UE has received the PHYSICAL CHANNELRECONFIG message, it sends NodeB the RL RECONFIG COMMIT message,indicating the time for NodeB to start compression mode.l After the UE completes related configuration according to new configuration data, itsends RNC the PHYSICAL CHANNEL RECONFIG COMPLETE message. Now thecompression mode is available.l The RNC immediately sends the measurement control message, which commandsUE to perform inter-RAT measurement. The message includes measurementparameters like the list of GSM cells, the information about frequency of cells,measurement filter coefficient.l The UE sends a measurement report, indicating the RSSI measurement value ofGSM cells.l The UE sends a measurement report, indicating the BSCI confirmation of GSM cells.l After the handover conditions are met according to judgment, the RNC sends aSRNS relocation request to CN. The request includes SRNS relocation type (the UEmust participate in inter-RAT handover), reason for SRNS relocation (usuallyrelocation desirable for radio reasons), source PLMN, source SAI, and target CGI(including PLMN and LAC).l After the GSM side allocates related resources, the CN sends RNC theRELOCATION COMMAND, which includes the IE layer 3 information. The IEcontains the related resources allocated by GSM network.l The RNC sends UE the HANDOVER FROM UTRAN COMMAND message. Themessage includes the RAB ID, activation time, GSM frequency, and GSM messagesin forms of BIT string.l The UE powers off the transmitter according to GSM configuration, so no signals arein uplink. Consequently the NodeB sends the SIR ERROR report. This message isoptional in the flow.l After the UE accesses the GSM network, the CN sends the IU RELEASECOMMAND message to inform RNC of releasing resources used by UE in theWCDMA network.l The RNC immediately sends CN the IU RELEASE COMPLETE message. Themessage 16 and message 17 are to release the radio resources of NodeB. What is
  • 178. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 178 of 201different from normal releasing flow is that the air interface does not send the RRCconnection release message, because the UE is using WCDMA network. Thereforethe NodeB releases radio resources without informing UE of the release.
  • 179. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 179 of 2017.9 Handover from GSM to WCDMADescription of Handover from GSM to WCDMAIf a GSM cell has WCDMA neighbor cells, the measurement control is sent in systeminformation. The dual-mode UE performs inter-RAT measurement in idle slots and reports themeasurement result. According to the measurement result, the BSC judges to start signalingflow for inter-RAT handover. The GSM network uses the time division multiple accesstechnology, so the inter-RAT measurement is performed in idle slots. The GSM system is notinvolved in supporting compression mode.Flows of Handover from GSM to WCDMAFigure 7-61 shows the signaling flow for handover from GSM to WCDMA.Figure 7-61 Signaling flow for handover from GSM to WCDMAFigure 7-62 shows the tracing signaling of handover from GSM to WCDMA
  • 180. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 180 of 201Figure 7-62 Tracing signaling of handover from GSM to WCDMASignaling Flow at UTRAN Sidel According to the handover algorithm and measurement information of the sourceBSS in the GSM network, the source BSS judges that UE must hand over to theUTRAN cell. After the BSS sends CN the handover request, the MSC sends RNCthe RANAP_RELOCATION_REQUEST massage. The message contains the IMSIof UE, CN field identity, the identity of target cell, encryption information, integrityprotection information, IU signaling connection ID, handover reason, RABconfiguration, and information about user plane.l The RNC allocates radio resources for the SRNS relocation and configures NodeBduring RL SETUP process. The NodeB start transmitting and receiving radio signals.l After the NodeB sets up RL, it replies the RL SETUP RESPONSE message.l The RNC allocates radio resources and other parameter packets. The parameterpackets include U-RNTI, RAB, transport layer information, and physical layerinformation. The parameters are configured to UE in three forms:− Complete configuration: clearly provide parameters in each layer− Pre-configuration (pre-defined): the system broadcast multiple sets of parametertemplates in the system information 16 and configure template number and necessaryparameter to UE. The UE listens to the system information of UTRAN and obtain theparameter configuration according to template number.− Pre-configuration (default): The protocol 25.331 provides 10 sets of defaultparameters and specifies an identity to each default parameter. The RNC configuresthe default identity and other necessary information to UE.l The RNC sends the previous information through the IU interface RELOCATIONREQUEST ACKNOWLEDGE message (in the IE RNC Container) to CN whichforwards the information to the source BSS. The source BSS sends the informationto UE. According to the default parameter identity configured by RNC, the UEobtains related access parameters in the pre-configuration (default) in the systeminformation. After this, the UE synchronizes to NodeB directly and later sends data inuplink.
