View
1.587
Download
1
Category
Tags:
Preview:
DESCRIPTION
Citation preview
August 11, 2000
Jim Luan, Lin Mubao
23/4/10 2
Drive Test Procedure
Drive Test
Netplan
FICS
Statistics Analysis
Problem Finding
VOT/GEP
Preparation
23/4/10 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
23/4/10 4
Preparation (2)
• Frequency Plan & Configuration map
• Software:TEMS, FICS, GEP, VOT
• Hardware: TEMS, GPS, Portable PC
• Test Problem Sheet
• Route
• Map
23/4/10 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
23/4/10 6
TEMS Introduction
• Interface
• Functions
23/4/10 7
Log File Process TEMS Log File
NetPlan
FICS
VOT/GEP
.CSV.FMT
Route Map
.STA
Excel VB
.NP/.TXT Much shorter cycle time by VOT and GEP.
23/4/10 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.
23/4/10 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
23/4/10 10
Undecoded BCCH (2)
23/4/10 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
23/4/10 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
23/4/10 13
No Handover (2)
23/4/10 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
23/4/10 15
Delay Handover (2)
23/4/10 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
23/4/10 17
Ping Pong Handover (2)
23/4/10 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
23/4/10 19
Negative Handover (2)
-59dBm before
HO
-66dBm after HO
23/4/10 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
23/4/10 21
OverShooting (2)
23/4/10 22
High Overlapping (1)
Description:– Cells have major rxlevel difference within
±5dB
Reason:– Overshooting– Too many cells in that area– Poor antenna downtilt
23/4/10 23
High Overlapping (2)
Over Lapping Area
-65dBm
-65dBm
-65dBm
-65dBm
23/4/10 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
23/4/10 25
No Dominant Server (2)
23/4/10 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
23/4/10 27
Poor Coverage (2)
23/4/10 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
23/4/10 29
Unreasonable Serving Area (2)Cell ID:101
BCCH: 35
Cell ID:102
BCCH: 40
Cell ID:103
BCCH: 45
23/4/10 30
Interference (1)
Description:– High rxlevel with rxquality
Reason:– Channel interference– Not using dominant server– No handover– Turn the corner with delay handover
23/4/10 31
Interference (2)
23/4/10 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
23/4/10 33
Handover Failure (2)
23/4/10 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
23/4/10 35
Handover Loss (2)
23/4/10 36
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
UL Drop (1)
23/4/10 37
UL Drop (2)
23/4/10 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
23/4/10 39
Drop Call (2)
23/4/10 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
23/4/10 41
Sudden Power Drop (2)
23/4/10 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)
23/4/10 43
MS Power Rapid Increase (2)
UL power rapid increase from 19 to
5 suddenly
23/4/10 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
23/4/10 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
23/4/10 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…
23/4/10 47
How NPM Help?• Provide cell statistics for VOT display• Provide BSS and system level 23 key statistics• Provide detail troubleshooting statistics
Recommended