[信息与通信]tems基础知识.ppt

August 11, 2000
Jim Luan, Lin Mubao
Drive Test Log analysis
2022/6/1
1
Drive Test Procedure
Drive Test
Netpladecoded 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
2022/6/1
12
No Handover <2>
2022/6/1
13
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
2022/6/1
14
Delay Handover <2>
2022/6/1
15
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
2022/6/1
16
Ping Pong Handover <2>
2022/6/1
17
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
2022/6/1
18
Negative Handover <2>
-59dBm before HO
-66dBm after HO
2022/6/1
19
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