GSM RF FEATURE (Part 1) June 23rd, 2000

August 11, 2000Jim Luan, Lin MubaoDrive Test Log analysis 2013/10/182Drive Test ProcedureDrive TestNetplanFICSStatistics AnalysisProblem FindingVOT/GEPPreparation 22013/10/183Preparation (1)Definition FileWithout it, it is impossible to observe overshooing neighborsGenDef7.exe can convert FP to definition file

Neighbor list with definition fileNeighbor list without definition file2013/10/185Drive TestFor Benchmark2 minutes per call10 15 minutes a log filesForce to appropriate band (GSM only, DCS only or Dual)For Special ProblemPlanning routeNo limitation

2013/10/186TEMS IntroductionInterfaceFunctions

2013/10/187Log File Process TEMS Log FileNetPlanFICSVOT/GEP.CSV.FMTRoute Map.STAExcel VB.NP/.TXTMuch shorter cycle time by VOT and GEP.72013/10/188TEMS .log file AnalysisUndecoded BCCHBSIC Undecode in Other SiteNo HandoverDelay HandoverPing Pong HandoverNegative HandoverOvershootingHigh OverlappingNo Dominant ServerPoor CoverageUnreasonable Serving AreaInterferenceHandover FailureHandover LossUL DropDrop CallSudden Power DropMS Power Rapid Increase

Below lists common problems which can be observed from Drive Test Log.82013/10/189Undecoded BCCH (1)Description:BSICs cant be decoded in 5sUsually consider 3 strongest neighborsReason:GCLK shift, only decode same site BSICsChannel interferenceNon-BCCH carrier, no dedicated spectrum for BCCH

92013/10/1810Undecoded BCCH (2)

102013/10/1811BSIC Undecode in Other SiteDescription:BSIC in same site can be decoded but not for other sitesHandover can only happen in intra-site basisIt is similar to former Undecoded BCCH caseReason:GCLK shiftGCLK recalibration is requiredNo one monitors OMC-R alarms112013/10/1812No Handover (1)Description:Neighbor BSIC is decoded and COMMON handover requirement is fulfilled but there is never a handoverReason:Missing neighborNo such neighbor in CM databaseIncorrect external neighborTarget cells LAC/BCCH/BSIC in add_neighbor is different from those in equip_rtfEngineer modifies external neighbor at MMI, not through GUINever use OMC-R Proxy Cell to propagate external neighbor informationN < hreqt. Great HO_MARGIN. Improper algorithm 1-7 settingMissing_rpt =1Serving cell overshoots/covers too far awayRefer to GSM BSS Statistics Analysis Handbook

122013/10/1813No Handover (2)

132013/10/1814Delay Handover (1)Description:Neighbor BSIC is decoded but handover occurs in much later timeReason:All possible neighbors suffer blockingLarge hreqt * hreqavequal_power_flag is enabled, full BTS/MS power must be reached before handoverLarge handover_recognized_period and bssmap_t7 settingRefer to GSM BSS Statistics Analysis Handbook

142013/10/1815Delay Handover (2)

152013/10/1816Ping Pong Handover (1)Description:Lot of handovers between cellsTime between Handover is around hreqt*hreqave of such HO causeReason:Improper hardware calibrationHardware faultUL/DL interferenceNegative handoverDifferent coverage footprint for antennas of a cell

162013/10/1817Ping Pong Handover (2)

172013/10/1818Negative Handover (1)Description:Serving cell hands over to a weaker neighborReason:ho_only_max_power is enabledqual_margin_flag is disabledho_margin_usage_flag is enabled with negative ho_margin_rxqual/rxlevNegative HO_MARGINMicro-cellular algorithms are enabled, especially type 5182013/10/1819Negative Handover (2)

-59dBm before HO-66dBm after HO192013/10/1820OverShooting (1)Description:Cell shoots at far distance but that location has closer cells aroundReason:Overshooting cell has small downtilt, 0 degree!Overshooting cell has too high altitudeCloser cells have overshooting as wellBSIC of closer cells cant be decoded202013/10/1821OverShooting (2)

212013/10/1822High Overlapping (1)Description:Cells have major rxlevel difference within 5dBReason:OvershootingToo many cells in that areaPoor antenna downtilt222013/10/1823High Overlapping (2)

