Network Optimization

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1 1 NETWORK OPTIMIZATION NETWORK OPTIMIZATION MobiNil, The Egyptian Company for Mobile Services February 2004

description

nw optimization

Transcript of Network Optimization

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NETWORK NETWORK OPTIMIZATION OPTIMIZATION

MobiNil, The Egyptian Company for Mobile Services

February 2004

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COURSE OUTLINES

OPTIMIZATION CONCEPTS

OPTIMIZATION ACTIVITIES

PARAMETERS OPTIMIZATION

CAPACITY ENHANCING TECHNIQUES

TYPICAL PROBLEMS & SOLUTIONS

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OPTIMIZATION CONCEPTS

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OPTIMIZATION CONCEPTS

INTRODUCTION

OPTIMIZATION PROCESS

KEY INDICATORS

REPORTS & ACTION PLANS

OPTIMIZATION TOOLS

INPUT DATA

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Subscriber Perception

To setup or receive a call everywhere, with a good voice quality

without interruption + Value added services.

Availability (Access, Capacity)

Audibility (Voice quality)

Mobility (Call Drop)

Roaming (Coverage bars display)

Introduction

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Why Network Optimization?

Changes in subscriber distribution

Changes in subscriber traffic behaviour

Changes in subscriber mobility profiles

Changes in subscriber growth

Uneven network expansion in various regions

Limitations in frequency resources

Introduction

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Objectives of Network Optimization Team

Providing the best Quality of Service and voice quality, the

minimum call drop and blocking rates in the covered area

using the available resources.

Manage and track the process of Radio Optimization

Daily monitoring of network performance

Ensure the targeted Quality of Service

Introduction

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Optimization Engineer Tasks

Minimize dropped calls and handover failures.

Reduce TCH/SDCCH blocking rate and congestion time.

Maximize coverage service area.

Support good audio quality.

Minimize transmission power level to reduce interference

and increase MS battery life.

Introduction

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Note

Quality of radio design is the base of efficient optimization.

The terrain constraints may lead, radio designers, not to

respect the grid giving the optimization engineer the

opportunity to express his optimization skills.

Introduction

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System optimization & performance involves applying a set of

techniques :

Identifying objectives

Isolate system components

Test plan

Taking actions

Conduct post analysis

Optimization Process

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The most familiar key indicators for any operator are:

Drop call rate Call setup success rate Call setup blocking rate TCH/SDCCH access failure HO causes HO failures

When operating with multiple vendor system, it is important to cross map the indicators reported from one vendor and find a corollary to it with the other vendor.

Key Indicators

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Setting Thresholds for Key Indicators

The threshold and the objective of the different key indicators must be set in a realistic way.

The objectives should be driven to improve the overall performance of the network factoring into it :

- The growth rate expected- Budget constraints

It is important to set aggressive goals to work for, but it is equally important to involve members of the staff whose job is to ensure that the mission statement is met.

Key Indicators

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Reports

It is very important to produce regular summary reports for various levels of management so that they know how the system is operating.

When delivering a report, take care to whom it is generated and include only the data needed to be seen.

Reports and Action Plans

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Action Plans

An action plan is the right consequence to the reports.

Establishing a quarterly and monthly action plan for improving the network is essential in ensuring its health.

Each quarter (long term plan), you should identify the worst 10% of your system following the KPIs.

Reports and Action Plans

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The quarterly action plan should be used as the deriving force for establishing the monthly plans.

The short-term action plans coupled with the long term action plans will help derive the success or failure of the overall mission.

Reports and Action Plans

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Radio Planning Tool

Coverage prediction Interference calculation Frequency Planning Traffic analysis Network database management

Optimization Tools

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GIS Tools

MapInfo Used for drive test measurement analysis & presentation.

GIMS

Advanced import and analysis tool built upon MapInfo. Its use is based on the output data from TEMS.

Optimization Tools

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OMC Statistics Monitoring

MARSMotorola Analysis & Reporting System

METRICA OMC statistics and KPI’s for Alcatel Network

RNO Parameters check & modifications, OMC statistics, KPI’s for Alcatel.

Optimization Tools

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Actix Analyzer

Drive test analysis

Q-voice measurements analysis

A & Abis traces analysis

Optimization Tools

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Measurement Tools TEMS

Drive test tools and field problems investigation.

TEMS:- drive test tool, check field problems.

TEMS Investigation:- advanced drive test tool, problem investigation and analysis in

field.

TEMS Light :- indoor measurements.

Optimization Tools

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Q-VoiceDrive test tool used for benchmarking & field detection of the voice quality problems. Also it is used to test new features and releases.

Spectrum Analyzer Measurement for external interference.

Optimization Tools

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Data gathering is an important issue that facilitate the work of the optimizer.

Data could be :- Raw data (Coverage maps, frequency plan, sites database ..etc).- Measurements data (Drive test, A-bis /A

captures, call traces, statistics …etc ).

Handling these data in optimum way will lead to better performance and output.

Input Data

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Plots/Maps Coverage (Global region and specific area) Best server map Frequency planning [Site location (X,Y), BCCH,

channels)]

Sites Database Radio parameters Neighbors list Channel configuration

Input Data

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Statistics and Indicators

Identify occasional faults on a subsystem (BSS, BTS) and establish corrective actions.

Detect and identify radio problem on a cell.

Statistics can be used to trace and verify big changes in the network (FP, parameters changes, implementations of problem solutions).

Predict network behavior according to traffic evolution.

Can’t reveal the cause of a problem, additional analysis via traces and/or drive test should be used.

Input Data

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Drive Tests

Present the real network performance experienced by subscribers.

Provide field information which is often very useful to solve specific problems.

Input Data

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Routes of drive tests must be specified to have valuable outputs:

- All sites and sectors should be tested within the route at least once.

- All major roads & highways should be tested.- All cells should be tested for handout and hand-in

within the routes if possible.- The routes should be approximately 2-3 hours in

duration.

Input Data

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Abis Interface Measurements

Drive tests give a snapshot view of the network.

Drive tests provide detailed information on the downlink only.

Not recommended to adjust cell and HO parameters based on a specific drive test.

Abis is the ideal source for level, quality and interference analysis.

Abis provides synchronized information on uplink and downlink.

Input Data

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A-Interface Measurements

This interface is standardized by ETSI and its implementation is mandatory.

Network optimization based on A-interface analysis makes the process objective and independent of vendor infrastructure.

Collecting data is usually easier (because of the reduced number of link connections) than for Abis or Drive Test data.

Analysis can be run at BSC level, then at cell and even at individual call level, with the same unique dataset.

Input Data

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Rules when solving a problem:

Change one thing at a time and test it.

If it does not work change it back before you do anything else.

Change the minimum number of parameters possible.

Go to the field and test it. Problems occur in the real world not on your PC.

Be as familiar as possible with the radio interface processes.

Keep in Mind!!

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OPTIMIZATION ACTIVITIES

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INTRODUCTION

STATISTICS MONITORING

FREQUENCY PLANNING

MEASUREMENTS ANALYSIS

TRAFFIC HANDLING

NEW SITES INTEGRATION

SOLVING COMPLAINTS

SITES REDESIGN

EVOLUTION REPORTS

OPTIMIZATION ACTIVITIES

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The radio optimization is built around three main tasks:

Detection of the problems

Analysis of the problems

Solving the problems

Introduction

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Operation & Maintenance Center (OMC)

OMC reports Network Performance through statistics.