  • 181. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 181 of 201l After the NodeB detects uplink synchronization, it sends RNC the RL RESTORE INDmessage.l After the RNC receives RL RESTORE IND message sent by NodeB, it sends CN theRELOCATION DETECT message, indicating that the UE has already handed overfrom the 2G network to the 3G network. The message does not contain othercontents.l The UE sends RNC the HANDOVER TO UTRAN COMPLETE message, indicatingthe completion of handover. The message might also contain the encryptedsequence number and its activation time for each CN field.l After the RNC receives the HANDOVER TO UTRAN COMPLETE message from UE,it immediately sends UE the UTRAN MOBILITY INFORMATION message. Thismessage contains the values of timers used by UE, related information about CNfield, UE ID, and so on.l After the RNC receives the HANDOVER TO UTRAN COMPLETE message from UE,it sends UE the UTRAN MOBILITY INFORMATION while it sends CN theRELOCATION COMPLETE message which contains nothing. After the RNCreceives the confirmation message from UE according to the 17th message, thehandover flow from the 2G network to 3G network is complete. The followingmessages are about the measurement control process of UE and NodeB, and aboutthe UEs query of capacity.
  • 182. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 182 of 2017.10 Handover from WCDMA to GPRSDescription of Handover form WCDMA to GRPSThe inter-RAT handover from WCDMA to GRPS caters for the handover from WCDMA PSdomain service to GPRS system. The RNC initiatively commands UE to reselect an inter-RATcell with signaling, which triggers inter-RAT handover. If the traffic flow for slow-speed PSservices, the UE might be in CELL PCH or URA PCH state, the UE can perform inter-RAThandover by initiatively originating cell reselection according to system information.Flows of Handover form WCDMA to GRPSThe inter-RAT handover flow initiatively originated by RNC proceeds as below:Figure 7-63 and Figure 7-64 shows the flow for handover from WCDMA to GPRS.
  • 183. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 183 of 201Figure 7-63 Flow of handover from WCDMA to GPRS (1)Figure 7-64 Flow of handover from WCDMA to GPRS (2)Figure 7-65 shows the tracing signaling of handover from WCDMA to GPRS.
  • 184. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 184 of 201Figure 7-65 Tracing signaling of handover from WCDMA to GPRSSignaling Flow at UTRAN SideThe signaling flow at UERAN side proceeds as blow:l The UE sends the measured 2D report, indicating the quality of the serving cell isworse.l The RNC sends NodeB the RL RECONFIG PREPARE message, indicating NodeBto prepare for starting compression mode. The message contains the samplingsequence of compression mode and related parameters of sampling sequence ofcompression mode, including TGSN, TGL, TGD, TGPL, compression mode method,downlink compression frame type, and power control parameters in compressionmode.l After the NodeB prepares resources, it sends RNC the RL RECONFIG READYmessage.l The RNC sends UE the PHYSICAL CHANNEL RECONFIG message, indicating UEto prepare for starting compression mode. The message contains TGCFN, TGMP,TGSN, TGL, TGD, TGPL, RPP, ITP, compression mode method, downlinkcompression frame type, and power control parameters in compression mode.l After the RNC confirms that the UE has received the PHYSICAL CHANNELRECONFIG message, it sends NodeB the RL RECONFIG COMMIT message,indicating the time for start compression mode.l After the UE completes related configuration according to the new configuration data,it sends RNC the PHYSICAL CHANNEL RECONFIG COMPLETE message. Thisindicates that the compression mode is ready.l The RNC immediately sends the measurement control and commands UE toperform inter-RAT measurement. The message contains the list of GSM cells, theinformation about frequency of cells, measurement filter coefficient.l The UE sends a measurement report, indicating the RSSI measurement value ofGSM cells.l The UE sends a measurement report, indicating the BSCI confirmation of GSM cells.
