Optimization technical introduction version1.011

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  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction (version 1.0 - update May 2003) chapter 1 : GSM architecture review - page : corporate training and development
  • Optimization technical introduction version1.011

    1. 1. Optimization: IntroductionOptimization: Introduction
    2. 2. Contents  Global indicators  Typical Radio Network Problem  Coverage Problem  Interference problem  Unbalanced power budget problem  Congestion problem  Problems and responsible partiesOptimization: Introduction
    3. 3. Global Indicators 4 stages of a call establishment, 2 stages (1&2) for location update : 1. Radio link establishment Phase 2. SDCCH Phase then only “Circuit Switch call” 3. TCH assignment Phase 4. Alerting/Connect PhaseOptimization: Introduction
    4. 4. Mobile Originated Call (MOC) MS BTS BSC MSCGlobal CHANNEL REQUEST (RACH) CHANNEL REQUIRED CHANNEL ACTIVATION (SDCCH) CHANNEL ACTIVATION ACK 1. Radio LinkIndicators IMMEDIATE ASSIGN COMMEND Establishment IMMEDIATE ASSIGN (AGCH) Phase SABM (L3 info) (SDCCH) ESTABLISH IND (L3 info) CR (Connection Request: L3 INFO) UA (L3 info) CC (Connection Complete) (SDCCH) LOCATION UPDATE REQUEST (IN CASE OF LU) AUTHENTICATION REQUEST AUTHENTICATION RESPONSE 2. SDCCH Phase CIPHERING MODE COMMAND CIPHERING MODE COMPLETE LOCATION UPDATE ACCEPT (IN CASE OF LU) TMSI REALLOCATION COMPLETE (IN CASE OF LU) SETUP CALL PROCEEDING ASSIGNMENT REQUEST PHYSICAL CONTEXT REQUEST PHYSICAL CONTEXT CONFIRM CHANNEL ACTIVATION (TCH) TCH allocation CHANNEL ALLOCATION ACK. ASSIGNMENT COMMEND (SDCCH) SABM ESTABLISH INDICATION TCH UA (L3 info) 3. TCH Assignment Phase ASSIGNMENT COMPLETE ASSIGNMENT COMPLETE ALERTING CONNECT 4. Alert and Connect Phase CONNECT ACK. CONVERSATION Optimization: Introduction
    5. 5. Global Indicators  Handover : Intracell HO MS BTS BSC MSC Measurement Report MEASUREMENT RESULT PHYSICAL CONTEXT REQUEST (old channel) PHYSICAL CONTEXT CONFIRM (old channel) CHANNEL ACTIVATION (new channel) CHANNEL ACTIVATION ACK (new channel) ASSIGNMENT CMD ASSIGNMENT COMMEND (old channel) SABM (L3 info) (SDCCH) ESTABLISH IND (new channel) UA (L3 info) (SDCCH) ASSIGNMENT CMP ESTABLISH COMPLETE (new channel) HANDOVER PERFORMED RF CHANNEL RELEASE (old channel) RF CHANNEL RELEASE ACK (old channel)Optimization: Introduction
    6. 6. Global Indicators  Handover : Internal HO Serving Target MS BSC MSC Cell Cell Meas. Report MEASUREMENT RESULT CHANNEL ACTIVATION CHANNEL ACTIVATION ACK. HO CMD HANDOVER COMMAND HANDOVER ACCESS HANDOVER DETECTION PHYSICAL INFORMATION SABM (L3 info) UA (L3 info) ESTABLISH INDICATION HANDOVER COMPLETE HO CMP HANDOVER PERFORMEDOptimization: Introduction
    7. 7. Global Indicators  Handover : External HO MS Serving Cell BSC MSC BSC Target Cell MS MEAS_REPORT MEAS_RESULT HO_REQUIRED CR (HO_REQUEST) CC CHANNEL_ACTIVATION CHANNEL_ACT_ACK HO_REQUEST_ACK HO_COMMAND (HO_COMMAND) HO_ACCESS HO_ACCESS HO_DETECTION HO_DETECTION PHYSICAL_INFO SABM (L3 info) ESTABLISH_INDICATION UA (L3 info) HO_COMPLETE HO_COMPLETE CLEAR_COMMAND Cause: HO_SUCCESSFUL Release of TCHOptimization: Introduction
    8. 8. Global Indicators Important indicators :  SDCCH Congestion  SDCCH Assignment Failure  SDCCH Drop  TCH Assignment Failure  Call Drop  Call Setup Success  Call Success  Outgoing Handover  Incoming Handover  Handover Causes Distribution (Better/ Level/Quality/MCHO/...)Optimization: Introduction
    9. 9. Global Indicators  SDCCH Congestion : MS BTS BSC CHANNEL REQUEST CHANNEL REQUIRED (RACH) NO FREE SDCCH !!! IMMEDIATE ASSIGN COMMEND IMM. ASS. REJECT (OPTION) (AGCH)  MS will try to request again for a certain of times  If still failures, it will  Wait for a certain of time without reception of immediate_assign message  Try an automatic cell_reselection in case of LU (no impact for subscriber)  Notify a network error for call establishment (call setup failure for subscriber)Optimization: Introduction
