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Basic dt gsm ok


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Drive Test & Problem analysis

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Basic dt gsm ok

  1. 1. Main Tools for Radio Network Optimization GSM Statistic Handling Tool NWS (C); SPOS&Turle, Statics (I) OSS Recording Tool PMR, RNO package (C) Cell Data Design Tools CNA (C); IPOS, BSSTool (I) Field Measurement TEMS only!!!Field Measurement Analysis TEMS, MapInfo (C); MCOM (I) Cell Planning Tool TEMS Cellplanner (C); MCOM (I)
  2. 2. Radio Network Growth Flow
  3. 3. Where does TEMS INVESTIGATION fit in Design & Rollout Operation & Improvement Model Tuning Traditional OptimizationNetwork Integration Test Network Feature Optimization Initial Tuning Verification of Network Changes GPRS Performance Verification Training
  4. 4. DESIGN & ROLLOUT PHASE Network Integration Test When a site is integrated to BSC it is tested • Call set up test • Timeslot test, forced call test* TEMS Pocket is the preferred tool for Network Integration Test
  5. 5. DESIGN & ROLLOUT PHASE Initial Tuning• Produce Coverage Plot• Identify Coverage Holes• Identify Interference Area• Optimize Neighbor Relations• Find Hardware/Installation Problems• Verify Parameter Setting
  6. 6. DESIGN & ROLLOUT PHASE GPRS Performance Verification• Application Performance Test • WWW, FTP, WAP etc.• Mobility Test • Cell Reselection, RA Update
  7. 7. OPERATION & IMPROVEMENT PHASE Traditional Optimization • Investigate & Trouble-shooting Specific Areas • Neighbor Relation Optimization • Coverage Issues
  8. 8. OPERATION & IMPROVEMENT PHASE Network Feature Optimization Parameter Settings: • MS, BTS Power Control • HCS • Idle Mode Behavior • Locating Algorithm • Frequency Hopping • Intra-cell Handover
  9. 9. OPERATION & IMPROVEMENT PHASE Verification of Network Changes Did a certain change in the network give desired results? • New coverage area? • Less interference? • Better speech quality? • Is handover possible?
  10. 10. TEMS Measurement & Analyzing Process ? Preparations Collect Data Analyze ReportClear objective Check equipment Save logfile Find problem Give answer areas to objectiveWhy should this Get input files Take notesmeasurement be Find solutions Prepare route Monitordone External Antenna? Changes in What should be Network changed?
  11. 11. Measurement Will Depend on Objective ? Preparations Possible ObjectivesClear objective Check equipment • Coverage analysisWhy should thismeasurement be Get input files • Trouble shooting Prepare routedone External antenna? • Scanning • Verify network changes
  12. 12. Performing Measurements withDrive Test • Large areas TEMS • Specific areasWalk TestScanning
  13. 13. Drive Test - Large area INPUT INPUT MEASUREMENT OUTPUTAcceptance Drive defined Plots & Report route/areaNew sites on air - Signal Strength Record LogfileFrequency Re-plan - Quality Long / Short callsBSC Re-homing Trouble Report / Assure no data loss Area for further investigation
  14. 14. Drive Test - Specific area INPUT Measurement OUTPUTStatistics Manipulate Trouble ReportCustomer complain - Forced handover - Identified problemLarge area drive test - Lock on to Frequency - SolutionTrouble Report - Layer 3 messages Analysis on-spot Rectify & Verify on-spot
  15. 15. Walk Test INPUT Measurement OUTPUT Statistics Add file marks (GPS) Trouble Report Customer complain Scanning Planning Report Micro cell planning - Antenna location Indoor cell planning - Frequency - HCS setting* TEMS Light is the preferred tool for indoor cell planning
  16. 16. Scanning INPUT Measurement OUTPUTFinding a new TEMS INV in Received SS onfrequency scanning mode different ARFCN Set ARFCN to scan plotArea NetworkScanning New frequency
  17. 17. Analyzing Measurements
  18. 18. Post-Processing TEMS Logfiles Geographical TEMS PresentationLogfiles Statistics Report Analysis
  19. 19. Problem CasesLow Signal Strength• Interference• Handover• Call Setup Failure• Dropped Call• Misc.