Over Lapping Area-65dBm-65dBm-65dBm-65dBm232013/10/1824No Dominant Server (1)Description:Rxlevel of best neighbors are close to that of serving cellReason:Poor antenna downtiltLack of near-by site242013/10/1825No Dominant Server (2)

252013/10/1826Poor Coverage (1)Description:Low rxlevel with rxqualityIn rural area, rxlevel is less than 15 (-95dBm)In city center, rxlevel is less than 35 (-75dBm)Different location has different threshold, noise level is the key pointReason:Lack of cell siteBSIC of dominant server cant be decodedDominant server has blocking or cell-barHandover problem. E.g. missing & incorrect neighbor, negative handover, no & delay handover262013/10/1827Poor Coverage (2)

272013/10/1828Unreasonable Serving Area (1)Description:Coverage area of the cell is incoherent to the antenna directionReason:Wrong cable connection to antennasIncorrect record of antenna orientationIncorrect ANTENNA_SELECT

282013/10/1829Unreasonable Serving Area (2)Cell ID:101BCCH: 35Cell ID:102BCCH: 40Cell ID:103BCCH: 45292013/10/1830Interference (1)Description:High rxlevel with rxqualityReason:Channel interferenceNot using dominant serverNo handoverTurn the corner with delay handover302013/10/1831Interference (2)

312013/10/1832Handover Failure (1)Description:MS fails to reach target cell, so return to source cellMS sends HO FAILURE and UL-SABM to source cell and there is responseReason:Channel interferencePoor coverageExternal interference at UL, like wideband repeatorRefer to GSM BSS Statistics Analysis Handbook

322013/10/1833Handover Failure (2)

332013/10/1834Handover Loss (1)Description:MS fails to reach target cell, but cant return to source cellMS sends HO FAILURE and UL-SABM to source cell but no responseReason:Channel interferencePoor coverageExternal interference at UL, like wideband repeatorRefer to GSM BSS Statistics Analysis Handbook342013/10/1835Handover Loss (2)

352013/10/1836Description:BSS doesnt receive UL SACCH for link_fail timesBSS stops transmitting DL powerReason:External interferenceChannel interferenceFaulty ancillary. UL path loss >>> DL path lossRefer to GSM BSS Statistics Analysis Handbook

UL Drop (1) 362013/10/1837UL Drop (2)

372013/10/1838Drop Call (1)Description:DL case: Radio_link_timeout counter decreases to 0UL case: link_fail counter decreases to 0Layer 2: BSS/MS send SABM/DISC in every T200 for N200+1 times, and no response from recipientReason:All cases in this presentationRefer to GSM BSS Statistics Analysis Handbook382013/10/1839Drop Call (2)

392013/10/1840Sudden Power Drop (1)Description:Dedicated ARFCN has significant non-power control rxlevel difference from rxlevel of BCCHReason:No/improper TX power calibrationFaulty ancillary. E.g. combiner, filter..Different cable lengths from BTS to antennasDue to air combing, so antennas have different coverage footprints

402013/10/1841Sudden Power Drop (2)

412013/10/1842Description:MS rapidly increases its TX power due toOptimised Power Control or UL SACCH multiframes arent received for link_fail - link_about_to_fail timesReason:Sudden UL interference, e.g. wideband repeator, channel interferenceToo much rapid power downl_rxlev_ul_p is too small

MS Power Rapid Increase (1)422013/10/1843MS Power Rapid Increase (2)

UL power rapid increase from 19 to 5 suddenly432013/10/1844How GEP Help?Help to identify below problem in VISUAL basisCo-channel interferenceAdjacent-Channel interferenceMutual neighborMissing neighborUnreasonable neighborIncorrect external neighbor

442013/10/1845How VOT Help?Help to identify below problem in VISUAL basisPing pong HOOvershootingNo dominant serverPoor coverageUnreasonable serving areaInterferenceHO failureHO lossDrop call452013/10/1846How CM Extractor Help?Extract most BSS parameter for referenceCell e.g. hreqave,hreqt,N,PBTS e.g. antenna_selectRTF check any incorrect external neighborNeighbor e.g. ho_margin, delay_timer462013/10/1847How NPM Help?Provide cell statistics for VOT displayProvide BSS and system level 23 key statisticsProvide detail troubleshooting statistics

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