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55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
55398742 drive-test-analysis
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55398742 drive-test-analysis

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  • 1. 3G RANOP 1 Module 4 – Drive Test Analysis For internal use 1 © Nokia Siemens Networks Presentation / Author / Date
  • 2. Note for teacher • A set of example traces (Nemo) with comments can be used to demonstrate failures. • Quickplace link: • http://qp2.connecting.nokia.com/QuickPlace/npcommunityqp/PageLibraryC2256F B8004C9ABD.nsf/h_Index/2F7CFD979368E6F9C22572CA0030D936/?OpenDoc ument&ResortDescending=14 For internal use 2 © Nokia Siemens Networks Presentation / Author / Date
  • 3. 3G RAN Optimization Cluster Preparation • Cluster health checks • Parameter consistency check • Neighbour list verification • Uplink interference as a problem indicator RF Optimisation and Neighbour Planning • RF optimisation • New Site Integration • Neighbour plan optimisation Signalling Flows • • • • Drive Test Analysis • Drive Survey Analysis • System Performance (RRC and RAB phases) For internal use 3 © Nokia Siemens Networks RRC Establishment RAB Establishment SHO ISHO Presentation / Author / Date Inter-System Working and Optimisation Parameter Optimisatio n HSDPA Optimisatio n • 3G<>2G Cell reselection • Neighbour Planning • Handover Process and compressed mode • 3G ISHO service analysis (AMR and PS) • GSM ISHO Optimisation • Use of Parameters to optimise network performance • HSDPA Air Interface Capacity • HSDPA Drive Test KPIs and Parameter Optimisation
  • 4. Module 4 – Drive Test Analysis Objectives After this module the delegate shall be able to:• Understand the different elements required for an effective drive test program • Understand how all aspects of drive data can be used to obtain a view of network performance • Differentiate between genuine (RF) and non-genuine (system) failures • Understand the KPIs that can be obtained For internal use 4 © Nokia Siemens Networks Presentation / Author / Date
  • 5. Drive Test Process Cluster Preparation • Define Cluster • Define Drive Route Data Preparation and Collection • Services to test • KPI definitions • Equipment • Exclusions • Call Patterns • OSS Alarms • Network Stats Data Analysis • Levels of Reporting • Failure Type Breakdown • Post Processing functionality • KPI Gap Analysis Why Drive the network? • New Site Integration • RF Tuning • Network Optimisation • Network Benchmarking (Golden Routes) For internal use 5 © Nokia Siemens Networks Presentation / Author / Date Trouble Shooting • Root Cause Analysis • Corrective Action • Further data logging (maybe)
  • 6. Drive Test Analysis – Test Equipment • Nemo Outdoor Multi with UE‟s, Scanner and GPS Land Unit NQMP FTP Server • Important to drive with Call logging equipment and 3G and 2G scanner in the same vehicle For internal use 6 © Nokia Siemens Networks Presentation / Author / Date
  • 7. Drive Test Analysis – Test Equipment, Scanner • The purpose of using the RF scanner is to be able to scan and measure all used carriers/cells and their corresponding DL scrambling codes. • For low coverage areas • For antenna installation problems • For missing neighbours • For coverage optimisation • With the scanner you can get the following info from the surrounding cells: • Different Scrambling codes • CPCIH RSCP value (dBm) • CPICH EcNo value (dB) For internal use 7 © Nokia Siemens Networks Presentation / Author / Date
  • 8. Drive Test Analysis – Test Equipment, UE • The Scanner measures all SCs, whereas the UE only measures SC signals from the cells that the system has informed/ordered the UE through the BCH (neighbour list) or via the “measurement control” message. • RSCP Active/Monitored Set • Carrier RSSI • Ec/No Active/Monitored Set • UL/DL Data Throughput • The BLER downlink • Pilot BER • Random Access Initial Tx Power • Random Access Preamble Count • Random Access Preamble Step • Random Access Tx Power • SIR target (UE dependent) • UE Tx Power • Call Statistic: AMR, CS and PS data calls For internal use 8 © Nokia Siemens Networks Presentation / Author / Date
  • 9. Drive Test Analysis – Call Patterns • Enough call samples have to be made to make the measurement statistically valid. • In a 50 call sample one dropped call will cause a change in performance of -2% • In a 500 call sample one dropped call will cause a change in performance of -0.2% • Call length should be defined at the beginning • We can use different call testing patterns for different optimisation techniques • Short Calls (for Calls setup performance and delay) • Long calls (for Drop call performance and SHO performance) AMR Call PS Call Mobile Originated Calls (MOC) • 2 min calls • 30 sec idle • UE in Dual mode (2G/3G) Mobile Terminated Calls (MTC) • 2 min calls • 30 sec idle • UE in dual mode (2G/3G) • • • • • • For internal use 9 © Nokia Siemens Networks Presentation / Author / Date GPRS Attach, PDP Context Activation FTP Download (1MB file)/FTP Upload (500 KB file) PDP Context Deactivation GPRS Detach Alternate download and upload with 30 sec idle time • Session is upload or download • UE in Dual mode (2G/3G)