Statistics are pegged based on call states detection by the BTS and BSC.

Some Statistics are also based on Signaling Messages.

OMC Vendors use their own terminology's and calculation methods to generate statistics.

Statistics Monitoring

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In general more or less all statistics indicate the same meaning.

It is essential to understand how statistics are pegged to derive conclusion on network performance.

Statistics should be used as a proactive approach to detect problems in the network.

Statistics Monitoring

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OMC - Report Types

Periodic Reports

Per cell basis every measurement period (30/60 minutes)

Indicate the trend in statistical measurement

Daily Averages

Per cell basis

Snapshot of cells performance and problems

Statistics Monitoring

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SDCCH Performance

SDCCH Congestion

No. of times all SDCCH's found busy, and a Channel Request received.

Statistics Monitoring

Channel Request

Immediate Assign Reject

SDCCH CONGESTION

RACH

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Reserves SDCCH

RACH

T3120

Re-transmission

AGCH

T3101

No Response from MS - T3101 Expires

T3120

Channel Request

Immediate Assignment

SDCCH FAILURE

SDCCH Failure

No. of times MS did not respond to Immediate Assignment within T3101 timer period.

Statistics Monitoring

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TCH Performance

TCH Holding Time

- Time (in secs) spent on TCH.

- Reported as Min, Max and Mean during the measurement period and also as daily average on per cell basis.

TCH Attempts

No of Channel Requests with cause as MOC & MTC

+ Channel Activation Requests for Handover.

Statistics Monitoring

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TCH Congestion

RACHChannel Request

Immediate Assignment

MM/CC Signaling on SDCCH

MSCAssign Request

BSC

No TCHAssign Failure

No of Times TCH not available No of Assignment Requests from MSC + Handover Requests

TCH Congestion =

Statistics Monitoring

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RACHChannel Request

Immediate Assignment

MM/CC Signaling on SDCCH

MSCAssign Request

BSC

Assign Failure

Assignment Command

Assignment Failure

No of Assignment Failures from MS Total No of TCH Assignments

TCH Failure =

TCH Failure

Statistics Monitoring

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TCH Drops

– BTS detects RF fink failure in the Uplink on TCH.

– RF link failure generally based on SACCH reports.

– Also Known as TCH_RF_Loss.

– Reported on periodic and daily average basis for each carrier and timeslot configured for TCH.

Statistics Monitoring

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BSS Counters

Combined into significant formulas: indicators

Used to monitor BSS network quality

Over complete network, with breakdown per cell/BSC

Drawbacks: NSS/PSTN/MS/User problems are not seen

Statistics Monitoring

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Call drop

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Drop - BSS

Drop - HO

Drop - Radio

% RTCH drop

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Call Drop• Radio• Handovers • BSS

Statistics Monitoring

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Call Setup Success• SDCCH Drop• TCH Assignment Failure

Call success

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Call drop

Assign f ail

SDCCH drop

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% Call setup

Statistics Monitoring

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Incoming Handovers• Radio• BSS• Congestion

Intra + inter BSC incoming handovers

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Congestion

Success

% Fail

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Statistics Monitoring

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Intra + inter BSC outgoing handovers

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Success

ROC

Drop - Radio

Drop - BSS

% Drop

% ROC

Outgoing Handovers• Failure• Drop• Congestion

Statistics Monitoring

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Objective

Optimum use of resources to flow a target traffic

Reduce Interference to reach the required quality

Frequency Planning

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Theoretical Frequency Planning

Automatic Frequency Planning

Frequency Planning

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Frequency Reuse

GSM uses concept of cells

One cell covers small part of the network

Network has many cells

Frequency used in one cell can be used in another cells

This is known as Frequency Reuse

Theoretical Frequency Planning

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F=1

F=2F=3

F=4,8

F=5,9

F=6,10

F=7

F=1

F=2F=3

F=4,8

F=5,9

F=6,10

F=7

F=1

F=2F=3

F=4,8

F=5,9

F=6,10

F=7

F= 1,2,3,4,5,6,7,8,9,10

Clusters

Co-Channel (Reuse) Cells

Theoretical Frequency Planning

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The hexagonal model is used to simplify the planning.

Hypothesis Flat earth (No Relief, no obstacle…..) Omni directional antennas Equal powers Uniform traffic (One group per cell)

Theoretical Frequency Planning

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Pattern Choice Targeted traffic (Number of TRx per cell)

Targeted C/I between reused frequencies (QOS)

Number of available frequencies

Number and density of sites (Radius of cells)

Theoretical Frequency Planning

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A

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Co Channel Reuse

Q = D/R

C / I > 9 dB R

D

Theoretical Frequency Planning

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Adjacent Channel Reuse

Adjacent ARFCN's should not be used in the same cell.

Adjacent ARFCN's can be used in adjacent cells, but as far as possible this should be avoided.

Taking into consideration the propagation effects, a factor of protection of 600 Khz should be used (Practically not possible in most of the networks due to tight reuse).

In the worst case, adjacent ARFCN's can be used in adjacent cells by setting appropriate handover parameters.

Theoretical Frequency Planning

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BTS

BTS

Omnidirectional Cell Low gain antennas Lesser penetration/directivity Receives interference from all

directions Lower implementation cost

Sectorial Cell High gain antennas Higher penetration/directivity Receives interference from

lesser directions Higher implementation cost

Cell Configuration

Theoretical Frequency Planning

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3,6,9A

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C 3,6,9B

3,6,9C

Receives interference from all directions

Interference in Omni Cells

Theoretical Frequency Planning

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A1

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Receives interference from lesser directions.

Sectored Cells

Theoretical Frequency Planning

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Reuse Patterns

Reuse Patterns ensures the optimum separation between co-channels.

Reuse pattern is a formation of a cluster with a pattern of frequency distribution in each cell of the cluster.

Same cluster pattern is then reused.

Reuse Patterns examples

Omni - Cells : 3 cell, 7 cell, 12 cell, 14 cell, 19 cells etc..

Sector - Cells : 3/9 , 4/12, 7/21.

Theoretical Frequency Planning

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A1

A2A3 B1

B3C1

C2C3

A1

A2A3 B1

B2B3C1

C2C3

A1

A2A3 B1

B2B3C1

C2C3

A1

A2A3 B1

B2B3C1

C2C3

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B1

B2B3

A1

A2A3

B2

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C2C3

C2C3 C2C3 C2C3

A1

3/9 Reuse Pattern

Theoretical Frequency Planning

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Adjacent channel interference is very difficult to avoid within the cluster itself.

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3/9 Reuse Pattern Frequency Allocation

Theoretical Frequency Planning

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D1

D2D3 C1

C3B1

B2B3

C1

C2C3 D1

D2D3A1

A2A3

A1

A2A3 B1

B2B3C1

C2C3

B1

B2B3 A1

A2A3C1

C2C3

C1

D1

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B1

B2B3

C2

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D2D3

D2D3

B2B3

B2B3

A1

4/12 Reuse Patterns

Theoretical Frequency Planning

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4/12 pattern avoids adjacent channels in adjacent cells

4/12 Reuse Pattern Frequency Allocation

Theoretical Frequency Planning

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Conclusion

Larger reuse patterns give reduction in interference.

