Drive test analysis
- 1. System Optimisation Group China GSM Core Engineering August 11, 2000 Jim Luan, Lin Mubao
- 2. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 2 Drive Test Procedure Drive Test Netplan FICS Statistics Analysis Problem Finding VOT/GEP Preparation
- 3. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 3 Preparation (1) • Definition File – Without it, it is impossible to observe overshooing neighbors – GenDef7.exe can convert FP to definition file Neighbor list with definition file Neighbor list without definition file
- 4. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 4 Preparation (2) • Frequency Plan & Configuration map • Software:TEMS, FICS, GEP, VOT • Hardware: TEMS, GPS, Portable PC • Test Problem Sheet • Route • Map
- 5. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 5 Drive Test • For Benchmark – 2 minutes per call – 10 – 15 minutes a log files – Force to appropriate band (GSM only, DCS only or Dual) • For Special Problem – Planning route – No limitation
- 6. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 6 TEMS Introduction • Interface • Functions
- 7. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 7 Log File Process TEMS Log File NetPlan FICS VOT/GEP .CSV.FMT Route Map .STA Excel VB .NP/.TXT Much shorter cycle time by VOT and GEP.
- 8. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 8 TEMS .log file Analysis • Undecoded BCCH • BSIC Undecode in Other Site • No Handover • Delay Handover • Ping Pong Handover • Negative Handover • Overshooting • High Overlapping • No Dominant Server • Poor Coverage • Unreasonable Serving Area • Interference • Handover Failure • Handover Loss • UL Drop • Drop Call • Sudden Power Drop • MS Power Rapid Increase Below lists common problems which can be observed from Drive Test Log.
- 9. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 9 Undecoded BCCH (1) Description: – BSICs can’t be decoded in 5s – Usually consider 3 strongest neighbors Reason: – GCLK shift, only decode same site BSICs – Channel interference – Non-BCCH carrier, no dedicated spectrum for BCCH
- 10. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 10 Undecoded BCCH (2)
- 11. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 11 BSIC Undecode in Other Site Description: – BSIC in same site can be decoded but not for other sites – Handover can only happen in intra-site basis – It is similar to former Undecoded BCCH case Reason: – GCLK shift • GCLK recalibration is required • No one monitors OMC-R alarms
- 12. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 12 No Handover (1) Description: – Neighbor BSIC is decoded and COMMON handover requirement is fulfilled but there is never a handover Reason: – Missing neighbor • No such neighbor in CM database – Incorrect external neighbor • Target cell’s LAC/BCCH/BSIC in add_neighbor is different from those in equip_rtf • Engineer modifies external neighbor at MMI, not through GUI • Never use OMC-R Proxy Cell to propagate external neighbor information – N < hreqt. Great HO_MARGIN. Improper algorithm 1-7 setting – Missing_rpt =1 – Serving cell overshoots/covers too far away – Refer to GSM BSS Statistics Analysis Handbook
- 13. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 13 No Handover (2)
- 14. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 14 Delay Handover (1) Description: – Neighbor BSIC is decoded but handover occurs in much later time Reason: – All possible neighbors suffer blocking – Large hreqt * hreqave – qual_power_flag is enabled, full BTS/MS power must be reached before handover – Large handover_recognized_period and bssmap_t7 setting – Refer to GSM BSS Statistics Analysis Handbook
- 15. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 15 Delay Handover (2)
- 16. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 16 Ping Pong Handover (1) Description: – Lot of handovers between cells – “Time between Handover” is around hreqt*hreqave of such HO cause Reason: – Improper hardware calibration – Hardware fault – UL/DL interference – Negative handover – Different coverage footprint for antennas of a cell
- 17. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 17 Ping Pong Handover (2)
- 18. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 18 Negative Handover (1) Description: – Serving cell hands over to a weaker neighbor Reason: – ho_only_max_power is enabled – qual_margin_flag is disabled – ho_margin_usage_flag is enabled with negative ho_margin_rxqual/rxlev – Negative HO_MARGIN – Micro-cellular algorithms are enabled, especially type 5
- 19. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 19 Negative Handover (2) -59dBm before HO -66dBm after HO
- 20. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 20 OverShooting (1) Description: – Cell shoots at far distance but that location has closer cells around Reason: – Overshooting cell has small downtilt, 0 degree! – Overshooting cell has too high altitude – Closer cells have overshooting as well – BSIC of closer cells can’t be decoded
- 21. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 21 OverShooting (2)
- 22. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 22 High Overlapping (1) Description: – Cells have major rxlevel difference within 5dB Reason: – Overshooting – Too many cells in that area – Poor antenna downtilt
- 23. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 23 High Overlapping (2) Over Lapping Area -65dBm -65dBm -65dBm -65dBm
