Azim-Basic Optimization Techniques

Basic Optimization Techniques

May 2008 Prepared by: Muhammad Azim Riaz (LCC)

Key Performance Indicator’s Indicator s (KPI) ¾ CSSR (Call Setup Success Rate) i. TCH Traffic/TCH Blocking ii SDCCH Traffic/SDCCH Blocking ii. iii. SDCCH Success Rate (SDR)

¾ Drop Call Rate (DCR) ¾ HOFR (Handover Failure) ¾ HOFR LOS (HO Failure due to lack of resource)

CSSR (Call Setup Success Rate)

CSSR Analysis: – High TCH Blocking Rate (low TCH Access Rate) – High SDCCH Blocking Rate (low SD Access Rate) – Low SDCCH Success Rate ((high g SDCCH Drop p Rate)) ¾ Check for normal RF conditions • BCCH • Tilts etc. • Check Ch k ffrom Report R t 166 what h t might i ht be b the th causes for f low l SDCCH success rate t

¾ Shifting of SDCCH to BCCH TRX moving it from Hopping TRX.

TCH Traffic and TCH Blocking

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Inadequate SDCCH/AGCH channel capacity preventing TCH assignment.

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Inadequate TCH resources resulting in channel assignment failure.

¾ TCH Traffic and TCH Blocking • TCH Traffic for MOC and MTC call ¾ 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 Rate

Traffic Distribution & possible solutions

Case Study: TCH_RAW_BLK

Congested Cell

DCS/GSM Traffic Balancing through parameters

By Using Aggressive FRU/FRL Settings

Coverage Prediction using ASSET 3G

TCH_UNAVAIL Impacting CSSR If 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 Desk Desk, but 1st confirm that the issue is there for some time.

Solutions for Reducing TCH Blocking

Solution ¾ Remove any TCH_UNAVAIL issue ¾ Use aggressive FRU & FRL settings ¾ Coverage Control (Down tilting, Reduce Antenna height) ¾ Parameter (Traffic Sharing, Aggressive PBGT settings) ¾ Increase Capacity (Add more TRX) ¾ Plan new sites in that area for Traffic Sharing

SDCCH Traffic & SDCCH Blocking

SDCCH Usage ¾ SMS ¾ Location Update ¾ IMSI Detach/Attach ¾ MOC&MTC Call ¾ Supplementary Service (Call waiting, call forwarding) ¾ High Blocking => High SD Traffic, low Availability

Solution ¾ Increase Capacity (add more SDCCH Timeslot) ¾ Reduce unnecessary Location update

SDCCH Traffic & SDCCH Blocking Rate

High SD_BLK Segment Analysis If 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 BLK

SD_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/Detach

SD Drops SD D Drops R Reason: ¾ Low Signal Level ¾ Interference ¾ Hardware Fault (BSC/BTS/TRX/TSL/Transmission)

SD Drops Analysis using report :: 166

DROP CALL RATE (DCR)

™Drop on Handover ¾ Interference on target cell ¾ Incorrect serving cell ™Low Signal Level/Quality ¾ RxLev/RxQual thresholds exceeded ¾ MS enter high attenuation area (building/tunnel etc) ™ High Co - Adjacent and/or External Interference ¾ Excessive interference on TCHs ¾ Excessive interference on CCHs ™Hardware degradation

DCR_USR from Optima Stats

DCR Distribution from Optima

DCR Analysis using Report :: 163

196 :: Quality Report

Interference due to Co Co--BCCH / Co Co--BSIC

Analyzing Quality issue using TEMS LOGS

Impact of Interference on DCR & CSSR

TA Report 232

Per NBR Attempt Report :: 153

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

Call Drop due to Intracell HO Failure

Radio Link Timeout Expiry due to HO Failure

Radio Link Timeout Expiry due to Weak Coverage Patch

Lack of Dominant Server

Handover Failure (HOFR)

™ Handover Failure Rate ¾ Co-BSIC/BCCH problem ¾ Freq Clash ¾ Traffic from large TA’s ¾ HW suspected issue ¾ Missing g neighbors g of any y neighbor g site ¾ Low Signal level ¾ Bad Quality

™ HOFR LOS = 100*HO Fail due to Neighbor Congested/Total HO request ¾ HOFR LOS solution ¾ Solve TCH Blocking of Target cell

Optimizing Neighbour Lists ™ Effects of poor maintenance: ¾ Unwanted legacy g y neighbours g ¾ Oversized neighbour lists ¾ Co-channel neighbour definitions ¾ Missing neighbours ¾ Unintentional 1-way neighbour definitions

™ Optimise by: ¾ Analyze neighbour performance from statistics. ¾ Utilize automated neighbour detection ¾ Identify inconsistent neighbour profiles ¾ Modify appropriate neighbour lists

Reports for HOSR/HOFR Analysis

¾ Adjacency discrepancies (060) ¾ Frequency check of adjacent cells (062) ¾ Adjacent cell double frequencies (069) ¾ Adjacent cells with the same NCC, BCC and frequency (076) ¾ Cells having high HO failure ratio (150) ¾ Adjacencies having high HO failure ratio (153)

Report :: 74 - ADJACENCIES OF CELLS

Analyzing 074 Using MapInfo Tools

Report :: 150 - CELLS HAVING HIGH HO FAILURE RATIO

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

Report :: 60 - ADJACENCY DISCREPANCIES

Routine Optimization Check Points ¾ Cluster definitions by investigating BSC borders, main cities, freeways, major roads. g g customer distribution, customer habits ((voice/data usage). g ) ¾ Investigating ¾ Running specific traces on Network to categorize problems. ¾ Checkingg trouble ticket historyy for previous p p problems. ¾ Checking any fault reports to limit possible hardware problems prior to test.