  • 10. PS Data KPI Report Drive Test Analysis – Defining KPIs KPI Thresholds Attach Time PDP Activation Time FTP Download Throughput FTP Upload Throughput AMR Statistics Threshold KPIs MOC Setup time MOC CCR 5 99 Event Call Attempts Call Setup Success Rate Call Setup Failure Rate Failures due to Tool (TSF) Failures due to Core Problem Failure ASU (Sync) Problem Failure due to Low Coverage Levels Call Setup Success and Setup Time > 5s Long Setup due to slow cell reselection Long Setup due to clash with InterRAT reselection Long Setup due to Unknown (suspect UE) Long Setup due to Unknown Average Call Setup Time Call Completetion Rate Call Drop Rate Call Drop Poor 3G Coverage Call Drop on GSM due to Interference Overall Call Completion Rate ISHO Attempt ISHO Success ISHO Failed ISHO Failed cause physical channel failure RAW Count 132 108 24 10 10 2 2 7 105 3 1 2 105 14 14 0 0 sec % Ratio 81.8% 18.2% 41.7% 41.7% 8.3% 8.3% 6.5% 0.0% 0.0% 0.0% 0.0% 3.66 97.2% 2.8% 33.3% 66.7% 79.5% END USER Count Ratio 122 108 88.5% 14 11.5% 100.0% 0.0% N/A 10 2 2 7 0 0 0 0 105 3 1 2 105 14 14 0 0 • Need to agree •What „raw‟ figures will contain •What „End User‟ will contain •Other cuts of Data For internal use 10 © Nokia Siemens Networks Presentation / Author / Date 71.4% 14.3% 14.3% 6.5% 0.0% 0.0% 0.0% 0.0% 3.66 97.2% 2.8% 33.3% 66.7% 86.1% 100.0% 0.0% N/A Value 4 2 110 55 Unit sec sec kbit/s kbits Signalling Statistics Count Attach Attempt 155 Attach Success 140 Attach Time more than threshold 5 Attach Time less than threshold 135 Attach Failed 15 Average Attach Setup Time Activate PDP Context Attempt 124 Activate PDP Context Success 124 Activation Time more than threshold 2 Activation Time less than threshold 123 Activate PDP Context Failed 0 Average PDP Context Activation Time FTP Download Attempts 51 FTP Download Success 48 FTP Download throughput more than threshold 25 FTP Download throughput less than threshold 23 Average FTP Download Throughput FTP Upload Attempts 32 FTP Upload Success 30 FTP Upload throughput more than threshold 20 FTP Upload throughput less than threshold 10 Average FTP Upload Throughput Data Transfer Cut-off Ratio PDP Context Dropped 4 Deactivate PDP Context Request 121 Deactivate PDP Context Accept 121 Deactivate PDP Context Failure 0 Detach Request 281 Detach Accept 129 Overall Data Session Completion Rate 78 Success rate RAU Statistics RAU Attempt RAU Success RAU Failed Count 22 13 9 Success rate Cell Reselection Statistics Count Cell Reselection from UMTS to GSM Attempts 2 Cell Reselection from UMTS to GSM Success 1 Cell Reselection from UMTS to GSM Delay E2E Cell Reselection from UMTS to GSM Delay Signalling Cell Reselection from GSM to UMTS Attempts 1 Cell Reselection from GSM to UMTS Success 0 Cell Reselection from GSM to UMTS Delay E2E Success rate Time in System GSM UMTS Seconds 171 16559 90.32% 3.57% 96.43% 9.68% 1.36 100.00% 1.60% 98.40% 0.00% 0.96 94.12% 52.08% 47.92% 107.02 93.75% 66.67% 33.33% 55.53 6.02% 3.23% 100.00% 0.00% 45.91% 62.90% 59.09% 40.91% 50.00% 15.27 N/A 0.00% N/A Ratio 1.02% 98.98%
  • 11. Drive Test Analysis – Test Case definition Examples Short calls to test Call Setup Success KPI ID Criteria Test Description KPI-01 Voice 12.2 kbps AMR CCSR •1 MOC+ 1 MTC in the same van, 2 Ues •1 call (party A to party B, party A terminates the call): 15 seconds call + 15 seconds idle. Party A to be logged •350 calls KPI-02 Voice DCR •1 MOC to PSTN, 1 Ue •1 call: 90 seconds call + 15 seconds idle •350 calls Long calls to test Drop call ratio KPI-03 Voice 3G2G Handover (inter- & intra-MSC) •1 MOC to PSTN, 1 Ue in dual mode •1 call: continuous call until 3G2G coverage border is passed •50 occurrences as a minimum •Call set-up trigger point: •Party A‟s UE sends 1st „RRC Connection Request‟ •Call completion trigger point: •Party A‟s UE receives „RRC Connection Release (cause normal)‟ •Successful completion if: •15 sec call duration (from RRC Conn. Request to RRC Conn. Release) •Party A‟s UE receives „RRC Connection Release (cause normal)‟ •Call Set-up trigger point: •3G UE receives „RRC: Downlink Direct Transfer (Alerting for NZ, Connect Acknowledge for AU)‟ •Call completion trigger point: •3G UE receives „RRC Connection Release (cause normal)‟ •Successful completion if: •90 sec call duration (from RRC Conn. Request to RRC Conn. Release) •3G UE receives „RRC Connection Release (cause normal)‟ •3G to 2G HO start point: •UE receives „RRC: Handover From UTRAN Command‟ •3G to 2G HO completion trigger point: •UE sends „Handover Complete‟ to 2G BSS •Successful completion if: •UE sends „Handover Complete‟ to 2G BSS … •PS PDP activation trigger point: •UE not PS attached •UE sends 1st „RRC Connection Request‟ •PS PDP activation completion trigger point: •UE receives „RRC: Downlink Direct Transfer (SM: Activate PDP Context Accept)‟ •Successful completion if: •UE receives „RRC: Downlink Direct Transfer (SM: Activate PDP Context Accept)‟ KPI-09 PS •Repeated FTP calls, 1 Mbyte file •Data Session Set-up trigger point: throughput download, 1 Ue •UE receives 1st DL packet downlink •384 kbps •Data Session Completion trigger point: •Average throughput •UE receives last packet •350 calls •Session output: For internal use •Average downlink throughput 11 © Nokia Siemens Networks Presentation / Author / Date KPI-08 PS PDP context activation •Same as 10 •350 occurrences Trigger Statistics •Cluster_AMR_Overall_CCSR_% = Call Completion / Call Attempts *100 Success Rate 98% •Cluster_AMR_Overall_DCR_% = 1 - Call Completion / Set up Calls *100 < 2% •Cluster_Voice_3Gto2G_HO_Overall_SR_% = HO Completion / HO Attempts *100 98% •Cluster_PDP_Context_Activation_SR_% = PDP Context Activation Completion / PDP Context Activation Attempts *100 98% •Cluster_PS_DL_Throughput = Average Throughput Over Data Sessions 200 Kbps
