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Part 3 optimization 3G

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Its about 3G Optimisation

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Part 3 optimization 3G

  1. 1. Part 3 : Optimization
  2. 2. Network Deployment Steps
  3. 3. Presentation / Author / Date Using Reporting Suite 3G RAN Reports or MS Access KPI QueriesWeekly KPI ( PLMN) < X % No action needed No Yes Yes No System Program (PLMN) Weekly KPI (RNC) < X % ? System Program (RNC) Daily KPI (WCEL) < X% Identify Call failure phases of bad performing KPIs, for example CSSR Identify failures root- causes and failure distribution of bad KPIs Identify Top50 Worst Cells based on highest number of root causes failures System Program (WCEL) Others 3G RAN Reports Others 3G RAN Reports Yes Mataching failure distribution into network topology System Program (WCEL) Solution Proposal Mapinfo High level PM data analysis and assessment
  4. 4. Presentation / Author / Date PM Data analysis process
  5. 5. Traffic Monitoring
  6. 6. Principles of traffic monitoring - bottlenecks Both interfaces and internal resources of WCDMA network should be monitored UserPlane RNC UE WBTS DNBAP AAL2 or IP SIG CNBAPPRACH FACH-c&u DCH Air Interface Iub Interface User Plane Iur Interface IuCS Interface User Plane SS7 (RANAP) IuPS Interface User Plane User Plane SS7 (RANAP) PCH WSP Resource Code Capacity Throughput Connectivity Unit Load DSP Usage D-RNC
  7. 7. Principles of traffic monitoring - reactive / proactiveReactive monitoring • Consider setup failure (already discussed in chapter 2) • Daily BH analysis needed Proactive monitoring • Consider amount of traffic • Weekly analysis enough
  8. 8. Principles Transmitted carrier power Node B reporting Total DL power R99 power HSDPA power Received total wideband power Code tree allocation Channel element allocation Iub transmission RNC processing load Number of users Traffic Monitoring
  9. 9. Node B informs RNC about air interface load by the following messages Common NBAP radio resource indication • Transmitted carrier power • Total power R99 + HSDPA • R99 power • Received total wideband power • Total power R99 + HSUPA • HSUPA power (calculated by Node B, not directly measured) Dedicated NBAP measurement report • Power of each dedicated radio link IuB C - NBAP D - NBAP Node B RNC Node B reporting
  10. 10. High total DL power High pilot pollution Otherwise Total DL power - optimization flow Check SHO parameter settings Check adjacent cell interference Neighbor analysis High SHO overhead Add second carrier
  11. 11. R99 power -
  12. 12. Number of radio resource indications falling into specific R99 power interval The definition of the load target depends on the presence of HSDPA users • No HSDPA user present → static load target PtxTarget • At least one HSDPA user present → dynamic load target PtxTargetPS R99 power -
  13. 13. HSPA power HSPA power includes • HS-PDSCH • All HS-SCCH • All HSUPA DL signaling channels (E-AGCH, E-RGCH, E-HICH)
  14. 14. DL power shared dynamically between R99 and HSDPA Realized by dynamic load target for NRT R99 traffic PtxTargetPS For RT R99 traffic still static load target PtxTarget PtxTargetPS is adjusted between • Minimum load target PtxTargetPSMin (default 36 dBm) • Maximum load target PtxTargetPSMax (default 40 dBm) RNC checks periodically, whether adjustment of PtxTargetPS needed Period defined by PtxTargetPSAdjustPeriod (default 5 RRI periods) PtxTargetPSMin ≤ PtxTargetPS ≤ PtxTargetPSMax HSDPA power - dynamic share with R99
  15. 15. HSDPA power - dynamic share with R99 PtxTargetPS adjusted under the following conditions 1) HSDPA congestion • Too much total DL power present in cell • PtxHighHSDPAPwr defines overload threshold for HSDPA cell (default 41 dBm) 2) DCH congestion • Too much R99 power present in cell • The offset is fixed to 1 dB PtxTotal ≥ PtxHighHSDPAPwr PtxNonHSPA ≥ PtxTargetPS - Offset
  16. 16. HSDPA Congestion HSDPA power - dynamic share with R99 HSDPA power congestion, if Ptxtotal ≥ PtxHighHSDPAPwr PtxMax 43 dBm PtxNC PtxNRTPtxNonHSDPA PtxTotal PtxTargetPSMin -10..50; 0.1; 36 dBm PtxTargetPSMax -10..50; 0.1; 40 dBm PtxHighHSDPAPwr -10..50; 0.1; 41 dBm PtxTargetPS If actual load target PtxTargetPS > optimum load target Decrease PtxTargetPS by PtxTargetPSStepDown (default 1 dB) Optimum load target
  17. 17. HSDPA power - dynamic share with R99 DCH Congestion PtxMax 43 dBm PtxNC PtxNRTPtxNonHSDPA PtxTargetPSMin PtxTargetPSMax PtxHighHSDPAPwr DCH power congestion, if PtxNonHSDPA ≥ PtxTargetPS - 1dB If actual load target PtxTargetPS < optimum load target Increase PtxTargetPS by PtxTargetPSStepUp (default 1 dB) PtxTotal PtxTargetPS Optimum load target
  18. 18. Noise rise due to real traffic Own cell load factor (throughput) i-factor PrxTarget e.g. 4 dB above PrxNoise RTWP sources -108 dBm Receiver noise figure (e.g. 2 dB) Thermal noise -108 dBm -106 dBm Intermodulation out of band (e.g. 1 dB) -105 dBm RTWP of empty cell MUST be equal PrxNoise PrxOffset e.g. 1 dB above PrxTarget High adjacent cell interference Low adjacent cell interference -101 dBm -100 dBm
  19. 19. Total UL power - role of BTS commissioning RTWP measured by BTS at antenna connector Then corrected due to • Feeder loss • MHA gain RTWPcorrected = RTWPmeasured + feeder loss – MHA gain Corrected RTWP reported to RNC With wrong settings wrong RTWP values reported Previous example for 2 GHz range Probably feeder loss underestimated → corrected RTWP underestimated
  20. 20. Total UL power Close to -112 dBm Often > -100 dBm Total UL power - optimization flow Check feeder loss / MHA gain commissioning setting Check HW Still below BTS receiver noise Check - High traffic density - HW - Intermodulation
  21. 21. SF=64 SF=32 SF=16 SF=8 SF=128 R99 code allocation - principles Code resource required depends on type of radio bearer • Signaling SF 256 for 3.4 Kbit/s, SF 128 for 13.6 Kbit/s • Voice HR SF 128 or SF 256 • Voice FR, 16K data SF 128 • 32K data SF 64 • 64K data SF 32 • 128K data SF 16 • 256K data, 384K data SF 8 Only 1 code per bearer allocated
  22. 22. Total blocking rate Blocking rate for SF16 Blocking rate for SF8 R99 code allocation - blocking Practical example – single cell Blocking per SF per hour Very high blocking especially for SF8 But still also for SF16 and sometimes even for SF32
  23. 23. R99 code allocation - re-arrangement Code tree quickly fragmented, if not re-arranged from time to time Then few users of high SF (low data rate) block huge amount of resources for users of low SF (high data rate) Re-arrangement performed • Periodically according CodeTreeOptTimer (default 1h) OR • If code tree occupation > CodeTreeUsage (default 40%) OR • If more than MaxCodeReleases consecutive releases of codes (default 40) Blocking before re-arrangement Blocking after re-arrangement
