GSM RF Optimization

2007.10.01

HUAWEI TECHNOLOGIES Co., Ltd.

www.huawei.com

HUAWEI Confidential

Confidential: Internal Open

GSM RF Optimization Basic

Wang SongGSM RNP Post-sale TS

HUAWEI TECHNOLOGIES Co., Ltd. Page 2HUAWEI Confidential

EtisalatMisr TK Project RNP Team TrainingCourse Contents

Concept of Optimization

KPI of radio network

Work flow of Optimization

Parameter adjustment principles

Optimization tools introduction

Common problems of Optimization


EtisalatMisr TK Project RNP Team TrainingConcept of 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.



Capacity

CoverageQuality

Optimize



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.

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


EtisalatMisr TK Project RNP Team Training

Concept of optimization






Course Contents


EtisalatMisr TK Project RNP Team TrainingKPI 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


EtisalatMisr TK Project RNP Team TrainingKPI of Radio Network

Typical Radio Network KPI

BTS3

BTS4

BTS1

BTS2

KPI Parameter Source

Call Drop Rate Stat. & DT

Congestion Rate Stat.

Handover Success Rate Stat. & DT

Busy Hour Traffic Stat.

TCH Utilization Stat. & Alarms

Call Setup success rate Stat. & DT

Coverage DT

Quality DT



Concept of optimization


Work flow of optimization




Course Contents


EtisalatMisr TK Project RNP Team TrainingFlow Chart of Network Optimization









Course Contents


EtisalatMisr TK Project RNP Team TrainingParameter Adjustment Principles

IDENTIFYPROBLEM

MAKECHANGES

MONITOR EFFECT

MAKECHANGES

•Parameter adjustment procedure



•Parameter Types

Radio Parameters Engineering Parameters

Handover Parameters

SI Parameters

CC&PWC Parameters

Antenna

Orientation

Antenna

D-tilt

Antenna

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.



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.









Course Contents


EtisalatMisr TK Project RNP Team TrainingDriving Test Tools

The following are the frequently used drive test tools:

Genex Probe and Assistant

TEMS

Ant Pilot and Ant



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


EtisalatMisr TK Project RNP Team TrainingSignaling Analyzer

Signaling Trace

In BSC6000 LMT, Interface signaling trace support:

A: BSSAP SCCP MTP3 MTP2

Abis: RSL OML LAPD

Pb: Application LAPD

Um

Single User

Other equipment : MA10 , K15

Signaling Analyze

Huawei MAINEX: Signal Analyze Tool


EtisalatMisr TK Project RNP Team TrainingSpectrum Analyzer

Scaner (Spectrum analyzer)

The spectrum analyzer is mainly used to test the characteristics of fre

quency, including spectrum, power of the adjacent channel, and fre

quency scanning etc.


EtisalatMisr TK Project RNP Team TrainingYBT250


EtisalatMisr TK Project RNP Team TrainingOMC

Huawei Wireless System OMC is M2000

Provides flexible means to record different information from the

network: Config /Alarms /Stats.

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

the network on a longer period of time


EtisalatMisr TK Project RNP Team TrainingOMC 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 alarmHigh 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



Measurement Units Related to Call

1 Immediate Assignment Measurement per Cell 11 Intra-Cell Handover Measurement per Cell

2 Assignment Measurement per Cell 12 Incoming Internal Inter-Cell Handover Measurement per Cell

3 Call Drop Measurement per Cell 13 Outgoing Internal Inter-Cell Handover Measurement per Cell

4 Short Message Measurement per Cell 14 Incoming External Inter-Cell Handover Measurement per Cell

5 Channel Activation Measurement per Cell 15 Outgoing External Inter-Cell Handover Measurement per Cell

6 Flow Control Measurement per Cell 16 Incoming Inter-RAT Inter-Cell Handover Measurement per Cell

7 KPI Measurement per Cell 17 Outgoing Inter-RAT Inter-Cell Handover Measurement per Cell

8 Channel Seizure Measurement per TRX 18 GSM Cell to GSM Cell Incoming Handover Measurement

9 Calls Discarded due to Overload per LAPD 19 GSM Cell to GSM Cell Outgoing Handover Measurement

10 Call Duration Measurement per BSC 20 Measurement of MRs upon Handover Initiation per Cell

The counters measured in such flows as immediate assignment, assignment, and handover during call can reflect the operation of the traffic of BSC.



