Dt Analysys

Main Tools for Radio Network Optimization GSM Statistic Handling Tool OSS Recording Tool Cell Data Design Tools Field Measurement

NWS (C); SPOS&Turle, Statics (I) PMR, RNO package (C) CNA (C); IPOS, BSSTool (I) TEMS only!!!

Field Measurement Analysis TEMS, MapInfo (C); MCOM (I) Cell Planning Tool

TEMS Cellplanner (C); MCOM (I)

Radio Network Growth Flow

Where does TEMS INVESTIGATION fit in

Design & Rollout

Operation & Improvement

Model Tuning

Traditional Optimization

Network Integration Test

Network Feature Optimization

Initial Tuning GPRS Performance Verification Training

Verification of Network Changes

DESIGN & ROLLOUT PHASE Network Integration Test When a site is integrated to BSC it is tested • Call set up test • Timeslot test, forced call test

* TEMS Pocket is the preferred tool for Network Integration Test

DESIGN & ROLLOUT PHASE Initial Tuning • Produce Coverage Plot • Identify Coverage Holes • Identify Interference Area • Optimize Neighbor Relations • Find Hardware/Installation Problems • Verify Parameter Setting

DESIGN & ROLLOUT PHASE GPRS Performance Verification • Application Performance Test • WWW, FTP, WAP etc. • Mobility Test • Cell Reselection, RA Update

OPERATION & IMPROVEMENT PHASE Traditional Optimization • Investigate & Trouble-shooting Specific Areas • Neighbor Relation Optimization • Coverage Issues

OPERATION & IMPROVEMENT PHASE Network Feature Optimization

Parameter Settings: • MS, BTS Power Control • HCS • Idle Mode Behavior • Locating Algorithm • Frequency Hopping • Intra-cell Handover

OPERATION & IMPROVEMENT PHASE Verification of Network Changes Did a certain change in the network give desired results? • New coverage area? • Less interference? • Better speech quality? • Is handover possible?

TEMS Measurement & Analyzing Process Preparations

Collect Data

Analyze

Report

Clear objective

Check equipment

Save logfile

Why should this measurement be done

Get input files

Take notes

Find problem areas

Give answer to objective

Prepare route

Monitor

?

Find solutions

External Antenna? Changes in Network

What should be changed?

Measurement Will Depend on Objective ?

Preparations

Clear objective

Check equipment

Why should this measurement be done

Get input files Prepare route External antenna?

Possible Objectives • Coverage analysis • Trouble shooting • Scanning • Verify network changes

Performing Measurements with Drive Test TEMS • Large areas • Specific areas Walk Test Scanning

Drive Test - Large area INPUT INPUT Acceptance New sites on air Frequency Re-plan BSC Re-homing

MEASUREMENT Drive defined route/area Record Logfile Long / Short calls Assure no data loss

OUTPUT Plots & Report - Signal Strength - Quality Trouble Report / Area for further investigation

Drive Test - Specific area INPUT

Measurement

OUTPUT

Statistics

Manipulate

Trouble Report

Customer complain

- Forced handover

- Identified problem

Large area drive test Trouble Report

- Lock on to Frequency

- Solution

- Layer 3 messages Analysis on-spot Rectify & Verify on-spot

Walk Test INPUT

Measurement

OUTPUT

Statistics

Add file marks (GPS)

Trouble Report

Customer complain

Scanning

Planning Report

Micro cell planning

- Antenna location

Indoor cell planning

- Frequency - HCS setting

* TEMS Light is the preferred tool for indoor cell planning

Scanning INPUT

Measurement

Finding a new frequency

TEMS INV in scanning mode

Area Network

Set ARFCN to scan

Scanning

OUTPUT Received SS on different ARFCN plot New frequency

Analyzing Measurements

Post-Processing TEMS Logfiles Geographical Presentation

TEMS Logfiles

Statistics Report

Analysis

Problem Cases Low Signal Strength • Interference • Handover • Call Setup Failure • Dropped Call • Misc.