Reuse patterns become more effective with sectorial cell configurations.

To implement large patterns (like 4/12, 7/21) , more channels are required.

So with less resources, the best way to plan is :

1. Use optimum no. of channels per cell.2. Thus, increase the pattern size.

Theoretical Frequency Planning

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Keep in Mind!!

Make a better frequency planning for BCCH than for TCH channels.

In the same region, to avoid the mobile to confuse two same BCCH frequencies, use different BSICs.

Keep some joker frequencies when possible.

Theoretical Frequency Planning

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Goal

Build a frequency plan fast with the required quality, and even when the grid is not respected.

Tools

AGORA RECSIM

Automatic Frequency Planning

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Advantages

Can be used with or without frequency groups

Better interference rate than with manual planning

Can include existing frequency planning

Time saving

Easy integration of sites

Automatic Frequency Planning

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Process

Computing the reuse matrixThe reuse matrix computes the minimal inter channel protection between two stations.

Frequency allocationDone from the reuse matrix as to have a minimal global interference.

Computing the interferencesto evaluate the quality of the frequency plan

Automatic Frequency Planning

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Drive Tests

Speech Quality

Abis Interface

A Interface

Measurements Analysis

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Drive tests present the real network performance experienced by subscribers.

Processing of drive tests generates statistical analysis of the reported measurements.

Plot of drive tests presents network real coverage.

Network optimization and redesign is highly dependant on drive tests.

Drive Tests

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Tools

TEMS for drive test and integration Actix Analyzer for post processing

Drive Tests

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TEMS is used for new site integration and live network optimization.

TEMS log files need to be analyzed on a map to filter problems such bad quality, handover failures, call drops, etc…

Post processing is done using MapInfo/GIMS and Actix Analyzer.

Drive Tests

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Quality Analysis

Spot poor quality areas

Check neighbor cells levels

Check neighbor frequencies

Determine the interferer

Drive Tests

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Call Drop

Check Radio condition before call drop.

Check for missing neighbor relations.

HO parameters may need to be re-tuned.

Drive Tests

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Statistics

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CDF (percent)dBm

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Histogram - RxQual (count) Histogram - RxQual (CDF)

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CDF (percent)

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Histogram - RxLev (count) Histogram - RxLev (CDF)

Rx-Qual Distribution Rx-Lev Distribution

Drive Tests

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Q-Voice

Q-Voice is one of the most advanced measurement tools in evaluating the voice quality in a cellular network as seen by network subscribers.

Data Collection Part:- QVM( Mobile part fixed in the measurement car).- QVS (Stationary part located at office).

Speech Quality

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Operation

Communication is setup between two parties; QVM and QVS, through a play button on the QVM.

A prerecorded speech sample (5 sec duration) is transmitted through the communication between previously mentioned parties .

The speech sample is evaluated in both direction; UL (from the QVM to the QVS) and DL (from the QVS to the QVM) and each sample is given a score called PACE (The speech Quality indicator).

Measurement data are saved on both the QVM and the QVS.

Speech Quality

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Post Processing

Represented in the QVP with access to the measurement data imported on a database server.

Graphical tools are available for analysis and reporting.

Speech Quality

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Speech Quality

Output Report

P2

16 Nov 2003

excellent good fair poor bad total2022 94 67 31 7 22212038 93 71 13 9 22241493 64 63 17 6 16431973 116 112 18 4 2223

UPLINK DOWNLINK GLOBAL TVOC 1 Jun 2003 14 Sep 2003 16 Nov 200395.3% 95.8% 93.2% MOBINIL 93.3% 93.5% 93.2%94.8% 94.0% 91.4% Vodafone 89.1% 91.9% 91.4%

MOBINIL UPLINK

MOBINIL DOWNLINK

Vodafone UPLINK

Voice quality of last campaign

Vodafone

Analysis and results of Measurements

PACE1.1Voice Quality (Mobiles1+2&3+4):

Measured Zone / ObjectiveDate of mesurement / hour

Vodafone DOWNLINK

Voice quality of the last three campaigns

TVOCMOBINIL

TVOC (Voice Quality indicator)

65.0%

70.0%

75.0%

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85.0%

90.0%

95.0%

100.0%

UPLINK DOWNLINK GLOBAL

MOBINIL

Vodafone

TVOC (Voice Quality indicator)

65.0%

70.0%

75.0%

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85.0%

90.0%

95.0%

100.0%

1 Jun 2003 14 Sep 2003 16 Nov 2003

MOBINIL

Vodafone

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Abis is the ideal source for level, quality and interference analysis.

Abis provides synchronized information on uplink and downlink.

Measurements must be carried around the network traffic busy hour.

K1205 protocol analyzer is used to record Abis data.

Abis data are carried on the RSL timeslots on the Abis PCM.

Recorded Abis data are further processed using Actix Analyzer.

Abis Interface

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Analysis of Level Distribution Shows the amount of traffic at particular RxLev values Validates proper neighbor declaration and HO settings Validates power control settings

Abis Interface

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Level versus TALevel plotted against TA can help identifying areas with high indoor traffic served by an outdoor cell.

Abis Interface

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92%

2% 2% 2% 1% 1% 1% 0%

88.4%

2.6% 1.9% 2.0% 1.4% 1.2% 1.9%0.5%

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Quality

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Dow nLink Quality Uplink Quality

Quality Analysis Quality distribution can validate frequency planning. Filtering poor quality samples and plotting against Level and

TA identifies whether interference or coverage problems.

Abis Interface

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Quality Analysis

Plotting quality against Rx-Lev identifies interference problems.

Abis Interface

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Space Distribution Provides an indication of geographical location of traffic. Space distribution of Rx-Lev samples is valuable when

adjusting antenna tilts.

Abis Interface

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Handover Analysis More powerful compared to BSS statistics and A-Interface

measurements. Provides details about incoming and outgoing HO attempts

on a TRX level. Incoming HO failures due to TRX problems can be spotted

directly.

Attempt Attempt163 151 92.6% 0 0 0.0%191 163 85.3% 0 0 0.0%354 314 88.7% 0 0 0.0%

SDCCHSuccess Success

TCHTRX

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Grand Total

Attempt Attempt138 138 100.0% 0 0 0.0%142 139 97.9% 0 0 0.0%280 277 98.9% 0 0 0.0%

1110004Grand Total

TCH

1100003

SDCCHTRX Success Success

INCOMING HO

OUTGOING HO

Abis Interface

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Handover Analysis HO attempts and success towards neighbor cells are

processed. HO causes per target cell cannot be analyzed. HO failures are further analyzed to identify cause and radio

conditions prior to handover.Cell Summary Stats (HO Matrix - Abis Analysis of Outgoing Handovers)

Target BCCH

Target BSIC #HO %HO

#HO tch-tch

#HO sdcch-sdcch

#HO sdcch-tch

4 11 2 5% 2 0 011 4 2 5% 2 0 014 2 2 5% 2 0 019 17 9 20% 9 0 021 16 3 7% 3 0 022 30 4 9% 4 0 0

Abis Interface

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Collecting data is usually easier (because of the reduced number of link connections) than for Abis or Drive Test data.