  • 185. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 185 of 201l After the conditions are met according to judgment, the RNC originates the SRNSrelocation flow and sends UE the CELL CHANGE ORDER FROM UTRAN message.The message indicates UE to handover to the GPRS network by originating cellreselection. The message contains the IEs of target cell like BSIC and BAND IND(900 or 1800), BCCH ARFCN, and NC mode.l Because the UE need to reselect a GRPS cell, it powers off the transmitter toWCDMA network. The NodeB sends the SIR ERROR report, which is optional in theflow.l Because the UE need to reselect a GRPS cell, it powers off the transmitter toWCDMA network. The NodeB sends the RL FAILURE report, which is optional in theflow.l After the UE accesses the inter-RAT cell,− If restoring the PDP context is not required, the RNC directly receives the IURELEASE COMMAND at the IU interface.− If restoring the PDP context is required, the UE obtains the SRNS CONTEXTinformation from the source RNC. The source RNC will receive the SRNSCONTEXT REQUEST message with mainly an RAB ID.l The RNC sends CN the SRNC CONTEXT RESPONSE message, indicating theGTP of each RAB ID and the uplink and downlink sequence number of PDCP.l The CN sends RNC the SRNS DATA FORWARD COMMAND message, indicatinguser plane to transmit data. By the message, the CN informs RNC of target transportlayer address and tunnel ID of each RAB data forward.l After data is transmitted, the CN sends RNC the IU RELEASE COMMAND message,indicating RNC to release the sources of the UE.l The RNC sends CN the IU RELEASE COMPLETE message. The message 18 andmessage 19 are to release the radio resources of NodeB. What is different fromnormal releasing flow is that the air interface does not send the RRC connectionrelease message, because the UE is using WCDMA network. Therefore the NodeBreleases radio resources without informing UE of the release.
  • 186. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 186 of 2017.11 Handover from GRPS to WCDMASignaling Flows of Handover from GRPS to WCDMAFigure 7-66 and Figure 7-67 shows the signaling flow for handover from GPRS to WCDMA.Figure 7-66 Signaling flow for handover from GPRS to WCDMA (1)
  • 187. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 187 of 201Figure 7-67 Signaling flow for handover from GPRS to WCDMA (2)Signaling Flow at UTRAN SideThe signaling flow at UTRAN side proceeds as below:l The UE reselects a UTRAN cell. During the reselection of UTRAN cell, the UEoriginates the RRC connection setup process, with the reason INTERRATCELLRESELECTION.l After the RNC connection is set up, the UE initiatively originates the INIT DT processand sets up the SCCP connection at IU interface and the signaling connection in theCN NAS layer. Later the UE NAS layer and CN NAS layer exchange messages byDT process.l The CN commands the RNC to allocate related resources by sends the RABASSIGNMENT REQUEST message at the IU interface. The message contains theRAB ID, QoS, uplink and downlink sequence number of GPT-U, and sequencenumber of PDCP.l The RNC allocates related resources and informs NodeB by sending RL SETUPmessage.l The RNC sends UE the RB SETUP REQUEST message to UE. The messagecontains the downlink sequence number of PDCP.l The UE sends RNC the RB SETUP COMPLETE message. The message containsthe downlink sequence number of PDCP. The RNC configure the uplink sequencenumber of PDCP from CN and the downlink sequence number from UE to the PDCPsample corresponding to the specified RAB.l The RNC sends CN the RAB ASSIGNMENT RESPONSE message.
  • 188. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 188 of 201l While the traffic flow is being restored, the RNC PDCP sample should drop CN datapacket of which the sequence number of downlink PDCP is smaller than thesequence number of downlink PDCP replied by UE. The UE should drop the datapacket of which the sequence number of uplink PDCP is smaller than the sequencenumber of uplink PDCP configured by UTRAN/CN.