    10. 10. Global Indicators  SDCCH Congestion : Main causes  Too much SDCCH “normal” traffic for cell SDCCH design  Logical cell design, extra TRX, new site  “Common Transport Effect”  Difficult to avoid for small cells  LA border at crowded area  Abnormal SDCCH traffic  “phantom” channel requests  Inadequate LAC design, causing too much LU  Redesign LAC  Problem with neighbor cells belong to other LACOptimization: Introduction
    11. 11. Global Indicators  SDCCH RF Failure : main causes MS BTS BSC MSC CHANNEL REQUEST CHANNEL REQUIRED (RACH) CHANNEL ACTIVATION (SDCCH) CHANNEL ACTIVATION ACK IMMEDIATE ASSIGN COMMEND IMMEDIATE ASSIGN (AGCH) ??? no message from MS  Real radio problems  Unbalanced power budget  Bad coverage  Interference In case of radio failure, MS will retry as in case of SDCCH congestionOptimization: Introduction
    12. 12. Global Indicators  SDCCH RF Failure : main causes  “Phantom/Ghost/Spurious/Dummy...RACH”  Channel request received but not sent : 3 causes 1. Noise decoding 2. Reception of channel request sent to a neighbor cell 3. Reception of HO_ACCESS sent to a neighbor cellOptimization: Introduction
    13. 13. Global Indicators  SDCCH RF Failure : main causes : Phantom RACH 1. Noise decoding  GSM 05.05: “0.02% of RACH Frame can be decoded without error without real input signal” (this extra-load has no impact for the system)  BCCH not combined: 156 phantom RACCH/hour (or about 0.08 Erlang SDCCH)  BCCH combined: 83 phantom RACH/hour  During period with low real traffic (night), high rate of phantom RACH  No impact for subscriber  But impact on indicator SDCCH RF access failureOptimization: Introduction
    14. 14. Global Indicators  SDCCH RF Failure : main causes : Phantom RACH 1. Channel request sent to neighbor cell  Subscriber is not impacted ( the real transaction is performed elsewhere)  But SDCCH RF access failure is impacted  Usual radio planning rules are sufficient to avoid the trouble (BSIC and BCCH frequency plan)Optimization: Introduction
    15. 15. Global Indicators  SDCCH RF Failure : main causes : Phantom RACH  Channel request due to handover  During HO, first message sent to target cell is HO access which is an access burst like channel_request  If received on BCCH, can be understood as a channel-request This case is the most dangerous  MS is sending usually a sequence of HO Access message, every frame !!  In some cases, this can create phantom RACH if the frequency of TCH is co- or adjacent to one of the interfered BCCH  Can block very easily SDCCHOptimization: Introduction
    16. 16. Global Indicators  SDCCH Drop : MS BTS BSC MSC Radio connection loss CONNECTION FAILURE INDICATION (cause : radio link failure) CLEAR REQUEST (cause : radio interface failure)  Loss of connection during SDCCH phase = SDCCH Drop  3 causes of SDCCH drop  Radio problems when connected on SDCCH  BSS problems (Transcoder and Internal BSS problems)  Call lost during an SDCCH HO (handover failure without reversion to old channel)Optimization: Introduction
    17. 17. Global Indicators  TCH assign failure : Congestion MS BTS BSC MSC ASSIGNMNET REQUEST no RTCH available on request cell ASSIGNMENT FAILURE cause No Radio Resources Available  4 sub causes of congestion  A: Queuing is not allowed  B: Queue is full  C: T11 expired  D: RTCH requests is de-queued due to a high priority (i.e. emergency call) request to be queuedOptimization: Introduction
