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Network Quality Technology for executives, Moscow - 13 September 2004 Author: Morten Raaum Presenter: Hans Myhre
Network Quality,as perceived by customer     Coverage     Capacity     Speech quality     Services quality     Custom...
GSM in the field                                           BTS   To BSC / MSC               To BSC / MSC     BTS          ...
Some practical experiences..   No network access (= no „Telenor‟ in the display)     – Lack of coverage     – Network ove...
GSM in the field                                             BTS               To BSC / MSC               To BSC / MSC    ...
How is Network Qualitymonitored by the operator?   Coverage    – Measurements by technical staff. Test telephone + laptop...
How is Network Qualitymonitored by the operator?   Speech quality    – The network counts Dropped calls and to some exten...
Capacity and quality– a trade off at a given funding
Capacity in the GSM radio network     Base station with antennas connected in a mast          – BTS contains a number of ...
Radio network capacity   Building blocks for capacity at the base stations: TRX     – 8 channels that are used for signal...
Radio network capacity       Base station configuration example:       3 TRXes, Omni directional cell         – 1 cell w...
Radio network capacity       Base station configuration example:       3 TRXes, Sectorised 1/1/1.         – 3 cells with...
Frequency planningRe-use of GSM channels isnecessary. In this example afrequency is re-used in every12th cell => reuse fac...
Resource: Frequency spectrum   Spectrum size strongly affect base station roll out.   Re-use of GSM channels is necessar...
Spectrum vs. investmentsCapacity case                                              Malaysia case..                       ...
Network Quality,some KPIs   Minutes per dropped call    – Summary of all traffic minutes divided by number of dropped cal...
Network Quality, some KPIs                      Network Utilisation                                                       ...
Benchmarking                                                            ReportTechnical KPIs                              ...
Network Quality,challenges   How to measure customer perceived quality?    – Unmanned active measurement units.   New an...
EnvironmentBase station location: Aim to minimise the effect of masts and antennas on the local environment.
Trøndelag theatre
Tree-mountedantenna..
Antenna
VindernTypical antenna-installation in a cityenvironment
Mini-BTS mounted on apole by the fjord
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Network quality

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Transcript of "Network quality"

  1. 1. Network Quality Technology for executives, Moscow - 13 September 2004 Author: Morten Raaum Presenter: Hans Myhre
  2. 2. Network Quality,as perceived by customer  Coverage  Capacity  Speech quality  Services quality  Customer care..
  3. 3. GSM in the field BTS To BSC / MSC To BSC / MSC BTS Handover Handover BTS To BSC / MSCTo BSC / MSC BTS
  4. 4. Some practical experiences.. No network access (= no „Telenor‟ in the display) – Lack of coverage – Network overload situation (users barred from access) – Network failure. 3 beeps/3-tone beeps at call setup – Blocking/error situations somewhere in the network – User error (e.g. non-existent number) Poor speech quality – Marginal coverage – Interference between base stations Dropped call – Poor quality of radio link – Blocking in target cell (moving mobile, handover situation) – Network failure (transmission) The mobile is the weakest link in the chain: Mass production units – Internal antenna – Increased software and processing complexity (WAP/GPRS/HSCSD/games&features)
  5. 5. GSM in the field BTS To BSC / MSC To BSC / MSC BTS No traffic channels available Handover Handover to non-optimal cell BTS Poor speech quality To BSC / MSC Dropped callTo BSC / MSC BTS
  6. 6. How is Network Qualitymonitored by the operator? Coverage – Measurements by technical staff. Test telephone + laptop. – Measurements by remotely controlled test systems (installed in bus, taxi etc). – Customer complaints and performance stats as input. Capacity – Network Maintenance Center / Operations center – The network counts # of events (pos./neg.) Post processing in Performance Management tool. – Tools for prognosis on capacity needs vs. required quality of the network (Grade of Service)
  7. 7. How is Network Qualitymonitored by the operator? Speech quality – The network counts Dropped calls and to some extent report on speech quality – Measurements by remotely controlled test systems / tech.staff. Services quality – Services are built up by combining equipment and software – External tools needed to ensure quality of delivery • Correct content / Response time • 3rd party content delivery • 3rd party Service Level Agreements (SLA)
  8. 8. Capacity and quality– a trade off at a given funding
  9. 9. Capacity in the GSM radio network Base station with antennas connected in a mast – BTS contains a number of TRX based on the need for capacity. Tx DOWNLINK Rx Rx UPLINK Tx TRX TRX TRXBTS cabinet