Signal Strength Case INPUT

TEMS Logfiles

Large area DT

Post-Processing

Specific area DT

Analysis

• Identify areas with low signal strength e.g. SS < -100dBm (outdoor) • Look at RxLev distribution (for acceptance) • Compare with design level or new requirements

Signal Strength Case – Possible Reasons • Shadowed Antenna • Antenna Direction • Antenna Height / down tilt • Output Power • Missing Neighbor Relation • Site Location • Faulty Hardware e.g. antenna & TMA • Cell is down

Signal Strength Case – Analysis Shadowed Antenna

Output Power

Faulty Hardware

Visit site

Check output power

Check antenna installation

Parameters

Check alarm & BTS Error log

Is there a better antenna position at same site?

BSPWRT - NON BCCH FREQ

Visit site

Height/down Tilt

BSPWRB - BCCH FREQ

Missing Neighbor

Site Location

Add reduce down tilt?

Is the call dragged?

Possible to move site?

Can antenna be placed lower or higher to give better coverage?

Is low SS due to missing neighbor relations

New antenna location at same site? Is it necessary to expand and build a new site?

Signal Strength Case – Possible Solutions • Change parameter BSPWR , BSPWRT. • Add neighbor relation. • Physical changes: • Antenna direction • Antenna height, tilt or position • New site as last option.

Interference Case TEMS Logfiles

INPUT Large area DT

Post-Processing

Specific area DT

Analysis

Identify areas with Rxqual > 5 Identify source using Map and STS New drive test around problem area?

Interference Case – Logfile analysis From logfile & map: What channel group suffer from interference? HOP or Non HOP? • Check Current channel information in TEMS INV, hopping channel and hopping frequency. Where does the interference come from? Cell name? • Study map and logfile, look for co-channel or adjacent channel interference. Does the interference lead to lower SQI? • Look at SQI measurement during high RxQual. Use STS & RNO to assist analysis.

Types of Interference • Co - Channel interference • Adjacent Interference CASE 1

BCCH 600 BCCH 595

CASE 2

High site

BCCH 590 BCCH 590 BCCH 590 BCCH 590

Interference Case – Possible Reasons • Poor frequency plan • No dominant cell --> low C/I ---> increased Rxqual • Frequency Hopping is off • External interference e.g. jammer Example of high Rxqual due to low Signal Strength

Interference Case – Possible solutions • Enable Frequency Hopping or add frequencies to Hopping group. • Enable BTS Power Control, MS power control and make it less aggressive. • Change frequency of interferer or interfered cell: – Possible to find new frequency by using TEMS Scanning.

• Down tilt or change antenna of interferer.

Handover Case INPUT Large area DT

Post-Processing

Specific area DT

Analysis

Look for:

Repeated handover (Ping Pong) Repeated Intra-cell handover Handover failure, Unrealistic handover

Repeated Handover (Ping Pong) - Examples

Repeated Handover (Ping Pong) - Possible Reason 1

Merry-go-round Handover, Offset > Hysterisis

Repeated Handover (Ping Pong) - Possible Reason 2 • Offset only in one direction e.g A-B for Inter BSC relation BSC 1

BSC

CELL A

A -> B OFFSET = -5dB

BSC

BSC 2

CELL B

No B -> A OFFSET

Repeated Handover (Ping Pong) – Other Possible Reasons

No dominant Server

• No dominant server • Locating penalty settings e.g. PSSBQ, PTIMBQ • Too small hysterisis setting

Repeated Handover (Ping Pong) – Possible Solutions Antenna direction Antenna Tilts Plan for new site Change Locating Parameter e.g. KHYST or LHYST

Repeated Handover (Ping Pong) – Possible Solution Change Parameter, KHYST or LHYST

Hysterisis

CELL A

CELL B Handover From A to B

Handover Case – Handover Reversion

Check layer 3 message Handover command BSC correct? Check reason for handover SS, RXQUAL Target cell?

