omd6010 traffic statistics analysis issue1.1

8/2/2019 OMD6010 Traffic Statistics Analysis ISSUE1.1

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OMD6010Traffic statistics analysis

ISSUE1.1

Wireless Curriculum

Development Section


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Brief Introduction for BSC Traffic Statistics

collectivity structure

menu introduction

key item introduction

Often-used Traffic Statistics Items analysis

Locating problems through traffic analysis

Case analysis for Traffic statistics

Content


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3

Main Structure of Traffic Statistics System

BM1

Call process data

BM data

Hardware data

Signaling data

BM

AM/CM

BAM

WS1 WS

OMC SERVERHUB


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Brief Introduction for BSC Traffic Statistics

Advanced Global Pre-set Counters Design

Once the host starts, the global counters begin

to work at different statistics points constantly andautomatically without manual interfere

Abundant and Powerful Statistics Functions


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Menu Introduction for BSC Traffic Statistics

Task list management

BSC traffic statistics platform provide features of registering new

taskdeleting registered taskrefreshing task list and exitingtraffic statistics system


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Menu Introduction to BSC Traffic Statistics

Task management

BSC traffic statistics provide the features of modifying task

name

modifying statistic period of permanent task

hangingup task activating task examining task information

querying task result and querying task running state


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Menu Introduction to BSC Traffic Statistics

Template management

Template management provide the features of Defining item

template object template time template user-defined

statistic item and refreshing all templates


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Brief Introduction for BSC Traffic Statistics item

TCH congestion rateTCH congestion rate (excluding HO) = TCHseizure failures (excluding HO) / Attempted TCHseizures (excluding HO) *100%

TCH congestion rate (including HO) = TCH seizurefailure (including HO) / Attempted TCH seizures(including HO) *100%


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TCH call drop rate

TCH call drop rate(%) = TCH call drop /Successful TCHseizures (all) *100%

SDCCH call drop rate

SDCCH call drop rate(%) = SDCCH call drop / SuccessfulSDCCH seizures (all) *100%

Brief Introduction for BSC Traffic Statistics item


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Brief Introduction for BSC Traffic Statistics Item

SDCCH Congestion Rate

SDCCH Congestion rate (%) = SDCCH seizurefailures due to SDCCH busy/ Attempted SDCCH

seizures *100%


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Radio Connection Successful Rate

Radio connection success rate(%)=(1-TCH

congestion Rate)(1-SDCCH congestion Rate)A key item used to show the performance of radio

service


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HO Successful Rate

Inter cell HO successful rate (%) = Successful Inter

cell handovers /Attempted Inter cell handovers *100%

Inter cell wireless HO successful rate(%)=SuccessfulInter cell handovers /Attempted Inter cell handovers*100%


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Brief Introduction to BSC Traffic Statistics Item

BSC Measurement Function

SCCP Measurement FunctionA-interface Operation and management

statistic

A-interface Equipment Maintenance

statistic

A-interface Trunk Board message

statistic

CPU Measurement Function

BSC Cell Broadcast Measurement

Function

MTP Measurement Function

Cell Measurement Function

Power-control Measurement Function

Call Drop Measurement Function

Site Initialization Measurement Function

BTS Initialization Measurement

Cell Broadcast StatisticOutgoing Inter-cell HO Measurement Function

Incoming Inter-cell HO Measurement Function

Undefined Adjacent Cell Measurement

Function

Defined Adjacent Cell Measurement Function

Receiving Quality Measurement Function

Receiving Level Measurement Function

Link Balance Measurement Function

LAPD Link Measurement Function

Cell Frequency Scan

GPRS Measurement Function


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Brief Introduction to BSC TrafficStatistics

Often-used Traffic Statistics Items

analysis

Locating Problems through Traffic

Statistics

Case analysis for traffic analysis

Content


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Systematical architectureFrom Above to Below, From Global to Local

Relativity

Relationship between all kinds of traffic statistics items

Integrality

Can observe the change trend of item over a week or dayby day



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Analysis Process

First we should analyze and compare the sub-item ofBSC measurement/C1 report statistics function tohave a roughly acknowledgement for the whole

network.