    18. 18. Global Indicators  TCH assign failure : Radio MS BTS BSC MSC ASSIGNMENT REQUEST PHYSICAL CONTEXT REQUEST PHYSICAL CONTEXT CONFIRM CHANNEL ACTIVATION (TCH) TCH allocation CHANNEL ALLOCATION ACK. ASSIGNMENT COMMEND (SDCCH) TCH Radio Problem ASSIGNMENT FAILURE Radio interface failureOptimization: Introduction
    19. 19. Global Indicators  TCH assign failure : BSS MS BTS BSC MSC ASSIGNMENT REQUEST PHYSICAL CONTEXT REQUEST PHYSICAL CONTEXT CONFIRM CHANNEL ACTIVATION (TCH) TCH allocation CHANNEL ALLOCATION ACK. ASSIGNMENT COMMEND (SDCCH) BSS ProblemOptimization: Introduction
    20. 20. Global Indicators  TCH Drop : Radio MS BTS BSC MSC Alerting Connection Phase or Communication : at any time Radio Problem CONNECTION FAILURE INDICATION (cause : radio link failure) CLEAR REQUEST (cause : radio interface failure)Optimization: Introduction
    21. 21. Global Indicators  TCH Drop : BSS MS BTS BSC MSC Alerting Connection Phase or Communication : at any time Radio Problem CONNECTION FAILURE INDICATION (Remote transcoder failure) CLEAR REQUEST (Equipment failure)  Transcoder reported problem  Abis transmission Problem: Microwave, Microwave antenna, fixed line problems.  Problem on TC boards (hardware problem)Optimization: Introduction
    22. 22. Global Indicators  TCH Drop : BSS MS BTS BSC MSC Alerting Connection Phase or Communication : at any time CLEAR REQUEST BSS problem O&M intervention Radio interface failure  Other BSS problem (excluding TC)  Hardware or software failures of BSC/BTSOptimization: Introduction
    23. 23. Global Indicators  TCH Drop : Handover MS BTS BSC MSC Alerting Connection Phase or Communication : at any time HO failure without reversion CLEAR REQUEST Radio interface message failure  Call drop during handoverOptimization: Introduction
    24. 24. Global Indicators  Intracell HO Failures  Congestion  Reversion to Old Channel (ROC)  Drop Radio  BSS problemOptimization: Introduction
    25. 25. Global Indicators  Intracell HO Failures : Congestion Serving MS BSC MSC BTS Measurement Report MEASUREMENT RESULT No Free TCH/SDCCH  Intracell HO Failures : Drop MS BTS BSC MSC ASSIGNMENT CMD ASSIGNMENT COMMAND (old channel) Release of old and new channelsOptimization: Introduction
    26. 26. Global Indicators  Intracell HO Failures : Reversion to Old Channel Serving Serving MS MSC BTS BSC ASSIGNMENT CMD ASSIGNMENT COMMEND (old channel) SABM (new channel) ESTABLISH IND (new channel) UA (new channel) X SABM (new channel) UA (new channel) X SABM (old channel) ESTABLISH INDICATION (old channel) UA (old channel) ASSIGNMENT FAIL ASSIGNMNENT FAILURE RF CHANNEL RELEASE (old channel) RF CHANNEL RELEASE ACK (old channel)Optimization: Introduction
    27. 27. Global Indicators  Internal HO Failures : Reversion to Old Channel Serving Target MS BSC MSC Cell Cell HO CMD HANDOVER COMMAND HANDOVER ACCESS HANDOVER DETECTION PHYSICAL INFORMATION SABM (L3 info) UA (L3 info) ESTABLISH INDICATION HANDOVER COMPLETE X SABM ESTABLISH INDICATION UM HO FAILURE HO FAILURE Release of new channelOptimization: Introduction
    28. 28. Global Indicators  Internal HO Failures : Drop Serving Target MS BSC MSC Cell Cell Meas. Report MEASUREMENT RESULT CHANNEL ACTIVATION CHANNEL ACTIVATION ACK. HO CMD HANDOVER COMMAND Clear_request Clear_command Release of old and new TCHOptimization: Introduction
    29. 29. Global Indicators  External HO Failures : Congestion MS Serving Cell BSC MSC BSC Target Cell MS MEAS_REPORT MEAS_RESULT HO_REQUIRED CR (HO_REQUEST) HO_FAILURE Cause: no radio resource available HO_REQUIRED_REJECT  External HO Failures : A int. Congestion MS Serving Cell BSC MSC BSC Target Cell MS MEAS_REPORT MEAS_RESULT HO_REQUIRED CR (HO_REQUEST) HO_FAILURE Cause: terrestrial circuit already allocated HO_REQUIRED_REJECT Requested trerestrial resource unavailable BSS not equippedOptimization: Introduction