Measurement Units Related to MR

Ce

llT

RX

After occupying a dedicated channel, MS will report measurement reports periodically. BSC performs power decisions and handover decisions according to the reported measurement reports. The units listed in the left table are used to measure the counters related to measurement reports and help the users to analyze and optimize the network performance.

1 Number of MRs per Cell

2 Power Control Messages per Cell

3 Neighbor Cell Level Measurement per Cell

4 Interface Band Measurement per TRX

5 TCHF Receive Level Measurement per TRX

6 TCHH Receive Level Measurement per TRX

7 Receive Quality Measurement per TRX

8 Uplink-and-Downlink Balance Measurement per TRX

9 Number of MRs based on TA per TRX

10 Radio Link Failure Measurement per TRX

11 Radio Link Failure Measurement based on TA per

TRX

12 RQI Measurement based on TA per TRX


EtisalatMisr TK Project RNP Team TrainingMeasurements Related to Channel

1 Channel Configuration Measurement per Cell

2 Channel Conversion Measurement per Cell

3 Channel Busy Duration Measurement per Cell

4 Measurement of Maximum Busy Channels per Cell

5 Channel State Measurement per Cell

6 Channel Assignment Request Measurement per Cell

7 Channel Assignment Failure Measurement per Cell

8Channel Assignment Concentric Cell Measurement

per Cell

9 Channel Assignment Queue Measurement per Cell

10 Channel Assignment GPRS Measurement per Cell

11 Channel Assignment Success Measurement per TRX

During operation, BSC performs dynamic adjustment to such channel resources as TCH, SDCCH, and PDCH to optimize the utilization of resources. At the same time, the system is required to regularly output the statistic about the state of the channels, such as busy, idle, or blocked. The previous data is very useful for you to learn about the operation condition of the system and the distribution condition of the traffic.









Course Contents


EtisalatMisr TK Project RNP Team TrainingCommon Problems of Optimization

The three most important performance criteria are coverage,

capacity and quality. they mainly correspond to the

following network problems:

Coverage

Congestion

Interference

Handover

TCH call drop

Dual-band or Dual-System Traffic Distribution


EtisalatMisr TK Project RNP Team TrainingCommon Problems --Coverage

Coverage Gap

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.



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)

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)


EtisalatMisr TK Project RNP Team TrainingCommon 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 com

pare the busy hour traffic of each cell with the calculated capacity i

n different GoS to judge the situation of traffic congestion .

Traffic balance

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

TS and MS.

Adjust parameters for cell selection, cell reselection and handover

Enable load handover and direct retry functions.


EtisalatMisr TK Project RNP Team TrainingCommon Problems --Interference

How to locate the interference

Interference band in TCH Measurement Function

( Statistics)

Receiving Level Measurement Function ( Statisti

cs)

Rx_Qual ( Drive test)

Uplink Frequency Scan in LMT

Scaner (YBT250)



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.


EtisalatMisr TK Project RNP Team TrainingCommon 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 ce

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


EtisalatMisr TK Project RNP Team TrainingCommon 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.


EtisalatMisr TK Project RNP Team TrainingCommon 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


EtisalatMisr TK Project RNP Team TrainingCommon Problems —Dual-band Network

Dedicate mode

Idle mode Calling mode

Cell select Direct retry

Hand over

Cell reselect

• Dual band network optimization elements


EtisalatMisr TK Project RNP Team TrainingExercise

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 RF Optimization

Documents

huawei confidentialpage

network problems

huawei confidential

network quality

network trends

new network

overall network performance

concept of optimization