Main Tools for Radio Network Optimization GSM Statistic Handling Tool NWS (C); SPOS&Turle, Statics (I) OSS Recording Tool PMR, RNO package (C) Cell Data Design Tools CNA (C); IPOS, BSSTool (I) Field Measurement 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 Verification of Network Changes GPRS Performance Verification Training 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 Find problem Give answer areas to objective Why should this Get input files Take notes measurement be Find solutions Prepare route Monitor done External Antenna? Changes in What should be Network changed? Measurement Will Depend on Objective ? Preparations Possible Objectives Clear objective Check equipment • Coverage analysis Why should this measurement be Get input files Prepare route • Trouble shooting done External antenna? • Scanning • Verify network changes Performing Measurements with TEMS Drive Test • Large areas • Specific areas Walk Test Scanning Drive Test - Large area INPUT INPUT MEASUREMENT OUTPUT Acceptance Drive defined Plots & Report route/area New sites on air - Signal Strength Record Logfile Frequency Re-plan - Quality Long / Short calls BSC Re-homing Trouble Report / Assure no data loss 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 - Lock on to Frequency - Solution Trouble Report - 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 OUTPUT Finding a new TEMS INV in Received SS on frequency scanning mode different ARFCN Area Network Set ARFCN to scan plot Scanning New frequency Analyzing Measurements Post-Processing TEMS Logfiles Geographical TEMS Presentation Logfiles Statistics Report Analysis Problem Cases Low Signal Strength • Interference • Handover • Call Setup Failure • Dropped Call • Misc. Signal Strength Case TEMS INPUT 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 alarm & BTS Error Check antenna installation Parameters log Is there a better antenna BSPWRT - NON BCCH FREQ Visit site position at same site? BSPWRB - BCCH FREQ Height/down Tilt Missing Neighbor Site Location Add reduce down tilt? Is the call dragged? Possible to move site? Can antenna be placed Is low SS due to missing New antenna location at lower or higher to give neighbor relations same site? Is it necessary better coverage? 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 INPUT Logfiles 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 BCCH 600 CASE 1 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. • Redo frequency plan. • Add new site. 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 2 CELL A CELL B A -> B OFFSET = -5dB 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 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 Measurement Type Initial Tuning •Large Area Drive Test (Acceptance Test) •Short Call Sequences Troubleshooting Post-Processing Output (Customer •Statistics Report complaint etc.) •Geographical Report showing failure positions Call Setup Failure – Input Activities, Troubleshooting Input Activities Measurement Type •Small Area Drive Test Initial Tuning •Lock on problem cell’s BCCH (Acceptance Test) •Force handover to the cell Troubleshooting Post-Processing Output (Customer •Geographical Report (if complaint etc.) 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 Configuration/cell SEKTOR A TCH TCH TCH TCH TCH TCH TCH TCH CHG1 SDCCH\8 BCCH TCH TCH TCH TCH TCH TCH CHG0 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 Cell Reselection Prediction • BCCH Scanning • Simulate the cell update with different CRH values CRH = 4 dB CRH = 8 dB CRH # HO 0 365 2 246 4 211 6 178 8 156 10 147 12 138 14 130 GPRS Field Measurement - Procedure Set up files ? Preparations Cell definitions TEMS, IP Sniffers GIMS … Excel Mapinfo Dig maps Charts / Tables 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 • Delay 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 Target Reselection Result Comments Cell time BSC1 16:30:42 D0241A D0241C 2s OK NA BSC1 16:33:18 D0241B D0242A 2s OK NA BSC1 16:35:04 D0242A D0248C 21 s OK This cell reselection was made to a cell located quite far away (not the closest), thus the RxLev was quite bad! BSC1 16:37:44 D0244B D0248C -- NA No throughput before or after the cell reselection. This is due to that the cell DF0242B were halted by some reason! BSC1 16:38:11 D0248C D0244B -- Failed The through put was never resumed and the FTP connection was aborted by the ftp-server!