During analyzing , if any important items (such as calldrop rate or HO successful rate) are abnormal, weshould do some further and detailed analysis for thecorresponding contents.



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Analysis Process

The cell that has one abnormal item and large faultytimes (call drop, congestion, handover failure and so on)

Using percentage and faulty times (call drop, congestion,handover failure and so on) together to decide whether

doing some further analysis or not



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Paging successful rate

immediate assignment successful rate

TCH congestion rate

call drop rate

handover successful rate

interference band

others



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Paging successful rate

Having relations with ATT ,coverage area,

random access performance

Having relations with the paging re-sending Mechanism

implemented by BSC or MSC


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Immediate assignment successful rate

When BTS receives RA message from MS, BTS willapply channel from BSC. If there is no channelsavailable, BSC will send Immediate assignmentrejection message which indicates the failure ofImmediate assignment.At the same time, MSs access

will be forbidden for some time.

The interference and collision between randomaccess both will affect immediate assignment

successful rate.


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TCH congestion rate(TCH fully occupied)

It is a key item used to assess cell load

When the load of the cell overruns the system limitation,trying to distribute some traffic to adjacent cells


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TCH Interference Band measurement

The result in each TCH interference band shows theaverage number of idle TCHs within this interference band

in one statistics period, which reflects the averageinterference level of the idle TCHs.

In urban and suburb area,because of different density ofbase station and the different frequency reuse pattern,theacceptable interference level is different.


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Call drop and the causes

TCH Call drop reason include four parts: Radio link disconnection when TCH seized

(Connection failure)

Radio link disconnection when TCH seized(Wrong indication)

Ground link disconnection when TCH seized (ABIS) A interface failure when TCH seized


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Analysis of Often-used Traffic Statistics Items

Call drop statistics points

TCH call drop rate =TCH call drop times / Successful TCH seizures (all)

*100%

Traffic density at average TCH call drop can also beused to assess the whole system call dropperformance:


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TCH/SDCCH RF lost Rate:

TCH/SDCCH RF lost Rate (%) = (Radio link disconnectionwhen seized (connection failure) + Radio linkdisconnection when TCH/SDCCH seized (error indication))

/Successful TCH/SDCCH seizures (all) *100%



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Seizure failure (congestion) and the causes

Assignment FailureEquipment FaultInvalid Ground Resource

Ground Resource already allocatedIllegal Message ContentsRadio Interface Failure and return to original channelNo Available ChannelOthers


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Seizure failure (congestion) statistics point

TCH congestion rate (excluding HO)(%)=(TCH seizure failures + TCH immediate assignmentfailures) / (Attempted TCH seizures + TCHimmediate assignments)*100%


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SDCCH congestion rate

SDCCH congestion rate=(Attempted SDCCH seizures meeting a SDCCH blocked state

/Attempted SDCCH seizures)100%


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SDCCH congestion rate statistics point

Attempted SDCCH seizure meeting a SDCCHblocked state is counted when there is a SDCCHseizure attempt but no SDCCH available.

Attempted SDCCH seizures (all):1:Receiving CH_REQ, and the channel type isSDCCH, or there is no TCH but SDCCH during veryearly assignment process;

2: Incoming interBSC inter cell HO and the handovertype SDCCH HO3:Incoming internal inter cell and intra-cell HO andthe handover type is SDCCH HO


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HO statistics point

Inter-cell HO successful rate=(Successful incominginternal inter cell handovers + Successful incominginterBSC inter cell handovers + Successful outgoing

internal inter cell handover + Successful outgoinginterBSC inter cell handover /(Incoming internal inter cell handovers + Attemptedincoming interBSC inter cell handovers + Outgoinginternal inter cell handovers + Attempted outgoing

interBSC inter cell handovers)*100%


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HO statistics point

Contrapose different objects such as BSC, dual-band 900/1800, incoming/outgoing HO, intra-cell

HO and so on there are different items.