  24. 24. 1514131211109876543210 ………. ………. 1514131211109876543210 1514131211109876543210 ………. ………. 1514131211109876543210 HSDPA code allocation - principles For HSDPA fixed SF16 But several codes per bearer available • Minimum guarantee of 5 codes • Maximum number set usually to 15 codes • Code resource has to be shared with R99 SF=8 SF=4 SF=2 SF=1 SF=16 R99 + HSPA signaling CH Guarantee for HSDPA Dynamically shared between R99 and HSDPA
  25. 25. Number of codes reserved for HSDPA can be adjusted dynamically in dependence on R99 traffic Possible levels configured with parameter HSPDSCHCodeSet 16 bit parameter to enable / disable each possible level individually HSDPA code allocation - dynamic share with R99 Examples 00000 00000 100000 = always 5 codes reserved (default) 11010 10100 100000 = number of reserved codes adjustable (5, 8, 10, 12, 14 or 15 codes, recommended) 0-4 codes always disabled11-15 codes 6-10 codes
  26. 26. Upgrade RNC checks periodically, whether more codes can be reserved for HSDPA Requirements for upgrade • Free adjacent codes to go to next higher level defined by HSPDSCHCodeSet • After upgrade still enough codes with SF128 available for R99 (at least HSPDSCHMarginSF128, default = 8) • Upgrade to 15 codes possible only with HSPDSCHMarginSF128 = 0 HSDPA code allocation - dynamic share with R99
  27. 27. HSDPA code allocation - dynamic share with R99 Downgrade due to NRT R99 traffic If a NRT R99 request cannot be served due to code blocking, HSDPA is downgraded only, if the actual number of codes exceeds Maximum code set – DPCHOverHSPDSCHThreshold • Default = 0 → HSDPA always has higher priority than incoming NRT R99 request • Threshold = 5 → HSDPA downgraded due to incoming NRT R99 request, if actually more than 15 - 5 = 10 codes reserved for HSDPA NumberofallocatedSF16codes DPCHOverHSPDSCHThreshold 6 7 8 9 10 11 12 13 14 15 Maximum code set 5
  28. 28. HSDPA code allocation - impact of HSUPA SF=1 SF=2 SF=4 SF=8 SF=16 SF=32 SF=64 SF=128 SF=256 14 HS-PDSCH codes14 HS-PDSCH codes Up to three HS- SCCH codes Up to three HS- SCCH codes Codes for common channels in the cell Codes for common channels in the cell Codes for associated DCHs and non-HSDPA users Codes for associated DCHs and non-HSDPA users E-AGCH (256)E-AGCH (256) E-RGCH/E-HICH (128)E-RGCH/E-HICH (128) New DL signaling channels occupying at least the following codes • 1 x SF256 by E-AGCH • 1 x SF128 by E-RGCH / E-HICH (these two channels share one code) Loss of a second code with SF16 → maximum of 14 codes for HSDPA
  29. 29. High code congestion Many DCH of low activity High code congestion - optimization flow Enable throughput based optimization (R99 DCH) Check SHO parameter settings Check adjacent cell interference High SHO overhead Enable code tree optimization Still high congestion Enable F-DPCH (associated DCH) Many associated DCH
  30. 30. •Principles •Transmitted carrier power •Received total wideband power •Code tree allocation •Channel element allocation •Monitoring •BTS channel cards •R99 dimensioning (optional) •HSDPA dimensioning (optional) •HSUPA dimensioning (optional) •Iub transmission •RNC processing load •Number of users Traffic Monitoring
  31. 31. For daily work often more convenient to know the percentage of occupied CE instead the absolute number Both for DL and UL six to indicate, how often total utilization falls into certain interval • 0-49 % • 50-69 % • 70-79 % • 80-89 % • 90-99 % • 100 % Monitoring - total utilization 80-89% 90-99% 70-79% 100%
  32. 32. Monitoring - total utilization 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%11.03.2010__09:00:00 11.03.2010__11:00:00 11.03.2010__13:00:00 11.03.2010__15:00:00 11.03.2010__17:00:00 11.03.2010__19:00:00 11.03.2010__21:00:00 11.03.2010__23:00:00 12.03.2010__01:00:00 12.03.2010__03:00:00 12.03.2010__05:00:00 12.03.2010__07:00:00 12.03.2010__09:00:00 12.03.2010__11:00:00 12.03.2010__13:00:00 12.03.2010__15:00:00 70.00 75.00 80.00 85.00 90.00 95.00 (100 or more)% M5001C20 (90 - <100)% M5001C19 (80 - <90)% M5001C18 (70 - <80)% M5001C17 (50 - <70)% M5001C16 (0 - <50)% M5001C15 Avg Ratio of Used CE for UL in BTS RNC_731A Practical example – UL on single BTS In most cases very high utilization Typically 80-89 % or 90-99 %
  33. 33. Both for DL and UL five additional to indicate, how often utilization by HSPA falls into certain interval • 0-19 % • 20-39 % • 40-59 % • 60-79 % • 80-100 % Monitoring - utilization by HSPA
  34. 34. Monitoring - utilization by HSPA 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 1 1 .0 3 .2 0 1 0 _ _ 0 9 :0 0 :0 0 1 1 .0 3 .2 0 1 0 _ _ 1 1 :0 0 :0 0 1 1 .0 3 .2 0 1 0 _ _ 1 3 :0 0 :0 0 1 1 .0 3 .2 0 1 0 _ _ 1 5 :0 0 :0 0 1 1 .0 3 .2 0 1 0 _ _ 1 7 :0 0 :0 0 1 1 .0 3 .2 0 1 0 _ _ 1 9 :0 0 :0 0 1 1 .0 3 .2 0 1 0 _ _ 2 1 :0 0 :0 0 1 1 .0 3 .2 0 1 0 _ _ 2 3 :0 0 :0 0 1 2 .0 3 .2 0 1 0 _ _ 0 1 :0 0 :0 0 1 2 .0 3 .2 0 1 0 _ _ 0 3 :0 0 :0 0 1 2 .0 3 .2 0 1 0 _ _ 0 5 :0 0 :0 0 1 2 .0 3 .2 0 1 0 _ _ 0 7 :0 0 :0 0 1 2 .0 3 .2 0 1 0 _ _ 0 9 :0 0 :0 0 1 2 .0 3 .2 0 1 0 _ _ 1 1 :0 0 :0 0 1 2 .0 3 .2 0 1 0 _ _ 1 3 :0 0 :0 0 1 2 .0 3 .2 0 1 0 _ _ 1 5 :0 0 :0 0 0 5 10 15 20 25 30 35 40 UL(90 - <100)% M5001C31 UL (80 - <90)% M5001C30 UL (70 - <80)% M5001C29 UL (50 - <70)% M5001C28 UL (0 - <50)% M5001C27 Max HSUPA Users M1031C1 Max HSDPA Users M1031C0 Avg ratio of Used CE for UL for HSUPA in BTS RNC_948A Avg ratio of Used CE for DL for HSUPA in BTS RNC_947A Practical example – UL on single BTS In most cases very high utilization due to HSUPA Typically 80-89 %
  35. 35. In general, each DCH occupies a certain number of CE in dependence on the type of service The CE occupation is the same for • FSMC/D/E and WSPF cards • R99 DCH and associated DCH R99 dimensioning Service CE SRB / voice / 16 K data 1 32 K data 2 64 K data 4 128 K data 4 256 K data 9 384 K data 12
  36. 36. Less CE needed for DCH of 256 K and 384 K All other rules remain unchanged R99 dimensioning Service CE SRB / voice / 16 K data 1 32 K data 2 64 K data 4 128 K data 4 256 K data 6 384 K data 8
  37. 37. High CE occupation - optimization flow High CE occupation Many DCH of low activity Enable throughput based optimization (R99 DCH) Check SHO parameter settings Check adjacent cell interference High SHO overhead Enable F-DPCH (associated DCH) Many associated DCH
  38. 38. Principles Transmitted carrier power Received total wideband power Code tree allocation Channel element allocation Iub transmission Implementation principles Monitoring options Examples RNC processing load Number of users Traffic Monitoring
  39. 39. M550 – CAC AAL2 Path Measurements 2 VCs with 8250 (ATM) cells per second per VC on 1 IMA group Examples - physical ATM traffic Two VC multiplexed by IMA Cell rate reserved by CAC per VC Configured bandwidth Maximum reserved bandwidth Minimum reserved bandwidth Free bandwidth Even maximum reserved bandwidth far below configured bandwidth No risk of physical congestion