  • 12. Need to Define the KPI measurement (from Drive test) • Call Setup Success - CSSR (voice, circuit switched data) • Successful call setup means that “DL/UL Direct Transfer (CC: Alerting)” message is received by UE. • Call Setup Time (voice, circuit switched) • Call setup delay is measured from L3 messages, starting from “RRC Connection Setup” message to “DL Direct Transfer (CC: Alerting)” message. • Call Drop (voice, circuit switched) • A dropped call occurs. The call will be dropped in case RRC connection release (not normal release) message has been send from RNC to UE. • Session Setup Success (packet switched) • This is related to PDP context activation. Successfully activated PDP context means that activate PDP context accept message has been sent from RNC to UE (RRC: downlink direct transfer (SM:activate PDP context Accept)). • Session Setup Time (packet switched) • The “session setup time” is the delay between the time the UE sends the data session activation request until GPRS attach and PDP context activation has been successfully completed. • Session Drop (packet switched) • Session drop rate can be defined as the number of successful PDP deactivations against number of successful PDP activations. For internal use 12 © Nokia Siemens Networks Presentation / Author / Date
  • 13. Definition of Call Set-Up Success Rate (CSSR) UE RNC BTS CN RRC: Connection Request RRC Connection Setup phase Resource Reservation in RNC, BTS, Transmission RRC: RRC Connection Request Setup RRC Connection Access phase RNC waits reply from UE RRC: RRC Connection Completed RRC: Initial Direct Transfer cm service request DIRECT TRANSFER (Call Proceeding) RANAP: Initial UE Message RAB Connection Setup phase RANAP: RAB Assignment Request Resource Reservation in RNC, BTS, Transmission Call Set-up Success Rate Call Set-up Time RRC: Radio Bearer Set-up RAB Connection Access phase RNC waits reply from UE RRC: Radio Bearer Setup Complete DIRECT TRANSFER (Alerting) DIRECT TRANSFER (Connect) DIRECT TRANSFER (Connect Acknowledge) For internal use 13 © Nokia Siemens Networks Presentation / Author / Date RANAP: RAB Assignment Response Successful call setup means that “DL/UL Direct Transfer (CC: Alerting)” message is received by UE
  • 14. Definition of the Call Completion Rate (CCR) MGW RNC Node B UE DIRECT TRANSFER (Alerting) DIRECT TRANSFER (Connect) DIRECT TRANSFER (Connect Acknowledge) Call Established Direct Transfer (Disconnect) Direct Transfer (Release) Call Drop Rate Direct Transfer (Release Complete) Iu Release Command Iu Release Complete RRC Connection Release RRC Connection Release Complete RRC Connection Release Complete RRC Connection Release Complete Radio Link Deletion Request Radio Link Deletion Response ALCAP: Release Request ALCAP: Release Response ALCAP: Release Request ALCAP: Release Response Call Released For internal use 14 © Nokia Siemens Networks Presentation / Author / Date Call Duration
  • 15. Definition of Session Setup Time - PS WBTS UE RNC CN UE already has an RRC connection INITIAL DIRECT TRANSFER (Attach Request) INITIAL UE MESSAGE (GPRS Attach) SCCP: Connection Request SCCP: Connection Confirm Downlink Direct Transfer (Authentication & Ciphering Request) Uplink Direct Transfer (Authentication & Ciphering Response) RANAP: Authentication & Ciphering Request RANAP: Authentication & Ciphering Response RANAP: Security Mode Command Security Mode Command RANAP: Security Mode Command Security Mode Command RANAP: Common ID Downlink Direct Transfer: Identity Request RANAP: Identity Request RANAP: Identity Response Uplink Direct Transfer: Identity Response Downlink Direct Transfer: Attach Accept Direct Transfer: Attach Complete Uplink Direct Transfer: Attach Complete INITIAL DIRECT TRANSFER (Active PDP Context Request) DIRECT TRANSFER (Active PDP Context Request) RRC: Radio Bearer Set-up RRC: Radio Bearer Set-up Complete RRC: Measurement Control DIRECT TRANSFER (Active PDP context Accept) For internal use 15 © Nokia Siemens Networks Direct Transfer: Attach Accept Presentation / Author / Date RANAP: RAB ASSIGNMENT REQUEST RANAP: RAB ASSIGNMENT RESPONSE Session Set-up Time
  • 16. Failure Breakdown • Non-genuine failures • Measurement system fault (Collection Tool or Analysis) • Genuine failures It is beneficial to categorise call failures during the analysis and reporting • RF issue (Coverage / Interference / Poor dominance) • Missing neighbour • System issue WBTS • System issue RNC • Core network issue • System • (Unknown ) UE WBT S For internal use 16 © Nokia Siemens Networks Iub Iu RNC Presentation / Author / Date Core NW