Fast locating the problem by analyzing differentitems


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Causes of handover

Power budget Bad uplink signal quality Bad downlink signal quality

Low uplink signal strength Low downlink signal strength Abnormal TA value Other reasons

HO types and times can be find inoutgoing/incoming cell HO measurement function


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HO failure reasons

No available channel Illegal frequency

Timer time outIllegal channelIllegal TAOther reasons


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Balance between uplink and downlink

All the measurement reports for certain TRX aresorted into different balance level, the sum alsoreflects the traffic carried on the TRX.

Distribution of measurement reports for eachTRX in one cell should be coincident except inunderlay/overlay cell.

Modifications are made considering powercontrol, receiving sensitivity of MS and BTS whensorting.


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Cell frequency scan

Show the signal levels received by mainantenna and diversity antenna

Reflecting the interference level on eachfrequencyThe difference between the measurementresults got by main and diversity antennareflects the difference between the twoantennas such as direction, gain, path lossand so on.


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Receiving level performance

Receiving level performance measurement is basedon TCH channel:The receiving level is divide into following bands:

Band 0 : -110~100dBmBand1 : -100~95dBmBand 2 : -95~90dBmBand 3 : -90~80dBmBand 4 : -80~70dBm

Band 5 : > -70dBm


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Content

Brief Introduction for BSC

Traffic Statistics

Analysis of Often-used Traffic

Statistics Items

Locating problems by the Aid of

Traffic Statistics

Case Analysis for Traffic Statistics


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General method of traffic analysis

Traffic Statistics Analysis

BSC Measurement Function

High call drop rate High congestion rate Low HO success rate

TCH

p

erformance

Calldrops

SDCCH

performance

Link

balance

Outg

oingHO

Ala

rmdata

Ala

rmdata

TCH

p

erformance

TCH

p

erformance

IncomingHO

Link

balance

Link

Balance

Ala

rmdata


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Work together with other network optimization

methods

Traffic Statistics Analysis

Drive Test: simulate common subscribers behaviorAnalyzing objects: Coverage/Quality/HO/Signaling etc.

CQT:Call Quality Test


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Traffic Statistics Analysis-call drop

Analysis Diagram

TCH call drop analysis

Cell with high call drop rate

Cell performancestatistics

Call Drop MeasurementHO performancemeasurement

Times of call drop

Data from

interference band

reasons ofcall drops

Uplink average level when

TCH call drops

Downlink average level when

TCH call drops

Uplink average quality when

TCH call drops

Downlink average quality

when TCH call drops

Average TA value when

TCH call drops

Outgoing-cell

HO success rate

incoming-cell

Successful HO rate

Times of HO

failure and re-establish

failure

Alarm and

hardware fault


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Call drop can be generally divided into 4 category, asfollowing:

Edge call drop:low receiving signaling level, large TA

Nearby low level call drop:low receiving signaling leveland small TA

BQ call drop: high receiving signaling level and bad

quality Sudden call drop: before call drop,the call is normal,

then call drop happened suddenly

Call drop Types

TCH call drop analysis


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Causes:

MS is out of cells effective coverage area, island phenomenon

caused by over-coverage or forgetting adding the neighbor and

Stand-along site

Solutions: Adding new site to guarantee the effective continuous coverage;

Adding neighbor to let the MS can handover to other cell;

Increasing antenna height, using high gain antenna, adjustingantenna down-tilt;

Modifying related parameters,such asSACCH multi-frames,Radio link time out,Margin HO threshold,HO statistictime, which will partly improve the call drop rate

Edge call drop


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Cause:

Poor coverage caused by complicated terrain structure orhigh dense low level buildings.

Solutions: Increasing ERP;

Adjusting antenna direction and down-tilt, making themain lobe point to high traffic area;

Adjusting call drop related parameters

Nearby low level call drop


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Causes:

Interference of the uplink or downlink

High transmission bit error rate(BER)

Interference source:

Repeater working different frequency band

Radar or other similar equipment

Improper frequency plan

Self-interference caused by BTS itself

BQ call drop( high signal level)


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Solution:

Wiping out illegal external interference;

Optimizing frequency planning;

Adjusting antenna&feeder system, avoiding island effect;

Avoiding transmission BER.