  20. 20. Signal Strength Case TEMS INPUT Logfiles Large area DT Post-ProcessingSpecific area DT Analysis• Identify areas with low signal strength e.g. SS < -100dBm (outdoor)• Look at RxLev distribution (for acceptance)• Compare with design level or new requirements
  21. 21. Signal Strength Case – Possible Reasons• Shadowed Antenna• Antenna Direction• Antenna Height / down tilt• Output Power• Missing Neighbor Relation• Site Location• Faulty Hardware e.g. antenna & TMA• Cell is down
  22. 22. Signal Strength Case – Analysis Shadowed Antenna Output Power Faulty HardwareVisit site Check output power Check alarm & BTS ErrorCheck antenna installation Parameters logIs there a better antenna BSPWRT - NON BCCH FREQ Visit siteposition at same site? BSPWRB - BCCH FREQ Height/down Tilt Missing Neighbor Site Location Add reduce down tilt? Is the call dragged? Possible to move site? Can antenna be placed Is low SS due to missing New antenna location at lower or higher to give neighbor relations same site? Is it necessary better coverage? to expand and build a new site?
  23. 23. Signal Strength Case – Possible Solutions• Change parameter BSPWR , BSPWRT.• Add neighbor relation.• Physical changes: • Antenna direction • Antenna height, tilt or position• New site as last option.
  24. 24. Interference Case TEMS INPUT Logfiles Large area DT Post-Processing Specific area DT AnalysisIdentify areas with Rxqual > 5Identify source using Map and STSNew drive test around problem area?
  25. 25. Interference Case – Logfile analysisFrom logfile & map:What channel group suffer from interference? HOP or Non HOP? • Check Current channel information in TEMS INV, hopping channel and hopping frequency.Where does the interference come from? Cell name? • Study map and logfile, look for co-channel or adjacent channel interference.Does the interference lead to lower SQI? • Look at SQI measurement during high RxQual.Use STS & RNO to assist analysis.
  26. 26. Types of Interference• Co - Channel interference• Adjacent Interference BCCH 600 CASE 1 BCCH 595 CASE 2 High site BCCH 590 BCCH 590 BCCH 590 BCCH 590
  27. 27. Interference Case – Possible Reasons• Poor frequency plan• No dominant cell --> low C/I ---> increased Rxqual• Frequency Hopping is off• External interference e.g. jammer Example of high Rxqual due to low Signal Strength
  28. 28. Interference Case – Possible solutions• Enable Frequency Hopping or add frequencies to Hopping group.• Enable BTS Power Control, MS power control and make it less aggressive.• Change frequency of interferer or interfered cell: – Possible to find new frequency by using TEMS Scanning.• Down tilt or change antenna of interferer.• Redo frequency plan.• Add new site.
  29. 29. Handover Case INPUT Large area DT Post-ProcessingSpecific area DT AnalysisLook for:Repeated handover (Ping Pong)Repeated Intra-cell handoverHandover failure,Unrealistic handover
  30. 30. Repeated Handover (Ping Pong) - Examples
  31. 31. Repeated Handover (Ping Pong) - Possible Reason 1 Merry-go-round Handover, Offset > Hysterisis
  32. 32. Repeated Handover (Ping Pong) - Possible Reason 2• Offset only in one direction e.g A-B for Inter BSC relation BSC 1 BSC 2 BSC BSC CELL A CELL BA -> B OFFSET = -5dB No B -> A OFFSET
  33. 33. Repeated Handover (Ping Pong) – Other Possible Reasons No dominant Server• No dominant server• Locating penalty settings e.g. PSSBQ, PTIMBQ• Too small hysterisis setting
  34. 34. Repeated Handover (Ping Pong) – Possible SolutionsAntenna directionAntenna TiltsPlan for new siteChange Locating Parameter e.g.KHYST or LHYST
  35. 35. Repeated Handover (Ping Pong) – Possible SolutionChange Parameter, KHYST or LHYST Hysterisis CELL A CELL B Handover From A to B
  36. 36. Handover Case – Handover ReversionCheck layer 3 messageHandover command BSC correct?Check reason for handover SS, RXQUALTarget cell?