  10. 10. Radio network capacity Building blocks for capacity at the base stations: TRX – 8 channels that are used for signalling (SMS, suppl.services etc) and speech/data. Call duration -> Erlang – 1 Erlang = 1 hour of speech for 1 user – Call duration 90 sec: 90s / 3600s = 0,025 Erl = 25 mErl – I.e. 1 Erlang: 40 calls of 90 seconds each. (1 Erl = 40 x 25 mErl) Theoretical capacity: Erlang‟s model and chosen Grade of Service. – GoS (%) Number of call attempts that may meet blocking in a busy hour. • Typical values used: 2-5% – Example, GoS=2% – 1 TRX 7 speech channels 2.9 Erlang 41% – 2 TRX 15 speech channels 9.0 Erlang 60% – 3 TRX 22 speech channels 14.9 Erlang 68% – 4 TRX 30 speech channels 21.9 Erlang 73%
  11. 11. Radio network capacity Base station configuration example: 3 TRXes, Omni directional cell – 1 cell with 3 TRX, GoS=2%: • Capacity = 14.9 Erl • 90 sec call duration (25mErl) • 14.9 / 0.025 = 596 calls in a busy hour (theoretical max!) TRX TRX TRX BTS  If we accept higher blocking figures we can carry more traffic with less customer satisfaction. 5% GoS used in this example => 17.1 Erl capacity => 684 calls (+15%)
  12. 12. Radio network capacity Base station configuration example: 3 TRXes, Sectorised 1/1/1. – 3 cells with 1 TRX each: • Capacity = 3 x 2,9 Erl = 8,7 Erl • 90 sec call duration • 8,7 / 0,025 = 348 calls in a busy hour TRX TRX TRX BTS If we accept higher blocking figures we can carry more traffic with less customer satisfaction. 5% GoS used in this example => 11.1 Erl capacity => 444 calls (+28%)
  13. 13. Frequency planningRe-use of GSM channels isnecessary. In this example afrequency is re-used in every12th cell => reuse factor 12
  14. 14. Resource: Frequency spectrum Spectrum size strongly affect base station roll out. Re-use of GSM channels is necessary. 1 TRX use 1 GSM channel Example, Malaysia: – 24.8 MHz => 124 GSM channels – # of TRX per cell: >6. Good capacity per base station (xx Erlang). Example, Russia: – 4 MHz => 20 GSM channels – Maximum ~1,5 TRX per cell = a denser base station network will be needed for serving increasing traffic (xx Erlang) Good radio/frequency planning and use of “smart” features enables a tight re-use of GSM channels – Power control • Mobile and BTS adjust their output power as low as possible, adjustment 2 times per sec. – Discontinuous Transmission (DTX) • Mobile and BTS only transmit when user actually speak. (User benefit: less power consumption) – Frequency hopping • Mobile and BTS jump from GSM channel to GSM channel (480ms), less affected by interference.
  15. 15. Spectrum vs. investmentsCapacity case  Malaysia case.. – 6TRX/cell= 34,6 Erl/cell – 900TRX, 150 cells and 50 BTS needed Area= 50km2 Population= 1 M  Russia case.. Subscribers= 346k – 1,5 TRX/cell= 5,8 Erl/cell 15 mErl/sub – 1343TRX, 895 cells and 299 BTS needed Traffic= 5190 Erl  We need 6 times as many sites for capacity reason!For illustration purpose only – the conclusions and calculations are simplified
  16. 16. Network Quality,some KPIs Minutes per dropped call – Summary of all traffic minutes divided by number of dropped calls during a period of time (e.g. Week/month) – Typical values: 50-150 minutes. Blocking/Congestion – Call attempts that meet blocking, all resources are occupied. – The network is dimensioned to meet a certain traffic level in the busy hour. Typical dimensioning values (GoS): 2 - 5 % Typical values measured in the networks: 0 - 50+ %
  17. 17. Network Quality, some KPIs Network Utilisation Cell utilization 160 140 120 100Utilization (%) 80 60 40 20 0 % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % % 10 13 16 19 22 26 29 32 35 38 41 44 47 50 53 57 60 63 66 69 72 75 78 81 84 88 91 94 97 1 4 7 0 10 Cell utilization distribution About 22% of the cells in the network are utilised > theoretical max = customers experience more blocking than acceptable in these cells!
  18. 18. Benchmarking ReportTechnical KPIs .................. .................. .................. Technical Financial KPIs Market HR Technical Access network OSS Core network OSS Events Events & alarms & alarms MSC BTS BSC MSC MSC PSTN MSC
  19. 19. Network Quality,challenges How to measure customer perceived quality? – Unmanned active measurement units. New and advanced services – Fast development and deployment of new services. – Increased complexity, both for network and mobile. 3.party content providers – Timeout... Not available... – Service Level Agreements. How do you know what is delivered? – New and advanced measurement systems for test&monitoring. Roaming – How well are we able to keep foreign roamers in our network – and how are our roamers abroad doing? – Advanced measurement systems (signalling) for test&monitoring.
  20. 20. EnvironmentBase station location: Aim to minimise the effect of masts and antennas on the local environment.
  21. 21. Trøndelag theatre
  22. 22. Tree-mountedantenna..
  23. 23. Antenna
  24. 24. VindernTypical antenna-installation in a cityenvironment
  25. 25. Mini-BTS mounted on apole by the fjord
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