  • 17. Failure Breakdown • The KPI measurement conditions should be used to define exclusion areas during drive test for acceptance of a cluster. • All failures happening in those area, that do not respect the coverage requirements should be discarded. Example of Call Success Crit eria RSCP S ig n a l above RSCP th re s h o ld Ec/No Call Call - 80dBm OK Call OK Call - (B) - 5dB NOK S ig n a l a b o v e E c /N o th re s h o ld  - 12dB - - 95dBm S ig n a l b e lo w RSCP th re s h o ld Call OK - 110dBm Threshold  Call - (A) - 20dB Call NOK Discard sample Time For internal use 17 © Nokia Siemens Networks Presentation / Author / Date S ig n a l b e lo w E c /N o th re s h o ld
  • 18. Failure Breakdown AMR Call Setup Failures C a ll S e t-u p F a ilu re s B re a k d o w n - B e n c h m a rk D riv e 0% 5% 5% C a ll S e tu p F a ilu re B re a k d o w n - F in a l D riv e 0% E q u ip m e n t 0% R e g is tra tio n C la s h E q u ip m e n t 0% 15% C o re N e tw o rk 19% 20% R e g is tra tio n C la s h 19% C o re N e tw o rk Fa il in 2 G Fa il in 2 G R AN (fixe d in n e xt re le a s e ) 0% S ite m a in te n a n c e (TMU K ) 0% R AN (fixe d in n e xt re le a s e ) 0% S ite m a in te n a n c e (TMU K ) 0% R AN (O th e r) 5% Mis s in g n e ig h b o u rs R AN (O th e r) 10% 0% 0% 10% 35% Mis s in g n e ig h b o u rs 3G RF 0% 3G RF s lo w c e ll R e s e le c tio n 0% S lo w c e ll re s e le c tio n s ite c o n fig u ra tio n & m a in te n a n c e s ite c o n fig u ra tio n & m a in te n a n c e (N o k ia ) O th e r (N o k ia ) O th e r 5% 52% C a ll S e t-u p E xC a p tio n s p F a ilu re s c e ll S e t-u C a ll S e t-u p F a ilu re s to ta l % E q u ip m e n t 0 0 .0 R e g istra tio n C la sh 0 0 .0 C o re N e tw o rk 0 0 .0 5 .0 F a il in 2 G 6 1 9 .4 0 0 0 .0 0 .0 R A N (fixe d in n e xt re le a se ) S ite m a in te n a n ce (T M U K ) 0 16 0 .0 5 1 .6 R A N (O th e r) 2 1 0 .0 R A N (O th e r) 0 0 .0 M issin g n e ig h b o u rs 1 5 .0 M issin g n e ig h b o u rs 0 0 .0 3G R F 7 3 5 .0 3G RF 3 9 .7 slo w ce ll R e se le ctio n 3 1 5 .0 S lo w ce ll re se le ctio n 0 0 .0 site co n fig u ra tio n & m a in te n a n ce (N o kia ) 0 0 .0 O th e r 1 5 .0 site co n fig u ra tio n & m a in te n a n ce (N o kia ) 0 0 .0 O th e r 6 1 9 .4 F a ilu re T yp e to ta l E q u ip m e n t 1 5 .0 R e g istra tio n C la sh 4 2 0 .0 C o re N e tw o rk 0 0 .0 F a il in 2 G 1 R A N (fixe d in n e xt re le a se ) S ite m a in te n a n ce (T M U K ) F a ilu re T yp e % For internal use 18 © Nokia Siemens Networks Presentation / Author / Date
  • 19. Drive Survey Analysis Process Summary Diagram For internal use 19 © Nokia Siemens Networks Presentation / Author / Date
  • 20. Non Genuine Call Setup Failure Scenarios • Measurement systems are often not perfect and may introduce errors in data collection or analysis • Examples of non-genuine failures seen: • Uplink: CM Service Abort within milliseconds from CM Service Request • Call attempt during Location Area update („LA clash‟) • User initiated “UL CC Disconnect” • Location Area update interpreted as call setup failure • Cell reselection back to 3G from 2G interpreted as call setup failure For internal use 20 © Nokia Siemens Networks Presentation / Author / Date
  • 21. Non Genuine Call Setup Failures • Measurement system failures by drive test tool • “CM Service Abort” within milliseconds from “CM Service Request” • No time for response from NW For internal use 21 © Nokia Siemens Networks Presentation / Author / Date
  • 22. Non Genuine Call Setup Failures • Measurement system failures by drive test tool • Call attempt during Location Area update (LA update clash) LA Update Request Call attempt RRC Release For internal use 22 © Nokia Siemens Networks Presentation / Author / Date
  • 23. Non Genuine Call Setup Failures Measurement system failures by Actix workbook • Successful or failed Location Area update interpreted as call setup failure LA Update Request RRC Connection for Inter-RAT cell reselection For internal use 23 © Nokia Siemens Networks Presentation / Author / Date
  • 24. Non Genuine Drop Call Scenarios Measurement system failure examples: • Drive test tool • User initiated “UL CC Disconnect” • Analysis Workbook • Inter-Rat cell reselection from 2G to 3G interpreted as drop call • Complete (e.g 90 seconds) call on either 3G or 2G • No drop in the log file / same drop listed twice For internal use 24 © Nokia Siemens Networks Presentation / Author / Date
  • 25. Genuine Call Setup Failure Scenarios • RF issue • Interference / Dominance / Coverage • Missing neighbour • System Issue - BTS • No response to “RRC Connection Request” • “RRC Connection Reject” to “RRC Connection Request” • System issue - RNC • “CC Disconnect” after “Call Proceeding” due to “DL RRC Connection Release” • Core NW • “CM Service Abort” after “CM Service Request” • System issue (test number) • “CC Disconnect” after “CC Progress” For internal use 25 © Nokia Siemens Networks Presentation / Author / Date