BQ call drop( high signal level)


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1:Find out cells with high call drop rate;

2:Further analysis of these cells traffic load and total call drop times;

3:Observing call drop performance included in the call drop

performance measurement task;4:Check the interference band distribution;

5:Classify the call drop according to the 4 typical characteristics ofcall drop.

Call drop analyzing process


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1.Interference (internal interference, external interference, andinterference from the equipment)

2. Poor coverage (no-signal area, and isolated island)

3. Unreasonable HO (neighbor cell plan and HO relatedparameters)

4. Link unbalanced (TMA, power amplifier, directions)

5. Unreasonable parameter setting ( RLT , and SACCH multi-frames)

6. Equipment problem (TRX, power amplifier, and TMA)

Main reasons


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Check call statistics:

Analyzing the appear disciplinarian of the interference

band in the traffic : change trend according to time andtraffic

Shut down TRX one by one to observe the interferencedistribution

1. Interference(internal/external)-1


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Check call statistics:

Check the percentage of HO caused by poor quality in all

HOs, and in the Receiving Quality Measurement Function,check the average receiving quality level for each TRX

In Call Drop Measurement Function: Check the averagelevel and quality for each call drop



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Solutions:

Through drive test, checking the interference and signal quality

distribution along the driving path By the aid of spectrum analyzer

HF, DTX, Power control(PC)

Fix equipment failure(such as: TRX self-oscillation, antennaintermodulation)



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Check statistics items:

1. In Power Control Performance Measurement , the averageuplink and downlink signal strengths are too low

2. In Receiving Level Performance Measurement , a lot of low

signal level records are found

3. In Cell Performance Measurement/Inter-cell HO MeasurementFunction, the average receiving signal level are too low whenHO is triggered

4. In Call Drop Performance Measurement , the signal level is toolow when call drop happens, or the TA value is abnormal.

5. In Defined Adjacent Cell Performance Measurement , theneighbor cells with low average signal level can be found

2. Coverage(outage area/island)


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Locating methods:

1. The average level for neighbor is too high in the defined neighbormeasurement (over-coverage).

2. In Power Control Performance Measurement , check whether theaverage distance between the MS and the BTS comply with thedesign concept;

3. In Power Control Performance Measurement , check whether the

maximum distance between the MS and BTS contains abnormalvalues.

4. In Outgoing Inter-cell HO Performance Measurement , whether theHO successful rate to a certain cell is low;

2. Coverage (no-signal area/island)


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Solutions:

Drive test in the estimated poor coverage area

Adjust the following parameters based on the drive test results:

BTS EIRP, Antenna down-tilt and height, MS min-access-level,adjacent cell relationship, the min-rx level required for HOcandidate cells

Add site

2. Coverage(outage area/island)


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Locating methods:

1. Check the HO parameters to see if there are any unsuitableparameter settings.

2. In Inter-cell HO Performance Measurement , check whether thereare many HO failures and re-establishment failures.

3. In Inter-cell HO Performance Measurement , check whether thereare many HOs and and many HO re-establishment successes.

4. In undefined Adjacent Cell Performance Measurement : checkwhether the signal level and the number of MRs for the undefinedneighbor cell exceed the normal value.

3. Unreasonable HO (neighbor planning and HO

parameters)


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5. In Outgoing Inter-cell HO Performance Measurement : finding outwhich cell's outgoing HO successful rate is low (for a specific cell);locating the the neighbor cell to which the HO successful rate islow, and doing further analysis of the causes from the target cell.

