Basic Optimization Techniques

May 2008Prepared by: Muhammad Azim Riaz (LCC)

Key Performance Indicator’s (KPI)Key Performance Indicator’s (KPI)Key Performance Indicator s (KPI)Key Performance Indicator s (KPI)

CSSR (Call Setup Success Rate)CSSR (Call Setup Success Rate)

i. TCH Traffic/TCH Blocking

ii SDCCH Traffic/SDCCH Blockingii. SDCCH Traffic/SDCCH Blocking

iii. SDCCH Success Rate (SDR)

Drop Call Rate (DCR)Drop Call Rate (DCR)

HOFR (Handover Failure)

HOFR LOS (HO Failure due to lack of resource)

CSSR (Call Setup Success Rate)CSSR (Call Setup Success Rate)

CSSR Analysis:CSSR Analysis:

– High TCH Blocking Rate (low TCH Access Rate)

– High SDCCH Blocking Rate (low SD Access Rate)

– Low SDCCH Success Rate (high SDCCH Drop Rate)( g p )

Check for normal RF conditions

• BCCH

• Tilts etc.

Ch k f R t 166 h t i ht b th f l SDCCH t • Check from Report 166 what might be the causes for low SDCCH success rate

Shifting of SDCCH to BCCH TRX moving it from Hopping TRX.

TCH Traffic and TCH BlockingTCH Traffic and TCH Blocking

Inadequate SDCCH/AGCH channel capacity preventing TCH assignment.

Inadequate TCH resources resulting in channel assignment failure.

TCH Traffic and TCH Blocking

• TCH Traffic for MOC and MTC call

Traffic in erlang

• 1 erlang means 1 subscriber occupied 1 circuit for 1 hour

• 1 erl = 1 (sub) * occupy time (sec)/3600

• High Blocking rate => High Traffic , Low Availability

TCH Traffic and TCH Blocking RateTCH Traffic and TCH Blocking Rate

Traffic Distribution & possible solutionsTraffic Distribution & possible solutions

Case Study: TCH_RAW_BLKCase Study: TCH_RAW_BLK

DCS/GSM Traffic Balancing through parametersDCS/GSM Traffic Balancing through parametersCongested Cell

By Using Aggressive FRU/FRL SettingsBy Using Aggressive FRU/FRL Settings

Coverage Prediction using ASSET 3GCoverage Prediction using ASSET 3G

TCH_UNAVAIL Impacting CSSRTCH_UNAVAIL Impacting CSSRIf TCH_Unavail is high on site then we have

to resolve it on priority basis, for that purpose we need to raise it on Service Deskpurpose we need to raise it on Service Desk,

but 1st confirm that the issue is there for some time.

Solutions for Reducing TCH BlockingSolutions for Reducing TCH Blocking

Solution

Remove any TCH_UNAVAIL issue

Use aggressive FRU & FRL settings

Coverage Control (Down tilting, Reduce Antenna height)

Parameter (Traffic Sharing, Aggressive PBGT settings)

Increase Capacity (Add more TRX)

Plan new sites in that area for Traffic Sharing

SDCCH Traffic & SDCCH BlockingSDCCH Traffic & SDCCH Blocking

SDCCH Usage

SMSLocation UpdateIMSI Detach/AttachMOC&MTC CallSupplementary Service (Call waiting, call forwarding)High Blocking => High SD Traffic, low Availability

Solution

Increase Capacity (add more SDCCH Timeslot)Reduce unnecessary Location update

SDCCH Traffic & SDCCH Blocking RateSDCCH Traffic & SDCCH Blocking Rate

High SD_BLK Segment AnalysisHigh SD_BLK Segment AnalysisIf SD BLK is high and we already have defined max. SD’s on 900, then we can ,

define SD TS on DCS

SD BLK might be high due to high # of location updates/IMSI Attach & Detach or DR

HO attempts

Effect of SD_AVAIL on SD BLKEffect of SD_AVAIL on SD BLK

SD_BLK due to Location UpdatesSD_BLK due to Location Updates

Too many location updates on this segment we can use aggressive

“cellreselecthysterisis” settings to avoid too many cell reselection in

idle mode.