  40. 40. Examples - logical ATM traffic Two VC multiplexed by IMA Number of AAL connections established by CAC per VC Even in busy hour number of AAL connections clearly below maximum of 248 No risk of logical congestion
  41. 41. Principles Transmitted carrier power Received total wideband power Code tree allocation Channel element allocation Iub transmission RNC processing load RNC block diagram Monitoring options Number of users Traffic Monitoring
  42. 42. After the patch is installed for the RNC, almost all the call drops with the cause being “Other” have disappeared and the PS call drop rate is obviously lower, as shown in the following table. The problem is thus solved. Solution Note: You can get the table on the right via custom report or “Performance Query” of Nastar. Case — High Call Drop Rate due to RNC Traffic Measurement Defect (Continued)
  43. 43. •Principles •Transmitted carrier power •Received total wideband power •Code tree allocation •Channel element allocation •Iub transmission •RNC processing load •Number of users Traffic Monitoring
  44. 44. Number of users - licenses R99 • No license for specific number of users per cell required • New user allocated, as long all types of RAN resources available HSPA • License for specific number of users per cell required • The following levels are available • 16 users • 48 users • 64 users • 72 users • If maximum number of users present, new user rejected, even if all types of RAN resources still available
  45. 45. RRC connection setup RAN resources reserved for signaling connection between UE and RNC RRC access Connection between UE and RRC RRC active UE has RRC connection If dropped, also active RAB dropped RAB setup Attempts to start call RAB setup access Connection between UE and core RAB active phase UE has RAB connection CSSR affected if any of the following events takes place • RRC Connection Setup Fail • RRC Connection Access Fail • RAB Setup Fail • RAB Setup Access Fail Setup Complete Setup Complete Access Complete Access Complete Active Complete Active Complete SetupSetup AccessAccess ActiveActive Attempts Setup failures (blocking) Access failures Access Active Release Active Release Active Failures Active Failures RRC Drop Success Phase: RRC and RAB Call setup - phases
  46. 46. [RACH] RRC Connection RequestRACH] RRC Connection Request UEUE Node BNode B RNCRNC ALCAP ERQ NBAP RL Setup Request [DCH] RRC Connection Setup Complete[DCH] RRC Connection Setup Complete L1 Synchronisation Start TX/RXStart TX/RX Start TX/RXStart TX/RX [FACH] RRC: RRC Connection Setup NBAP RL Setup Response AC to check to accept or reject RRC Connection Request AC to check to accept or reject RRC Connection Request ALCAP ECF NBAP Synchronization Indication RRC Connection Setup phase RRC Connection Access phase RRC Connection Active phase Allocation of UTRAN resources Waiting for UE reply Three phase for RRC Call setup – successful RRC establishment Signalling and trigger =
  47. 47. RRC Connection – SETUP and ACCESS PHASE [RACH] RRC Connection RequestRACH] RRC Connection Request UEUE Node BNode B RNCRNC ALCAP ERQ NBAP RL Setup Request [DCH] RRC Connection Setup Complete[DCH] RRC Connection Setup Complete L1 Synchronisation Start TX/RXStart TX/RX Start TX/RXStart TX/RX [FACH] RRC: RRC Connection Setup NBAP RL Setup Response AC to check to accept or reject RRC Connection Request AC to check to accept or reject RRC Connection Request ALCAP ECF NBAP Synchronization Indication RRC Connection Setup phase RRC Connection Access phase Allocation of UTRAN resources Waiting for UE reply Three phase for RRC Signalling and trigger =
  48. 48. 1. RRC setup attempts. 2. RRC setup attempts per setup cause. (SEE NEXT SLIDE) 3. RRC setup failures due to • handover control , • admission control • transport (Transmission)• RNC internal • frozen BTS • BTS • ICSU overload 4. RRC setup failure per cause. 5. RRC setup complete. 6. RRC access failures due to • radio interface • UE• RNC internal 7. RRC access complete. 8. Special reason: RRC active release due to • SRNC Relocation • Pre-emption • User inactivity • RNC HW resources • ISHO to GAN • Inter-system handover to GSM • IF inter-RNC hard handover • Inter-frequency inter- RNC hard handover 9. RRC active failures due to • Iu interface (transport) • radio interface (synchronisation) • BTS • Iur interface (DRNC) • RNC internal • UE • Transmission 10. RRC active complete
  49. 49. 1. RAB setup attempts. Separate counter per each RAB type. 2. RAB setup failures due to • admission control • transport (transmission) • RNC internal • frozen BTS • BTS (RT only) • anchoring (NRT only) • capacity license (for CS voice RAB only) 3. RAB setup complete. Separate counter per each RAB type. 4. RAB access failures due to • UE • RNC internal 5. RAB access complete. Separate counters per each RAB type. 6. Special reason: RAB active release due to • SRNC relocation • pre-emption • capacity license pre- emption (only for CS voice RAB) 7. RAB active failures due to • Iu interface (transport) • radio interface (synchronisation) • BTS • Iur interface (DRNC) • RNC internal • UE • Transmission 8. RAB reconfiguration attempts. 9. RAB reconfiguration failures. 10. RAB active complete. Separate counters per each RAB type.
  50. 50. Drop Call Analysis Presentation / Author / Date
  51. 51. Case 1: Drop due to missing neighbor Problem: Detected Nighbor (DN) UE sends a Measurement Report that contains an event1a means adding a new RL (cell) to Active Set If the reported cell is not in the current neighbor cell list and the reported Ec/No is better than the best serving cell Ec/No in AS by some dBs (set by a RNC parameter) If for any reason the new cell can not be added to AS, call will be released
  52. 52. Case 1: Drop due to missing neighbor “DN” cell better than the serving cell DL BLER gets worse “DN” cell better than the serving cell DL BLER gets worse
  53. 53. Case 2: Drop due to Poor Coverage (low RSCP) Problem: Poor DL coverage When UE gets to an area with low RSCP ( < -105 dBm) regardless Ec/No values there is high risk for drop. UE will likely ramp up the transmitted power and reach its max power. The DL BLER will probably increase and SIR target cannot maintain anymore, finally the call drops.
  54. 54. Case 2: Drop due to DL Poor Coverage Very bad RSCP UE max Tx power and high DL BLER Very bad RSCP UE max Tx power and high DL BLER
  55. 55. Case 3: PS: Session Error due to Poor DL Coverage UE enters a very low coverage area (RSCP < – 105 dBm). The packet connection is carried on a 64/64 DCH Channel as consequence of the low coverage conditions. The UE will likely ramp up its power to the maximum, goes to Idle Mode and the Application and RLC throughputs go to zero. At this point the RAS application will start the Session Timeout timer, if the throughput is not resumed the Session Error event is triggered with cause “session timeout”.