  • 189. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 189 of 2017.12 Parameters of Handover from 3G to 2G NetworkHandover Judgment ProcessNow the periodic report is used in inter-frequency handover judgment.According to the protocol 25.331, the 2D event indicates that the quality of active set is lowerthan a threshold. In the current handover algorithms (including inter-frequency handoveralgorithm), the 2D event report serves as a rule for starting compression mode and performinginter-frequency or inter-RAT measurement. Therefore, if the quality of UE active set is worse ininter-RAT measurement, you need to measure the inter-RAT quality only. If the quality of UEactive set becomes better, namely, the UTRAN receives the 2F event report, the UE stopscompression mode and stops inter-RAT measurement. For the detailed judgment of 2D/2Fevent, see the 3GPP TS 25.331.The following paragraphs describe the inter-RAT handover judgment algorithm using periodicreports.After the network receives the periodic report filtered by layer 3, it compares the obtainedinter-RAT measurement result with the preset threshold. The network starts delay trigger timerTrigger-Timer if the following formula is met:Mother_RAT + CIO >= Tother_RAT + H/2 (formula 1)Wherein,l Mother_RAT indicates the obtained inter-RAT measurement result.l CIO indicates the cell individual offset, namely, the offset configured by theinter-RAT cell.l Tother_RAT indicates the inter-RAT quality threshold.l H indicates hysteresis. The hysteresis helps to reduce mal-operations due tofluctuation of signals.After the Trigger-Timer starts and before it expires, the Trigger-Timer is stopped and the networkkeeps waiting for receiving inter-RAT measurement report if the following condition is met:Mother_RAT + CIO < Tother_RAT - H/2 (formula 2)If the Trigger-Timer expires, the system judges for inter-RAT handover.List of Handover ParametersTable 7-7 lists the parameters of handover from 3G to 2G.
  • 190. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 190 of 201Table 7-7 Parameters of handover from 3G to 2GParameter MeaningDefaultconfigurationMMLCommands formodifyingandqueryingApplicationscopeFilterCoefFilter coefficientat layer 3 ofinter-RATmeasurementD3For RNCs:inter-RAThandoveralgorithmparameter:set RNCs byexecutingSETINTERRATHO, queryRNCs byexecutingLSTINTERRATHO.For cells:inter-RAThandoveralgorithmparameter:add cells byexecutingADDCELLINTERRATHO,query cellsby executingLSTCELLINTERRATHO, andmodify cellsby executingMODCELLINTERRATHORNC/CellGsmRSSICSThd,GsmRSSIPSThd,GsmRSSISIGThdThe judgmentthreshold forinter-RAThandover21, namely, –90 dBmHystThdInter-RAThandoverhysteresis4, namely, 2 dBTimeToTrigForVerifyThe time totrigger delayverified byinter-RAT0, namely, 0sTimeToTrigForNonVerifyNon-verifieddelay trigger time65535, namely,handover tonon-verified GSMcell is prohibited.PenaltyTimeForSysHoInter-RAThandover penaltytime30, namely, 30sInterRatCSThdFor2DRSCP,InterRatPSThdFor2DRSCP,InterRatSigThdFor2DRSCP,InterRatCSThdFor2FRSCP,InterRatPSThdFor2FRSCP,InterRatSigThdFor2FRSCPThestarting/stoppingthreshold forinter-RATmeasurementwith RSCP as themeasurementvalue (CS, PS,and singlesignaling)The default values ofthem are as below:InterRatCSThdFor2DRSCPInterRatPSThdFor2DRSCP: –95;InterRatCSThdFor2FRSCPInterRatPSThdFor2FRSCP: –90;InterRatSigThdFor2DRSCPInterRatSigThdFor2FRSCP: –115For RNCs:set RNCs byexecutingSETINTERFREQHO andquery RNCsby executingLSTINTERFREQHO.For cells:RNC/Cell
  • 191. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 191 of 201InterRATCSThdFOR2DEcNo,InterRATPSThdFOR2DEcNo,InterRATSigThdFOR2DEcNo ,InterRATCSThdFor2FEcNo,InterRATPSThdFOR2FEcNo,InterRATSigThdFOR2FEcNoThestarting/stoppingthreshold forinter-RATmeasurementwith Ec/No as themeasurementvalue (CS, PS,and singlesignaling)–24, namely, –24dBmadd cells byexecutingADDCELLINTERFREQHO,query cellsby executingLSTCELLINTERFREQHO,and modifycells byexecutingMODCELLINTERFREQHOHYSTTHDHysteresis. Thehysteresis andinter-RAT qualitythreshold decideswhether to triggerinter-RAThandoverjudgment. It canbe smaller inareas with smallshadow fading. Itcan be greater inareas with greatshadow fading.4CellIndividalOffsetThe individualoffset ofinter-RAThandover cells.The UE uses itwith the initialmeasured valueof the cell as themeasurementresult forhandoverjudgment of UE.0Set cells byexecutingADDINTERRATNCELL, querycells byexecutingLSTINTERRATNCELL, andmodify it byexecutingMODINTERRATNCELLCell& Note:Table 7-7 lists the starting/stopping threshold of compression mode and inter-RAT handoverthreshold in terms of signaling, CS, and PS.The new protocol CR defines that the UE will not report the not verified GSM measurement.