SD Utilization by IMSI Attach/DetachSD Utilization by IMSI Attach/Detach

SD DropsSD Drops

SD D RSD D RSD Drops Reason:SD Drops Reason:

Low Signal LevelInterferenceHardware Fault (BSC/BTS/TRX/TSL/Transmission)

SD Drops Analysis using report :: 166SD Drops Analysis using report :: 166

DROP CALL RATE (DCR)DROP CALL RATE (DCR)

Drop on Handover

Interference on target cellIncorrect serving cellIncorrect serving cell

Low Signal Level/Quality

RxLev/RxQual thresholds exceededMS enter high attenuation area (building/tunnel etc)

High Co - Adjacent and/or External Interference

Excessive interference on TCHsExcessive interference on TCHsExcessive interference on CCHs

Hardware degradation

DCR_USR from Optima StatsDCR_USR from Optima Stats

DCR Distribution from OptimaDCR Distribution from Optima

DCR Analysis using Report :: 163DCR Analysis using Report :: 163

196 :: Quality Report196 :: Quality Report

Interference due to CoInterference due to Co--BCCH / CoBCCH / Co--BSICBSIC

Analyzing Quality issue using TEMS LOGSAnalyzing Quality issue using TEMS LOGS

Impact of Interference on DCR & CSSRImpact of Interference on DCR & CSSR

TA Report 232TA Report 232

Per NBR Attempt Report :: 153Per NBR Attempt Report :: 153

Drop due to Non RF reason (TXN or NSS end)Drop due to Non RF reason (TXN or NSS end)

Call Drop due to Intracell HO FailureCall Drop due to Intracell HO Failure

Radio Link Timeout Expiry due to HO FailureRadio Link Timeout Expiry due to HO Failure

Radio Link Timeout Expiry due to Weak Coverage PatchRadio Link Timeout Expiry due to Weak Coverage Patch

Lack of Dominant ServerLack of Dominant Server

Handover Failure (HOFR)Handover Failure (HOFR)

Handover Failure Rate

Co-BSIC/BCCH problem

Freq Clash

Traffic from large TA’s

HW suspected issue

Missing neighbors of any neighbor siteg g y g

Low Signal level

Bad Quality

HOFR LOS = 100*HO Fail due to Neighbor Congested/Total HO request

HOFR LOS solution

Solve TCH Blocking of Target cell

Optimizing Neighbour ListsOptimizing Neighbour Lists

Effects of poor maintenance:Effects of poor maintenance:

Unwanted legacy neighboursg y g

Oversized neighbour lists

Co-channel neighbour definitions

Missing neighboursMissing neighbours

Unintentional 1-way neighbour definitions

Optimise by:Optimise by:

Analyze neighbour performance from statistics.

Utilize automated neighbour detection

Identify inconsistent neighbour profilesIdentify inconsistent neighbour profiles

Modify appropriate neighbour lists

Reports for HOSR/HOFR AnalysisReports for HOSR/HOFR Analysis

Adjacency discrepancies (060)Adjacency discrepancies (060)

Frequency check of adjacent cells (062)

Adjacent cell double frequencies (069)

Adjacent cells with the same NCC, BCC and frequency (076)

Cells having high HO failure ratio (150)

Adjacencies having high HO failure ratio (153)

Report :: 74 Report :: 74 -- ADJACENCIES OF CELLSADJACENCIES OF CELLS

Analyzing 074 Using MapInfo ToolsAnalyzing 074 Using MapInfo Tools

Report :: 150 Report :: 150 -- CELLS HAVING HIGH HO FAILURE RATIOCELLS HAVING HIGH HO FAILURE RATIO

Report :: 76 Report :: 76 -- ADJACENT CELLS WITH THE SAME NCC,BCC AND ADJACENT CELLS WITH THE SAME NCC,BCC AND FREQUENCYFREQUENCY

Report :: 60 Report :: 60 -- ADJACENCY DISCREPANCIESADJACENCY DISCREPANCIES

Routine Optimization Check PointsRoutine Optimization Check Points

Cluster definitions by investigating BSC borders, main cities, freeways, major roads.

Investigating customer distribution, customer habits (voice/data usage).g g ( g )

Running specific traces on Network to categorize problems.

Checking trouble ticket history for previous problems.g y p p

Checking any fault reports to limit possible hardware problems prior to test.