Analysis can be run at BSC level, then at cell and even at individual call level, with the same unique dataset.

Measurements must be carried around the network traffic busy hour.

K1205 protocol analyzer is used to record A data.

Recorded A-interface data are further processed using Cigale or Actix Analyzer.

A-Interface

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Call Drop Radio Handover BSS

A-Interface

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Handover Statistics Ho Causes per neighbor Ho Failure per neighbor

A-Interface

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Handover Statistics TRX upgrades Frequency addition

A-Interface

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Handover StatisticsPing Pong Handovers

A-Interface

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Handover Statistics Incoming vs Outgoing HO Uni-directional neighbor relations

A-Interface

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Call Duration Faulty CICs Transcoder problems

A-Interface

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Busy Hour

1 Hour of the day in which Traffic is maximum. Also referred to as Peak Hour. Busy Hour is not a fixed hour, its timing will vary in different

locations.

Busy Hour may also be different for different resources

SDCCH busy hour: typically morning hours (frequent on/offs and updates)

TCH busy hour:heavy call traffic hour (could be back home hours)

Traffic Handling

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Set Up TimeAverage time spent on a resource before getting response from the called end.

Holding TimeAverage time spent on any dedicated resource.

Blocked CallA call request rejected due to unavailability of resource.

Traffic Handling

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Sites should be designed to support busy hour traffic.

Call Setup Blocking & SDCCH Setup Blocking should satisfy the required Grade of Service.

Special events should have special treatment to handle expected traffic (Mobile Shelters).

Traffic Handling

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Delivering the frequency plan and the neighbor files of the new site.

Site should be integrated before putting it on air.

During integration, each sector must be checked for call setup and handover.

Each TRx must be checked to detect any faulty hardware.

The counters should be closely checked the first few days after the site is on air to detect any problem.

New Sites Integration

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Quality of Service is a measure of Network Quality.

Quality of Service is judged by the customer.

Customer expects same quality as PSTN.

Increase in mobile penetration led to increase the demand for excellent quality.

Solving Complaints

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Customer Complaints

I am getting "No Service“. My handset regularly displays Network Search. I get a 3 beep tone, when I dial a number. My friends call me, but I keep on missing calls. Speech quality is bad. I can never keep up with my call on this street, it DROPS ! My friend has competitor's phone, that works well .

Can you get something out of this ?Can you figure out the technical problems ?

Solving Complaints

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Access Quality

Speech Quality

Retaining Quality

Solving Complaints

Categories of user quality

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Parameters tuning

Site redesign

New site if needed

Solving Complaints

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Minimizing the bad effect of overlapping and overshooting which have very bad influence on the performance of the network.

Enhancing the coverage of poor covered areas.

Solving customers complaints.

Sites Redesign

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103

Each optimizer has to deliver a weekly/monthly evolution report showing the evolution of his zone according to the following indicators:

Call drop rate BH call setup TCH blocking rate BH call setup success rate BH TCH traffic carried Uplink quality HO rate Downlink quality HO rate

Evolution Reports

104

104

Regular Consistency Checks

Defined template for BSS parameters.

Inconsistency checks.

One of the most common problems with networks is that database is incorrectly specified on the OMC-R or/and the BSCs.

It is essential to verify that database is correctly specified. It only needs a small error to cause many problems.

Other Activities

105

105

Alarms Monitoring

Failures and faults can not be considered as optimization operations.

However, we can not make any optimization without solving network faults.

Other Activities

106

106

PARAMETERS OPTIMIZATION

107

107

POWER CONTROL OPTIMIZATION HANDOVER OPTIMIZATION CALL DROP OPTIMIZATION TRAFFIC OPTIMIZATION

PARAMETERS OPTIMIZATION

108

108

Power Control Window

Fast Power Control

Power Control Optimization

109

109

Power Control Thresholds

Upper and lower limits Power increase step size Power decrease step size

av_rxlev_ul

l_rxlev_ul_p

u_rxlev_ul_p

-110 dBm

-47 dBm

Normal step Size

Normal Power Control

Power Control Optimization

110

110

Power Control Window

Analysis done on the Uplink power control window.

Use Abis measurements to plot quality vs level.

Determine the optimum power control window.

The optimum window will depend on the frequency reuse pattern and noise floor.

Power Control Optimization

111

111

-110

-105

-100

-95

-90

-85

-80

-75

-70

-65

-60

-55

-50

-45

0

1

2

3

4

5

6

70

2000

4000

6000

8000

Nb

of S

ampl

es

UL Level

UL RxQual

UL PC Window [-90,-80] [0,2+1]

Power Control Optimization

-110

-105

-100

-95

-90

-85

-80

-75

-70

-65

-60

-55

-50

-45

0

1

2

3

4

5

6

70

1000

2000

3000

4000

5000

UL Level

UL RxQual

UL PC Window [-96,-86] [0,2+1]

112

112

This feature causes the mobile and BSS to respond more effectively to changing power level and quality conditions.

The range of power steps is modified so that the step size will be changed dynamically based on the average received level.

The target received level is the middle between U_RXLEV_UL_P and L_RXLEV_UL_P.

Fast Power Control

113

113

Adaptivestep size

av_rxlev_ul

-110dBm

-47dBm

l_rxlev_ul_p

u_rxlev_ul_p

Target Received Level

av_rxlev_ul

l_rxlev_ul_p

u_rxlev_ul_p

-110dBm

-47dBm

Normal step Size

Fast Power Control Normal Power Control

Fast Power Control versus Normal Power Control

Fast Power Control

114

114

Adaptive Power Increase

Adaptive Power Inc_Step_Size = min [MS_P_INC, Max_POW_INC, (power max- MS_TXPWR)]

Where:Max_POW_INC : max power increasepower max : max power of the MSMS_TXPWR : actual power of the MSMS_P_INC is evaluated by the following algorithm

Fast Power Control

115

115

Av_RXLEV_UL <L_RXLEV_UL_P

Yes

Av_RXQUAL_UL =<L_RXQUAL_UL_P

+OFFSET_RXQUAL_FH

Yes

NO

NO

Bad level onlyMS_P_INC = roundup [ POW_INC_FACTOR*

( TARGET_RXLEV_UL - AV_RXLEV_UL])

Bad level and qualityMS_P_INC = roundup { MAX [POW_INC_FACTOR*(TARGET_RXLEV_UL - AV_RXLEV_UL), POW_INC_STEP_SIZE]}

Bad Quality onlyMS_P_INC = POW_INC_STEP_SIZE

MS_P_INC

Fast Power Control

116

116

Adaptive Power Reduction

Adaptive Power Red_Step_Size = MIN [MS_P_RED, Max_POW_RED, (MS_TXPWR - power min)]

Where;Max_POW_RED : max power reductionpower min : min power of the MSMS_TXPWR : actual power of the MSMS_P_RED is evaluated by the following algorithm

Fast Power Control

117

117

Av_RXLEV_UL >U_RXLEV_UL_P

Yes

Av_RXQUAL_UL =>U_RXQUAL_UL_P

Yes

NO

NO

Good level onlyMS_P_RED = roundup{MAX

[ POW_RED_FACTOR* (AV_RXLEV_UL -TARGET_RXLEV_UL ), ]2 dB}

Good level and qualityMS_P_RED = roundup { MAX [POW_RED_FACTOR*(AV_RXLEV_UL - TARGET_RXLEV_UL), POW_RED_STEP_SIZE]}

Good Quality onlyMS_P_RED =

POW_RED_STEP_SIZE

MS_P_RED

Fast Power Control

118

118

Fast Power Control

119

119

The average level and quality used are averaged with window size A_QUAL_PC and A_LEV_PC.