  56. 56. PS: Session Error due to Poor DL Coverage App throughput ~64kbps Very low RSCP App throughput ~64kbps Very low RSCP
  57. 57. FINAL WORDS For network tuning, we need to rely on field measurements which require extensive drive tests Finding the best possible configuration for antenna heights, tilts, azimuths and parameter setting for all the present cells/sectors in the network and also for any new sites that might be needed to improve coverage Power adjustment can also be used for network tuning but can become complicated and result in poor network performance Use of Remote Electrical Tilt (RET) Antenna is preferred over mechanical tilt antenna Neighbour definition is of prime importance in UMTS network (Soft handover gain and interference reduction). Keep neighbour list upto 20. Automated tools are needed that could suggest the best possible neighbour relations, antenna heights and tilts by using both the field measurements and the propagation models & simulations Skilled people, right methods and advanced tools are needed to perform 3G tuning and optimisation
  58. 58. Presentation / Author / Date Call Drop analysis Top (N) drops Cell and its Neighbour Cells availability Alarms/Tickets Configuration & Parameter audit SHO Success Rate < 90%? Conf OK ? Site OK ? ISHO Failures Iur performance Investigation Iur Audit adjacent sites for alarms, Availability, configuration and capacity Traffic Neighbours Performance’ (use SHO success per adjs counters to identify badly performing neighbours) & Map 3G Cell at RNC border? NO YES New site ? Analyse last detailed radio measurements RF and IFHO neighbour optimisation No cell found ratio >40 % ISHO Success Rate < 90% RF and ISHO neighbour optimisation 3G cell covers over a coverage hole ? 3G cell at inter-RNC border ? Wrong reference clock (10MHz tuning) No cell found ratio > 90 % and enough ADJG 2G Cell Doctor 2G Investigation : TCH blocking or TCH seizure failure (interference) NO YES YES YES NO YES NO YES YES SHO ISHO Top iss ues SHO based on DSR, CPICH EcNo difference, SHO branch setup fail BTS/Iub HHO RSSI & BSIC time, ISHO cancellation Max HSPA users in cell/RNC,RNC licensed capacity:Max AMR/Iups throughput Relocation success in target RNC HSDPA IFHO failures, reject CM for IFHO
  59. 59. Presentation / Author / Date Call Drop analysis 1. Check high call drop cells and its neighbouring cells of any faulty alarms 2. Identify call drop root cause failure distribution and main failure contributor (radio, Iu, BTS, Iur, MS, RNC) 3. Check SHO KPI if performance < 90% ( leads to radio failure) • Check if cells are at RNC border (check Iur capacity and SRNC relocation problem) • Detect badly performing neighbours using HO success rate per adjacency counters (M1013) • High incoming HO failure rate in all adjs – check sync alarms • Assessing neighbor list plan and visualization check with map • Evaluate HO control parameters and trigger threshold 4. Check ISHO KPI if RT ISHO < 90% or NRT < 80% (leads to radio failure)  Check missing neighbour (M1015), GSM frequency plan neighbour RNC and MSC database consistency audit, check alarm of reference clock in 3G or in 2G, check 2G TCH congestion  Check RRC Drop ISHO RT / NRT
  60. 60. Presentation / Author / Date Call Drop analysis 5. Detecting DL or UL path loss problem if RAB drop due to radio (dominant call drop cause > 50%)  Check UL Lost Active KPI from Iub counters (active L1 synchronization failure) to check UL/DL path loss problem  Check ASU failure rate (UNSUC_ASU) which link to NO RESPONSE FROM RLC  Mapping radio failures with Tx power and CPICH related parameters -> CPICHToRefRABOffset, PTXDPCH MAX  Check Call reestablishment timer -> T315  Ecno distribution for bad coverage issue (M1007C38-M1007C47) 6. Check core network parameter setting if RAB_ACT_FAIL_XXX_IU  Check SCCP SGSN/RNC IuPS Tias/Tiar if RAB_ACT_FAIL_BACKG_IU 7. If high RAB_ACT_FAIL_XXX_BTS  Check if any BTS faulty alarm (7653 cell faulty alarm)  If no alarms, COCO detach/attach 8. If high RAB_ACT_FAIL_XXX_MS • Check physical channel reconfiguration failure rate (IFHO, ISHO, code optimisation)
  61. 61. HSDPA Low Throughput Presentation / Author / Date
  62. 62. HSDPA Throughput Analysis Presentation / Author / Date
  63. 63. Good CQI but poor HSDPA throughput Presentation / Author / Date
  64. 64. COMMON CALL PERFORMANCE ISSUES Presentation / Author / Date
  65. 65. Common Call Performance Issues Presentation / Author / Date
  66. 66. Common Call Performance Issues Presentation / Author / Date
  67. 67. Common Call Performance Issues Presentation / Author / Date
  68. 68. Common Call Performance Issues Presentation / Author / Date
  69. 69. Common Call Performance Issues Presentation / Author / Date
  70. 70. Presentation / Author / Date Common Call Performance Issues
  71. 71. Presentation / Author / Date Video Call Performance Issues
  72. 72. Presentation / Author / Date Video Call Performance Issues
  73. 73. Presentation / Author / Date ISHO Performance Issues
  74. 74. Soft Handover Neighbour Tuning Presentation / Author / Date
  75. 75. Active Set Usage M1013 (These counters are referred to cell addition and cell replacement – no target for deletion) Absolute Value must be considered not Failure Rate!
  76. 76. Active Set Usage High # out- going attempts? In – out pairs? Zero attempts? Ping-Pong No Adjs Low used Adjs Yes Yes Yes Unbalanced WCEL High # attempts for a source? Unbalanced ADJS Yes Mino r Filtering over attempts must be taken into count that: - statistical data must stabilized over time. - traffic distribution is not considered and a double-check to localize the event and DT feedback is required to understand if fenomena is traffic driven or cell dependent High # out- going fails for a defined ADJS? Major Failure ADJS Yes High # fails for a source? Failure WCEL Yes Min or Filtering over failure in absolute terms it is possible to find the major critical events
  77. 77. Active Set Usage Filtering criteria: Major - High number of failures for a defined out-going adjs failure( ADJS) - high number of fail for a defined source failure WCEL( ) Minor - high number of attempts in-comig and out-going for a defined pair with occasional failure ping-pong( ) Filtering action are required to find bi-lateral corrispondence - very low number of attempt with failure low used adjs( ) - zero number of attempt for declared adjs stabilized value no adjs– ( ) - high number of attempts with occsional failure for an out-going adjs unbalanced ADJS( ) Either in-coming or out-going condition is sufficient - high number of attempts with occsional failure for a defined source unbalanced WCEL( )
  78. 78. Failure ADJS Once anlyzed the RSCP, the coverage plot taking care to the evaluation of intersite-distance, it is easy to understand if target can be used. If not only down tilt is possible or DERR (ADJS object Paremeter) cell to avoid the failure during SHO. Down tilt must be carefully anlyzed. If from Ec/No the cell can be recovered an individual offset or filtering (ADJS object Parameter) can be introduced Failure ADJS Analyze RSCP from DT & NWP coverage plot considering inter-site distance Target act as polluter? Down tilt Yes Analyze Ec/No from DT Down tilt possibile? DERR cell Yes Ec/No offset Very low value of RSCP that not allow the adjs to be used … Attempt Fail Attempt Fail Attempt Fail Attempt Fail Source_cell_A 2 1 23 1 442 34 4 0 Source_cell_B 1 0 11 0 53 25 345 0 … Source_cell_Z 322 54 15 0 2 0 12 0 Target_cell_A Target_cell_ZTarget_cell_CTarget_cell_B
  79. 79. Failure ADJS – Individual Ncell Offset time P CPICH 1 P CPICH 2 P CPICH 3 Reporting Range Reporting Event 1B Reporting Event 1A AdjsEcNoOffset to modify measurement reporting behaviour. Effectively 'moves' cell border (shrinks or enlarges cell) Enlarging Cell 3 by x dB Ec/Io
  80. 80. Failure ADJS – Forbidding Neighbour Cell Time P CPICH 1 P CPICH 2 P CPICH 3 PCPICH3 is forbidden to affect the reporting range as its quality is quite unstable. Report ing Range AdjsDERR to forbid a cell from reporting range calculation in some instances Ec I/ o
