Drive tesllog analysis by noorbaduk

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									  August 11, 2000

Jim Luan, Lin Mubao
            Drive Test Procedure
                  Preparation
                   Drive Test
                       FICS
             Netplan          VOT/GEP
               Statistics Analysis
                Problem Finding
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                  Preparation (1)
• Definition File
     – Without it, it is impossible to observe overshooing neighbors
     – GenDef7.exe can convert FP to definition file
                                            Neighbor list
      Neighbor list with                  without definition
       definition file                           file




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            Preparation (2)
•   Frequency Plan & Configuration map
•   Software:TEMS, FICS, GEP, VOT
•   Hardware: TEMS, GPS, Portable PC
•   Test Problem Sheet
•   Route
•   Map


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                  Drive Test
• For Benchmark
     – 2 minutes per call
     – 10 – 15 minutes a log files
     – Force to appropriate band (GSM only, DCS
       only or Dual)
• For Special Problem
     – Planning route
     – No limitation

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            TEMS Introduction
• Interface
• Functions




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              Log File Process
                 TEMS Log File
                        FICS
              .FMT         .CSV    .STA
             Excel VB
            .NP/.TXT                 Much shorter
                                     cycle time by VOT
             NetPlan                 and GEP.

            Route Map          VOT/GEP
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                TEMS .log file Analysis
    Below lists common problems which can be observed from Drive Test Log.
•   Undecoded BCCH                      •   Poor Coverage
•   BSIC Undecode in Other Site         •   Unreasonable Serving Area
•   No Handover                         •   Interference
•   Delay Handover                      •   Handover Failure
•   Ping Pong Handover                  •   Handover Loss
•   Negative Handover                   •   UL Drop
•   Overshooting                        •   Drop Call
•   High Overlapping                    •   Sudden Power Drop
•   No Dominant Server                  •   MS Power Rapid Increase
    2010-3-18                                                           8
            Undecoded BCCH (1)
Description:
     – BSICs can’t be decoded in 5s
     – Usually consider 3 strongest neighbors
Reason:
     – GCLK shift, only decode same site BSICs
     – Channel interference
     – Non-BCCH carrier, no dedicated spectrum for
       BCCH

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            Undecoded BCCH (2)




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    BSIC Undecode in Other Site
Description:
     – BSIC in same site can be decoded but not for
       other sites
     – Handover can only happen in intra-site basis
     – It is similar to former Undecoded BCCH case
Reason:
     – GCLK shift
            • GCLK recalibration is required
            • No one monitors OMC-R alarms

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                     No Handover (1)
Description:
     – Neighbor BSIC is decoded and COMMON handover requirement is
       fulfilled but there is never a handover
Reason:
     – Missing neighbor
            • No such neighbor in CM database
     – Incorrect external neighbor
            • Target cell’s LAC/BCCH/BSIC in add_neighbor is different from those in
              equip_rtf
            • Engineer modifies external neighbor at MMI, not through GUI
            • Never use OMC-R Proxy Cell to propagate external neighbor information
     –   N < hreqt. Great HO_MARGIN. Improper algorithm 1-7 setting
     –   Missing_rpt =1
     –   Serving cell overshoots/covers too far away
     –   Refer to GSM BSS Statistics Analysis Handbook
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            No Handover (2)




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            Delay Handover (1)
Description:
     – Neighbor BSIC is decoded but handover occurs in
       much later time
Reason:
     – All possible neighbors suffer blocking
     – Large hreqt * hreqave
     – qual_power_flag is enabled, full BTS/MS power must
       be reached before handover
     – Large handover_recognized_period and bssmap_t7
       setting
     – Refer to GSM BSS Statistics Analysis Handbook

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            Delay Handover (2)




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            Ping Pong Handover (1)
Description:
     – Lot of handovers between cells
     – “Time between Handover” is around hreqt*hreqave of
       such HO cause
Reason:
     –   Improper hardware calibration
     –   Hardware fault
     –   UL/DL interference
     –   Negative handover
     –   Different coverage footprint for antennas of a cell


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            Ping Pong Handover (2)




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            Negative Handover (1)
Description:
     – Serving cell hands over to a weaker neighbor
Reason:
     – ho_only_max_power is enabled
     – qual_margin_flag is disabled
     – ho_margin_usage_flag is enabled with negative
       ho_margin_rxqual/rxlev
     – Negative HO_MARGIN
     – Micro-cellular algorithms are enabled, especially type 5

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                Negative Handover (2)

-59dBm           -66dBm
 before            after
  HO               HO




    2010-3-18                           19
               OverShooting (1)
Description:
     – Cell shoots at far distance but that location has
       closer cells around
Reason:
     –   Overshooting cell has small downtilt, 0 degree!
     –   Overshooting cell has too high altitude
     –   Closer cells have overshooting as well
     –   BSIC of closer cells can’t be decoded

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            OverShooting (2)




