KEY PERFORMANCE INDICATORS

Call Drop Rate (%) = No. of Drop Calls / No. of Calls

= Rate of Drop Calls (system+radio+handover) over the total amount of calls with a

successful end.

Call Setup Success Rate (%) = (1-SDCCH Drop Rate) * (1-RTCH Assign Unsuccessful Rate)

= Rate of calls going until RTCH successful assignment

( from SDCCH seizure to RTCH seizure )

Handover Incoming = HO Incoming Success / HO Incoming Request

Success Rate (%) = Rate of Incoming External and Internal Intercell RTCH and SDCCH HO

successes over the total amount of Incoming External and Internal Intercell HO

requests.

DEFINITION OF TERMS

CALL DROP RATE

Main Causes of Call Drop

1. Drop Call due to Radio Problem

2. Drop Call due to Handover Problem

3. Drop Call Due to System Problem

GSM RadioProblem

Bad Settingsfor HO

Algorithm

Isolated Cell

ClockProblem

CommunicationDuration

Unbalanced

InterferedFrequency

BadAdjacencyP lanning

W rongHandov er

CALL DROP DUE TO RADIO PROBLEM

CALL DROP DUE TO HANDOVER PROBLEM

GSMHandoverProblem

DuplicateBCCH,BSIC

Target CellCongested

CELLInterfered

WrongHandover

Declaration

CoverageProblem

Bad Settingsof PowerControl

Algorithm

ClockProblem

Too much TCHTraffic

RTCH always busy

FU Blocked

Loss of TCHresources

Some Planned Adjacencies arenot declared at OM CR

Some Operational Adjacenciesare not Planned

Adjacencies not declared onboth side

InterferedFrequency

CALL DROP DUE TO SYSTEM PROBLEM

GSMSystemProblem

RemoteTranscoder

Problem

BSS InternalFailures

SystemProblem on

BSC

SystemProblem on

Cell

CALL SETUP SUCCESS RATE

Main Causes of Call Setup Problem

1. RTCH Assignment Failure Problem

2. SDCCH Drop Problem

TCHAssignment Fail

Problem

TCH AssignFail System

TCH AssignFail Radio

RadioEquipment

Problem

AbisProgramming

Problem

FU Blocked

CALL SETUP PROBLEM DUE TO RTCH ASSIGNMENT FAIL

CALL SETUP PROBLEM DUE TO SDCCH DROP PROBLEM

SDCCH DropProblem

SDCCH DropSystem

SDCCH DropHO

SDCCH DropRadio

Link Failure

ProcessorRestart

BSS Int.Problem

SDCCH HO notActivated

TCH RadioProblem

StandaloneSDCCH HO

Problem

TCH HOProblem

HANDOVER SUCCESS RATE

TOPICS TO BE DISCUSSED:

• Few Handovers on Better Cell

• Intra Cell Handover Problem

• Incoming Handover Problem

• Outgoing Handover Problem

FEW HANDOVERS ON BETTER CELL

FewHandoverson Better

Cell

Too manyHO onQuality

Too manyHO on Level

InterferedFrequency

PotentialInterferer

AdjacentInterferer

Co-channelInterferer

ExternalInterferer

Problem ofUplink

Reception

Problem ofDownlink

Transmission

INTRACELL HANDOVER PROBLEM

Main Causes of Intracell Handover Problem

1. Congestion Problem

2. HO Failure with Reversion to Old Channel

3. HO Fail with Drop Call

INTRACELL HANDOVER PROBLEM DUE TO CONGESTION PROBLEM

Problem ofCongestion

RTCH alwaysBusy

FU Blocked

Loss of TCHResource

Too M uch TCHTraffic

INTRACELL HANDOVER PROBLEM DUE TO REVERSION TO OLD CHANNEL

HO Fail withReversion to Old

ChannelInterfered Cell

InterferedFrequency

INTRACELL HANDOVER PROBLEM WITH CALL DROP

HO Fail withDropped Call

SystemProblem on

BSC

Bad Settings ofIntracell HO

Timer

Dropped Calldue to System

Failure

Dropped Calldue to Radio

Failure

SystemProblem on

Cell

InterferedFrequency

Interfered Cell

PROBLEM OF UNSUCCESSFUL INCOMING HANDOVER

Main Causes of Incoming Handover Problem

1. Problem of HO Congestion

2. HO Failure Problem

PROBLEM OF UNSUCCESSFUL INCOMING HANDOVER DUE TO CONGESTION

Problem ofHO

Congestion

Problem ofToo M uch

TCH Traffic

RTCH AlwaysBusy

FU Blocked

Loss of TCHResources

Problem ofHO Failures

HO Failure -System

HO Failure -Radio

Wrong HORelationship

OutgoingProblem onServing Cell

Outgoing Problemon Internal Serving

Cell

Outgoing Problemon External Serving

Cell

DuplicateBCCH, BSIC

ClockProblem

InterferedCell

SystemProblem on

BSC

SystemProblem on

Cell

InterferedFrequency

InterferedFrequency

InterferedCell

CoverageProblem

Bad Settings ofHO Algorithm

Bad Settings ofPower Control

Algorithm

InterferedCell

InterferedFrequency

CoverageProblem

Bad Settings ofHO Algorithm

Bad Settings ofPower Control

Algorithm

PROBLEM OF UNSUCCESSFUL INCOMING HANDOVER DUE TO HANDOVER FAILURE PROBLEM

PROBLEM OF UNSUCCESSFUL OUTGOING HANDOVER

Main Causes of Unsuccessful Outgoing Handover

1. Problem of High Handover Reversion

2. Problem of Drop Calls

PROBLEM OF UNSUCCESSFUL OUTGOING HANDOVER DUE TO HIGH HANDOVER REVERSION

Pb of High HOReversion

Congestion onTarget Cell

Incoming Pb onTarget Cell

Congestion onInternal Target Cell

Incoming Pb onInternal Target Cell

Congestion onExternal Target Cell

Incoming Pb onExternal Target Cell

Too M uch TCHTraffic

FU Blocked

Loss of TCHResources

RTCH Always Busy

Congestion onTarget Cell

Congestion onTarget Cell

Congestion onTarget Cell

Congestion onTarget Cell

Interfered Cell

Duplicate(BCCH,BSIC)