  81. 81. Failure WCEL KPI(1) ? Failure WCEL Tune 1A Yes KPI(2) ? Tune 1C Yes Analyze Ec/No &BLER from DT & NWP coverage plot considering inter-site distance WCEL polluted/interfered? Yes Analyze Ec/No from DT Pollution/Interference Most of the Target failure during the 1A or 1C event. Once anlyzed the Ec/No, BLER, the coverage plot taking care to the evaluation of intersite- distance, it is easy to understand if the WCEL is interferered/Polluted If not, two KPIs allow to separate the dominant contribute among the 1A and 1C. Relaxing the parameters an improvement should be achieved The following gives the number of attempts per event RT Services KPI 1 M1007C10 CELL ADD REQUEST ON SHO FOR( ) = _ RT TRAFFIC KPI 2 M1007C12 CELL REPL REQUEST ON SHO( ) = _ FOR RT TRAFFIC NRT Services KPI 1 M1007C27 CELL ADD REQUEST ON SHO( ) = _ FOR NRT TRAFFIC KPI 2 M1007C29 CELL REPL REQUEST ON SHO( ) = _ FOR NRT TRAFFIC The failure rate for all the procedure can be estimated as well ADD REPL FAIL ONSHO FOR x( )_ _ _ _ / ADD REPL REQ ON SHO FOR x ADD REPL( )_ _ _ _ _ + ( )_ FAIL ONSHO FOR x_ _ _ M1007C14 M1007C12 M1007C14/ + M1007C36 M1007C11 M1007C36/ + M1007C30 M1007C27 M1007C30/ + M1007C37 M1007C28 M1007C37/ + M1007C31 M1007C29 M1007C31/ + … Attempt Fail Attempt Fail Attempt Fail Attempt Fail Source_cell_A 2 1 23 15 442 34 124 23 Source_cell_B 1 0 11 0 53 0 345 0 … Source_cell_Z 322 1 15 0 2 0 12 0 Target_cell_A Target_cell_ZTarget_cell_CTarget_cell_B
  82. 82. Failure WCEL - 1A RNC Strongest CPICH in AS: time Ec/Io P CPICH 3 P CPICH 1 P CPICH 2 1A AdditionWindow determines the relative threshold used by the UE to calculate the reporting range of event 1A. The threshold is either relative to the CPICH Ec/No measurement result of the best active set cell (0), or to the sum of active set measurement results (<>0) AdditionTime defines the 'time-to-trigger' interval between the cell entering the reporting range and the UE sending the measurement report to the RNC with the 1A event AdditionReportingInterval defines the period of time that the UE wait, if the RNC is unable to add Ncell to AS, before sending further reports periodically, with interval AdditionReportingInterval, until the Ncell moves out of reporting range, or RNC adds Ncell to AS. Measurement Report Add to the AS? no ActiveSetWeightingCoefficient is used to weight either the measurement result of the best active set cell (0) or the sum of measurement results of all active set cells (<>0)
  83. 83. Failure WCEL - 1C time weakest CPICH in AS Ec/Io P CPICH 3 P CPICH 1 P CPICH 2 P CPICH 4 AS has 3 cells ReplacementReportingInterval If the RNC is not able to replace the active cell with the monitored cell, the UE continues reporting after the initial report by reverting to periodical measurement reporting. The parameter Replacement Reporting Interval determines the interval of periodical measurement reports when such reporting is triggered by the event 1C. ReplacementWindow determines the margin by which the CPICH Ec/No measurement result of the monitored cell (MNew) must exceed the CPICH Ec/No measurement result of the an active set cell (MInAS) before the UE can send the event 1C triggered Measurement Report to the RNC: MNew >= MInAs + ReplacementWindow / 2 ReplacementTime Defines the period of time the monitored cell must continuously stay within the reporting range before the UE can send a Measurement Report to the RNC in order to replace an active set cell with the monitored cell (event 1C). Measurement Report RNC AS update? no 1C
  84. 84. NO ADJS No Adjs Remove ADJS Zero attempts? Statistic Stable? Yes Repeat Analysis Yes DT analysis for the Adjs Comparing the ADJS plan provisioned into the network with the M1013 matrix, it is easy to find if one declared ADJS is not used (not present in the list) Statistic data must be stabilized before decide to remove it and DT analysis can help n estimating the amount of residual noise if down tilt is not possible … Attempt Fail Attempt Fail Attempt Fail Attempt Fail Source_cell_A 2 1 0 - 442 34 124 23 Source_cell_B 0 - 11 0 53 0 345 0 … Source_cell_Z 322 1 15 0 2 0 12 0 Target_cell_A Target_cell_ZTarget_cell_CTarget_cell_B
  85. 85. Low used ADJS Low used Adjs Remove ADJS Analyze DT result and NWP data Monitored Qual from DT acceptable? Alter. ADJS present? Yes Interference evaluation Yes ADJ Offset It is not difficult in live network to find some pair working with very low For low used ADJS has to be intended and ADJS that has few number of attemps in one day (e.g <3) with occasional failure. The ADJS removal has to be considered as the last option, after the quality has been monitored by drive test result, considering the overall capability of the target to be recovered (e.g. inter-site distance, power budget) and other options are available for that area. Statistic data must be stabilized before decide to remove it and DT analysis can help in estimating the amount of residual noise if down tilt is not possible … Attempt Fail Attempt Fail Attempt Fail Attempt Fail Source_cell_A 2 1 25 4 442 34 124 23 Source_cell_B 245 23 11 0 53 0 345 0 … Source_cell_Z 322 1 3 1 2 1 123 20 Target_cell_A Target_cell_ZTarget_cell_CTarget_cell_B
  86. 86. Unbalanced ADJS Unbalance ADJS Ec/No offset Analyze RSCP from DT & NWP coverage plot considering inter- site distance e traffic distribution Target act as polluter? Down tilt Yes Analyze Ec/No from DT & evaluate unbalance Down tilt possibile? DERR cell Yes Attempt over the same UE? Yes An high number of attempt could be an indication of a problem and even in case of the failure is not associated an evaluation is required. The key point is the inviduation of the attempt distribution, that in case are not justified but partcualar populated area, coluld generate lot of signalling. The attempts could be genarated by 1B event ever the same UE not counted in the M1013. The possibility to recover the ADJS is the favourite option and the down tilt carefully analyzed considering the failure associated. No action required … Attempt Fail Attempt Fail Attempt Fail Attempt Fail Source_cell_A 54 3 345 10 23 1 124 5 Source_cell_B 25 1 11 0 137 3 … Source_cell_Z 32 2 45 2 Target_cell_A Target_cell_ZTarget_cell_CTarget_cell_B
  87. 87. Unbalanced WCEL KPI(1) ? Unbalanced WCEL Tune 1A Yes KPI(2) ? Tune 1C Yes Analyze RSCP from DT & NWP coverage plot considering inter-site distance and traffic distribution WCEL interfered polluted? Yes Analyze Ec/No from DT Interference / pollution Attempt over the same UE? Yes No action required An high number of attempt could be an indication of a problem and even in case of the failure is not associated an evaluation is required. The key point is the inviduation of the attempt distribution, that in case are not justified but partcular populated area, coluld generate lot of signalling. The attempts could be genarated by 1B event ever the same UE not counted in the M1013. The possibility to have an interference/pollution increase respect to the unbalanced ADJS. The optimization should be performed at WCEL level The KPI reported are the same of Failure WCEL … Attempt Fail Attempt Fail Attempt Fail Attempt Fail Source_cell_A 543 13 345 10 876 7 124 5 Source_cell_B 25 1 11 0 137 3 … Source_cell_Z 32 2 45 2 Target_cell_A Target_cell_ZTarget_cell_CTarget_cell_B
  88. 88. Ping Pong Ping-pong Analyze RSCP from DT & NWP coverage plot considering inter-site distance One of them act as polluter? Analyze Ec/No from DT Comparable value? Histeresys using Ec/NoOffset on the pair Not stable, Fading? Filtering Yes Yes Down tilt Down tilt possibile? DERR cell Yes Yes Attempt from the same UE? No action required pollution In this particular case the high number of attempt is concentrated in a pair From A >> B and from B >>A as in the picture As in the previous case could be an indication of a problem and even in case of the failure is not associated an evaluation is required to avoid to use a lot signalling. The optimization should be performed at ADJS level considering that the filtering option could get to smoother measured value … Attempt Fail Attempt Fail Attempt Fail Attempt Fail Source_cell_A 54 3 345 10 23 1 124 5 Source_cell_B 987 13 11 0 137 3 … Source_cell_Z 32 2 45 2 Target_cell_A Target_cell_ZTarget_cell_CTarget_cell_B
  89. 89. Ping Pong - Filtering Node B UTRAN RNC UE Measurement Control [ ] I am in the CELL_DCH sub-state Measurement Type: Intra-frequency measurements Reporting events: 1A: Event 1A triggered when CPCIH Ec/Io of the measured cell enters UE reporting range for a defined period of time 1B: Event 1B triggered when CPICH EC/I0 of the measured cell drops out of the UE reporting range for a defined period of time 1C: Event 1C triggered when CPICH EC/IO of the measured cell enter in AS by a defined margin for a defined period of time System Information [ ] EcNoFilterCoefficient EcNoAveragingWindow Applied for averaging of periodical meas. reports Ec/NoFilterCoeff controls the higher layer filtering of physical layer measurements before the event evaluation and measurement reporting is performed by the UE.
