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Testing of GSM network

Testing of GSM network. Katja.Koivu@omnitele.fi. Contents. GSM network quality audit Network quality benchmarking Optimisation Statistics / Operation & Maintenance measurements Field measurements GPRS measurements Testing of special features. GSM Radio Network Quality Audit

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Testing of GSM network

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  1. Testing of GSM network Katja.Koivu@omnitele.fi

  2. Contents • GSM network quality audit • Network quality benchmarking • Optimisation • Statistics / Operation & Maintenance measurements • Field measurements • GPRS measurements • Testing of special features

  3. GSM Radio Network Quality Audit and Optimisation

  4. Background • On what basis does the customer rate GSM operator’s quality ? • Prices • Coverage area • Call blocking/dropping • Speech quality • Customer service • Else? • The user experienced service quality in GSM links directly to the performance of the radio network • Differentiation from competitors Radio network quality related!

  5. Optimisation outcome ? • Network optimisation is a tradeoff between quality, • traffic/revenues and investments. • Without fine-tuned network the customer complaints are increased, • work load is increased and marketing becomes inefficient • Do you know how your network is performing ? GSM network indicators of European operator customer Direct impact on customer satisfaction !

  6. Network quality benchmarking How does your network’s quality match against the competitors ? …and against the world standard ? Example benchmarking statistics

  7. Field measurements • Benchmarking • Troubleshooting • statistics, customer complaints • Base station start-up • Testing equipment • Testing software e.g. TEMS Ericsson in a laptop • Test mobile phones (one or more) • Indoor/outdoor antenna • Cables + battery chargers

  8. Field measurements • Testing route • Roads, train • Hot spot, pedestrian • Urban, suburban, rural • Test setup • Idle mode • Continuous call • Call sequence (90s calls / 15s idle) • Tested frequencies: 900/900E/1800

  9. Example – Call Success Rate

  10. Example – SQI

  11. Network quality benchmarking • Could there be an indicator that shows your network is underperforming ? Independent benchmark needed • What kind of action should be taken to improve the situation ? Correctly targeted network optimisation Example benchmarking statistics

  12. Network optimisation process INPUTS Customer Feedback MANAGEMENT MARKETING Benchmarking NETWORK PLANNING Field measurements and performance evaluations CUSTOMER SERVICE Postprocessing Operation & Maintenance Measurements Continuous process!

  13. Optimisation targets Effective and economic use of network ! Satisfied customers Maximum utilisation of hardware

  14. Troubleshooting Omnitele’s engineers are experienced to encounter all the major issues effecting the quality of GSM networks • Handover problems • Quality problems • Coverage problems & New site location identification • Network layers fine-tuning • Capacity problematics • LAC optimisation • New feature implementation (software and hardware) • Micro cells introduction • Indoor coverage fine-tuning • BSS parameter fine-tuning

  15. Dual Band considerations Utilisation • Traffic steering between • 900/1800 layers • Parameter optimisation • Coverage/capacity • GPRS strategy

  16. 5,13 13,1 13,8 6,13 Frequency planning & interference analysis • Interference analysis • Used by turns with the allocation in order to validate (and optimize, if necessary) the frequency (reuse) plan • Frequency planning objectives • QoS objectives • Overall C/Ic and C/Ia requirements • Cell-to-cell C/Irequirements • Interference check per channel • Evaluation of the significance of the residual interference • HO/Cell selection margin should be included in the analysis • C/Ic (and C/Ia ) statistics per channel • Interference per network • On the dominance area • C/Ic (and C/Ia ) statistics • Shows the overall interference picture

  17. Interference reduction means • Optimising is done frequency by frequency • Antenna redirection • the most predictable • coverage is in danger • Antenna tilting • ideally very useful: steepens the slope • in practice difficult to predict • should be always measured • useful for large clearence angles • Power reduction • UL/DL interference power balance is lost • coverage is lost • not recommended • All interference reduction means may generate problems in other frequencies Reducing interference Improves network quality!

  18. Optimising adjacencies & LAC • Missing neighbours very often result in unnecessary dropped calls and bad quality • Correct neighbour relations can be determined by analysing measurement results Unnecessary LAC updates can easily increase the singalling load significantly Increased signalling reduces the room for payload ! Are your adjacencies and LACs optimised ?