    30. 30. Global Indicators  External HO Failures : Reversion to Old Channel MS Serving Cell BSC MSC BSC Target Cell MS MEAS_REPORT MEAS_RESULT HO_REQUIRED CR (HO_REQUEST) CC CHANNEL_ACTIVATION CHANNEL_ACT_ACK HO_REQUEST_ACK HO_COMMAND (HO_COMMAND) HO_ACCESS X HO_ACCESS X SABM ESTABLISH_INDICATION UA HO_FAILURE(reversion to pld channel) CLEAR_COMMAND Radio interface fail: Reversion to old channel Release connectionOptimization: Introduction
    31. 31. Global Indicators  External HO Failures : Drop MS Serving Cell BSC MSC BSC Target Cell MS MEAS_REPORT MEAS_RESULT HO_REQUIRED CR (HO_REQUEST) CC CHANNEL_ACTIVATION CHANNEL_ACT_ACK HO_REQUEST_ACK HO_COMMAND (HO_COMMAND) HO_ACCESS X HO_ACCESS X SABM X SABM X SABM X CLEAR_COMMAND Radio interface fail Release connectionOptimization: Introduction
    32. 32. Global IndicatorsImportant indicators : SDCCH Congestion Rate  Definition: Rate of SDCCH not allocated during radio link establishment procedure due to congestion on Air interface  Comment: Check SDCCH Erlang : if not critical, SDCCH availability/allocation problem, or HO access on a nearby cell side effect or interference on the carrier handling SDCCH (the last 2 can lead to high rate if Phantom RACHOptimization: Introduction
    33. 33. Global IndicatorsImportant indicators : SDCCH Assign Failure Rate  Definition: Rate of SDCCH seizure failed (BSS problem, radio access problem) during radio link establishment procedure over the total amount of SDCCH seizure requests during radio link establishment procedureOptimization: Introduction
    34. 34. Global IndicatorsImportant indicators : SDCCH Drop Rate  Definition: Rate of dropped SDCCH (SDCCH is established for any transaction OC, TC, LU, ...)  Comment: Drop radio + Drop HO + Drop BSSOptimization: Introduction
    35. 35. Global IndicatorsImportant indicators : TCH Assign Failure/Congestion Rate  Definition:  TCH Assign Failure Rate: Rate of RTCH seizure failed (BSS problem, radio access problem) during normal assignment procedure over the total amount or RTCH request for normal assignment procedure  TCH Assign Congestion Rate: Rate of RTCH not allocated during normal assignment due to congestion on Air interfaceOptimization: Introduction
    36. 36. Global IndicatorsImportant indicators : Call Drop Rate  Definition: Rate of dropped calls over the total amount of calls with a successful end  Comment:  Drop BSS + Drop radio + Drop HO  TCH drop occurring after successful assignment but before speech connection are considered as call drop even if from customer’s point of view it is a call setup failureOptimization: Introduction
    37. 37. Global IndicatorsImportant indicators : Call Setup Success Rate  Definition: Rate of calls going until TCH successful assignment, that is not interrupted by SDCCH drop neither by assignment failures  Comment:  Subscriber : call not established at the first attemptOptimization: Introduction
    38. 38. Global IndicatorsImportant indicators : Call Success Rate (BSS view)  Definition: Rate of calls going until normal release, that is not interrupted by SDCCH drop neither by assignment failures and neither by CALL DROP  Comment:  1 call success =  1 call successfully established  Without any call dropOptimization: Introduction
    39. 39. Global IndicatorsImportant indicators : Outgoing Handover Success Rate  Definition: Rate of outgoing external and internal intercell TCH and SDCCH handover successes over the total amount of outgoing external and internal intercell TCH and SDCCH handover requiredOptimization: Introduction
    40. 40. Global IndicatorsImportant indicators : Incoming Handover Success Rate  Definition: Rate of incoming external and internal intercell TCH and SDCCH handover successes over the total amount of outgoing external and internal intercell TCH and SDCCH handover requestsOptimization: Introduction