Clock Problem

Wrong HORelationshipDeclarations

System Drop duringExternal HO

System Drop duringInternal HO

PROBLEM OF UNSUCCESSFUL OUTGOING HANDOVER DUE TO DROP CALLS

Pb of Drop Calls

HO Drop Radio

HO Drop System

Radio Drop duringExternal HO

Radio Drop duringInternal HO

System Drop duringExternal HO

System Drop duringInternal HO

OPTIMIZATION TECHNIQUES

1 2

Channel Request Channel Request

Imm Assignment Imm Assignment

Service Request Service Request

Signalling SDCCH Signalling: :

Signalling SpeechTCH

RLT = 0 ; DROPS RLT = 0 ; DROPSSDCCH DROP ! TCH DROP !

3 SDCCH / TCH

Handover Command

Hand Access

Handover Failure

HANDOVER FAILURE DROP !

DROP CALL PROBLEM ANALYSIS

• SDCCH Drops - Causes

– Coverage

– Interference & Multipath

– BTS performance

• TCH Drops - Causes

– Coverage

– Interference & Multipath

– BTS performance

• Handover Failure - Causes

– Threshold parameters

– Missing neighbors

DROP CALL PROBLEM CAUSES

DROP CALL PROBLEM SOLUTIONS

– Optimize Coverage– Interference Management– Optimize neighbors– Optimize handover

parameters– Effective Frequency Hopping– Use of DTX & Power control

1

Channel RequestRACH .

:RACH

max_retransNO RESPONSE FROM N/WACCESS FAILURE !

2

Channel RequestRACH

Imm Assign Reject

SDCCH BLOCKED !

3

Channel Request

Imm Assignment

Service Request

Signalling:

Signalling

NO TCH ASSIGNMENTMobile Returns To IdleTCH BLOCKED !

CALL SETUP PROBLEM ANALYSIS

`̀

– Optimize Coverage– Interference Management– Optimize Capacity– Effective Frequency Hopping– Use of DTX & Power control

CALL SETUP PROBLEM SOLUTIONS

MOBILE A BTS A BSC A MSC BSC B BTS B MOBILE B

SYS INFO 5 & 6 BTS MEAS. RESULT

MEASUREMENT REP MS MEAS. RESULT

SACCH

HANDOVER REQ’D

HANDOVER RQSTCHANNEL ACT.

ACT. ACK.

HO RQST ACK

HANDOVER ACCESSHANDOVER DETECT

FACCH

HO COMMANDHO COMMAND DATA REQUEST

RELEASE RQST PHYSICAL INFO

PHYSICAL INFO

SABM EST INDICATION

UA

HO COMPLETE DATA INDICATION HO COMPLETE

CLEAR CMD

CLEAR CMPLT

RELEASE RF CHNL RELEASE

RF CHNL REL. ACK. RELEASE CMPLT

INTER - BSC HANDOVER

HANDOVER PROBLEM SOLUTIONS

– Optimize Coverage– Interference Management– Optimize Neighbors– Optimize Handover

parameters

ADDITIONAL INFORMATION

SYSTEM INFORMATION TYPE 5

- Neighbour cells description which gives the ARFCN’s of the neighbour cells to be monitored and reported by the mobile. Note that this also an offset and a bit map listing up to 124 ARFCN’s.

SYSTEM INFORMATION TYPE 6

1. Cell Identity (CI) to identify any cell in a given location area.2. Location Area Identification including:

• The Mobile Country Code (MCC)• The Mobile Network Code (MNC)• The Location Area Code (LAC)

3. Cell Options including• Power Control Enabled• DTX Enabled• The value of the Radio Link Timeout counter

4. PLM permitted which lists the network color codes (NCC’s) which the mobile can use.

ADDITIONAL INFORMATION

TYPES OF HANDOVERS

• PREVENTATIVE HO

- Improve Call Quality or Minimize Interference

1. Power Budget – Based on Downlink Signal Levels - Uses Power Budget HO Margin - If Neighbor is better than Serving Cell by more than the margin, initiate HO.

2. Timing Advance – Based on Timing Advance - If Serving Cell Timing Advance is greater than a set distance and Neighbor Cell is better than the serving cell by more than the margin then initiate HO.

ADDITIONAL INFORMATION • RESCUE HO

- Prevent Dropped Calls or Poor Quality Calls

1. Level – Intended to HO a call before the signal level gets so low that quality is affected

- Triggered on both UPLINK and DOWNLIK

- Uses HO Level Margin

- If Serving Cell RXLev ( UL or DL ) is lower than a set value, and Neighbor Cell is better than the serving cell by more than the margin, then initiate HO.

2. Quality – Intended to HO the Call Before the Quality level gets so low that the customer notices

- Triggered on both UPLINK and DOWNLIK

- Uses Quality HO Margin

- If Serving Cell RXQual ( UL or DL ) is lower than a set value, and Neighbor Cell is better than the serving cell by more than the margin, then initiate HO.

END OF PRESENTATION