  • 26. Genuine Drop Call scenarios • RF issue • Interference / Dominance / Coverage • Missing Neighbours • System issue BTS • Sudden “CC Disconnect” due to “DL RRC Connection Release” • Sudden drop to idle, no disconnect messaging • System issue RNC • Sudden “CC Disconnect” due to “DL RRC Connection Release” For internal use 26 © Nokia Siemens Networks Presentation / Author / Date
  • 27. Failure Location • Analyse the signalling flow to find the location of failure and potential cause • UE log may only capture some of the messages For internal use 27 © Nokia Siemens Networks Presentation / Author / Date
  • 28. Module 4 – Drive Test Analysis Call Setup Failure Analysis For internal use 28 © Nokia Siemens Networks Presentation / Author / Date
  • 29. AMR CS Call Phases UE WBTS DRNC SRNC 1. Cell search, BCCH decoding & RACH access 2. RRC connection set-up 3. UE <--> CS-CN signalling 4. RAB set-up 5. UE <--> CS-CN Signalling 6. Service Established 7. Branch addition/deletion & Active set update 8. Service Released For internal use 29 © Nokia Siemens Networks Presentation / Author / Date CN
  • 30. Call Setup Failure Analysis Process Start A Best server‟s RSCP > -102dBm Missing Neighbour ? Yes Best server‟s Ec/No > -12dB Coverage Optimization No No Yes No Dominance Optimization Neighbour list Optimization Yes B UL coverage & RACH parameter. Optimization (changing serving cell) No AICH(ACK) received? Report & Finish (Check failure cause) No Yes “RRC Connection Setup” received? No Yes D Report & Finish (Reason of problem: L1 sync fail) No No AC optimization (check PrxNoise & interferer around BTS) (DCH) “RRC Connection setup Completed” sent from UE? Report & Finish “Radio Bearer setup failure”Received? Yes For internal use 30 © Nokia Siemens Networks E Report & Finish Check failure cause (Not radio problem/cell update) Presentation / Author / Date C Yes Yes Report & Finish (Check failure cause) “RRC Setup Reject” received?
  • 31. Call setup failures – RF issue • RF issue? Coverage / Interference / Dominance See the example in Module 3 – RF Optimisation For internal use 31 © Nokia Siemens Networks Presentation / Author / Date A
  • 32. Call setup failures – Missing Neighbour • Missing neighbour analysis over the whole route (3G-3G, 3G-2G) • Search for failures due to missing 3G-3G neighbours • Search for failures due to missing 3G –2G neighbours • It is suggested to place 2G scanner to the test vehicle For internal use 32 © Nokia Siemens Networks Presentation / Author / Date A
  • 33. Call Setup Failure Analysis- Block B - B • The purpose of this activity is to check the Random Access Process is working adequately by investigating whether AI (Acquisition Indicator) has been received through DL AICH • If AICH was not received by UE, the cause of the problem can be classified into: • Inadequate RAN parameter related to Random Access: RAN parameter settings for pre-amble transmission or open loop power control information is not correct. • UL Coverage limit: UL coverage of UE is smaller compared to serving cells DL coverage so that UE‟s Tx power cannot reach serving cell. • The Basic theory for RACH setup procedure and planning parameters can be found in Module 6 – Parameter Optimisation For internal use 33 © Nokia Siemens Networks Presentation / Author / Date
  • 34. B Call Setup Failure Analysis- Block B WBTS UE RNC Preamble/RACH Acquisition Indicator/AICH RRC: RRC Connection Request/PRACH NBAP: RADIO LINK SETUP REQUEST NBAP: RADIO LINK SETUP RESPONSE RRC: RRC CONNECTION SETUP/FACH L1 Synchronisation NBAP: SYNCHRONISATION INDICATOR RRC: RRC CONNECTION SETUP COMPLETE/DCH UE in CELL_DCH state For internal use 34 © Nokia Siemens Networks Presentation / Author / Date
  • 35. B RACH Process L1 ACK / AICH Downlink BS Not detected UEtxPowerMaxPRACH PowerRampStepPRACHpreamble …… Uplink MS …… Preamble Preamble 1 2 Message part PowerOffsetLastPreamblePRACHmessage PRACH_preamble_retrans # PRACH preambles transmitted during one PRACH cycle without receiving AICH response RACH_tx_Max # preamble power ramping cycles that can be done before RACH transmission failure is reported Initial preample power: •Ptx = CPICHtransmissionPower-RSCP(CPICH) +RSSI(BS) + PRACHRequiredReceivedCI For internal use 35 © Nokia Siemens Networks Presentation / Author / Date
  • 36. Call Setup Failure Analysis- Block B- B • Solutions for RACH optimisation No To increase PRACH_Preamble_retrans Or PowerRampStepPRACHPreamble Max UE Tx power hit the UE_P_MAX(24dBm)? Yes Yes Is UL Interference abnormally HIGH? Report there might be an interfering source Nearby the serving cell No Change the Serving cell to cover the problem Area => UE is too far to reach the serving cell For internal use 36 © Nokia Siemens Networks Presentation / Author / Date
  • 37. Call Setup Failure Analysis- Block B Open loop Power Control parameters from RACH Info message For internal use 37 © Nokia Siemens Networks Presentation / Author / Date B
  • 38. Call setup failures – System issue BTS C • No response to “RRC Connection Request” • Good RF conditions • Wrong MHA settings or cable loss settings can cause the site not to “hear” the UE • PrxNoise statistics, receive link parameters and HW units to be checked (faulty MHA, wrong MHA parameters, wrong cable / feeder loss parameters, faulty units) For internal use 38 © Nokia Siemens Networks Presentation / Author / Date