  37. 37. Handover Reversion – Common ReasonDuplicates of BSIC BCCH combinations in neighboring list Handover command? BSC 610_12 606_33 610_31 610_31 Serving cell Neighbor cell 2 Neighbor cell 1 608_32 608_32 Road
  38. 38. Handover Reversion – Other ReasonsUplink interference in target cellDownlink interference at MSSolutionsInterference Investigation• MRR• Statistics• Scanning
  39. 39. Handover Case – Repeated Intra-cell HandoverPossible ReasonsWrong intra-cell handover settingsExternal Uplink InterferencePossible SolutionsConsider to change parameters:• SSOFFSETUL, SSOFFSETDL• QOFFSETUL, QOFFSETDLA wrong setting of parameters will cause “unnecessary” IHOTurn off Intra-cell Handover?
  40. 40. Handover Case– Unrealistic Handover
  41. 41. Unrealistic Handover – Reason & SolutionPossible ReasonsWrong locating settings, in Serving or Target cellNote: Could be on purpose e.g. Dual Band network with HCSSolution• Fix locating settings e.g. MSRXSUFF, BSRXSUFF
  42. 42. Call Setup Failure
  43. 43. Call Setup Failure – Input Activities, Initial Tuning Activities Measurement Type •Large Area Drive Test Initial Tuning •Short Call Sequences(Acceptance Test)Troubleshooting Post-Processing Output (Customer •Statistics Report complaint etc.) •Geographical Report showing failure positions
  44. 44. Call Setup Failure– Input Activities, Troubleshooting Input Activities Measurement Type •Small Area Drive Test Initial Tuning •Lock on problem cell’s BCCH (Acceptance Test) •Force handover to the cell Troubleshooting Post-Processing Output (Customer •Geographical Report (if complaint etc.) necessary)
  45. 45. Call Setup Failure Analysis - Initial Tuning Scenario• Check the TEMS statistics report (Blocked Call) if there is Call Setup Failure.• If yes, identify the problem cells and which logfile from geographical report.• Replay the logfile and jump to the Blocked Call event.• Check if there is any successful call setup to the problem cell.
  46. 46. Call Setup Failure Analysis - Initial Tuning Scenario cont.• Review the layer 3 messages to check at which sequence the failure occur (random access, SDCCH, TCH assignment etc.).• Check STS report on the problem cell. Is there any traffic (SDCCH & TCH) in the cell, SDCCH & TCH seizures, congestion etc.• Check fault report & CDD configuration.
  47. 47. Call Setup Failure Analysis - Troubleshooting Scenario• Before performing drive test, check STS report & fault report.• If can not identify the problem, perform drive test.• During measurement, lock the BCCH of the problem cell.• Review the layer 3 messages to check at which sequence the failure occur (random access,
  48. 48. Call Setup Failure Analysis - Possible reasons with ranking• Low Signal Strength• Interference• High Congestion on SDCCH• High Congestion on TCH• Transmission Fault• Faulty TRU/Hardware• Central Processor Overload• Software File Congestion
  49. 49. Call Setup Failure Analysis - Possible solutions• Low signal strength  Signal strength analysis.• Interference  Interference analysis.• High Congestion on SDCCH: Define more SDCCHs. Activate adaptive configuration of logical channel feature and immediate assignment to TCH.• High Congestion on TCH: Add capacity/Tune coverage array. Activate assignment to worse cell.
  50. 50. Failed Call Setup (Blocked Call) Example Multiple Channel Requests. Successful Random Access after the third try.  Congestion in SDCCH.
  51. 51. Dropped Call Case - Input• Statistics Report• Note from drive test.
  52. 52. Dropped Call Case - Analysis• From plot, identify which & where in logfile the dropped call occurs.• In the log file, Jump the drop call event.• Check if there is a disrupt in the recording. If yes  could be a false drop due to TEMS mobile disconnection during recording!!!