To disable fast power control and use the fixed power control step size, set the parameters

max_pow_inc = inc_step_size max_pow_red = red_step_size pow_inc_factor =1 pow_red_factor =1

Fast Power Control

120

120

Parameter Per Definition Stage 1 Stage 2POW_INC_FACTOR Cell Weighting factor for power increase 0.8 0.8POW_RED_FACTOR Cell Weighting factor for power reduction 0.5 0.5MAX_POW_INC Cell Maximum Power increase in one power command 8 16MAX_POW_RED Cell Maximum Power reduction in one power command 6 6POW_RED_STEP_SIZE Cell Power reduction step size in case of power command

triggered on quality criterion2 2

POW_INC_STEP_SIZE Cell Power increase step size in case of power command triggered on quality criterion

4 4

U_RXLEV_UL_P Cell Upper uplink level threshold for power control -86 -86L_RXLEV_UL_P Cell Lower uplink level threshold for power control -96 -96U_RXQUAL_UL_P Cell Upper uplink quality threshold for power control 0 0L_RXQUAL_UL_P Cell Lower uplink quality threshold for power control 2 2

Field TrialThe following parameters were set

Fast Power Control

121

121

El_Khatib_MSTXPWR

0%

10%

20%

30%

40%

50%

60%

70%

High(33dBm-29dBm) Medium(27dBm-21dBm) Low(19dBm-13dBm)

Before

After1

After2

Fast Power Control

To highlight the change in the MS power distribution, the MS_TX_PWR was classified into 3 categories: high, medium, low.

122

122

El_Mounira_MSTXPWR

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

High(33dBm-29dBm) Medium(27dBm-21dBm) Low(19dBm-13dBm)

Before

After1

After2

Fast Power Control

123

123

Conclusion

The MS_TXPWR was decreased obviously, this was noticed from Abis traces and drive tests.

This saves the battery of the mobiles and can decrease the uplink interference in the area.

The effect of dynamic power increase was not noticed in the Abis traces.

No obvious change in the counters or the QVoice.

Fast Power Control

124

124

Quality Handover Average Window Optimization

HO Margin Optimization

Power Budget Limitation

Handover Optimization

125

125

Bad Pace Analysis Factors affecting speech quality Handovers are the major cause for bad pace

Bad PACE Repartition

0.00%

10.00%

20.00%

30.00%

40.00%

50.00%

60.00%

70.00%

80.00%

Bad Level(Coverage)

Poor Quality Poor Leveland Quality

HO event HO w ith Level HO w ithquality

HO w ithquality and

Level

DL UL

Handover Optimization

126

126

Quality Handover Average Window Optimization

Determine optimum length for quality HO window

Determine value based on speech quality analysis

Measure HO/Call

Handover Optimization

127

127

Abis measurements show a degradation of average DL quality after changing the window from 4 to 6 SACCHs

Speech quality also degraded in DL

Avg DL Qual before HO (4SACCHs)

0

5

10

15

20

25

30

35

0 1 2 3 4 5 6 7

RxQual DL

Nb

of H

Os

0%

20%

40%

60%

80%

100%

120%

Avg DL Qual before HO (6SACCHs)

0

2

4

6

8

10

12

14

16

18

0 1 2 3 4 5 6 7

Rx Qual DL

Nb o

f HO

s

0%

20%

40%

60%

80%

100%

120%

Handover Optimization

128

128

UL Quality has been slightly impacted .

Avg UL Qual before HO (4SACCHs)

0

5

10

15

20

25

30

0 1 2 3 4 5 6 (blank)

Rx Qual UL

Nb

of H

Os

0%

20%

40%

60%

80%

100%

120%

Avg UL Qual before HO (6SACCHs)

0

5

10

15

20

25

0 1 2 3 4 5 6 (blank)

Rx Qual ULN

b of

HO

s

0%

20%

40%

60%

80%

100%

120%

Handover Optimization

129

129

Measure the qualtiy Handovers decrease on the tested cell(s). Determine the optimum “quality HO decrease” versus “speech

quality”.

Quality handovers

0

1000

2000

3000

4000

5000

6000

0

10

20

30

40

50

60

UL

DL

% Quality

Handover Optimization

130

130

Suez HO Performance

0

20000

40000

60000

80000

100000

120000

20/08/01 27/08/01 03/09/01 10/09/01 17/09/01

UL Level UL Quality DL Level DL Quality

Suez City

0

0.2

0.4

0.6

0.8

1

1.2

1.4

20/08/01 27/08/01 03/09/01 10/09/01 17/09/01

Cal Drop % HO Per Call

Handover Optimization

Results on Suez City

131

131

HO Margin Optimization

HO_margin increase from 5 to 6.

0

2000

4000

6000

8000

10000

12000

14000

16000

8/25/01 9/1/01 9/8/01 9/15/01

DL_LEV

DL_QUAL

UL_LEV

UL_QUAL

PBGT Volume

20000

25000

30000

35000

40000

8/24/01 8/31/01 9/7/01 9/14/01

Handover Optimization

132

132

HO/Call decreased Speech quality improved

Handovers Per Call

0.350.370.390.410.430.450.470.49

TVOC Jul 11 2001 Aug 23 2001 Sep 22 2001

MOBINIL 93.4% 93.4% 95.9%

CLICK 95.0% 95.6% 95.8%

85.0%

90.0%

95.0%

100.0%

Jul 112001

Aug 232001

Sep 222001

TVOC (Voice Quality indicator)

MOBINIL

CLICK

Handover Optimization

133

133

Cause = 12 (Power Budget HO)EN_PBGT_HO = ENABLE

PBGT(n) > HO_MARGIN(0,n)

And AV_RXLEV_PBGT_HO <= RXLEV_LIMIT_PBGT_HO

Power Budget Limitation

The parameter RXLEV_LIMIT_PBGT_HO is a threshold on the downlink received level, above which it is not necessary to trigger a handover on power budget.

This adds limitation to the PBGT HO, which can be used in dense areas to decrease the number of Handovers.

Handover Optimization

134

134

Cell Type Parameter ValueMicro cells -55Macro cells -65

Field Trial

The parameter RXLEV_LIMIT_PBGT_HO was generalized on a dense area.