  • 39. Call setup failures – System issue BTS C • “RRC Connection Reject” after “RRC Connection Request” • Good RF conditions • Admission Control can reject too many (or admit too many) connection requests due to wrong PrxNoise measurements. • PrxNoise statistics, receive link parameters and HW units to be checked For internal use 39 © Nokia Siemens Networks Presentation / Author / Date
  • 40. Call Setup Failure Analysis C • UE has the appropriate DL/UL coverage but if RNC does not allow to set up the RRC connection of the requested RAB (Radio Access Bearer), Call setup will fail. • Admission Control (AC) is involved in RRC connection setup. AC can reject RRC reject RRC connection Setup due the DL Load, UL load or DL Spreading codes • Marginal Load Area: • If measured UL (PrxTotal) or DL (PtxTotal) load exceeds target thresholds (PrxTarget and PtxTarget) AC can still admit new RAB to the cell if a new noncontrollable load keeps below target thresholds (in practice this means that AC can admit only new controllable load RABs i.e. NRT RABs) • Overload Area: • If measured UL (PrxTotal) or DL (PtxTotal) load exceeds overload thresholds (PrxTarget + PrxOffset and PtxTarget + PtxOffset) then AC can't admit more RABs to the cell For internal use 40 © Nokia Siemens Networks Presentation / Author / Date
  • 41. Call Setup Failure Analysis C • During the pre-optimization phase it is unlikely that AC will stop an RRC connection setup during the drive testing because there are normally very few UEs in the network. (Traffic loading is trivial) • However, it should be checked that measured PtxTotal and PrxTotal are less than PtxTarget (e.g. 40dBm) and PrxTarget (e.g. 4dB, 60% loading) respectively. • If DL AC does not allow RRC setup check the Tx power of WBTS, # of channels transmitted, Signaling messages. • If UL AC does not allow RRC setup: Check out if there is an interfering source nearby the serving cell. For internal use 41 © Nokia Siemens Networks Presentation / Author / Date
  • 42. Call Setup Failure Analysis D To check if Layer 1 Synchronization (slot/frame sync) has failed • If “RRC Connection Setup” was received by UE but UE does not send “RRC Connection Setup Completed”, we will report “L1 synchronization failure” and have to check L1 system messages. For internal use 42 © Nokia Siemens Networks Presentation / Author / Date
  • 43. Call setup failures – System issue RNC • “CC Disconnect” after “Call Proceeding” • Good RF conditions • Failures in RAB setup occur between the “RAB Assignment Request” being received from Core Network and the RAN sending out Radio Bearer Setup. Therefore the failure is between BTS and Core Network. For internal use 43 © Nokia Siemens Networks Presentation / Author / Date E
  • 44. Call setup failures – System issue RNC • “CC Disconnect” after “Call Proceeding” (cont.) • An example (site shows high values on counter “RAB_STP_FAIL_CS_VOICE _BTS” during the drive test • In the recent check the counter showed no failures. For internal use 44 © Nokia Siemens Networks Presentation / Author / Date E
  • 45. E Call setup failures – Core NW • “CM Service Abort” after “CM Service Request” • Good RF conditions • “Security Mode Command”message not received by UE, thus the failure is believed to be at Core Network. UE N ode B MGW RNC R R C C onnection E stablishm ent Initial D irect T ransfer (C M S erv ice R equest) S C C P : C onnection R eque st S C C P : C onnection C onfirm Location R eporting C ontrol C om m on ID S ecurity M ode C om m and • R R C : In itia l D irec t T ran s fer m e ss ag e is s e n t u s in g ac k no w led ge d m od e R LC to th e C S c o re d o m a in . R o u tin g is to be b as e d u p on th e lo c a l P -T M S I • T h e N A S m e s sa ge is n o t rea d b y th e R N C b u t is fo rw ard ed to th e m u ltim e d ia g a te w a y. T h e N A S m e ss a ge in c lud es th e IM S I a s a U E id e n tity • T h e S C C P : C o nn e c tion R eq u es t m e ssa g e es ta b lish es th e co n ne c tion o rien ta te d s ign a llin g link in th e s a m e w a y a s it w a s for th e R R C c on n ec tio n p ha se .T h is d o es n o t re se rv e a n y re so urce s for th e A M R c a ll its e lf. • T h e C on ne c tio n C o n firm m e ss ag e id entifie s th e R N C w ith a de s tin a tion lo ca l re feren ce w h ic h is th e s a m e as th e so urce referen ce w ith in the C o nn ec tio n R eq u es t m e ss ag e • T h e C on ne c tio n C o n firm m e ss ag e id entifie s th e C S c ore w ith a s o urc e lo ca l refere nc e • T h e C S c ore se nd s a R A N A P : L o c a tion R e po rtin g C o n tro l m e ss ag e to th e R N C req ue s tin g in form a tion reg ard ing th e lo ca tio n of a p a rticu lar U E • T h e R A N A P : C o m m o n ID m es sa g e s pe c ifie s th e IM S I b e lo n g in g to th e U E For internal use 45 © Nokia Siemens Networks Presentation / Author / Date • T h e S e cu rity M o d e C o m m a nd m es sa ge trig g ers the s ta rt or s to p of c ip h ering a n d in teg rity p ro tec tio n .