Handover Reversion – Common Reason Duplicates of BSIC BCCH combinations in neighboring list

BSC

Handover command? 610_12

606_33 610_31

610_31

Serving cell

Neighbor cell 2

Neighbor cell 1 608_32 608_32

Road

Handover Reversion – Other Reasons Uplink interference in target cell Downlink interference at MS Solutions Interference Investigation • MRR • Statistics • Scanning

Handover Case – Repeated Intra-cell Handover Possible Reasons Wrong intra-cell handover settings External Uplink Interference Possible Solutions Consider to change parameters: • SSOFFSETUL, SSOFFSETDL • QOFFSETUL, QOFFSETDL A wrong setting of parameters will cause “unnecessary” IHO Turn off Intra-cell Handover?

Handover Case – Unrealistic Handover

Unrealistic Handover – Reason & Solution Possible Reasons Wrong locating settings, in Serving or Target cell Note: Could be on purpose e.g. Dual Band network with HCS

Solution • Fix locating settings e.g. MSRXSUFF, BSRXSUFF

Call Setup Failure

Call Setup Failure – Input Activities, Initial Tuning Activities Initial Tuning (Acceptance Test)

Troubleshooting (Customer complaint etc.)

Measurement Type •Large Area Drive Test •Short Call Sequences

Post-Processing Output •Statistics Report •Geographical Report showing failure positions

Call Setup Failure – Input Activities, Troubleshooting Input Activities Measurement Type Initial Tuning (Acceptance Test)

Troubleshooting (Customer complaint etc.)

•Small Area Drive Test •Lock on problem cell’s BCCH •Force handover to the cell

Post-Processing Output •Geographical Report (if necessary)

Call Setup Failure Analysis - Initial Tuning Scenario • Check the TEMS statistics report (Blocked Call) if there is Call Setup Failure. • If yes, identify the problem cells and which logfile from geographical report. • Replay the logfile and jump to the Blocked Call event. • Check if there is any successful call setup to the problem cell.

Call Setup Failure Analysis - Initial Tuning Scenario cont. • Review the layer 3 messages to check at which sequence the failure occur (random access, SDCCH, TCH assignment etc.). • Check STS report on the problem cell. Is there any traffic (SDCCH & TCH) in the cell, SDCCH & TCH seizures, congestion etc. • Check fault report & CDD configuration.

Call Setup Failure Analysis - Troubleshooting Scenario • Before performing drive test, check STS report & fault report. • If can not identify the problem, perform drive test. • During measurement, lock the BCCH of the problem cell. • Review the layer 3 messages to check at which sequence the failure occur (random access,

Call Setup Failure Analysis - Possible reasons with ranking • • • • • • • •

Low Signal Strength Interference High Congestion on SDCCH High Congestion on TCH Transmission Fault Faulty TRU/Hardware Central Processor Overload Software File Congestion

Call Setup Failure Analysis - Possible solutions • Low signal strength  Signal strength analysis. • Interference  Interference analysis. • High Congestion on SDCCH: Define more SDCCHs. Activate adaptive configuration of logical channel feature and immediate assignment to TCH.

• High Congestion on TCH: Add capacity/Tune coverage array. Activate assignment to worse cell.

Failed Call Setup (Blocked Call) Example Multiple Channel Requests. Successful Random Access after the third try.  Congestion in SDCCH.

Dropped Call Case - Input • Statistics Report • Note from drive test.

Dropped Call Case - Analysis • From plot, identify which & where in logfile the dropped call occurs. • In the log file, Jump the drop call event. • Check if there is a disrupt in the recording. If yes  could be a false drop due to TEMS mobile disconnection during recording!!!

Dropped Call Case - Analysis (cont) • Check the Radio environment just before drop: – If High Rxqual for a longer period of time and RLINKT expire  Interference problem. – If Low SS DL, SSDL < MSSENS ( -104dBm)  low signal strength problem. – If TA > 63  too far from the cell.