Handover Optimization

135

135

Handover_Per_Call_on_Area

0.540.560.580.6

0.620.640.660.680.7

TOT_TMHOCO

Ho per Call Decreased

Handover Optimization

136

136

Better_cell_HO_Area

200000250000

300000350000

400000450000

500000

Better cell

Imperative_HO_Area

050000

100000150000200000250000300000350000400000

Level

Quality

Interf

Handover Optimization

137

137

Call drop

02000400060008000

100001200014000160001800020000

0

0.2

0.4

0.6

0.8

1

1.2

1.4

Dr op - BSS

Dr op - HO

Dr op - Radio

% RT CH dr op

% Cal l Dr op

Total RTCH traffic

0

5000

10000

15000

20000

25000

30000

0

5

10

15

20

25

30

35

Erlang total

Duration avg

Handover Optimization

138

138

Oum_Kalthoum_S3

0.40.450.5

0.550.6

0.650.7

0.750.8

0.850.9

TOT_TMHOCO

Detailed RTCH traff ic

0

10

20

30

40

50

60

70

80

90

100

0

1

2

3

4

5

6

7

8

9

Erlang total

Erlang BH

Cell Analysis HO/Call decreased Traffic Increased TCH congestion may result

Handover Optimization

139

139

The parameter RXLEV_LIMIT_PBGT_HO can be used on cell basis for the following objectives:

Decreasing number of unneeded handovers.

Increasing coverage area of serving cell thus keeping the traffic inside for longer time.

Tuning the parameter is based on the required cell radius.

Great care must be taken to avoid any impact.

Handover Optimization

140

140

RxLev_Access_Min Optimization

Radio Link Timeout Optimization

Call Drop Optimization

141

141

RxLev_Access_Min Optimization

Measure call drop versus gain in coverage

Determine optimum value for RxLev_Access_Min

Identify poor coverage spots where traffic can be generated

Call Drop Optimization

142

142

RxLevAccessMin - MNasr1 BSC

0

50

100

150

200

250

300

350

20-Aug-01 27-Aug-01 03-Sep-01

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

TCH Traffic Carried (Erlangs) Drop Call Rate (%)

Changing RxLev_Access_Min from -102dBm to -108dBm

Call Drop Optimization

143

143

Radio Link Timeout Optimization

Radio Link Failure is based on SACCH messages

It is controlled by the Radio Link Counter ( S )

The max value of ' S ' is broadcasted on BCCH

If MS is not able to decode SACCH message, ' S ' decreases by 1

If MS is able to decode SACCH message, ' S ' increases by 2

If ' S ' reaches 0, Radio Link failure is declared

Call Drop Optimization

144

144

Radio Link Timeout Optimization

Test different radio link timeout values

Measure Call Drop and Call Duration

Determine optimum value

High values of radio link timeout may result in TCH congestion

Call Drop Optimization

145

145

RLT - Higaz2 BSC

41.5

42

42.5

43

43.5

44

44.5

45

45.5

46

46.5

01/08/01 08/08/01 15/08/01 22/08/01 29/08/01

0

0.2

0.4

0.6

0.8

1

1.2

1.4

TCH Mean Holding Time (s) Drop Call Rate (%)

Changing RLT from 10 to 14 seconds

Call Drop Optimization

146

146

Traffic Handover

This feature provides smooth traffic distribution among the cells according to the traffic situation of each cell.

The parameter EN_TRAFFIC_HO(0,n) when enabled has two effects:

• It adds modifications to the standard PBGT handovers.• It enables a new kind of handovers which is Traffic

Handover (cause 23).

Traffic Optimization

147

147

If EN_TRAFFIC_HO(0,n) = Enable, then

Cause 12: Power Budget HOPBGT(n) > HO_MARGIN(0,N) + max(0,

DELTA_HO_MARGIN(0,n))

Cause 23: Traffic HOIf DELTA_HO_MARGIN(0,n) < 0dBPBGT(n) > HO MARGIN(N)+ DELTA_HO_MARGIN(0,n)

Traffic Optimization

148

148

DELTA_HO_MARGIN(0,n) Evaluation

If Traffic_load(0)= High and Traffic_load(n)=low DELTA_HO_MARGIN(0,n) = - DELTA_DEC_HO_MARGIN

If Traffic_load(0)=Low and Traffic_load(n)=high DELTA_HO_MARGIN(0,n) = DELTA_INC_HO_MARGIN

If Traffic_load(0)= Traffic_load(n)DELTA_HO_MARGIN(0,n) = 0

Where:DELTA_DEC_HO_MARGIN, DELTA_INC_HO_MARGIN are two cell parameters.

Traffic Optimization

149

149

Averaging A_Traffic_Load

Thresholds Comparison with N_Traffic_Load averages

Load Samples

Av_Traffic_Load

Traffic_Load

A_Traffic_Load:Cell parameter that defines the averaging window of load samples.

N_Traffic_Load: Cell parameter that defines the number of averages to be compared with the thresholds.

Thresholds are: High_Traffic_Load, Low_Traffic_Load,

Ind_traffic_Load.

Traffic Load Evaluation Process

Traffic Optimization

150

150

Traffic Optimization

151

151

Field Trial

The trial was on Hares_S1 which suffers from congestion 28%.

The best neighbors are chosen from A traces. Their traffic conditions were checked to ensure there will be enough resources to handle incoming traffic.

Traffic Optimization

152

152

Name Per Definition Proposed

Value

A_Traffic_Load Cell Averaging window size for traffic load. 8

N_Traffic_Load Cell Number of consecutive load averages used in traffic load evaluation process.

3

High_Traffic_Load Cell Load threshold used to determine when traffic load is high. 70%

IND_Traffic_Load Cell Load threshold used to determine when traffic load is indefinite. 65%

LOW_Traffic_Load Cell Load threshold used to determine when traffic load is low. 60%

En_Traffic_HO Per neighbour This flag enables/disables the detection of traffic handover cause. Enable

Delta_INC_HO_Margin Cell Correction factor penalizing handover cause “Power Budget” when traffic is low in the serving cell and high in the neighbour cells

5

Delta_DEC_HO_Margin Cell Correction factor favouring handover cause “Traffic HO” when traffic is high in the serving cell and low in the neighbor cells

5

Parameter Settings for Hares_S1

Traffic Optimization

153

153

Name Per Definition Proposed

Value

A_Traffic_Load Cell Averaging window size for traffic load. 8

N_Traffic_Load Cell Number of consecutive load averages used in traffic load evaluation process.

