Main Tools for Radio Network Optimization GSM Statistic Handling Tool OSS Recording Tool Cell Data Design Tools Field Measurement Field Measurement Analysis Cell Planning Tool
NWS (C); SPOS&Turle, Statics (I) PMR, RNO package (C) CNA (C); IPOS, BSSTool (I) TEMS only!!! TEMS, MapInfo (C); MCOM (I) 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. • Verify or isolate the problem using STS (Drop call and reasons).
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