  19. Optimising parameters study theoretically the impact of the intended change select the set of performance parameters and test cells new conclusions change the cell parameters under optimisation measure with a test MS - happy with the results ? + measure the performance and compare to the ref. performance - happy with the results ? + apply the changes permanently in the network/service area

  20. O&M based performance parameters • QOS as well as RF and capacity planning parameters assessed per cell, per BSC and per network • RF planning parameters • Number of calls • TCH RF loss rate • SDCCH RF loss rate • TCH mean holding time • Handovers per call • Cumulative UL/DL level statistics • Idle channel UL interference • Power balance • QOS parameters • Dropped call rate • Dropped call rate due to radio • Cumulative UL/DL quality statistics • TCH BH blocking rate • SDCCH BH blocking rate • (Call setup success rate) • (Handover success rate) • Capacity planning parameters • TCH BH traffic (e.g. weekly and average of daily BH traffics) • BH activity per subscriber (segment) • Total TCH time (per subscriber) • SDCCH weekly BH traffic • BH paging load

  21. Example – BH traffic 20 June: 290 000 subs  17 mErl/subscriber Mean holding time ? -> BHCA/subscriber

  22. Conclusion • The GSM network optimisation process consists of complex technical measurements and analysis • Every network is individually planned and thus have individual problems which decrease the quality • Professionally performed optimisation will increase customer satisfaction GSM network indicators of European operator customer How to increase the quality and capacity with minimum investments ?

  23. How can Omnitele assist you?Radio network quality audit and optimisation

  24. Performing the quality audit To observe and follow the quality of the network Why? Where? Predefined areas Regularly, e.g. once a year How often? With measurements By comparing How? Who? Independent from the operator and vendor

  25. Network quality audit -- Objectives -- Complete analysis of the quality perceived by subscribers Location of interference, inadequate signal strength and quality, congestion Proposal for corrective actions in both short and long term Comparison to the competitors and world class standard On-the-job training for Operator’s own staff

  26. Network quality audit -- Area definition -- The most important cities, roads, suburbs Areas representing different kind of coverage, different subscriber density etc. Same basic area every time, expanded with possible new coverage areas

  27. Measurement route definition • ca. 1/3 of the # of cells in the area • 30 min. of driving for each • covering the whole sub-service area • distinction of areas with different required coverage probabilities • following the foreseen traffic distribution • all HO pairs tested • closing loops & major highways • marketing should be consulted • emphasis on • the city • the most important roads • the most important suburbs • the areas with foreseen difficulties

  28. Network quality audit -- Regularity -- Once a year if the network is quite stable More often if the network is still under construction In addition to complete quality audit weekly measurements are recommended

  29. Network quality audit --The auditor -- Should be independent from the Operator´s Technical Department and the Vendor Should have experience from other networks Because, then ... The comparison will be objective The Operator gets the information what is the performance level of the network compared with the other networks

  30. Quality audit -- Comparison -- Predefined criteria the network should fulfill Quality Index (measured indicators) Comparison with competitors Comparison with previous quality audits By Quality Index

  31. Why Omnitele ? • Long and extensive experience on radio network planning • Dimensioning and nominal planning • Site planning • Parameter planning • Network tuning and optimisation • Experience from several equipment suppliers Projects: • GSM planning in Finland • Radiolinja project (world’s first GSM network) • GSM1800 city networks • Ongoing Finnish 2G project (3rd Finnish operator) • GSM planning abroad • Italy Czech republic • Netherlands Brazil

  32. Why Omnitele ? • GSM network dimensioning/nominal planning for start-up operators • Tanzania • Jordan • Pakistan • Network audits and optimisation projects • Finland • Radiolinja • City networks • Finnish 2G • Abroad: • Greece Ivory Coast Kuwait • Togo Jersey Czech Republic • Guernsey Faroe Islands Cyprus • Andorra Bahrain

  33. GPRS Optimisation in general

  34. Optimisation Process • Output • Optimal parameter settings: • Dedicated/dynamic radio capacity allocation • Traffic steering between the radio layers • Coding scheme adaptation • Different timers • Optimal hardware configuration • Protocol optimisation • Key performance indicator definition and measurements • Future plan – winner strategy • Input • The business strategy for GPRS • Existing and desired quality of the network (field measurements & OMC studies): • Congestion • QoS of the existing network • Interference • Different vendor solutions • Required services and expected usage Best quality with minimum investment

  35. Measurement System Set-up End End - - to to - - End data performance End data performance Data at Data at Data at Data at application layer application layer application layer application layer GPRS layer data performance GPRS layer data performance Data at Data at Data at Data at RLC/LLC layer RLC/LLC layer RLC/LLC layer RLC/LLC layer RF performance RF performance Air Air - - interface interface Air Air - - interface interface Server GPRS Mobile

  36. Monitored Key Performance Indicators (KPI) • C/I of the measured channels • Average RLC throughput (kbit/s) • Average LLC throughput (kbit/s) • Average number of timeslots used by a single user • CS usage (% of time in the CS1/CS2 *) • Average cell reselect time • Network response time (RTT) • RLC bit error rate *) Available only in networks with dynamic CS adaptation

  37. GPRS Parameter Planning (1) • Goals: • To handle GPRS in cells with high CS (speech) traffic • To steer the GPRS traffic to wanted cells • Adequate definition of GPRS timers • Radio interface capacity division between CS/PS • Optimise the performance of specific service Optimised end-user experience !

