GSM RF Optimization

2007.10.01

Confidential: Internal Open

GSM RF Optimization Basic Wang Song GSM RNP Post-sale TS

www.huawei.com

HUAWEI TECHNOLOGIES Co., Ltd.

HUAWEI Confidential

EtisalatMisr TK Project RNP Team Training

Course Contents

Concept of Optimization KPI of radio network Work flow of Optimization Parameter adjustment principles Optimization tools introduction Common problems of Optimization HUAWEI TECHNOLOGIES Co., Ltd.

HUAWEI Confidential

Page 2


Concept 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.


HUAWEI Confidential

Page 3



Capacity

Quality

Coverage

Optimize HUAWEI TECHNOLOGIES Co., Ltd.

HUAWEI Confidential

Page 4



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


HUAWEI Confidential

Page 5



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.


HUAWEI Confidential

Page 6


Concept of Optimization • Input for Optimization

CUSTOMER COMPLAINTS

OPTIMIZE TRAFFIC STATISTICS


HUAWEI Confidential

DRIVE TEST

Page 7


Course Contents

Concept of optimization KPI of radio network Work flow of Optimization Parameter adjustment principles Optimization tools introduction Common problems of Optimization HUAWEI TECHNOLOGIES Co., Ltd.

HUAWEI Confidential

Page 8


KPI 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


HUAWEI Confidential

Page 9


KPI of Radio Network Typical Radio Network KPI 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


HUAWEI Confidential

BTS1

BTS3

BTS4

Page 10

BTS2


Course Contents

Concept of optimization KPI of radio network Work flow of optimization Parameter adjustment principles Optimization tools introduction Common problems of Optimization HUAWEI TECHNOLOGIES Co., Ltd.

HUAWEI Confidential

Page 11


Flow Chart of Network Optimization


HUAWEI Confidential

Page 12


Course Contents


HUAWEI Confidential

Page 13


Parameter Adjustment Principles •Parameter adjustment procedure

MONITOR EFFECT

IDENTIFY PROBLEM

MAKE MAKE CHANGES CHANGES HUAWEI TECHNOLOGIES Co., Ltd.

HUAWEI Confidential

Page 14


Parameter Adjustment Principles •Parameter Types

Radio Parameters Engineering Parameters Antenna

SI Parameters Handover Parameters

D-tilt CC&PWC Parameters


Antenna

Antenna

Height

Orientation

HUAWEI Confidential

Page 15


Parameter Adjustment Principles 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.


HUAWEI Confidential

Page 16


Parameter 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.


HUAWEI Confidential

Page 17


Course Contents


HUAWEI Confidential

Page 18


Driving Test Tools

The following are the frequently used drive test tools:

Genex Probe and Assistant TEMS Ant Pilot and Ant


HUAWEI Confidential

Page 19


Driving Test Tools 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


HUAWEI Confidential

Page 20


Driving Test Tools Example: Drive test data


HUAWEI Confidential

Page 21


Signaling 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


HUAWEI Confidential

Page 22


Spectrum Analyzer Scaner (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.


HUAWEI Confidential

Page 23

YBT250



HUAWEI Confidential

Page 24

OMC


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


HUAWEI Confidential

Page 25


OMC Traffic Statistics

BSC performance measurement functions High drop High block

List of alarm

rate

rate Drop call

Rx_q & Rx_l measure

measure

TCH

Drop

statistics

measure

Low HO suc rate

List of alarm

Hardware Conk out

Rx_q & Rx_l

balance between UL

measure

& DL

List of alarm

HO

TCH

measurement

statistics Incoming cell HO Outgoing cell HO

Signalling test HUAWEI TECHNOLOGIES Co., Ltd.

List of alarm

instrument

HUAWEI Confidential

Page 26


Measurement Units Related to Call 1

Immediate Assignment Measurement per Cell

11Intra-Cell Handover Measurement per Cell

2

Assignment Measurement per Cell

12Incoming Internal Inter-Cell Handover Measurement per Cell

3

Call Drop Measurement per Cell

13Outgoing Internal Inter-Cell Handover Measurement per Cell

4

Short Message Measurement per Cell

14Incoming External Inter-Cell Handover Measurement per Cell

5

Channel Activation Measurement per Cell

15Outgoing External Inter-Cell Handover Measurement per Cell

6

Flow Control Measurement per Cell

16Incoming Inter-RAT Inter-Cell Handover Measurement per Cell

7

KPI Measurement per Cell

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

8

Channel Seizure Measurement per TRX

18GSM Cell to GSM Cell Incoming Handover Measurement

9

Calls Discarded due to Overload per LAPD

19GSM Cell to GSM Cell Outgoing Handover Measurement

Call Duration Measurement per BSC

20Measurement of MRs upon Handover Initiation per Cell

10

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


HUAWEI Confidential

Page 27


Measurement Units Related to MR 1Number of MRs per Cell

Cell

2Power Control Messages per Cell 3Neighbor Cell Level Measurement per Cell 4Interface Band Measurement per TRX 5TCHF Receive Level Measurement per TRX 6TCHH Receive Level Measurement per TRX 7Receive Quality Measurement per TRX

TRX

8Uplink-and-Downlink Balance Measurement per TRX 9Number of MRs based on TA per TRX 10Radio Link Failure Measurement per TRX 11Radio Link Failure Measurement based on TA per TRX

12RQI Measurement based on TA per TRX


HUAWEI Confidential

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.

Page 28


Measurements 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

8

Channel 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


HUAWEI Confidential

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.

Page 29


Course Contents


HUAWEI Confidential

Page 30


Common 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


HUAWEI Confidential

Page 31


Common 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.


HUAWEI Confidential

Page 32


Common 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)


HUAWEI Confidential

Page 33


Common Problems --Coverage 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)


HUAWEI Confidential

Page 34


Common Problems --Coverage Coverage Problem Solution:

Adjust Radio parameters Adjust antenna parameters Use booster, low loss combiner and tower mount amplifier Add new site (last resort)


HUAWEI Confidential

Page 35


Common 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.


HUAWEI Confidential

Page 36


Common Problems --Interference How to locate the interference

Interference band in TCH Measurement Function ( Statistics) Receiving Level Measurement Function ( Statistics) Rx_Qual ( Drive test) Uplink Frequency Scan in LMT Scaner (YBT250)


HUAWEI Confidential

Page 37


Common Problems --Interference 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)


HUAWEI Confidential

Page 38


Common Problems --Interference 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).


HUAWEI Confidential

Page 39


Common Problems --Interference Means to decrease the interference :

Increase the reuse distance between the cofrequency 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.


HUAWEI Confidential

Page 40


Common 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.


HUAWEI Confidential

Page 41


Common Problems --Handover 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)


HUAWEI Confidential

Page 42


Common Problems --Handover 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.


HUAWEI Confidential

Page 43


Common 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.


HUAWEI Confidential

Page 44


Common 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 HUAWEI TECHNOLOGIES Co., Ltd.

HUAWEI Confidential

Page 45


Common Problems —Dual-band Network • Dual band network optimization elements

Cell select

Direct retry

Idle mode

Calling mode

Dedicate mode

Cell reselect


Hand over

HUAWEI Confidential

Page 46


Exercise Questions

Please write down KPI for normal network Please write down the work flow for radio network optimization How to do for traffic balance


HUAWEI Confidential

Page 47



HUAWEI Confidential

Page 48

GSM RF Optimization

Recommend Documents