  90. 90. Pollution
  91. 91. Polluter Detection The best way to individuate a Polluter is the Drive Test A feedback can come from coverage plot, RNP feedback and Counters A polluter can be of different type: 1. PSC Pollution Too high reuse factor for the PSC. New PSC plan is required 2. DL Noise raise ADJS signal strength out of usage window (will be never utilized by the UE) A down tilt or power reduction is the solution evaluating all the side effects 3. Dominant site A dominant site over-shooting the ADJ becoming congested A down tilt or power reduction is the solution evaluating all the side effects
  92. 92. PSC Pollution A confirm for the polluter of the first type can come from the counter M1007C38-47 CELL SPECIFIC CPICH EC NO - CLASS x/ Pollution Criteria: The M1007C38-47 gives an indication of Ec No distribution value/ measured during event 1A . Having the distribution highly unbalanced normally centered on class 2, 3, 4( ) we have an indication of a probable problem. For example unbalancing towards the scarce value of Ec No but/ continuing to add cells to AS could give an indication of pollution Polluted WCEL Yes High number of class0-3? High number of class>6? Not Polluted WCEL Yes Isolated/unavailable WCEL
  93. 93. DL Noise Raise The NO ADJS and low used ADJS criteria before presented can give a confirm for a pollution of this type. After the statistical data are stabilized, making across-check with the provisioned ADJS Plan the probable polluters are individuated. This is obviously a cautelative estimation to be integrated and confirmed by drive test results … Attempt Fail Attempt Fail Attempt Fail Attempt Fail Source_cell_A 2 1 25 4 0 - 124 23 Source_cell_B 245 23 11 0 53 0 345 0 … Source_cell_Z 322 1 3 1 0 - 123 20 Target_cell_A Target_cell_ZTarget_cell_CTarget_cell_B
  94. 94. Dominant site Filtering the M1013 pairs for the recurrent target cell with associated occasional failure we have an estimation of the probable polluters For the polluters, originating failures a down tilt is required Polluted Cell Criteria: SHO over head can give a soft help in individuating cell where polluter overshooting site can be present or where unbalanced cell/ criteria could apply ( ) ( ) %1001 T_NRT_IN_ACT_SETHREE_CELLM1007C21T_RT_IN_ACT_SETHREE_CELLM1007C2 NRTN_ACT_SET_TWO_CELL_IM1007C20RTN_ACT_SET_TWO_CELL_IM1007C1 NRTN_ACT_SET_ONE_CELL_IM1007C19RTN_ACT_SET_ONE_CELL_IM1007C0 3T_NRT_IN_ACT_SETHREE_CELLM1007C21T_RT_IN_ACT_SETHREE_CELLM1007C2 2NRTN_ACT_SET_TWO_CELL_IM1007C20RTN_ACT_SET_TWO_CELL_IM1007C1 NRTN_ACT_SET_ONE_CELL_IM1007C19RTN_ACT_SET_ONE_CELL_IM1007C0 RNC_79BOverheadHandoverSoft ⋅                     − + ++ + ⋅+ +⋅+ + == … Attempt Fail Attempt Fail Attempt Fail Attempt Fail Source_cell_A 2 1 25 4 26 3 124 23 Source_cell_B 245 23 11 0 53 0 … … … Source_cell_Z 245 45 Target_cell_A Target_cell_ZTarget_cell_CTarget_cell_B
  95. 95. Cell Reselection
  96. 96. Cell Reselection List GSM MS starts WCDMA measurements if : RLA_C< F(Qsearch_I) for 0<Qsearch_I<=7 or RLA_C> F(Qsearch_I) for 7<Qsearch_I<=15 If, for suitable UMTS cell & for a period of 5 s: CPICH RSCP > RLA_C + FDD_Qoffset CPICH Ec/No ≥ FDD_Qmin and WCDMA cell reselection BCCH: FDD_Qmin, FDD_Qoffset Cell Reselection 2G -> 3G Start measurement
  97. 97. Depending on operator´s 2G – 3G interworking strategy parameter Q_search_I should planned accordingly. Configuration 1 RLA_C< F(Qsearch_I) ( 0<Qsearch_I<=6 ) GSM 3G Configuration 2 RLA_C> F(Qsearch_I) ( 7<Qsearch_I<=15 ) In the best case, 3G cell measurements are restricted to the condition: RLA_C level > –78 dBm GSM 3G In the best case, 3G cell measurements are possible when RLA_C level < –74 dBm GSM 3G Configuration 3 RLA_C< ∞ (always). (Qsearch_I=7) 2G -> 3G Measurement
  98. 98. 2G -> 3G Cell Re-selection Parameters Qsearch_I and Qsearch_P define the threshold for non-GPRS/GPRS (respectively) capable UEs to measure 3G neighbour cells when a running average of the received downlink signal level (RLA_C) of the serving cell below (0-7) or above (8-15) the threshold Value 0 1 … 6 7 8 9 10 … 14 15 dBm -98 -94 … -74 Always -78 -74 -70 … -54 Never FDD_Qoffset and FDD_GPRS_Offset the non-GPRS/GPRS (respectively) capable UEs add this offset to the RLA_C of the GSM cells. After that the UE compares the measured RSCP values of 3G cells with signal levels of the GSM cells Value 0 1 2 3 … 8 … 14 15 dBm Always -28 -24 -20 … 0 … 24 28 Always select irrespective of RSCP value Reselect in case RSCP > GSM RXLev (RLA_C) +28dB If RLA_C < -94 UE starts 3G measurements UE always measures 3G cells If RLA_C > -70 UE starts 3G measurements FDD_Qmin, defines minimum Ec/No threshold that a 3G cell must exceed, in order the UE makes a cell reselection from 2G to 3G.