  • 46. Call setup failures – System Issue (test number) • • • • E “CC Disconnect” after “CC Progress” Cause: recovery on timer expiry The call goes via IN SCP to a recording. A static test was done by Nokia Customer Care and in few instances the call dropped after 30 seconds of recording passed. Hence the problem is associated with the test number not the RAN 30 sec Cause: recovery on timer expiry For internal use 46 © Nokia Siemens Networks Presentation / Author / Date
  • 47. Module 4 – Drive Test Analysis Drop Call Analysis For internal use 47 © Nokia Siemens Networks Presentation / Author / Date
  • 48. Call Drop Failure Analysis Process Start SHO Failure Analysis Yes SHO Failed No ISHO Failure Analysis Yes ISHO Failed No No Best server’s RSCP > -102dBm No Best server’s Ec/No > -12dB B For internal use 48 © Nokia Siemens Networks Investigate possible BTS or RNC problem Presentation / Author / Date No Missing Neighbour A Yes Coverage Optimization Yes Dominance Optimization Neighbour list Optimization
  • 49. Call Drop Failure Analysis Process (SHO Analysis) Start Yes Check Iur Check neighbour definition parameters Fix SC Clash Yes Yes No SC Clash C Yes No DL ASU received Yes No Load Optimisation Inter RNC HO Congestion on target cell UE Tx Power Max No Check RF Levels D Yes No DL Tx Power Max Uplink Interference Yes Load Optimisation/ External Interferer Yes No Yes Link Unbalanced For internal use 49 © Nokia Siemens Networks Presentation / Author / Date CPICH Optimisation
  • 50. A Drop call failures – RF issue • RF drops mostly due to poor dominance or interference • Poor coverage could lead to ISHO, although poor dominance or interference can cause ISHO to fail. • Rapid field drop can cause drop due to coverage • Poor dominance or interference can cause Compressed Mode (CM) to start even if RSCP is still good. • In CM UE transmits with higher power (more interference) and spends less time on 3G (less accurate measurement reporting) • Poor dominance or interference can lead to Active Set update failures and eventually to drop call. For internal use 50 © Nokia Siemens Networks Presentation / Author / Date Poor dominance causes Active Set update failures
  • 51. A Drop call failures – RF issue DL synchronisation is lost -> UE has stopped transmitting TrChAgg and DL DPCCH BER high For internal use 51 © Nokia Siemens Networks Presentation / Author / Date
  • 52. A Drop call failures – RF issue Fairly good CPICH Pilot EcNo Transport Channel BER. Btw UE<->RNC (MAC layer) Sometimes DPCCH BER (btw UE<->WBTS) can be a better indicator of what's happening to the dedicated channel than the CPICH EcNo, in particular in the case that power control may not be tracking well For internal use 52 © Nokia Siemens Networks Presentation / Author / Date
  • 53. Drop call failures – System issue BTS B • Sudden drop to idle, no disconnect messaging • Site malfunctions to be checked • In the example below site had faulty unit (WTR) Drop to IDLE For internal use 53 © Nokia Siemens Networks Presentation / Author / Date
  • 54. Drop call failures – System issue RNC B DPCCH BER • “CC Disconnect” due to “DL RRC Connection Release” • No response to UL Measurement Reports • In the example site had no alarms, good RF & BER • Not able to add SC265 to Active Set, next call on the same cell => no failure. • Difficult to troubleshoot if the failure does not happen systematically => follow up in the next weeks drive / do a separate drive test in the area For internal use 54 © Nokia Siemens Networks Sudden “RRC Connection Release” Presentation / Author / Date
  • 55. C Drop call failures (SC conflict) • Sudden drop to idle mode (no disconnect messaging) Transport channel BLER 100% • Cause of the failure: overshooting site and SC reuse • Short term solution to add overshooting neighbour in ADJS definitions Cell ABC, SC258 For internal use 55 © Nokia Siemens Networks Presentation / Author / Date
  • 56. D Drop Call - Uplink Interference UL interference from the SIB7 message For internal use 56 © Nokia Siemens Networks Presentation / Author / Date
  • 57. Drop Call – Link Balance • UL & DL Power Control commands can help indicating problems in link balance. • PC frequency is 1500 Hz, thus ideally the sum of PC commands to increase or decrease power is 1500 D UE RX power control message: DL reception weak -> UE is ordering WBTS to increase power. • E.g. if the sum of UL PC commands is < 1500, this would indicate UE is starting to loose synchronization • in Compressed Mode there is less PC commands, UE spends time on 2G Sum of UL PC commands < 1500, UE not receiving all the PC commands. For internal use 57 © Nokia Siemens Networks Presentation / Author / Date
  • 58. Drop call failures – System issue RNC or BTS ? • “CC Disconnect” due to “DL RRC Connection Release” is just a consequence of failure which can be due to different reasons • From UE point of view L3-messaging does not identify the point of failure distinctly • BTS or RNC failure? => Suspect BTS first, then RNC • Rule out BTS failures • Check the site performance from Counters (Iub, Service level, cell resources SHO, etc) and that site is carrying traffic • PrxNoise, receive link parameters, alarms • SC–reuse • UE performance ? • Identified causes for Active Set Update failure • “Deaf” sites (PrxNoise) • Faulty HW • SC-reuse For internal use 58 © Nokia Siemens Networks Presentation / Author / Date