- 24. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 24 No Dominant Server (1) Description: – Rxlevel of best neighbors are close to that of serving cell Reason: – Poor antenna downtilt – Lack of near-by site
- 25. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 25 No Dominant Server (2)
- 26. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 26 Poor Coverage (1) Description: – Low rxlevel with rxquality – In rural area, rxlevel is less than 15 (-95dBm) – In city center, rxlevel is less than 35 (-85dBm) – Different location has different threshold, noise level is the key point Reason: – Lack of cell site – BSIC of dominant server can’t be decoded – Dominant server has blocking or cell-bar – Handover problem. E.g. missing & incorrect neighbor, negative handover, no & delay handover
- 27. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 27 Poor Coverage (2)
- 28. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 28 Unreasonable Serving Area (1) Description: – Coverage area of the cell is incoherent to the antenna direction Reason: – Wrong cable connection to antennas – Incorrect record of antenna orientation – Incorrect ANTENNA_SELECT
- 29. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 29 Unreasonable Serving Area (2) Cell ID:101 BCCH: 35 Cell ID:102 BCCH: 40 Cell ID:103 BCCH: 45
- 30. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 30 Interference (1) Description: – High rxlevel with rxquality Reason: – Channel interference – Not using dominant server – No handover – Turn the corner with delay handover
- 31. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 31 Interference (2)
- 32. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 32 Handover Failure (1) Description: – MS fails to reach target cell, so return to source cell – MS sends HO FAILURE and UL-SABM to source cell and there is response Reason: – Channel interference – Poor coverage – External interference at UL, like wideband repeator – Refer to GSM BSS Statistics Analysis Handbook
- 33. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 33 Handover Failure (2)
- 34. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 34 Handover Loss (1) Description: – MS fails to reach target cell, but can’t return to source cell – MS sends HO FAILURE and UL-SABM to source cell but no response Reason: – Channel interference – Poor coverage – External interference at UL, like wideband repeator – Refer to GSM BSS Statistics Analysis Handbook
- 35. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 35 Handover Loss (2)
- 36. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 36 Description: – BSS doesn’t receive UL SACCH for link_fail times – BSS stops transmitting DL power Reason: – External interference – Channel interference – Faulty ancillary. UL path loss >>> DL path loss – Refer to GSM BSS Statistics Analysis Handbook UL Drop (1)
- 37. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 37 UL Drop (2)
- 38. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 38 Drop Call (1) Description: – DL case: Radio_link_timeout counter decreases to 0 – UL case: link_fail counter decreases to 0 – Layer 2: BSS/MS send SABM/DISC in every T200 for N200+1 times, and no response from recipient Reason: – All cases in this presentation – Refer to GSM BSS Statistics Analysis Handbook
- 39. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 39 Drop Call (2)
- 40. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 40 Sudden Power Drop (1) Description: – Dedicated ARFCN has significant non-power control rxlevel difference from rxlevel of BCCH Reason: – No/improper TX power calibration – Faulty ancillary. E.g. combiner, filter.. – Different cable lengths from BTS to antennas – Due to air combing, so antennas have different coverage footprints
- 41. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 41 Sudden Power Drop (2)
- 42. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 42 Description: – MS rapidly increases its TX power due to • Optimised Power Control or • UL SACCH multiframes aren’t received for link_fail - link_about_to_fail times Reason: – Sudden UL interference, e.g. wideband repeator, channel interference – Too much rapid power down – l_rxlev_ul_p is too small MS Power Rapid Increase (1)
- 43. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 43 MS Power Rapid Increase (2) UL power rapid increase from 19 to 5 suddenly
- 44. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 44 How GEP Help? Help to identify below problem in VISUAL basis • Co-channel interference • Adjacent-Channel interference • Mutual neighbor • Missing neighbor • Unreasonable neighbor • Incorrect external neighbor
- 45. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 45 How VOT Help? Help to identify below problem in VISUAL basis • Ping pong HO • Overshooting • No dominant server • Poor coverage • Unreasonable serving area • Interference • HO failure • HO loss • Drop call
- 46. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 46 How CM Extractor Help? Extract most BSS parameter for reference • Cell – e.g. hreqave,hreqt,N,P… • BTS – e.g. antenna_select… • RTF – check any incorrect external neighbor • Neighbor – e.g. ho_margin, delay_timer…
- 47. System Optimisation Group China GSM Core Engineering 02/01/12 Motorola Internal Use Only 47 How NPM Help? • Provide cell statistics for VOT display • Provide BSS and system level 23 key statistics • Provide detail troubleshooting statistics