  99. 99. Cell Re-selection Example-Weaker WCDMA Non GPRS case t Serving GSM Cell Neighbour WCDMA Cell Ec/No RSCP/ RLA_C 5 sec. Cell re-selection to WCDMA FDD_Qmin=0 (-20 dB) FDD_Qoffset =6 (-8 dB) Qsearch_I=0 (-98 dBm) RLA_C Measurements starts (serving cell) Minimum Quality Requirement for WCDMA Ec/N0 RSCP
  100. 100. Cell Re-selection Example-Weaker WCDMA GPRS case t Serving GSM Cell (Best) Neighbour WCDMA Cell Ec/No RSCP/ RLA_C 5 sec. Cell re-selection to WCDMA FDD_Qmin =-20 dB FDD_GPRS_Qoffset =10 (8 dB) Qsearch_P=0 (-98 dBm) RLA_P Measurements starts (serving cell) Minimum Quality Requirement for WCDMA Ec/N0 RSCP
  101. 101. Cell Reselection 3G -> 2G Whilst camping in a 3G cell the UE performs intra-frequency, inter-frequency, and inter-system measurements based on the measured CPICH EcNo. Serving cell parameters Sintrasearch, Sintersearch and SsearchRAT are compared with Squal (CPICH Ec/No – Qqualmin) in S-criteria for cell re-selection 1 - None (Squal > Sintrasearch ) 2 - WCDMA intra-frequency (Sintersearch< Squal ≤ Sintrasearch) 3 - WCDMA intra- and inter- frequency, no inter-RAT cells (SsearchRAT < Squal ≤ Sintersearch) 4 - WCDMA intra- and inter-frequency and inter-RAT cells (Squal ≤ SsearchRAT ) Sintrasearch Sintersearch SsearchRAT WCDMA CELL 1234
  102. 102. Cell Reselection 3G -> 2G First ranking of all the cells based on CPICH RSCP (WCDMA) and RSSI (GSM) Rs = CPICH RSCP + Qhyst1 Rn= Rxlev(n) - Qoffset1 First ranking of all the cells based on CPICH RSCP (WCDMA) and RSSI (GSM) Rs = CPICH RSCP + Qhyst1 Rn= Rxlev(n) - Qoffset1 Rn (GSM) > Rs (WCDMA) And Rxlev (GSM) >QrxlevMin Rn (GSM) > Rs (WCDMA) And Rxlev (GSM) >QrxlevMin YesNo Cell re-selection to GSM Cell re-selection to GSM Neighbour WCDMA or GSM cell calculation with offset parameter Serving WCDMA cell calculation, with hysteresis parameter UE starts GSM measurements if CPICH Ec/No =< qQualMin + sSearchRAT UE starts GSM measurements if CPICH Ec/No =< qQualMin + sSearchRAT SintraSearch SinterSearch SsearchRAT CPICH EcNo qQualMin Second ranking only for WCDMA cells based on CPICH Ec/No Rs = CPICH Ec/No + Qhyst2 Rn=CPICH_Ec/No(n)-Qoffset2 Second ranking only for WCDMA cells based on CPICH Ec/No Rs = CPICH Ec/No + Qhyst2 Rn=CPICH_Ec/No(n)-Qoffset2 Cell re-selection to WCDMA cell of highest R value Cell re-selection to WCDMA cell of highest R value
  103. 103. Cell Reselection 3G -> 2G UE ranks the serving cell and the measured neighboring cells to find out if reselection should be made • All the measured suitable cells (S-criteria) are included in the ranking. • Criteria for a suitable cell (S-criteria) is defined as – WCDMA intra-frequency neighbour cell: CPICH Ec/No > AdjsQqualmin and CPICH RSCP > AdjsQrexlevmin – WCDMA inter-frequency cell: CPICH Ec/No > AdjiQqualmin and CPICH RSCP > AdjiQrexlevmin – GSM cell: Rxlev > Qrxlevmin Ranking is done using Criteria R, and the UE reselects to the cell with highest R-criteria. R-criteria is defined as: • For serving cell: Rs = Qmeas,s + Qhysts • For neighboring cell Rn = Qmeas,n – Qoffsetts,n Qmeas is CPICH Ec/No for WCDMA cell and RxLev for GSM cell
  104. 104. How to avoid ping pong ? When phone is camped on 3G, GSM measurements can start when CPICH Ec/Io of serving cell is below Ssearch_RAT + QqualMin. When phone is camped on GSM, cell reselection to 3G is possible if CPICH Ec/Io of the candidate is above FDD_Qmin. Therefore, to avoid ping pongs between 3G and GSM the following condition should be met: FDD_Qmin >= QqualMin + Ssearch_RAT QqualMin=-18 dB Ssearch_RAT=4 dB CPICH Ec/Io FDD_Qmin >= -12 dB QqualMin +Ssearch_RAT t Camping on 3G Measure GSM Camping on 3G
  105. 105. How to avoid ping pong ? Parameters for cell reselections • Qqualmin = -18dB Ssearch_RAT =2dB -> the 3G->2G cell reselection starts when Ec/No hits -16dB • FDDQmin(GPRSFDDQmin) = -14dB (6) and QsearchP/QsearchI = always The cell reselection paramters 3G -> 2G and 2G -> 3G provide only 2dB hysteresis which is not enough and should be noticed from the RNC statistics as high amount of INTR_RAT_CELL_RE_SEL_ATTS from all the RRC Connection Setup Attempts • Recommendation is to adjust the FDDQmin from -14dB to -10dB (or even up to -8dB) to provide 6 to 8 dB hysteresis between 3G to 2G cell reselection and 2G to 3G cell reselection • Another parameter to tune is Qrxlevmin On top of Treselection the above parameters will slow down further the 2G to 3G and 3G to 2G cell reselections
  106. 106. Treselection How long the reselection conditions must be fulfilled before reselection is triggered? Treselection Impacts all cell reselections : Inter RAT, intra frequency and inter frequency The UE reselects the new cell, if the cell reselection criteria (R-criteria, see next slide) are fulfilled during a time interval Treselection As this parameter impacts on all the cell reselections too long Treselection timer might cause problems in high mobility areas but too short timer causes too fast cell reselections and eventually causes also cell reselection ping pong Recommended value 1s should work in every conditions i.e. enough averaging to make sure that correct cell is selected However careful testing is needed to check the performance of different areas • (Dense) Urban area, slow moving UEs with occasional need for fast and accurate (to correct cell) reselections e.g. outdoor to indoor scenarios or city highways – in some cases cell by cell parameter tuning is performed to find most optimal value between 0s and 2s but typically 1s is optimal value when workload is considered as well • Highways, fast moving UEs must reselect correct cell – typically 1s works the best (however occasionally also 0s might be needed in fast speed outdoor to indoor cell reselections e.g. tunnels) • Rural areas, slow or fast moving UEs need very often reselect between different RATs and make proper cell reselections even when the coverage is poor – typically 1s works the best • Location Area Borders, usually the coverage is fairly poor – typically 1s works the best but sometimes to reduce location area reselection ping pong 1s is used when going from LA1 to LA2 and 2s from LA2 to LA1
  107. 107. IRATHO
  108. 108. IRATHO As M1013 described in PartI, M1015 return statistic for intesystem HO. The filtering criteria can be replicated with the exception of ping-pong Filtering criteria: Major - High number of failures for a defined out-going adjg (failure ADJG) - high number of fail for a defined source (failure WCEL) Minor - very low number of attempt with failure (low used adjg) - zero number of attempt for declared adjs– stabilized value (no adjg) - high number of attempts for an out-going adjs (unbalanced ADJG) out-going condition is sufficient - high number of attempts for a defined source (unbalanced WCEL) Same procedures can be applied to the case considering that the event related are 1E and 1F
  109. 109. 1E/1F Events for CPICH Ec/No and RSCP time Cell 1 Cell 2 Cell 3 e.g.P-CPICHEc/No HHoEcNo(RSCP)Cancel Defines the threshold of Ec/No(RSCP) that must be exceeded by a measurement of an active set cell to be canceled the event 1F related HHoEcNo(RSCP)CancelTime determines the time period during which the CPICH RSCP of the active set cell must stay better than the threshold HHoRscpCancel before the UE can trigger the reporting event 1E. HHoEcNo(RSCP)Thres hold determines the absolute CPICH Ec/No threshold which is used by the UE to trigger the reporting event 1F. When the measured CPICH Ec/No of all active set cells has become worse than or equal to the threshold in question, the RNC starts inter- frequency or inter-RAT (GSM) measurements in compressed mode for the purpose of hard handover. HHoEcNo(RSCP)TimeHysteresis determines the time period during which the CPICH Ec/No of the active set cell must stay worse than the threshold HHoEcNoThreshold before the UE can trigger the reporting event 1F. 1E 1F
