gsm rn optimization

OMF000501 GSM RN Optimization ISSUE1.4

Wireless Training Department

Course ContentsCourse Contents

Concept of RN optimization

KPI of radio network

Work flow of RN optimization

Parameter adjustment principles

RN optimization tools introduction

Common problems of RN optimization

Concept of RN Optimization Concept of RN Optimization

Radio network optimization means network performance

improvement utilizing existing network resources.

Steps in general

Data collection and verification

Data analysis

Parameter and hardware adjustment

Optimization result confirm and reporting

The purpose is increasing the utilization of network resources

and solving the existing and potential problem on the network,

identifying solutions for future network planning.

Concept of RN Optimization Concept of RN Optimization

Capacity

CoverageQuality

Optimize

Concept of RN OptimizationConcept of RN Optimization

Due to the mobility of subscribers and complexity of radio

wave propagation, most of network problems are caused by

increasing subscribers and the changing environments.

RN Optimization is a continuous process that is required as

the network evolves


In the following case, the network should be optimized

New network or expansion on existing network

The network quality decreased seriously and there are many

complaints from subscribers.

An event occurs suddenly which affects the network

performance seriously.

The number of subscribers increased and affects the network

performance gradually.


TRAFFICSTATISTICS

DRIVE TEST

CUSTOMERCOMPLAINTS

OPTIMIZE

• Input for Optimization

KPI of Radio NetworkKPI of Radio Network

KPI (KEY PERFORMANCE INDICATORS)

Indicates overall performance of network over a period of time

Good way to monitor network trends and anticipate future problems

Data obtained from drive test and traffic statistics

KPI of Radio NetworkKPI of Radio Network

Typical Radio Network KPI

BTS3

BTS4

BTS1

BTS2

Drive testQuality

Drive testCoverage

OMC/Drive testCall Setup success rate

OMCTCH Utilization

OMCBusy Hour Traffic

OMC/Drive testHandover Success Rate

Drive testCongestion Rate

OMC/Drive testCall Drop Rate

SourceKPI Parameter

Flow Chart of Network OptimizationFlow Chart of Network Optimization

Parameter Adjustment Principles Parameter Adjustment Principles

IDENTIFYPROBLEM

MAKECHANGES

MONITOREFFECT

MAKECHANGES

•Parameter adjustment procedure


•Parameter Types

Radio Parameters Engineering Parameters

Handover Parameters

Handover Parameters

Handover Parameters

Antenna

Orientation

Antenna

D-tiltAntenna

Height


Adjustment of cell data parameters

Adjust the cell parameters according to the features of actual

radio channel traffic and signaling load. The parameters are for

cell select,cell reselect,call setup, handover etc, so as to

improve the overall network performance and service quality to

the end user.

Another basic principle of radio parameter adjustment is to

maximize the current network resource, traffic sharing in the the

whole network, increase the utilization of the equipment, so as

to increase the profit-investment ratio.

Parameter Adjustment PrinciplesParameter Adjustment Principles

According to the feature of problem to be solved, there are

two types of radio parameter adjustment.

Solve static problems: Analyze the average traffic and signaling

flows of the network and solve the network problems that

existed long time

Solve traffic overload and congestion problems during some

special period caused by special events.

Driving Test ToolsDriving Test Tools

The following are the frequently used drive test tools:

TEMS and GIMS

Ant Pilot and GSM 2000

SAFCO Walkabout & SAFCO OPAS

TS9951

NEPTUNE


Drive test Tool application

Identify specific problems in the network

Attend to customer complaints

Perform network benchmarking with other operators

Collect periodic network data for reporting

Check coverage in new areas


Example: Drive test data

Signaling AnalyzerSignaling Analyzer

Signaling analyzer

In real time, MA-10 signaling analyzer can trace A-bis interface

signaling message, A-G interface signaling message, SS7

signaling message of ISUP, TUP and INAP, and also bit error

rate of transmission system.

For further analysis the signaling message files can be saved

during online tracing, then they can be opened for analysis at

anytime.

Spectrum AnalyzerSpectrum Analyzer

Spectrum analyzer

The spectrum analyzer is mainly used to test the characteristics

of frequency, including spectrum, power of the adjacent channel,

and frequency scanning etc.

OMC Traffic StatisticsOMC Traffic Statistics

OMC

Provides flexible means to record different information from the

network

Able to sample large amounts of data to give a better picture of

the network on a longer period of time

OMC Traffic StatisticsOMC Traffic Statistics

Signalling test instrument

BSC performance measurement functions

TCH statistics Drop measure

Low HO suc rate

HO measurement

Incoming cell HO

Outgoing cell HO

List of alarm High block rate

Rx_q & Rx_l measure

Hardware Conk out

balance between UL & DL

List of alarmHigh drop rate

Drop call measure

Rx_q & Rx_l measure

List of alarm TCH statistics

List of alarm

Common Problems of RN OptimizationCommon Problems of RN Optimization

The three most important performance criterias are coverage,

capacity quality. they mainly correspond to the following

network problems:

Coverage

Congestion

Interference

Handover

TCH call drop

Dual-band network traffic distribution

Common Problems --Coverage Common Problems --Coverage

Coverage

Coverage hole

Coverage hole may exist when coverage areas of two BTS

do not overlap or there are some big obstacles in the

coverage area, this lead to no signal or very poor signal

level.