3

High_Traffic_Load Cell Load threshold used to determine when traffic load is high. 90%

IND_Traffic_Load Cell Load threshold used to determine when traffic load is indefinite. 85%

LOW_Traffic_Load Cell Load threshold used to determine when traffic load is low. 80%

En_Traffic_HO Per neighbour This flag enables/disables the detection of traffic handover cause. Enable

Delta_INC_HO_Margin Cell Correction factor favouring handover cause “Power Budget” when traffic is high in the serving cell and low in the neighbour cells

5

Delta_DEC_HO_Margin Cell Correction factor penalizing handover cause “Power Budget” when traffic is high in the serving cell and low in the neighbor cells

5

Parameters Settings for Neighbor Cells

Traffic Optimization

154

154

RTCH congestion

0

5000

10000

15000

20000

25000

30000

35000

40000

0

10

20

30

40

50

60

70

Congestion

Request

% Cong

% Cong max

% Call setup

60.00%65.00%70.00%75.00%80.00%85.00%90.00%95.00%

100.00%

% Call setup

Hares_S1

Traffic Optimization

155

155

Intra + inter BSC incoming handovers

0

10000

20000

30000

40000

50000

60000

70000

0

10

20

30

40

50

60

70

80

90

Fail - BSS

Fail - Radio

Congestion

Success

% Fail

% Cong

Intra + inter BSC outgoing handovers

0

5000

10000

15000

20000

25000

0

5

10

15

20

25

30

Success

ROC

Drop - Radio

Drop - BSS

% Drop

% ROC

Traffic Optimization

156

156

Handover Causes

0100020003000400050006000700080009000

10000Better Cell

Level

Quality

Interf

Traff ic

Traffic Optimization

157

157

Handover Causes

05000

1000015000200002500030000350004000045000

Better Cell

Level

Quality

Interf

Distance

Gen Capt

Traffic

Neighbor Cells

Call drop

0

200

400

600

8001000

1200

1400

1600

1800

2000

0

0.2

0.4

0.6

0.81

1.2

1.4

1.6

1.8

2

Drop - BSS

Drop - HO

Drop - Radio

% RTCH drop

% Call Drop

Traffic Optimization

158

158

Forced Directed Retry Traffic Handover1 FDR is triggered when the cell

resources are unavailableTraffic HO is triggered after High_traffic_load is fulfilled which can be adjusted.

2 FDR is dependent on the target cell DL_RXLEV

Taffic HO depends on difference between serving and neighbors DL_LEV

3 No limitation on incoming PBGT_HO Incoming PBGT_ HO is penalized if the cell load is high

4 FDR is triggered only on call setup Traffic HO is triggered on both call setup & HO

5 FDR can be triggered to external neighbor ( no restrictions on available resources)

Traffic Ho can not be triggered to external neighbor

Difference Between FDR & Traffic HO

Traffic Optimization

159

159

CAPACITY ENHANCING TECHNIQUES

160

160

CAPACITY ENHANCING TECHNIQUES

INTRODUCTION FREQUENCY HOPPING CONCENTRIC CELLS MICRO CELLULAR TECHNOLOGY HALF RATE

161

161

Capacity enhancing solutions include:

Macro cellular technology Frequency hopping Micro cellular technology In-building solutions Dual band technology Directed retry Concentric cells Half Rate

Introduction

162

162

Basic considerations in choosing the best solution:

Available frequency spectrum

Capacity requirements

Mobile handset availability

Network environment

Ease of future expansion

Introduction

163

163

A technique adopted in GSM specifications as it is able to overcome two specific problems:

- Multipath Fading

- Interference

This allows a tighter frequency reuse thus carrier upgrading can be performed, resulting in an increased capacity while maintaining network quality.

If no carrier upgrading is performed, frequency hopping allows quality to be improved while maintaining capacity.

Frequency Hopping

164

164

Frequency Hopping

Multipath Fading

Considering urban environments, radio signals reach the receiver due to reflections and diffraction on different paths resulting in fading effects.

The received signal levels are varying dependent on the applied frequency and on the receiver location.

Slow MS may stay in a fading notch for a long period of time and suffer from a severe loss of information.

165

165

Frequency Hopping

Frequency hopping introduces frequency diversity and combats multipath fading.

Fast moving mobiles do not stay in long and deep fading holes, so they do not suffer severely from this type of fading.

The improvement results in an increased receiver sensitivity under fading conditions and therefore in improved quality in uplink and downlink directions compared to a non-hopping configuration.

166

166

Frequency Hopping

Interference

Without hopping, some receivers (MS or BTS) are not interfered, while others, receiving on another frequency, will experience strong interference.

This interference can be permanent such as BCCH frequencies in downlink direction or some fixed interferers incorrectly radiating in the GSM band.

167

167

Frequency Hopping

With frequency hopping, the interfering scenario will change from TS to TS, due to hopping. Thus all receivers (MS and BTS) experience an averaged level of interference.

This will lead to calls having an average quality rather than extreme situations of either good or bad quality (all the calls will suffer from a controlled interference but only for short and distant periods of time, not for all the duration of the call).

168

168

From the BTS point of view one distinguishes: Baseband Hopping (BBH) Synthesizer frequency hopping(SFH)

Baseband Hopping (BBH)

Each transceiver (TRx) is transmitting on one fixed frequency. Hopping is performed by switching the mobiles from burst to burst to different TRXs.

The amount of hopping frequencies N(hop) is determined by the number of TRXs N(TRx): N(hop) <= N(TRx).

Frequency Hopping

169

169

Baseband Hopping

Frequency Hopping

Frame 0 Frame 1 Frame 2

Carrier A

Carrier B

Carrier C

Carrier D

8 TS / 8x577µs

Frame ….

170

170

Synthesizer Frequency Hopping (SFH)

the TRXs do not get fixed frequency assignments, they may change their frequency from TS to TS according to a predefined hopping sequence.

The number of applicable hopping frequencies may be larger than the number of equipped TRxs:

N(hop) >= N(TRx).

Since no hopping on the BCCH frequency is allowed, synthesizer frequency hopping must not be performed on the BCCH TRx.

Frequency Hopping

171

171

Synthesizer Frequency Hopping

Frequency Hopping

Frame 0 Frame 1 Frame 2

Frequency A

Frequency B

Frequency C

Frequency D

8 TS / 8x577µs

Frame ….

Frequency E

Frequency F

Frequency G

Frequency I

TRX 1TRX 2

TRX 3TRX 4

TRX 5

172

172

Hopping Modes

Frequency hopping can be performed in two modes:

Cyclic hopping mode Random hopping mode

While in cyclic hopping mode the same hopping sequence will be used periodically, in random hopping mode a pseudo random sequence will be used in order to achieve uncorrelated hopping sequences.

Frequency Hopping

173

173

Hopping Parameters

Mobile Allocation List (MA List)

List of frequencies to be used in a hopping sequence. MA List is limited by GSM recommendations to 64.

Hopping Sequence Number (HSN)

Parameter determining how the frequencies within the MA List are arranged.

Range: 0...63Cyclic: HSN = 0Random: HSN = 1...63

Frequency Hopping

174

174

Mobile Allocation Index Offset (MAIO)

Hopping sequence starting point in the MA List. If there are N frequencies in the MA List:

then MAIO = {0,1,…,N-1}.

Frequency Hopping

175

175

A concentric cell is made of two concentrically arranged zones within the same cell:

The inner zone and the outer zone.

Concentric Cells

F1

F2

MS1

BS1

MS2

176

176

Concentric Cells

Two ways of using concentric cells :Capacity Oriented By using it on an interfered cell and guaranteeing a high received level in the inner zone. This allows an additional TRX in the inner zone with a reduced reuse cluster size.

F1

F1F2

MS1

BS1MS2

C1

I1

C2

F2

I2

177

177

Concentric Cells

QoS Oriented By using it on an interfering cell to bring down the level of

interference by powering down the inner zone carriers. If a frequency is interfered, it is possible to convert it to an

inner zone frequency.

F1

MS1

BS1 BS2MS2

F1InterferenceF1

178

178

Mounted below roof top level. Radius of 300m or smaller. Propagation is primarily line of sight. Improved propagation properties, experience less severe

fading and require lower transmitter powers than conventional macrocells.