  • 192. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 192 of 2017.13 Data Configuration for Supporting Bi-directional Roaming andHandover Between WCDMA and GSM/GPRSTo support bidirectional roaming and handover between 3G networks and GSM/GPRS, tosupport PLMN selection, to support reselection from the 2G network to the 3G network by UE,and to support reselection from the 3G network to the 2G network by UE, data configuration isnecessary in the 2G and 3G system.2G MSC Data ConfigurationIf the system support the handover from the 2G network to the 3G network, data configurationon the 2G MSC is necessary. According to the 2G-to-3G interoperation strategy of Huawei, thehandover from the 2G network to the 3G network supports cell reselection, so dataconfiguration on the 2G MSC is unnecessary.Data Configuration on the 2G MSCData configuration on the 2G MSC proceeds as below:l Add the matching record of 3G MSC/VLR code corresponding to RNC IDs in the listof cell in the location area. The RNC ID is in the format of: MCC + MNC + LAC +RNC-ID. Select GCI as the type of location area. Select Near VLR area as theproperty of location area.l Add the corresponding LAI record and the corresponding 3G MSC/VLR code. LAI =MCC + MNC + LAC. Select Near VLR area as the property of location area.l Change the supported MAP version to PHASE 2PLUS in the MAP function flowconfiguration table.l Configure the data at the MTP layer and guarantee the signaling transmissionbetween the 2G MSC and the 3G MSC.l Configure the data at the SCCP layer, configure the corresponding record of the 3GMSC in the GT list, SCCP SSN list, and SCCP DSP list, and guarantee thetransmission of MAP handover-related signaling between MSCs.l Configure inter-MSC trunk data like configuring common data.The following paragraphs take Huawei 2G MSC as example. For the MSC, two tables are usedfor data configuration: location area cell table and neighbor cell table.l Location Area Cell Configuration TableFigure 7-68 shows the data configuration of target 3G cell in the location area cell table.
  • 193. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 193 of 201Figure 7-68 Data configuration in the location area cell tablePay attention to the following fields:− GCI code− Location area MSC code− Location area VLR code− Type of location area− Property of location areaContent of GCI code: corresponding to LAI and RNC ID of the target 3G cell forhandover. Query the LAI by running the command LST AC. Query the RNC ID byrunning the command LST RNCBASIC. You can also obtain the PLMN code of theRNC by running the command LST RNCBASIC.Content of location area MSC code: the code of MSC configured by MSOFTX3000of the corresponding 3G network. Query it by running the command LST INFOMSCcommand on the MSOFTX3000 client.Type of location area: LAI + RNC ID correspond to GCI.Property of location area: the configuration is Near VLR area.l Neighbor Cell Configuration TableFigure 7-69 shows the data configuration of neighbor cell configuration table.