    41. 41. Global IndicatorsImportant indicators : Handover Cause Distribution  Definition: Distribution of Handover requests by cause: UL Qual, UL Lev, DL Qual, DL Lev, Better Cell, UL Interference, DL Interference, Interband, Micro cells HO, Concentric cell causesOptimization: Introduction
    42. 42. Typical Radio Problems i. Coverage Problem ii. Interference problem iii.Unbalanced power budget problem iv. Congestion problemOptimization: Introduction
    43. 43. Typical Radio Problems Several sources of information for optimization  QoS indicators  Coverage predictions  Customer complaints  Drive tests  Abis/A traces  Other teams information (NSS statistics)Optimization: Introduction
    44. 44. i. Coverage Problem Bad coverage : A network facing coverage problems has bad RxLev. RxQual can be bad at the same time. Sometimes the RxLev can look OK on the street (i.e. from drivetest) but coverage inside the buildings can be poor due to building losses. Building losses can range from 10 to 30 dB or more.Optimization: Introduction
    45. 45. i. Coverage Problem  Indications :  Customers complain about dropped calls and/or “No Network”  OMC QoS indicators – TCH failure rate – Call drop rate – Low proportion of better cell HO – High rate of DL & UL Level HO (possibly also DL/UL quality HO)  A interface indicators – High rate of Clear Request message, cause radio interface failure  Drive Test – Poor RxLev ( < -95 dBm)Optimization: Introduction
    46. 46. i. Coverage Problem  Investigation and Optimization :  If actual coverage is not the one predicted by planning tool – Check antenna system (azimuth, crossed sector?) – Check prediction in the tool (EIRP, Clutter Type, Obstructing building?). Most of the time the prediction will be incorrect, as it is only a computer simulation – Increase or decrease antenna down-tilt – Check BTS output power set in the OMC-R (BS_TXPWR_MAX: should always be set at 0)Optimization: Introduction
    47. 47. i. Coverage Problem  Investigation and Optimization :  If actual coverage OK compared to predicted ones – Improve coverage by adding Macro site, Microcell site (Border or Shadow areas), or IBC site (In-building coverage). – Use parameter setting ex. Bi-layer Handover.Optimization: Introduction
    48. 48. i. Coverage Problem Example on thresholds :  From Drive test or Abis Interface  RxLev < -95 dBm and  RxQual > 4Optimization: Introduction
    49. 49. ii. Interference Problem Interference : A network facing interferences problems presents good RxLev and bad RxQual in the same time on some areas.Optimization: Introduction
    50. 50. ii. Interference Problem  Indications :  Customers complain about bad speech quality (noisy calls) and/or call drops  OMC QoS indicators – SDCCH/TCH Drop – Low proportion of better cell HO – High rate of DL/UL quality HO and interference HO – Low HO success rate  A interface indicators – High rate of Clear Request message, cause radio interface failure  Drive Test – RxQual > 4 with RxLev > -85 dBmOptimization: Introduction
    51. 51. ii. Interference Problem Typical causes :  GSM interferences  Co-channel  adjacent  Non GSM Interference  Other Mobile Network  Other RF sourcesOptimization: Introduction
    52. 52. ii. Interference Problem Level Co-channel interference :  C/I = Carrier-to-interference ratio  +12 dB is taken into account for +12 dB Alcatel ( +9 dB according to GSM standard) (i.e. interference can be 9  12 dB weaker than serving cell to cause poor RxQual). f(cell1)=f(cell2) FrequencyOptimization: Introduction