6. The incoming HO successful rate is low, and the HO parameter

setting is unsuitable in the original cell.7. TCH performance measurement: the amount of HOs are not

proportionate to the amount of successful TCH seizures for call(HOs/callls>3)


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Solutions:

1. Adding the missing neighbor cells.2. Adjusting HO parameters.

3. Unreasonable HO (neighbor planning and HOparameters)


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Locating methods:

1. analyzing Link Balance Performance Measurement item incall statistics system, and analyzing whether the uplink and

downlink are unbalanced based on the system relevantparameters

2. checking Call Drop Performance Measurement in callstatistics system, and analyzing the average received signallevel and quality of the both uplink and downlink before the

call was dropped3. checking Power Control Performance Measurement in call

statistics system, and analyzing the average received signallevel of both the uplink and downlink

4. Unbalanced uplink and downlink (tower amplifier,

power amplifier, and antenna directions)


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Locating methods:

1. Checking all relevant parameters :

2. In system information table, check the counter of RadioLink time-out;

3. In cell attribute information table, check SACCH multi-frames, and the timer for Radio Likn connection.

Solutions:Modify the unsuitable configuration of the above parameters.

5. Unsuitable wireless parameters setting (Radio Link

time-out, SACCH multi-frames)


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Locating methods:

1. TCH Measurement Function: abnormal number of A interfacefailures during TCH seizure.

2. TCH Measurement Function: TCH availability abnormal.

3. TCH Measurement Function: many call drops caused by groundlinks disconnection.

4. Link Balance Measurement Function: the traffic for each TRX

belongs to one cell is of great difference.

5. BSC Measurement Function: assignment failure (Equipment failure).

6. Equipment problem (TRX, power amplifier, tower

amplifier, etc.)


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Solutions:

Observing transmission and board alarms (TC board failure, Ainterface PCM synchronization alarm, LAPD link disconnected,power amplifier board alarm, HPA alarm, TRX alarm, andCUI/FPU alarm); analyzing if transmission is disconnected orfailure boards existing (for example, the TRX cant work).

6. Equipment problem (TRX, power amplifier, tower

amplifier, etc.)


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Traffic Statistics Analysis-SDCCH call drop

SDCCH call drop analysis: refer to TCH call drop analysis

SDCCH call drop


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Traffic Statistics Analysis-HO

Analysis diagram

HO analysis

Low HO Success Rate

Causes:

1,no available chan.

2,others

HO Measurement

Function

Alarm(Clock),

Hardware FaultTCH Measurement

Function

Outgoing-Cell Failure

in BSC

Incoming-cell

Failure in BSC

Outgoing Inter-cell

Handove

Measurement Function

Incoming Inter-cell

HO

Measurement Function

Cause of Failure in

BSC

1.Illegal Channels

2.Illegal Carrier

3.Illegal TA

4.Timer out

5.Others

ffi S i i A i O


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General method:

1:Cells with low HO successful rate(all cells/ part cells)

2:HO failure direction(outgoing-cell HO failure or incoming-cell HOfailure)

3:HO failure relation(between serving cell and target cell: betweenserving cell and all the neighbor cells or between serving cell andparts of cell)

HO failure analysis


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1:Finding out low HO successful rate cells

2:Finding out cells with too many HO failures

3:Comaring the incoming cell HO failure times and outgoing cell

HO failure times, to see which one of them is the dominant.

4:Registering a task to measure the incoming cell HO andoutgoing cell HO performance.

5:Finding out HO failure regularity(fail to all neighbor cells or only

part of the cells, HO failure is caused by all trigger conditionsor only part of them)

HO failure analysis process


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Unreasonable HO parameters

Hardware failure(TRX board fault)

Congestion

Interference

Coverage

Uplink/downlink unbalanced

Clock(Inner clock, external clock)

Potential causes for HO failure

T ffi St ti ti A l i HO


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Locating method and solutions:

1. Checking whether the HO parameter thresholds such as TA, BQand HO function switch are suitable or not.

2. The times of HO are much more than successful TCH seizures forcall. If HO/call>3, then it is likely that the Ping-Pong HOphenomenon will take place. So you should thoroughly checkthe parameter setting and adjust them (layer setting, inter-layHO hysteresis, inter-cell HO hysteresis, PBGT threshold, etc.).

3. Inter-cell HO Measurement: When the handover happens theaverage signal level and it is possibly caused by the HOthresholds such as the margin threshold are too low.