Over shooting

In the actual network, the high BTS antenna can propagate

far away along a road and serve in area which it’s not

suppose to serve in; which result in the "isolate Island"

problem.

Common Problems --CoverageCommon Problems --Coverage

Check and solve the coverage problem:

Power control measurement Function ( Statistics)

Receiving Level Measurement Function ( Statistics)

Cell Measurement Function ( Statistics)

Inter-cell Handover Measurement Function ( Statistics)


Check the coverage problem:

Call Drop Measurement Function ( Statistics)

Defined Adjacent Measurement Function (Statistics)

Undefined Adjacent Measurement Function ( Statistics)

Outgoing Inter Cell Handover Measurement Function ( Statistics)

Rx Level data ( Drive test)


Coverage Problem Solution:

Adjust Radio parameters

Adjust antenna parameters

Use booster, low loss combiner and tower mount amplifier

Add new site (last resort)

Common Problems --CapacityCommon Problems --Capacity

Capacity

TCH congestion

Check TCH congestion rate: attempted TCH seizers failure for all

(no radio resource available ) on OMC traffic statistics data, or

compare the busy hour traffic of each cell with the calculated

capacity in different GoS to judge the situation of traffic congestion .

Traffic balance

Adjust the antenna height, downtilt, and change the TX power of

BTS and MS.

Adjust parameters for cell selection, cell reselection and handover

Enable load handover and direct retry functions.

Common Problems --InterferenceCommon Problems --Interference

How to locate the interference

Interference band in TCH Measurement Function

( Statistics)

Receiving Level Measurement Function ( Statistics)

Rx_Qual ( Drive test)


How to locate the interference

Ratio of handovers for uplink/downlink quality ( Statistics)

Receiving Quality Measurement (Statistics)

Call drop measurement function ( Statistics)

Too many handover failure and reestablishment failures

( Statistics)


Check and solve the interference problems

Check the place with interference and conversation quality by

drive test.

Use spectrum analyzer to find out the interference in the

frequency band.

Enable frequency hopping, DTX and power control functions.

Check and eliminate equipment problems (if any).


Means to decrease the interference :

Increase the reuse distance between the co-frequency and

adjacent frequencies.

Decrease the transmitting power of BTS.

Adjust the antenna height, azimuth, down-tilt.

Use the anti-interference technologies, such as frequency

hopping, power control, DTX, and so on.

Common Problems --HandoverCommon Problems --Handover

Common handover problems:

Handover failure and handover delay lead to bad quality or

call drop.

Frequent handover decreases the conversation quality and

increases system signaling load.

Unreasonable proportion of outgoing inter-cell handover to

incoming inter-cell handover results in imbalanced traffic.


Check and solve handover problems:

Check the handover parameters (OMC)

Inter-cell Handover Measurement Function (Statistics)

Undefined Adjacent Cell Measurement Function (Statistics)

Outgoing Inter Cell Handover Measurement Function (Statistics)

Incoming Inter Cell Handover Measurement Function (Statistics)

TCH Measurement Function (Statistics)


Causes of abnormal handover and solutions:

The outgoing inter cell handover threshold is too low.

The adjacent cells is congested.

There are undefined adjacent cells relationship.

The handover hysteresis and handover priority are not reasonable.

The handover statistics times N and P are not set reasonable.

In HCS network coexisting with other vendor’s cells, the external

cell’s parameters (such as LAC, CI and BCCH) must be corrected.

Common Problems —Call DropCommon Problems —Call Drop

TCH call drop

During the GSM network operation, call drop is the main reason

the subscribers complain. It usually refers to the call dropped

after TCH channel seized or conversation connected, which can

be located via traffic statistics or drive test.

There are many call drop causes. Such as poor signal strength,

interference and improper parameters.

There are two important counters related call drop, radio link

timeout (RLT downlink) and SACCH multi-frame number (uplink)

sent in system information. These two counters should be set

properly according to the traffic and coverage.

Common Problems —Dual-band NetworkCommon Problems —Dual-band Network

Optimization for dual-band network

Take the following special approaches when optimize the dual-

band network, most of the approaches are same as single-band

network optimization:

When GSM 900M and GSM 1800M network belong to a same LAC

the features of two network are basically same. Parameters such as

CRO can be set flexibly according to the traffic, thus can balance

the traffic and avoid cell congestion.

When GSM 900M and GSM 1800M network has there own location

area code, CRH and CRO should be set properly to avoid frequent

location update.

Adjust layer thresholds to balance traffic between GSM 900 and

GSM 1800

Common Problems —Dual-band NetworkCommon Problems —Dual-band Network

Dedicate mode

Idle mode Calling mode

Cell select Direct retry

Hand over

Cell reselect

• Dual band network optimization elements

ExerciseExercise

Questions

Please write down KPI for normal network

Please write down the work flow for radio network optimization

How to do for traffic balance

gsm rn optimization

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