    53. 53. ii. Interference Problem Co-channel interference :  Indications  Downlink and/or Uplink Interference  High rate of quality handover, call drop, and call setup failure  Investigation  Drive test analysis  Lumpini: Co-channel checking  Check prediction to verify which cell could be causing the interference  Frequency plan C/I < 12 dBOptimization: Introduction
    54. 54. ii. Interference Problem Co-channel interference :  Optimization  Antenna optimization  Change frequency  Reduce BTS power (not an option in TA Orange network)  Concentric cellOptimization: Introduction
    55. 55. ii. Interference Problem Co-channel interference: Optimization: Concentric cell  Concept  Conclusion from Alcatel trial on Orange’s network (Suburban area)  Concentric cell is difficult to optimize, and hence is rarely used in the network today.Optimization: Introduction
    56. 56. ii. Interference Problem Adjacent channel interference :  C/A = Carrier-to-adjacent ratio  -6 dB is taken into account for Alcatel ( -9 dB according to GSM standard). Level f(cell1) f(cell2) -6 dB E.g. f(cell1)= Ch.573 f(cell2)= Ch.574 f(cell2)=f(cell1)+1 FrequencyOptimization: Introduction
    57. 57. ii. Interference Problem Adjacent channel interference :  Indications  Downlink and/or Uplink Interference  High rate of quality handover, call drop, and call failure  Investigation  Adjacent HO statistics (if they are defined as neighbors). If they often handover, then adjacent channel interference could be a problem.  Drive test analysis  Lumpini: Adjacent channel checking  Cell coverage prediction  Frequency plan C/I < -6 dBOptimization: Introduction
    58. 58. ii. Interference Problem Adjacent channel interference :  Optimization  Antenna optimization  Change frequency  Reduce BTS power (not an option in TA Orange network)  Concentric cellOptimization: Introduction
    59. 59. ii. Interference ProblemInterference : Forced Directed Retry MS should connect to Cell_A, but no TCH available. MS connects to Cell_B with forced directed retry MS is emitting at high level (due to long distance from Cell_B) Cell_B: Ch.573  UL interference for Cell_C Cell_B is emitting at high level (if DL PC is being used)  DL interference at Cell_C MS is serving on the 2nd or 3rd best Cell_A: Ch.569 server: increases chances of Cell_C: Ch.572 interference problem (poor C/I & C/A as “C” is lower)Optimization: Introduction
    60. 60. ii. Interference Problem Non GSM interference :  Other mobile network  Inter-modulation with GSM BTS/MS receiver  Other RF interferers  Radar  Shop anti-theft mechanism  Medical devices  Other man-made radio transmission  Illegal usage of GSM frequencies (e.g. illegal imported devices, illegal usage of other organization, ...)  ...Optimization: Introduction
    61. 61. iii. Unbalance power budget Problem  A cell facing unbalanced power budget problems presents a too high path-loss difference between UL and DL (often DL>UL)  Lower Rx diversity gain of cross polarized antenna in rural area compared to dense area  Crossed feeders  Traffic not directly in boresight of antenna, where cross-polar discrimination is lower  Loose connectors  Faulty antenna, feeder, TMA  Rule : try to have delta as small as possible to avoid access network possible only in 1 direction (usually BTS->MS : OK and MS->BTS : NOK), i.e. uplink limited Optimization: Introduction
    62. 62. iii. Unbalance power budget Problem  Indicators :  OMC QoS indicators – High ratio of Uplink level Handover cause – Low incoming HO success rate – DL level looks OK for HO, but UL is too weak when HO is attempted – Degradation of TCH failures and OC call drop indicators  A interface indicators – High rate of Clear Request message, cause radio interface failure  O&M Alarms – Voltage Standing Wave Ratio (VSWR) – TMA Optimization: Introduction