1. Unreasonable HO (neighbor cell planning and HO

parameters)


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Objects needed to by analyzed:

Low incoming HO successful rate cells

Neighbor of the low incoming HO successful rate cell

Methods:

1. The target cell contains active channels, but NACK or TIMEOUT.

2. TCH availability abnormal.

3. Lots of call drops due to ground links disconnection.

4. If the call drop rate and congestion rate of this cell are high, someequipment in this cell may have some fault.

2. Hardware failure

T ffi St ti ti A l i HO


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Locating methods:

5. Observing transmission and board alarms (TC board failure, Ainterface PCM sync alarm, LAPD link disconnected, power

amplifier board, HPA, TRX alarm board, and CUI/FPU alarm);analyzing if the transmission is disconnected or boards fail (forexample, the TRX is damaged).

6. Checking if there is a clock alarm.

7. When BTS HO access are limited by the access level and quality,it is necessary to pay attention to the relevant parameter settings(RACH access threshold, random access error threshold.)

2. Hardware failure


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Objects needed to analyzed:

Low incoming HO successful rate cells

Neighbor of the low incoming HO successful rate cell

Locating methods:

1. After eliminating the above unreasonable parameter setting andequipment fault, the following problems still exist:

A. In incoming inter cell HO Measurement: many HO failure(congestion):

B. In inter-cell HO Measurement Function: if the outgoing HO

attempts is far more than outgoing HOs, that means a lot ofchannel requests are rejected by the target cell; it is possiblecaused by the congestion of the target cell;

2. Making sure that the congestion really exists according to full-busy time, etc., from TCH performance measurement; using

following method to solving the problem

3. Congestion


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Solutions:

1. Adjusting cells coverage (adjusting the transmitting power of theBTS, the MS minimum access level, the RACH access threshold,

the random access error threshold, and the antenna down-tilt)2. Adjusting main cell parameters (adjusting CRO, start load

handover threshold, cell priority and cell handover parameter)

3. Expanding the cell or adjusting the carrier configurations fordifferent cells

3.Congestion

Traffic Statistics Anal sis HO


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After solving parameter settingshardware failureand congestion problems. Referring to TCH call dropanalysis, analyzing and solving parameter settingsinterferencecoverage and unbalanced link problemfor adjacent cell.

4. Others

T ffi S i i A l i TCH i


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Traffic Statistics Analysis-TCH congestion

1. limited system capacity

2. Serious interference3. Coverage

4. Antenna and feeder problem

5. Unreasonable parameter settings(system information)

Potential causes:

TCH congestion Analysis

T ffi S i i A l i TCH i


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Locating methods:

1. The traffic of per line is too high.

2. When the channel availability is 100%, there are many channel

requests rejected due to channel busyness, and it lasting for a

long time.

3. Abnormal heavy Traffic and the distribution is unbalanced.

4. Incoming Handover Measurement shows that there

are too many incoming handover failures (due to congestion).

1. Insufficient system capacity or traffic distributionunbalanced


T ffi St ti ti A l i TCH ti


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Solution:

1. Expanding system capacity or adjusting the carrier configurationsbetween the busy and the none-busy cell.

2. Adjusting cells coverage (adjusting the transmitting power of theBTS, the antenna direction, down-tilt, height, etc.).

3. Adjusting relevant cell parameters (CRO, minimum MS accesssignal level, start load handover.).

4. Adjusting cell priorities and cell handover parameters.

1. Insufficient system capacity or traffic distribution

unbalanced




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Interference brings unacceptable BER which will affects theassignment command and the process, results in assignmentfailure.

Downlink Interference in the idle mode makes MS DSCdecrease to 0, make MS reselect to another cell with low signallevel, this is the other potential reason for seizure failure.

If TCH seizure times (include HO) minus TCH seizure meet busy

times is large, there should have some interference.Solutions:

Refer to locating and solving TCH call drop caused byinterference

2. Interference(internal interference/external interference)




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Methods:

Cell Frequency Scan: checking the measurement results for thesame frequency got from main receiving antenna and diversityreceiving antenna .