  110. 110. IRATHO – Triggering reason 4. DL DPCH approaches its maximum allowed power FMCG: GSMcauseTxPwrDL 5. Quality deterioration report from UL outer loop PC FMCG: GSMcauseUplinkQuality 3. UE Tx power approaches its maximum allowed power, event 6A/6D FMCG: GSMcauseTxPwrUL 2 . Low measured absolute CPICH RSCP, events 1E/1F FMCG: GSMcauseCPICHrscp 1. Low measured absolute CPICH Ec/No, event 1E/1F FMCG: GSMcauseCPICHEcNo GSMcauseX These parameters indicates whether a handover to GSM caused by low measured absolute CPICH Ec/No of the serving cell is enabled (1) 6 . Others - Load and Service based HO - IMSI based HO - Emergency ISHO Triggering reason gives an indication
  111. 111. IRATHO – Triggering reason ∑ = Allcauses RTNxxxCMODWHHOIS RTNxxxCMODWHHOIS percCausexxx )_(____ )_(____ __ It’s important to know which is the most frequent triggering reason: It’s possible to diffentiate between quality and coverage reasons and understand the network limiting factors: 1. CPICH coverage 2. Pilot pollution 3. UL/DL Service coverage In actual case is possible to dsciminate between low CPICH coverage triggered by high# RSCP attempts or probable pilot pollution triggered by high # Ec/No attempts A KPI that gives reason for that is
  112. 112. IRATHO – Triggering reason High # Ec/No? Start UL level limiting Yes High # RSCP? High # UE Tx pwr? High # UL Qual? New site required or new Parametrization for IRATHO UL qual limiting Yes Load analisys and UL interference evaluation DL Qual limiting Yes DL interference/ Pollution should be evaluated DL level limiting Yes CPICH power analisys/ new site required UL DL This condition should be the dominannt one without associated failure Enabling all the causes a screaning on the network is returned individuating the limiting factor and the required action. High # DL DPCH? Service limiting Yes New planning for service is required End
  113. 113. IRATHO - Failure Failure can happen at different point: Before decision - Before CM - During CM - Measuring GSM cell After decision - Drop Utran and ue have to treated as particular case UE Node B RNC RRC: Measurement Report RRC: Measurement Control NBAP: Radio Link Reconfiguration Prepare NBAP: Radio Link Reconfiguration Ready NBAP: Radio Link Reconfiguration Commit RRC: Physical Channel Reconfiguration RRC: Physical Channel Reconfiguration Complete NBAP: Compressed Mode Command RRC: Measurement Report RRC: Measurement Control GSM RSSI Measurement ISHO triggering (5 reasons are possible) Initial Compressed Mode Configuration CN RANAP: SRNS Context Request RANAP: SRNS Context Response RANAP: IU Release Command RANAP: IU Release Complete RRC: Cell Change Order from UTRAN RANAP: SRNS Data Forward Command
  114. 114. CM not possible The following KPI gives an indication of the number of CM procedure not started If CM fails one of the following mus be checked: Not enough resources – AC reject CM. Evaluate interference Expand capacity (see PartI) RNCRNCUEUE RRC: Measurement Report (3,4,5) RRC: Measurement Control BTSBTS Admission Control check for CM Admission Control check for CM NBAP: Radio Link Reconfiguration Prepare NBAP: Radio Link Reconfiguration Ready NBAP: Radio Link Reconfiguration Commit RRC: Physical Channel Reconfiguration RRC: Physical Channel Reconfiguration Complete NBAP: Compressed Mode Command RRC: Measurement Control RRC: Measurement Report NBAP: Compressed Mode Command RRC: Measurement Control RRC: Measurement Report BSIC verification phase for target cell RX Level measurement phase for all ISHO neighbours AC is responsible for checkiing if CM is possiblle ∑+ j jMODIS_HHO_W_COS_STA_NOT_PIS_COM_MOD OS_STA_NOT_PIS_COM_MOD Considering that M1010C2 (INTER SYST COM MOD STA NOT POS FOR RT) is updated if it is not possible to start inter-system compressed mode measurement due to radio resource congestion, BTS- or UE-related reasons to have a better insight on radio congestion it could be better to use, e.g. for UL the M1002C361 REQ FOR COM MODE UL REJECT TO INT SYST HHO IN SRNC and the M1002C357 REQ FOR COM MODE UL TO INT SYST HHO IN SRNC and use the following : M1002C361/M1002C357
  115. 115. NO Cell Found Missing ADJG could be the reason or a dedicated parameter tuning for the 1F event. The KPI can be madified taling care of the WO_CMOD events The following KPI gives an indication of the number of GSM cell not found NO Cell Found means: there is no suitable gsm target cell in terms of RX Level OR the target gsm is suitable but its BSIC verification fails AND the maximum number of measurement reported are received AND maximum measurement interval is not expired Compressed Mode start No Cell Found Counters HHO Attempt Counters … measurement fail … measurement not fail ∑ ∑ = Allcauses Allcauses RTNxxxCMODWHHOIS RTNxxxCELLNOHHOIS RateFailMeasISHO )_(____ )_(____ ___
  116. 116. NO Cell Found High # NO Cell? ADJG Addition? Yes Verify ADJG Yes Start Reduce “Cancel” Increase “Time hysteresis” Good GSM coverage in the near field? Yes Coverage anlisys End End Good GSM coverage in the far field? Reduce “thershold” New site requiredGSMCause=Ec/ Nol? Yes Pollution evaluation
  117. 117. DROP & UNSUCCESS IRATHO ∑ ∑ = Allcauses Allcauses RTNxxxATTHHOIS RTNxxxHHOISDRPSCON RateDropISHO )_(___ )_(____ __ In this case the optimization is required and pass through the evaluate of GSM and 3G plot coverage. Optimize If necessary number of ADJG or NWP parameters otherwise tune RNW parameters. Thresholds can be relaxed to favourite an early exit from 3G layer RRC Drop Counters RRC Drop Counters HHO Attempt Counters HHO Attempt Counters ISHO Success Counters ISHO Success Counters ISHO Unsuccess Counters ISHO Unsuccess Counters UE Failure Counter UE Failure Counter UTRAN Failure Counter UTRAN Failure Counter Optimization for unsuccess is not possible because the reason are: - physical channel failure (the UE is not able to establish the phy. - Protocol error - Inter-Rat protocol error - Unspecified Drop are related to drop call occurred during the procedure
  118. 118. 3G –> 2G Unbalancing VOICECSCOMPACCRAB RTxxxATTHHOIS ISHOCallVoicePerc Allcauses ____ ____ ___ ∑ = This topic present the inherent problem due to the fact that the 2G layer is not involved in the analisys. Few consideration can be performed under some assumption: The following KPIs used over a cluster for CS voice service gives the percentage of the CM started over all the RAB, giving an idea of the attempted mobility procedure requested for a cluster where the 3G coverage should be assured Once Correlated with voice drop due to radio link failure and rrc drop during ISHO, the KPI can help operator in understand the ISHO strategy. Similar KPI is possible for PS Threshold to shrink the HO area or inhibit the procedure has to be setted Better to use completes: failures, normal & SRNC reloc on denominator and use the KPI inside the 3G cluster or difining a polygon where 3G service is required

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