  • 194. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 194 of 201Figure 7-69 Data configuration of neighbor cell configuration tablePay attention to the following fields:− GCI code− Neighbor cells− The GCI code of 2G source cell corresponding to GCI code.− Fill from the neighbor cell 1 to the neighbor 2…. The content to be filled in theneighbor cell 1 is the LAI + RNC ID of target 3G cell for handover. Query the LAI oftarget 3G cell by running the command LST AC. Query the RNC ID by running thecommand LST RNCBASIC.Added Data Configuration on BSCsl SI for Supporting the Roaming from GSM to WCDMATo support the roaming from GSM to WCDMA, the GSM BSS must complete sendingthe following system information:− Add data of WCDMA cells, including downlink frequency, primary scramble,diversity indicator, MCC, MNC, LAC, RNC ID, and CELL ID.− Add the information about inter-RAT cell measurement and roaming control in theidle mode. The information contains the following parameters:Qsearch_I: the level threshold for searching for 2G cells in the idle modeFDD_Qoffset: the level offset of 3G cell reselectionFDD_Qmin: the level threshold of 3G cell reselection− The previous information contained in the system information 2ter and 2quater is sentto UE.− The UE perform inter-RAT cell reselection based on previous information.l SI for Supporting the Handover from GSM to WCDMATo support the handover from GSM to WCDMA, the GSM BSS must complete sendingthe following system information:
  • 195. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 195 of 201Add the data of the WCDMA cell. The data contains:− Downlink frequency point− Primary scramble− Diversity indicator− MCC− MNC− LAC− RNC ID− CELL ID− Level threshold for handing over to the cellAdd the measurement control information of inter-RAT cells for UE in theconnection mode, including Qsearch_C, namely, the level threshold for searching for3G cells in the connection mode.The previous information contained in the system information MEASUREMENTINFORMATION is sent to UE.When the level of UE in the serving cell meets the conditions for Qsearch_C, thesystem starts measure 3G cells and sends the periodic reports to BSC.The BSC originates the handover to WCDMA.The following paragraphs take the configuration of Huawei BSC as example.l Adding External 3G CellsAdding external 3G cells proceeds as below:− Select setting up cells dynamically− Add external cells− Add external 3G cells, as shown in Figure 7-70.
  • 196. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 196 of 201Figure 7-70 Configuration table for external 3G cellsPay attention to several fields: MCC, MNC, LAI, RNC ID, CELL ID, downlinkfrequency point, and scramble. Using system defaults is recommended for unlistedfields.− MCC: query it by running the command LST RNCBASIC on the corresponding RNCclient− MNC: query it by running the command LST RNCBASIC on the correspondingRNC client− LAI: query it by running the command LST AC on the corresponding RNC client− RNC ID: query it by running the command LST RNCBASIC on the correspondingRNC client− CELL ID: query it by running the command LST CELL on the corresponding RNCclient& Note:The query result is decimal. It can be filled in the CELL ID field after it is converted to hex andremoved of the highest bit.Downlink frequency point: query it by running the command LST CELL on thecorresponding RNC client and then inputting the corresponding CELL ID in the CELLScramble: query it by running the command LST CELL on the corresponding RNCclient and then inputting the corresponding CELL ID in the CELLl Configuring Target 3G Cells as the Inter-RAT Neighbor Cell of GSMConfiguring target 3G cells as the inter-RAT neighbor cell of GSM proceeds as below:− Select setting cells dynamically
  • 197. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 197 of 201− Modify the property of external cells− Select external cells− Modify the neighbor relationship, as shown in Figure 7-71.Figure 7-71 Configuration table for GSM inter-RAT neighbor cells& Note:The target cell for handover from the 3G network can be the directional neighbor cell of GSMonly.l Configuring Parameters for 2G ReselectionConfiguring parameters for 2G reselection proceeds as below:− Select setting cells dynamically− Select the current cell− Modify the parameters for inter-RAT system information, as shown in Figure 7-72.
  • 198. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 198 of 201Figure 7-72 Configuration table for 2G reselection parametersThe configuration table for 3G system information includes the following parameters:− Type of measurement reports: common measurement reports− Number of best cells in the GSM band: the default value is 3− Threshold for searching for 3G cells in the idle mode: the values range from 0 to 15− Offset of FDD cell reselection: When the mean receiver level of 3G cells isFDD_Qoffset greater than that of the serving cell, the UE can reselect 3G cells. 0 =–∞ (always select a cell if acceptable), 1 = –28 dB, 2 = –24 dB, …, 15 = 28 dB.Select 0 for easy handover.− The minimum Ec/No threshold for FDD cell reselect: level threshold for 3G cellreselection: when the receiver level of 3G cell is greater than the FDD_Qmin, the cellcan be a candidate cell for reselection.− Other default valuesl Configuring 2G Handover ParametersFigure 7-73 shows the parameter configuration table for inter-RAT handover.