Uplink\downlink Balance Measurement : MR numbers in eachlevel.

Solutions:

Check antenna direction, down-tilt , and the connections.

3. Antenna and Feeder problems




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Locating methods:

Check parameters such as MS min access level, cellreselection

related parameter.

Solution:

Adjust the improper parameters.

4. Improper parameters setting




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Methods and solutions:

Refer to coverage analysis for TCH call drop rate .

5. Coverage(Outage area/island)


T ffi St ti ti A l i SDCCH ti


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Traffic Statistics Analysis-SDCCH congestion

Improper parameters(system message)

Insufficient system capacity

Improper LAC planning

Interference

SDCCH Congestion Rate

Main reasons that will affect SDCCH congestion rate:

Traffic Statistics Analysis SDCCH congestion


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Locating methods:

Random Access Performance Measurement:

Immediate assignment successful times/immediateassignment times>85%

Above formula shows the rate of est_ind times from MS andthe immediate assignment command times from BSC. If therate is abnormal, potential improper parameters existing in

the system message.

1. Improper parameters




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Solutions:

Parameter adjustment(Random Access Error Threshold, RACHAccess Threshold, Max. Resend times, Tx-integer)

Location Update related parameters(dual-band networkparameters such as CRO, cell reselection hysteresis, T3212)

In dual band network, many location update maybe be causedby dual band handovers. So for dual band network HOparameters also need to be adjust.

1. Improper parameters


Traffic Statistics Analysis SDCCH congestion


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Capacity problem under some special condition:

Border between different location are, nearby the railway,sudden a great amount of location update.

In this case, adding more SDCCH channel, enable SDCCH auto-allocation feature or adding TRX will be the suggested solution.

2. Insufficient system capacity




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Examples:

LAC border is along a street or a rail way: themovement of the MS and the multi-path propagation

will bring frequent location update.

3. Improper LAC planning




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RACH threshold is low, at the same time, there is someinterference in the system, which will bring a lot ofillusory SDCCH channel requests.

4. Interference


Content


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Content

Brief Introduction for BSC Traffic

Statistics

Analysis of Often-used Traffic Statistics

Items

Locate problems by the Aid of Traffic

Statistics

Case analysis for Traffic Statistics

Case analysis one


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y

Description

Some networks handover successful rate was always very low

because of the congestion (about 70%), referring to busy hour

traffic statistics of Nov the 24th.

In the evening of Dec the 3th, urban site D was expanded fromS2/2/2 to S3/3/3.

Busy hour handover successful rate didnt got improved after

expansion, in some period of time handover successful rate was

lower than old value, referring to busy hour traffic statistics of Decthe 3th , at the same time lots of subscribers began to complain

networks quality.

Case analysis one


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y

Site location diagram

Case analysis one


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y

traffic statistics of Nov the 24thCell handover radio handover Intra-BSC Intra-BSC TCH

successful successful incoming incoming congestiongrate rate HO failure times HO failure times

(no channel available (others)

D1 53.41% 90.02% 397 18 47.53%

D2 49.82% 93.98% 389 2 67.23%

D3 57.67% 90.06% 314 51 48.31%

D3 61.25% 91.67% 502 25 40.61%

A2 78.40% 89.07% 0 33 0

A3 77.14% 93.80% 0 20 0

F

2 76.36% 76.36% 0 12 0E1 66.22% 88.10% 26 63 5.33%

E2 92.73% 94.44% 0 2 0

E3 83.25% 91.91% 0 6 0

B3 83.48% 95.53% 0 5 0.75%

Case analysis one


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y

traffic statistics of Dec the 3th

Cell handover radio handover Intra-BSC Intra-BSC TCH

name success rate success rate incoming HO incoming HO congestionfailure times failure times rate (all busy)

(no channel available) (other reason)

Case analysis one


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y

Disposing process

Analyzing traffic statistics before expansion and after expansion,we found handover failure caused by no available channel, radiohandover success rate was normal before expansion. In Urban areamany cells radio handover successful rate began to drop afterexpansion, therefore we could say the cause of handover failureafter expansion has been changed.