  53. 53. Dropped Call Case - Analysis (cont)• Check the Radio environment just before drop: – If High Rxqual for a longer period of time and RLINKT expire  Interference problem. – If Low SS DL, SSDL < MSSENS ( -104dBm)  low signal strength problem. – If TA > 63  too far from the cell.• If DL radio is good, check the TX power. If there is MS power down regulation when the MS is close to the cell. If full power  suspect uplink interference or antenna, TMA problem.• Verify or isolate the problem using STS (Drop call and reasons).
  54. 54. Miscellaneous Case 1From TEMS Logfile• Good Signal strength DL, Good Rxqual DL• No call set up possible unless very close to site = high SS• Dropped call when SS < approx. -75dBmAnalysis• Since DL SS & Rxqual is goodSuspect UL problems e.g. external uplink interferenceConclusionTMA power turned off
  55. 55. Miscellaneous Case 2 From TEMS Logfile • TCH has lower Signal strength than BCCH (Own BCCH included in BA-list) • BTS power control = OFF Conclusion Antenna cable for TCH is swapped between sectors (CDU-A) SEKTOR C Configuration/cell SEKTOR A TCH TCH TCH TCH TCH TCH TCH TCHCHG1 SDCCH8 BCCHCHG0 TCH TCH TCH TCH TCH TCH SEKTOR B
  56. 56. Miscellaneous Case 3From TEMS Logfile• Fail to perform Call SetupAnalysis• Check if any success call setup to the same cell  No• Check if handover is possible  Yes• Suspected wrong cell definition in MSC but Cell is properlydefined in MCS and LAConclusion• Corrupted block in MSC
  57. 57. GPRS Verification & Optimizationwith TEMS Investigation
  58. 58. GPRS Measurement Activities• GPRS Performance Prediction• GPRS Field Measurement
  59. 59. GPRS Performance Prediction - Overview• GPRS RNAP Service uses TEMS Inv to predict following performance: – Throughput – Cell Reselection & Routing Area Update
  60. 60. GPRS Throughput Prediction• Perform Throughput prediction for each coding scheme
  61. 61. Cell Reselection Prediction• Dedicated mode drive test HO types LA HO (10) HO int. (220) LA HO at BQ (1) HO int. at BQ (11) BSC3 serving Other BSC
  62. 62. Cell Reselection Prediction• BCCH Scanning• Simulate the cell update with different CRH values CRH = 4 dB CRH = 8 dB CRH # HO 0 365 2 246 4 211 6 178 8 156 10 147 12 138 14 130
  63. 63. GPRS Field Measurement - Procedure Set up files ? Preparations Cell definitions TEMS, IP Sniffers GIMS … Excel Mapinfo Dig maps Charts / Tables Graphical presentation of route Report
  64. 64. GPRS Field Measurement - Type of Measurements• Application Performance Test – Ping – WWW – FTP – WAP• Mobility Performance Investigation – Cell Reselection – RA Update
  65. 65. GPRS Field Measurement - Application Performance Test• Attached performance – Attached Time = Attach Complete msg – Attach Request msg – Attach Success Rate• PDP context activation performance – PDP context activation = Activate PDP Context Accept msg – Activate PDP context request• Throughput on RLC level•
  66. 66. GPRS Application Test Tools• General – Windump, Commview, Ethereal, Protocol Analyser for Gb• PING – MS DOS ping command• WWW – IE, Netscape• FTP – DOS FTP, WS_FTP, TEMS built in sequence
  67. 67. GPRS Field Measurement - Mobility Performance Investigation• Number of Cell Reselection & RA Update• TCP Outage Time• Cell Reselection Failure
  68. 68. Mobility test CRH = 4, CRO = 4
  69. 69. . Cell Reselection Sample ReportRouting Area Time Cell Target Reselection Result Comments Cell time BSC1 16:30:42 D0241A D0241C 2s OK NA BSC1 16:33:18 D0241B D0242A 2s OK NA BSC1 16:35:04 D0242A D0248C 21 s OK This cell reselection was made to a cell located quite far away (not the closest), thus the RxLev was quite bad! BSC1 16:37:44 D0244B D0248C -- NA No throughput before or after the cell reselection. This is due to that the cell DF0242B were halted by some reason! BSC1 16:38:11 D0248C D0244B -- Failed The through put was never resumed and the FTP connection was aborted by the ftp-server!