  38. GPRS Parameter Planning (2) • Omnitele has profound hands-on experience with • Alcatel GPRS parameters • Ericsson GPRS parameters • Nokia GPRS parameters Troubleshooting… Daily planning & Optimising… Drive tests…

  39. Measuring GPRS network performance • Data flow behaviour • Re-transmissions • Cell re-selections, RA updates etc. • Number of time slots used per mobile • Coding scheme usage RLC and LLC Throughput

  40. GPRS Network performance benchmarking

  41. Why benchmark the network performance ? • Performance of the GPRS networks vary significantly • between the operators • The QoS status of operator’s GPRS network is best • determined by benchmarking the network performance • against competitors’ performance and/or world class operators • operating in different markets

  42. Benchmarking Results Examples • Example country: • Three nation-wide GPRS operators • Same drive routes in the benchmarking • Significant differences in KPI’s of the three operators

  43. Improving the Performance of Your Network • After benchmarking the GPRS performance, the problem areas will be identified • Recommendations for improvements are given • Service optimisation plan will be made

  44. BSC Measurements • In addition to end-to-end field measurements, BSC measurements can be performed from the BSC of the benchmarked operator • Better overall picture of the problem cells: Suggestions to improvements • Some of the key issues that can be identified from BSC are: • Overall GPRS traffic • Blocking of GPRS calls • Retransmissions • PCU loading • Note: The BSC measurements can only be benchmarked against Omnitele archive since there is no access to competitors’ BSC

  45. How can Omnitele assist you ?

  46. Example of Omnitele ’s GPRS Projects Network acceptance and optimisation 1Introduction 2Description of field measurements 2.1 GPRS measurement model 2.1.1Application layer performance measurements 2.1.2GPRS layer performance measurements 2.1.3RF performance measurements 2.2 Monitored Key Performance Indicators 2.2.1Carrier to Interference ratio for the measured channels (dB) 2.2.2Coding scheme usage (%) 2.2.3RLC/LLC throughput (kbit/s) 2.2.4Cell reselection time (s) 2.2.5Routing area update time (s) 2.2.6Network response time (s) 3Findings during the Installation 3.1 Alcatel acceptance tests 3.1.1MFS acceptance tests 3.1.2Core acceptance tests 3.2 Detected problems 3.2.1MFS 3.2.2Core 4Integration testing 4.1 Carrier to Interference ratio 4.2 Coding scheme usage 4.3 Throughput 4.3.1Normal cell load throughput measurements 4.3.2High cell load throughput measurements 4.4 Cell reselection 4.5 routing area update time 4.6 Network response time 4.6.1Pinging with Windows Command prompt 4.6.2Pinging with different intervals between the pings 5GPRS Parameter fine-tuning 5.1 Further routing area update testing 5.2 Optimisation of the coding scheme usage 5.2.1CS_Lev parameter 5.2.2CS_Qual_1_2 / CS_Qual_2_1 5.2.3TBF_CS_Period1 / TBF_CS_Period2 5.3 Congestion control 5.4 network response time optimisation 5.5 Other investigated issues 5.5.1Frequency scans in the east coast 5.5.2Missing adjacencies 6Comparison of finnish GPRS operators’ network Performance indicators 6.1 Throughput 6.2 Cell Reselection time (s) 7comparison of different vendors’ GPRS features 7.1 Automatic Link adaptation (ALA) 7.2 Congestion control 7.3 Multiplexing users into the Timeslots 7.4 TRX preference 8suggestions for GPRS network development 8.1 Alcatel GPRS core rel2 and BSS software B7 8.2 Traffic monitoring 8.3 Air-Interface compression software 9Conclusion

  47. How Can Omnitele Assist You? • Contract negotiations: • Assistance in definition of the technical framework to the system specifications: How should the GPRS system perform? • Hands-on experience: Alcatel, Ericsson and Nokia GPRS systems • Implementation: • Verification of the system performance: Specification of the operator acceptance tests and system integration tests • Parameter planning, parameter fine-tuning and optimisation of the GPRS network • Service optimisation: • WAP&Web: Parameters&timers • Content optimisation: Performance Enhancement Proxy selection process • MMS: Radio capacity optimisation • GPRS performance benchmarking • Comparison of your GPRS network’s performance to your competitors

  48. Please visit our web site www.omnitele.fi for more information

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