2g logs analysis
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Transcript of 2g logs analysis
22/10/17 2
Drive Test Procedure
Drive Test
NetplanFICS
Statistics AnalysisProblem Finding
VOT/GEP
Preparation
22/10/17 3
Preparation (1)• Definition File
– Without it, it is impossible to observe overshooing neighbors– GenDef7.exe can convert FP to definition file
Neighbor list with definition
file
Neighbor list without definition
file
22/10/17 4
Preparation (2)• Frequency Plan & Configuration map
• Software:TEMS, FICS, GEP, VOT• Hardware: TEMS, GPS, Portable PC
• Test Problem Sheet• Route• Map
22/10/17 5
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
22/10/17 7
Log File Process TEMS Log File
NetPlan
FICS
VOT/GEP
.CSV.FMT
Route Map
.STAExcel VB.NP/.TXT Much shorter
cycle time by VOT and GEP.
22/10/17 8
TEMS .log file Analysis
• Undecoded BCCH• BSIC Undecode in Other Site
• No Handover• Delay Handover• Ping Pong Handover• Negative Handover• Overshooting• High Overlapping• No Dominant Server
• Poor Coverage• Unreasonable Serving Area
• Interference• Handover Failure• Handover Loss• UL Drop• Drop Call• Sudden Power Drop• MS Power Rapid Increase
Below lists common problems which can be observed from Drive Test Log.
22/10/17 9
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
22/10/17 11
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
22/10/17 12
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
22/10/17 14
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
22/10/17 16
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
22/10/17 18
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
22/10/17 20
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
22/10/17 22
High Overlapping (1)Description:
– Cells have major rxlevel difference within ±5dB
Reason:– Overshooting– Too many cells in that area– Poor antenna downtilt
22/10/17 24
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
22/10/17 26
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
22/10/17 28
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
22/10/17 29
Unreasonable Serving Area (2)
Cell ID:101BCCH: 35
Cell ID:102BCCH: 40
Cell ID:103BCCH: 45
22/10/17 30
Interference (1)Description:
– High rxlevel with rxqualityReason:
– Channel interference– Not using dominant server– No handover– Turn the corner with delay handover
22/10/17 32
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
22/10/17 34
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
22/10/17 36
Description:– BSS doesn’t receive UL SACCH for link_fail times
– BSS stops transmitting DL powerReason:
– External interference– Channel interference– Faulty ancillary. UL path loss >>> DL path loss
– Refer to GSM BSS Statistics Analysis Handbook
UL Drop (1)
22/10/17 38
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
22/10/17 40
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
22/10/17 42
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
MS Power Rapid Increase (1)
22/10/17 44
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
22/10/17 45
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
22/10/17 46
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…