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August 11, 2000

Jim Luan, Lin Mubao


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Drive Test Procedure

Drive Test

Netplan

FICS

Statistics Analysis

Problem Finding

VOT/GEP

Preparation


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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 withdefinition file

Neighbor listwithout definition

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 ProcessTEMS Log File

NetPlan

FICS

VOT/GEP

.CSV.FMT

Route Map

.STAExcel VB

.NP/.TXT M uch shortercycle time by VOTand GEP.


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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.


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Undecoded BCCH (1)Description:

BSICs cant 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 isfulfilled but there is never a handover

Reason: Missing neighbor

No such neighbor in CM database Incorrect external neighbor

Target cells LAC/BCCH/BSIC in add_neighbor is different from those inequip_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 inmuch 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 before

HO

-66dBmafterHO


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OverShooting (1)Description:

Cell shoots at far distance but that location hascloser 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 cant 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)

Over Lapping Area

-65dBm

-65dBm

-65dBm

-65dBm


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No Dominant Server (1)

Description: Rxlevel of best neighbors are close to that of

serving cellReason:

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 cant 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 directionReason:

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

BCCH: 40

Cell ID:103

BCCH: 45


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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 cant return to sourcecell

MS sends HO FAILURE and UL-SABM to source cell

but no responseReason:

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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Description: BSS doesnt 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)


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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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Description: MS rapidly increases its TX power due to

Optimised Power Control or

UL SACCH multiframes arent 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)


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MS Power Rapid Increase (2)

UL power rapidincrease 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

Documents

54600526-drive-test-logs-analysis-131231111324-phpapp01