This document provides an overview of drive test procedures and methods for analyzing issues found during drive tests. It discusses preparation steps, how to perform drive tests, and how to analyze log files. Common problems that can be identified include undecoded BCCH, no handover, ping pong handovers, interference, and dropped calls. Analysis tools like GEP, VOT, CM Extractor, and NPM are described for visualizing problems.

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