• If DL radio is good, check the TX power. If there is MS power down regulation when the MS is close to the cell. If full power  suspect uplink interference or antenna, TMA problem.

Miscellaneous Case 1 From TEMS Logfile • Good Signal strength DL, Good Rxqual DL • No call set up possible unless very close to site = high SS • Dropped call when SS < approx. -75dBm Analysis • Since DL SS & Rxqual is good Suspect UL problems e.g. external uplink interference Conclusion TMA power turned off

Miscellaneous Case 2 From TEMS Logfile • TCH has lower Signal strength than BCCH (Own BCCH included in BA-list) • BTS power control = OFF Conclusion Antenna cable for TCH is swapped between sectors (CDU-A) SEKTOR C

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH SDCCH\8

TCH TCH

CHG0

BCCH

CHG1

TCH

Configuration/cell

SEKTOR A

SEKTOR B

Miscellaneous Case 3 From TEMS Logfile • Fail to perform Call Setup Analysis • Check if any success call setup to the same cell  No • Check if handover is possible  Yes • Suspected wrong cell definition in MSC but Cell is properly defined in MCS and LA Conclusion

• Corrupted block in MSC

GPRS Verification & Optimization with TEMS Investigation

GPRS Measurement Activities • GPRS Performance Prediction • GPRS Field Measurement

GPRS Performance Prediction - Overview

• GPRS RNAP Service uses TEMS Inv to predict following performance: – Throughput – Cell Reselection & Routing Area Update

GPRS Throughput Prediction • Perform Throughput prediction for each coding scheme

Cell Reselection Prediction • Dedicated mode drive test

HO types LA HO (10) HO int. (220) LA HO at BQ (1) HO int. at BQ (11) BSC3 serving Other BSC

Cell Reselection Prediction

• BCCH Scanning • Simulate the cell update with different CRH values CRH = 4 dB

CRH = 8 dB

CRH 0 2 4 6 8 10 12 14

# HO 365 246 211 178 156 147 138 130

GPRS Field Measurement - Procedure

?

Preparations

Excel

Set up files Cell definitions TEMS, IP Sniffers …

GIMS

Mapinfo Charts / Tables

Dig maps

Graphical presentation of route Report

GPRS Field Measurement - Type of Measurements • Application Performance Test – – – –

Ping WWW FTP WAP

• Mobility Performance Investigation – Cell Reselection – RA Update

GPRS Field Measurement - Application Performance Test • Attached performance – Attached Time = Attach Complete msg – Attach Request msg – Attach Success Rate

• PDP context activation performance – PDP context activation = Activate PDP Context Accept msg – Activate PDP context request

• Throughput on RLC level •

GPRS Application Test Tools • General – Windump, Commview, Ethereal, Protocol Analyser for Gb

• PING – MS DOS ping command

• WWW – IE, Netscape

• FTP – DOS FTP, WS_FTP, TEMS built in sequence

GPRS Field Measurement - Mobility Performance Investigation • Number of Cell Reselection & RA Update • TCP Outage Time • Cell Reselection Failure

Mobility test CRH = 4, CRO = 4

Cell Reselection. Sample Report Routing Area

Time

Cell

Reselection time 2s 2s 21 s

Result

Comments

D0241A D0241B D0242A

Target Cell D0241C D0242A D0248C

BSC1 BSC1 BSC1

16:30:42 16:33:18 16:35:04

OK OK OK

16:37:44

D0244B

D0248C

--

NA

16:38:11

D0248C

D0244B

--

Failed

NA NA This cell reselection was made to a cell located quite far away (not the closest), thus the RxLev was quite bad! No throughput before or after the cell reselection. This is due to that the cell DF0242B were halted by some reason! The through put was never resumed and the FTP connection was aborted by the ftp-server!

BSC1

BSC1