  • 59. Module 4 – Drive Test Analysis Drive Test Analysis Reporting For internal use 59 © Nokia Siemens Networks Presentation / Author / Date
  • 60. Drive Test Analysis – Reporting Levels Senior Management Regional Optimisation Manager Optimiser • Very High Level KPIs that give a users perception of the network (Network KPI) • KPIs that provide an Engineering view of network performance e.g CSSR, CDR, OCSR, SHO performance. (KPIs required for each optimisers area) • Highly detailed KPIs that give a detailed picture of network performance at an Engineering level and allow root cause analysis • The different reporting levels may want to see KPIs based on different cuts of the data (e.g. raw or end user) • Processing Drive Data to provide the information required at the bottom level means that the higher level information can be easily extracted For internal use 60 © Nokia Siemens Networks Presentation / Author / Date
  • 61. KPI reporting • Non-genuine failures to be removed from the raw KPI‟s C a ll C o m p le tio n C a ll S e tU p S u c c e s s R a te “Final KPI‟s” 9 7 .5 % 9 7 .9 % 3 .1 % 2 .1 % O ve ra ll C a ll S u c c e s s R a te 9 4 .5 % 9 5 .9 % C a ll C o m p le tio n C a ll C o n n e c tio n tim e < = 8 s 9 7 .6 % 9 7 .6 % C a ll S e tU p S u c c e s s R a te C a ll D ro p R a te C a ll D ro p R a te 9 8 .1 % 9 8 .6 % 1 .3 % 0 .3 % O ve ra ll C a ll S u c c e s s R a te 9 6 .8 % 9 8 .2 % C a ll C o n n e c tio n tim e < = 8 s 9 7 .6 % 9 7 .6 % No No No No No of of of of of C all A ttem pts (w ithin coverage) C all S etup F ailures S uccessful C all S etups C all D rops C om pleted C alls Non-genuine drops removed 630 12 618 8 610 Final KPI‟s C a ll C o m p le tio n C a ll S e tU p S u c c e s s R a te C a ll D ro p R a te 9 7 .5 % 9 7 .9 % 1 .3 % 0 .3 % O ve ra ll C a ll S u c c e s s R a te 9 6 .2 % 9 7 .6 % C a ll C o n n e c tio n tim e < = 8 s 9 7 .6 % 9 7 .6 % No No No No No For internal use 61 © Nokia Siemens Networks of of of of of C all A ttem pts (w ithin coverage) C all S etup F ailures S uccessful C all S etups C all D rops C om pleted C alls Presentation / Author / Date 634 16 618 8 610 625 13 612 2 610 Non-genuine call setup failures removed 621 9 612 2 610
  • 62. KPI reporting • Weekly KPI trends (non-genuine failures should be excluded) All Routes 100% 800 90% 700 80% 600 70% 60% 500 50% 400 40% 300 30% 200 20% 100 10% For internal use 62 © Nokia Siemens Networks Presentation / Author / Date k0 2 w k5 2 w k5 1 w k5 0 w k4 9 w k4 8 w k4 7 w k4 6 w k4 5 w k4 4 w k4 3 w k4 2 0 w w k4 1 0% Call SetUp Success Rate Call Drop Rate Overall Call Success Rate Time on 3G Time on 2G Call Attempts
  • 63. KPI reporting BTS failure chart (call setup failure & drops) • Cumulative number of failures that occurred per site over time • If the UE is spending only a small percentage of time on 3G problems may not be identified. Cell_D Cell_A CELL_C CELL_B For internal use 63 © Nokia Siemens Networks Presentation / Author / Date
  • 64. BTS failure examples: CELL_A • Long history of failures (over weeks 46, 47, 02) • Call Setup failure scenarios: • “CC Disconnect” after “CC Call Proceeding” • “CM Service Abort” after “CM service Request” • 3rd sector showing low average PrxNoise –108 dBm Commissioning data (feeder loss) was found incorrect. • After this site was still failing, not carrying traffic. • Alarm “7750 – failure in WCDMA BTS O&M Connection” • COCO rebuilt (27.1.05) For internal use 64 © Nokia Siemens Networks Presentation / Author / Date
  • 65. BTS failure examples: CELL_B • Failures only on week 49 • No response to “RRC Connection Request” • No alarms • At WBTS: MHA parameters ok • At RNC: MHA=0, cable loss = 3 dB (DPCCH init pwr) • PrxNoise checked OK, OMC statistics showed the site carried traffic during the drive. • No failures in the following weeks drives For internal use 65 © Nokia Siemens Networks Presentation / Author / Date
  • 66. BTS failure examples: CELL_C • Failures over weeks 44, 45, 49, 50 • No response to “RRC Connection Request” most frequent failure, also one case of sudden drop to idle. • Test calls were made, the counters were not incremented during the test. Protocol analyser proved no activity in Iub. The counters were incremented only after site reset. • Alarm “WSMA RR-bus error” • The site had faulty WTR, incorrect feeder loss in the commissioning file. For internal use 66 © Nokia Siemens Networks Presentation / Author / Date
  • 67. BTS failure examples: CELL_D • Failures on weeks 47 and 48 • No response to “RRC Connection Request” • Incorrect feeder loss in commissioning data. For internal use 67 © Nokia Siemens Networks Presentation / Author / Date
  • 68. Module 4 – Drive Test Analysis Summary • Services to be measured and KPIs to be calculated need to be clearly defined • Various call patterns exist to exercise the KPIs • Reporting Levels should be understood • Define and agree exceptions in advance For internal use 68 © Nokia Siemens Networks Presentation / Author / Date
  • 69. Version control Version Date Status Owner RAN04 2006 Base version Mike Roche, Steve Hunt, Gareth Davies, Pekka Ranta RAS051_v1.0 24. 04. 2007 Example case available Kirsi Teräväinen Minor changes checked for RAS051 level For internal use 69 © Nokia Siemens Networks Presentation / Author / Date

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