    63. 63. iii. Unbalance power budget Problem  Investigation :  Abis monitoring: – ABS(delta Path loss) > 10 » Check if problem is occurring for 1 TRX or all. – ABS(delta path loss) = ABS(UL Path loss – DL Path loss) – UL Path loss = MS transmitted power – measured received UL level – DL Path loss = BTS transmitted power – combiner loss – measured received DL level – Large difference between uplink and downlink level triggered HO.  Use PM observation counter (in OMC-R) – RT11 Optimization: Introduction
    64. 64. iii. Unbalance power budget Problem  Optimization : This equipment should be checked  TRX types (MP, HP)  Antennas or common RF components, TMA (common to all TRX of the BTS)  TRX RF cables, LNA Optimization: Introduction
    65. 65. iv. TCH congestion Problem TCH Congestion :  TCH Congestion rate (TCH Assignment Phase) is too high (more than 2%)  Rule : try to meet the offered traffic (asked by users) by providing the right number of resources (TRX extension)Optimization: Introduction
    66. 66. iv. TCH congestion Problem  Indications :  Customers complain about “Network busy”  OMC QoS indicators – High “TCH Congestion rate”, “RTCH Assignment fail-Congestion” – Low “incoming Intra/Inter BSC HO success rate” (no TCH available) – High “Directed Retry rate or Congestion Relief (Motorola)” if activated  A interface indicators: “BSS Congestion failure in OC” – High rate of Assignment Failure message, No radio resource available  Drive Test – Handover to better cell is slow, or never occursOptimization: Introduction
    67. 67. iv. TCH congestion Problem  Optimization :  Special events : – Foreseeable: football match, important meeting, Exhibition, etc. » Add some extra TRXs » Add special mobile BTSs (Cell on Wheel) » Activate HR (may not always be possible due to BSC capacity limitations) – Not foreseeable: car crash on the highwayOptimization: Introduction
    68. 68. iv. TCH congestion Problem  Optimization :  Daily periodic problems : At busy hour: – Hardware solution : » Add TRX(s) » Concentric cell » New site » Optimize cell boundaries (i.e. antenna optimization) to share traffic with surrounding cellsOptimization: Introduction
    69. 69. iv. TCH congestion Problem  Optimization :  Daily periodic problems : At busy hour: – Software solution : » Directed Retry » Traffic Handover » Half Rate (Alcatel) » Congestion Relief (Motorola) » Flow control (Motorola)Optimization: Introduction
    70. 70. Problems and responsible parties  Coverage problem :  If the measured RxLev does not match the prediction – Check the prediction, check panoramic pictures for obstructions – Field Operation team to check physical configuration (tilt, azimuth, antenna height...). Also check for faults in the antenna system (VSWR, sweep antennas, DTF test, etc.) – If Field Operation find no problem, antenna optimization may be required (if necessary)Optimization: Introduction
    71. 71. Problems and responsible parties  Coverage problem :  Ifthe field reality match the prediction – RF team to add new sites (tri-sector, micro cellular, indoor cells) to improve poor/no coverage area (Optimizer requests for some new sites to RF team regarding to the drive test result)Optimization: Introduction
    72. 72. Problems and responsible parties  Interference problem :  Optimization team to identify the interference source and request Spectrum Management team to correct it in case of internal source (new frequency planning...)  Unbalanced power budget problem :  Field Operation team to check the impacted BTS (Antenna, TMA, RF cables, LNA, diversity system...) according to request from Optimizer.Optimization: Introduction
    73. 73. Problems and responsible parties  TCH Congestion problem :  Regional RF to request TRX expansion.Optimization: Introduction

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