Frequency planning management. Bandwidth division. Handover and access management. New HO power budget types.

Micro Cellular Technology

179

179

Twice the TCH capacity with the same number of TRXs (using 2 TCH/HR on one timeslot).

Equal voice quality in good radio conditions.

Less resistant to errors.

HR impossible for data.

The MS as well as the MSC must support half rate coding.

Half Rate

180

180

TYPICAL PROBLEMS & SOLUTIONS

181

181

COVERAGE INTERFERENCE UNBALANCED POWER BUDGET CONGESTION (TCH & SDCCH) CALL DROP QUALITY CALL SETUP SUCCESS

TYPICAL PROBLEMS & SOLUTIONS

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DefinitionA network facing coverage problems presents bad Rx-Lev and Rx-Qual at the same time in some areas.

Symptoms - High drop call rate - High rate of DL quality and level handovers - Low proportion of better cell handover

Coverage

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1. If actual coverage is not the one predicted by radio network planning tools then:

- Check antenna system.- Check the parameter bs_txpwr_max (max_tx_bts)to be increased if value is different from planned power budget.

2. If actual coverage is the one predicted then:- Indoor traffic.- If black spot close to cell border, ease outgoing HO.

Coverage

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DefinitionInterference is the presence of good RxLev and bad RxQual at the same time in the same area.

Symptoms - SDCCH/TCH Drop - Low proportion of better cell HO - High rate of DL/UL quality HO and interference HO

Interference

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Typical Causes

1. GSM interference - Co-channel - Adjacent

Channel

2. External interference - Other mobile

network - Other RF sources

Interference

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FrequencyF(BTS1)=F(BTS2)

-9dB

Level

serving

neighbor

GSM Interferences

1. Co-channel interference

Interference occurs if the neighbor level is lower than the serving by <= 9dB(C/I<9dB)

Interference

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Level

FrequencyF(BTS1)=F(BTS2)+1

9dBneighbor

serving

2. Adjacent channel interferenceInterference occurs if the neighbor level is higher than the serving by >= 9dB ( C/I <-9dB)

Interference

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Symptoms of GSM Interference– High rate of quality HO (specially downlink quality)– High rate of call drop– High rate of call failure

Solution– Change of frequency– Down-tilt of interferer, or even change of antenna

orientation– Reduction of BS power– Concentric cell implementation

Interference

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Non GSM InterferenceOther RF interferer : Radar, medical device, army communication devices ...

Symptoms of External Interference– High rate of quality HO (specially uplink quality)– High rate of call drop– High rate of call failure– High rate of interference on idle

Solution– Change of interfered frequency

Interference

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DefinitionA cell facing unbalanced power budget problems presents a too high path loss difference between UL and DL. Always try to have delta as small as possible.

Symptoms– High ratio of uplink quality HO– Low incoming HO success rate – High ratio of call drop rate

Typical CausesMainly hardware problems

Unbalanced Power Budget

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DefinitionTCH congestion rate is too high

Symptoms– High TCH congestion rate– High directed retry rate if activated– Low incoming intra/inter BSC HO success rate

Typical Causes– Special events (football match, car crash…..).– Cell not correctly dimensioned to support daily peak hour

traffic.

TCH Congestion

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Solution– Hardware solution: add new TRxs – Software solution : half rate/ forced directed retry/

concentric cells

TCH Congestion

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TCH Congestion

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SDCCH Congestion

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Is there any site out of service near by?

Is it a border cell?

TCH_RF_LOSS> threshold

Yes

Yes

No

Yes

Contact BSS

Check if thereis a need for a

new site

Handover_Failures> threshold

Yes

Yes

No

No

Go to TCH_RF_LOSS problem

Go to Ho_Failure problem

Drop_Call_Rate>Threshold

High Drop Call Rate

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T C H _assignm ent_fa ilure> threshold

YesC heck R T F sta tus to

know if D R I is notfunction ing

D L_quality>threshold

Proceed w ith C T Pto determ ine thein terfered carrier

( D isable baseband hopping)

C heck frequencyplan and try to

determ ine poss ib lein terferers

U L_quality>threshold

In terference

U se C T P to check ifthere is path-loss in

downlink>uplink

C ontact w ithBSS

N o

PathBalance

U se C T P tocheck if there is

path-loss indownlink>uplink

C ontact w ithBSS

PathBalance

Externa l_ in terference

C ontact BSS todeterm ine the

in terferedfrequency

C hange thein tereferedfrequency

T ry to so lveneighbor T C H

congestionProblem s

YesFor a ll ne ighbors

T C H _C ongestion>threshold

Proceed w ith C T Pto determ ine thein terfered carrier

( D isable baseband hopping)

C heck frequencyplan and try to

determ ine poss ib lein terferers

In terferenceN o

N o

T C H _R F_LO SS> threshold Yes

Radio Dropped Calls

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Handover Failures> threshold

HO Dropped Calls

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Dist_HO > threshold

Level_HO >30

Overshoot-Use drive test to determine the overshoot spot

-Change antenna orientation(down tilt)-change MS_max range

Coverage-Investigate for the need of new site

- Up tilt antenna

TRX_Duration<18s

Check for Adjacent or Co channel frequency

Use traces to check path losses in UL??

UL_quality>threshold

Hardware problemContact BSS

yes

yes

yes

No

No

No

yes External interferenceChange the interfered freq

Interference_on_idle(Motorola) or interference_bands(Alcatel) >threshold??

Peaks of interference not proportional to traffic??

yes

GSM interferenceChange one of the interfered freq.

yes

UL Quality HO

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Dist_HO > threshold

Level_HO >30

Overshoot-Use drive test to determine the overshoot spot

-Change antenna orientation(down tilt)-change MS_max range

Coverage-Investigate for the need of new site

-Up tilt antenna

TCH_Duration<18s

InterferenceChange the interfered freq

Use traces to check path losses in DL??

DL_quality>threshold

Hardware problemContact BSS

yes

yes

yes

No

No

No

For any carrier BER >1.12%

yesyesCheck for Adjacent or Co channel frequency

DL Quality HO

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Handover_Success_Rate < threshold or < average of week + margin

BTS_fail_rate>xx Out__BSC_Success_rate< Out_MSC_Success_rate<

Check neighbor parameters

For all neighbors in same BSC Check

In_BSC_Success_rate<XX

For all external neighbors Check

In_MSC_Success_rate<XX

For these neighbors Check:

Check BCCH/BSIC of neighbors and serving

-point neighbors with same BCCH/ BSIC -point neighbors with same BCCH/ BSIC as serving

yes

Change interfered frequency

UL/DL quality handover >xx

Check the parameterEN_INTRA_REPEATED=0

yes

Change interfered freq

HO Failures

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201

Call_setup_success_rate<threshold

TCH_access_failure>thr

Hardware problemReset

SD_Drop_rate>thr TCH_blk_rate>thr

SD_drop_radio/ SD_drop>xx

SD_drop_BSS_pb/ SD_drop>XX

For the interfered carrier:Change the frequency

TCH congestion Pb

BSS pbm

Call Setup Success