Security Level:
2008-7-18
Call Drop Analysis Trainning Document www.huawei.com
HUAWEI TECHNOLOGIES CO., LTD.
Huawei Confidential
Content
What is call drop? The types of call drop Basic call drop reasons Call drop issues during DT Call drop cases
HUAWEI TECHNOLOGIES CO., LTD.
Huawei Confidential
Page 2
What is Call Drop? The abnormal channel released during call due to the reasons such as: 1. Blind/poor coverage area; 2. Bad quality; 3. Irrationality parameters configuration; . . . n. Hardware problems.
HUAWEI TECHNOLOGIES CO., LTD.
Huawei Confidential
Page 3
What is Call Drop? I can not allocate channel for you!!!
Hello……? Hello……? Hello……? Why call drop again?
HUAWEI TECHNOLOGIES CO., LTD.
Huawei Confidential
Page 4
The types of call drop TCH call drop The abnormal TCH channel released after TCH channel has been allocated to MS SDCCH call drop The abnormal SDCCH channel released after SDCCH channel has been allocated to MS
HUAWEI TECHNOLOGIES CO., LTD.
Huawei Confidential
Page 5
Basic call drop reasons Radio Link Time out T3103 Time out System problems (hardware)
HUAWEI TECHNOLOGIES CO., LTD.
Huawei Confidential
Page 6
Radio Link Time out MS MS
BTS BTS
BSC BSC
MSC MSC
(1) Measurement report (2) Measurement result
Connection failure (3) Clear REQ (radio interface failure)
(1)
Dedicated Channel Mode Set Up
(2)
Abis Monitor Activation
(3)
Can not Decode SACCH, and Then Radio Link Time out.
HUAWEI TECHNOLOGIES CO., LTD.
Huawei Confidential
Page 7
T3103 Time out MS MS
BTS1 BTS1
BTS2 BTS2 Handover
BSC BSC
MSC MSC
Indication Ch_Act Ch_Ack
Handover command Handover
Handover Access
Physical info(TA) SABM UA Handover
Set T3103
command HO_DETECT EST Indication
Complete
HUAWEI TECHNOLOGIES CO., LTD.
Reset T3103
HO_Complete
Huawei Confidential
Page 8
System problems (hardware) DDRU board is not on working; High VSWR(>1.2); The feeder connector is loose;
HUAWEI TECHNOLOGIES CO., LTD.
Huawei Confidential
Page 9
Call drop issues during DT Coverage; Interference; Handover; Antenna & feeder system; Others;
HUAWEI TECHNOLOGIES CO., LTD.
Huawei Confidential
Page 10
Coverage issues & reason Discontinuous coverage area; Reason: very lower RexLev, especially due to single site Overshooting; Reason: call drop after handover delay Uplink & downlink is imbalance; Reason: MS can not transmit & receipt signal, the call drop will happen when BTS can not allocated channel
HUAWEI TECHNOLOGIES CO., LTD.
Huawei Confidential
Page 11
Coverage issues DT
HUAWEI TECHNOLOGIES CO., LTD.
Huawei Confidential
Page 12
Coverage issues DT
HUAWEI TECHNOLOGIES CO., LTD.
Huawei Confidential
Page 13
Coverage issues
HUAWEI TECHNOLOGIES CO., LTD.
Huawei Confidential
Page 14
DT analysis suggestions Enhance TOP or increase antenna height or decrease down tilt, otherwise add new sites for discontinuous coverage area; Check the neighbour cells and their antenna parameters or TOP for overshooting area; Make the Balance of uplink and downlink (need OMC data);
HUAWEI TECHNOLOGIES CO., LTD.
Huawei Confidential
Page 15
Interference issues Co-channel & adjacent channel interference; Reason: frequency planning problems Repeater interference; Reason: another type of co-channel & adjacent channel interference that due to the repeater nearby; Exterior interference; Reason: there are exist some ARFCNs that used by other operators or other communication devices
HUAWEI TECHNOLOGIES CO., LTD.
Huawei Confidential
Page 16
Interference issues DT
HUAWEI TECHNOLOGIES CO., LTD.
Huawei Confidential
Page 17
Interference issues 114
116 Interference
112
118
124 110
102
102
Interference
110 123
116 Broad band Repeater
113 Interference
HUAWEI TECHNOLOGIES CO., LTD.
Huawei Confidential
Page 18
DT analysis suggestions Check the frequency planning of neighbour around service cell, modify it if any Co-channel & adjacent channel; Otherwise, find any broad band repeater near by; Check the interference come from other communication devices (should inform operator if any);
HUAWEI TECHNOLOGIES CO., LTD.
Huawei Confidential
Page 19
Handover Abnormal handover parameters configuration; Reason: lower rexlev set for handover & irrationality margin for handover Missing neighbour; Reason: MS can not find the proper neighbour cell for handover Co-BCCH & Co-BISC (50% HOSR); Congestion (Deficiency Channel for allocating); BTS clock asynchronization (MS can not decode signal);
HUAWEI TECHNOLOGIES CO., LTD.
Huawei Confidential
Page 20
DT analysis suggestions Optimization handover parameters; Add missing neighbour; Change the BSIC; Increase AMR ratio if possible or expansion capacity; Calibrate BTS clock (BSS hardware problem).
HUAWEI TECHNOLOGIES CO., LTD.
Huawei Confidential
Page 21
Antenna & feeder system Antenna issue Reason: Cross cable connection for Co-site neighbour cells; Antenna Tilt issue; Reason: Antenna Tilt issue is not identical (monopole) Antenna azimuth issues; Reason: Antenna azimuth issues is not identical (monopole) Installation issues for Antenna & feeder system Reason: loose connector for feeder & jumper or higher VSWR
HUAWEI TECHNOLOGIES CO., LTD.
Huawei Confidential
Page 22
DT analysis suggestions Solve cross cable connection issues; Adjust identical tilt for monopoles for same cell; Adjust identical azimuth for monopoles for same cell; Fasten the feeder & jumper connectors and decreasing the VSWR by using proper activities.
HUAWEI TECHNOLOGIES CO., LTD.
Huawei Confidential
Page 23
Others The software version issue Reason: The software version issue of BTS is not updated; BTS hardware issues; Reason: some BTS hardware alarms (BSS)
HUAWEI TECHNOLOGIES CO., LTD.
Huawei Confidential
Page 24
DT analysis suggestions Updated the BTS software version; Inform BSS engineers to check the hardware issues and solve them.
HUAWEI TECHNOLOGIES CO., LTD.
Huawei Confidential
Page 25
Thank you www.huawei.com