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            High Overlapping (1)
Description:
     – Cells have major rxlevel difference within
       ±5dB
Reason:
     – Overshooting
     – Too many cells in that area
     – Poor antenna downtilt


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            High Overlapping (2)
                        -65dBm
                                          -65dBm
    Over Lapping Area




                                          -65dBm


                                 -65dBm
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            No Dominant Server (1)
Description:
     – Rxlevel of best neighbors are close to that of
       serving cell
Reason:
     – Poor antenna downtilt
     – Lack of near-by site



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            No Dominant Server (2)




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                  Poor Coverage (1)
Description:
     –   Low rxlevel with rxquality
     –   In 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
         point
Reason:
     –   Lack of cell site
     –   BSIC of dominant server can’t be decoded
     –   Dominant server has blocking or cell-bar
     –   Handover problem. E.g. missing & incorrect neighbor, negative
         handover, no & delay handover

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            Poor Coverage (2)




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 Unreasonable Serving Area (1)
Description:
     – Coverage area of the cell is incoherent to the
       antenna direction
Reason:
     – Wrong cable connection to antennas
     – Incorrect record of antenna orientation
     – Incorrect ANTENNA_SELECT


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 Unreasonable Serving Area (2)
                          Cell ID:101
                          BCCH: 35


            Cell ID:102              Cell ID:103
            BCCH: 40                 BCCH: 45




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                Interference (1)
Description:
     – High rxlevel with rxquality
Reason:
     –   Channel interference
     –   Not using dominant server
     –   No handover
     –   Turn the corner with delay handover

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            Interference (2)




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             Handover Failure (1)
Description:
     – MS fails to reach target cell, so return to source cell
     – MS sends HO FAILURE and UL-SABM to source cell
       and there is response
Reason:
     –   Channel interference
     –   Poor coverage
     –   External interference at UL, like wideband repeator
     –   Refer to GSM BSS Statistics Analysis Handbook

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            Handover Failure (2)




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               Handover Loss (1)
Description:
     – MS fails to reach target cell, but can’t return to source
       cell
     – MS sends HO FAILURE and UL-SABM to source cell
       but no response
Reason:
     –   Channel interference
     –   Poor coverage
     –   External interference at UL, like wideband repeator
     –   Refer to GSM BSS Statistics Analysis Handbook


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            Handover Loss (2)




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                     UL Drop (1)
Description:
     – BSS doesn’t receive UL SACCH for link_fail times
     – BSS stops transmitting DL power
Reason:
     –   External interference
     –   Channel interference
     –   Faulty ancillary. UL path loss >>> DL path loss
     –   Refer to GSM BSS Statistics Analysis Handbook


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            UL Drop (2)




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                  Drop Call (1)
Description:
     – DL case: Radio_link_timeout counter decreases to 0
     – UL case: link_fail counter decreases to 0
     – Layer 2: BSS/MS send SABM/DISC in every T200 for
       N200+1 times, and no response from recipient
Reason:
     – All cases in this presentation
     – Refer to GSM BSS Statistics Analysis Handbook



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            Drop Call (2)




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            Sudden Power Drop (1)
Description:
     – Dedicated ARFCN has significant non-power control
       rxlevel difference from rxlevel of BCCH
Reason:
     –   No/improper TX power calibration
     –   Faulty ancillary. E.g. combiner, filter..
     –   Different cable lengths from BTS to antennas
     –   Due to air combing, so antennas have different
         coverage footprints

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            Sudden Power Drop (2)




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   MS Power Rapid Increase (1)
Description:
     – MS rapidly increases its TX power due to
            • Optimised Power Control or
            • UL SACCH multiframes aren’t received for link_fail -
              link_about_to_fail times
Reason:
     – Sudden UL interference, e.g. wideband repeator,
       channel interference
     – Too much rapid power down
     – l_rxlev_ul_p is too small
2010-3-18                                                            42
    MS Power Rapid Increase (2)



                        UL power rapid
                      increase from 19 to
                           5 suddenly




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            How GEP Help?
Help to identify below problem in VISUAL basis
• Co-channel interference
• Adjacent-Channel interference
• Mutual neighbor
• Missing neighbor
• Unreasonable neighbor
• Incorrect external neighbor


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            How VOT Help?
Help to identify below problem in VISUAL basis
• Ping pong HO
• Overshooting
• No dominant server
• Poor coverage
• Unreasonable serving area
• Interference
• HO failure
• HO loss
• Drop call

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        How CM Extractor Help?
Extract most BSS parameter for reference
• Cell – e.g. hreqave,hreqt,N,P…
• BTS – e.g. antenna_select…
• RTF – check any incorrect external neighbor
• Neighbor – e.g. ho_margin, delay_timer…




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            How NPM Help?
• Provide cell statistics for VOT display
• Provide BSS and system level 23 key statistics
• Provide detail troubleshooting statistics




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