  • 199. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 199 of 201Figure 7-73 Parameter configuration table for inter-RAT handoverPay attention to the following parameters:− Handout permission: select it.− Permission for handover algorithm of a 3G better cell: select it.− 2G/3G cell handover priority selection: select 3G cell for handover as priority− 2G cell selection threshold: the greater the threshold is, the difficult the handover to2G is. The recommended value is 63.RSCP threshold for handover to a better 3G cell: the smaller the value is, the difficult thehandover to 3G is. The recommended value is 10.Ec/No threshold for handover to a better 3G cell: the smaller the value is, the difficult thehandover to 3G is. The recommended value is 10.Statistics time for a better 3G cell: the recommended value is 5.The lasting time for handover to a better 3G cell: the smaller the value is, the easier andfaster the handover is. Pay attention to frequent handover. The recommended value is 4.l Added Data Configuration on 3G MSCsAdded data configuration proceeds as below:− Add the cell information about location area near the 2G MSC to the list of cells of3G MSC location area. LAI = MCC + MISSING NEIGHBOR CELL + LAC. SelectLAI as the type of location area. Select Near VLR area as the property of locationarea. Add the corresponding 2G MSC/VLR code. GCI = MCC + MNC + LAC + CI.Select GCI as the type of location area. Select Near VLR area as the property oflocation area. Add the corresponding 2G MSC/VLR code.− If inter-PLMN cell reselection is necessary, the MSC must configure the equivalentPLMN list: ADD EPLMN, and add the inter-PLMN MCC and MNC. The equivalent
  • 200. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 200 of 201PLMN is the PLMN which provides equivalent services to subscribers. The networkside decides whether to tell the control list to UE. The MSC sends the list to UE uponupdate acceptance and the UE saves it. When the UE reselects an inter-PLMN cell, itreselects a cell from the list by priority.− Configure the data at MTP layer and guarantee the signaling transmission betweenthe 2G MSC and the 3G MSC.− Configure the data at SCCP layer. Configure the corresponding record of 2G MSC inthe GT table, SCCP SSN table, and SCCP DSP table.− Configure the trunk data between MSCs in the same way as configuring commondata.l Necessary Data Configuration for RNCData Configuration for Supporting Roaming from WCDMA to GSM/GPRSTo support the roaming from WCDMA to GSM/GPRS, the UTRAN must completesending the following system information:− Add GSM cells and configuration the following data:MCCMISSING NEIGHBOR CELLLACCELL IDNCCBCCFREQ_BANDFrequency numberCIOADD GSMCELL: MCC="460", MNC="10", LAC="0x0fa0", CID="0x0102",NCC=0, BCC=0, BCCHARFCN=60, BANDIND=DCS1800_BAND_USED,RATCELLTYPE=GSM;ADD INTERRATNCELL: CELLID=123, MCC="460", MNC="10", LAC="0x0fa0",CID="0x0102", CELLINDIVIDALOFFSET=50, QOFFSET1SN=-50,QRXLEVMIN=-58;− Configure the measurement point for FACH to inter-frequency FDD measurement,inter-frequency TDD measurement, or inter-RAT measurement. If inter-RAT roamingis necessary, configure the measurement point for FACH to inter-RAT measurement;otherwise, according to SIB11, the RNC will not send RNC information about GSMneighbor cells.MOD CELLMEAS: CELLID=123, INTERFREQINTERRATMEASIND=INTER_RAT,FACHMEASIND=REQUIRE, FACHMEASOCCACYCLELENCOEF=3;− Configure the SearchRAT of the GSM network by running the command MODCELLSELRESEL.
  • 201. W-Handover and Call Drop Problem Optimization Guide For Internal Use2009-10-10 Huawei Confidential Page 201 of 201− After configuration of these information, the SsearchRAT contained in SIB3 is sentand information about GSM neighbor cells contained in SIB11 are sent.l Data Configuration for Supportint Inter-RAT Handover from WCDMA to GSMTo support the inter-RAT handover from WCDMA to GSM, configure the followingparameters:− Add GSM cells and configuration the following data:MCCMISSING NEIGHBOR CELLLACCELL IDNCCBCCFREQ_BANDFrequency numberCIO− Configure inter-RAT measurement control by running the command MODCELLMEAS.