Analyzing urban sites location diagram, we found out lots of cellsradio handover successful rate were low , moreover these cells hadhandover relations with site D . Therefore we think the handoverhad some relation with site D.


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Case analysis one


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traffic statistics of Dec the 7thCell handover radio handover Intra-BSC Intra-BSC TCH

successful successful incoming incoming congestiongrate rate HO failure times HO failure times

(no channel available (others)

Case analysis one


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Conclusion and suggestion

We can get the conclusion from this case, paying attention to the

difference between radio handover successful rate and handover

successful rate can help us to locate network problem.

Handover problem sometime accompanies with call drop and other

network phenomena, it is a important clew of locating problem.

Case analysis two


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Description

When we observed the traffic statistics , we find out call drop rateof one cell are very high, busy hour call drop rate exceed 2%

From traffic statistics performance measurement, it was easy tofind that the average uplink level is 1 (-109dBm), while the downlinklevel was 26 (-84dbm), High call drop rate was because of uplink/down link unbalanced.

From uplink/downlink performance measurement, we found outone TRX was normal, but for the other TRX, the times for each levelincreased level by level (from level to level 10). Times of level 1 is 0,while times of level 11 is 5833, this proved that downlink was betterthan uplink.

Case analysis two


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Analyzing and processing

We excluded the cause of antenna&feeder because only one TRX

is abnormal, therefore we could said that trouble maybe caused by

uplink channel problem of TRX.

When we changed the TRXthe soft jumper line and the CDU, the

problem was solved, we found that the polarization diversity

receiving port of CDU had some fault.

Case analysis three


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Description

After cut over the M1800 network, some subscribers complainedthat when the mobile resided in the M1800 network and made a call,they often heard the voice: the user you are calling is not in theservice area. we found this problem really existing after lots of calltest, but it war normal when mobile call other mobile in M900network.

It was difficult to find out the regularity of the problem from call test.All of the urban M1800 cells had this problemthe.

It was normal for mobile being called or calling other mobile fromM900 network.

Case analysis three


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From BSC traffic statistics, we found paging messages from MSC

to BSC was much more larger than that BSC sent to cells.

Therefore we think BSC lost the paging message.

Tracing Abis signal of GSM900 and GSM1800 site in same area, we

found out lots of paging messages being lost in Abis interface of

GSM1800 site.

Case analysis three


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Disposal process

Thinking of the LAC of all cells in BM1 had been re-allocated just

nowand we reload only data to BM1. AM couldnt send paging

message normally due to cell module information table was notupdated , it was apt to lose messages between modules when

paging message was sent from MSC to BM2, and then through AM

to BM1.

The problem was solved after we reloaded all the modules.

Case analysis four


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Description

1. In a local network, the wireless connection was low. After analyzing

the traffic statistics ,we found that SDCCH congestion only occurred

at a few sites.2. Analyzing traffic measurement : in the congested cell, busy hour

SDCCH seizure times wae 300 to 400 . The configuration for all of

the BTS is S1/1/1. Each cell had one SDCCH/8 channels. Normally,

they were capable of dealing with 300-400 SDCCH seizure. But it

was very strange that there were dozens of SDCCH congestion in

each cell at busy hours.

Case analysis four


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1.Registering SDCCH Performance Measurement, we found that most

SDCCH seizure were for location update. After analyzing the cells

location, we found that the above congested BTSs were located at the

cross area of two location area along railway lines. So we thought that

SDCCH congestion should be caused by massive location update.

Case analysis four


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2. Registering SDCCH Performance Measurement for five minutes, we

found that most of the location update happened in a specific 5 minutes.

After checking the train timetable we found that 4 or 5 trains pass by in

this period. When the trains passed by, a large amount of location

update happened suddenly, which resulted in congestion.

3. So we should Add SDCCH channel or enable SDCCH dynamic

allocation feature to solve the congestion.


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omd6010 traffic statistics analysis issue1.1

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