Layer 3 Uplink 17:52:15.637 FACCH ASSIGNMENT COMPLETE Call Connect Success 17:59:15.637 Frequency Hopping Status 17:59:15.637
Layer 3 Downlink17:59:16.996 CCCHIMMEDIATE ASSIGNMENT Layer 3 Downlink 17:59:17.135 CCCHIMMEDIATE ASSIGNMENT Layer 2 Uplink 17:59:17.348 RACHRANDOM_ACCESS_BURST Layer 3 Uplink 17:59:17.348 RACHCHANNEL REQUEST Layer 3 Downlink 17:59:17.469 CCCHIMMEDIATE ASSIGNMENT Layer 3 Downlink 17:59:17.967 SDCCH AUTHENTICATION REQUEST
Layer 3 Uplink 17:59:18.706 SDCCHAUTHENTICATION RESPONSE Layer 3 Downlink 17:59:18.909 SDCCH SETUP
Incoming Call 17:59:18.909
Layer 3 Uplink 17:59:19.177 SDCCH CALL CONFIRMED Layer 3 Downlink 17:59:19.613 SDCCH ASSIGNMENT COMMAND
Layer 3 Uplink 17:59:19.836 FACCH ASSIGNMENT COMPLETE Call Connect Success 17:59:19.836
Layer 3 Uplink 17:59:19.954 FACCH ALERTING Layer 3 Downlink 17:59:20.002 FACCH PROGRESS Layer 3 Downlink 17:59:20.120 FACCH ALERTING Call Connect Success 17:59:20.120
Layer 3 Uplink 17:59:20.144 FACCH CONNECT Layer 3 Downlink 17:59:20.238 FACCH CONNECT ACKNOWLEDGE Call Connect Success 17:59:20.238
Layer 3 Downlink 17:59:20.250 FACCH CONNECT
Layer 3 Uplink 17:59:20.274 FACCH CONNECT ACKNOWLEDGE Call Connect Success 17:59:20.274
至此,进入通话状态…………… Carrier Interference18:00:30.640 Cellular System: GSM 900 Channel C/I: 3.3
Timeslot C/I: 此时刻,无线链路开始出现恶化C/I=3.3 RX Quality 18:00:00.673 Quality Full: 6
Quality Sub: 7 Quality Sub=7质量恶化 RX Level 18:00:31.133 -87dB 开始恶化 Radio Link Timeout 18:00:31 Radio Link Timeout: 63 RLT开始计数
Frame. Error Rate 18:00:31.133 FER Full: 96 % FER Sub: 100 %
FER TCH: 100 % FER=100%
被叫释放过程 Layer 3 Downlink 18:00:31.812 FACCH RELEASE Call Disconnect 18:00:31.812
Layer 3 Downlink 18:00:33.796 SDCCH CHANNEL RELEASE Layer 2 Uplink 18:00:34.064 SDCCH DISC-CMD
从18:00:31开始到18:01:01,经过64个SACCH,RLT=0,无线链路超时掉话.
原因: 车辆自南向北行驶,服务小区4492在18:00:16秒开始信号减弱,本应正常切换到4491,但BSC迟迟没有下发HO_COMMAND,导致在18:00:31 C/I=3.3手机从此开始无法解码下行信息,与网络失去联系. 方案: 调整 4492 到 4491 和 362 的切换门限 加快切换,避免由于信号衰减导致的C/I变低,与网络失去联系并掉话 效果:已经解决
Call Disconnect 18:01:01.638
TOM解释 Status: Dropped call (i.e., network release) 主叫并未上发Disconnect,这是正常挂断与掉话得最根本的区别
§3.6切换失败信令流程
Handover failure, reconnection to the old traffic channel
1 Layer 3 Downlink 18:37:54.320 FACCH HANDOVER COMMAND 2 Handover Attempt 18:37:54.320 Type: Handover between cells Current Cellular System: GSM 900 Current Channel Number: 86（1672） Current Time Slot: 1
Attempted Cellular System: GSM 900
Attempted Channel Number: 68 （9791室内覆盖） Attempted Time Slot: 1
3 Layer 3 Downlink 18:37:54.533 FACCH PHYSICAL INFORMATION 4 Layer 3 Downlink 18:37:54.634 FACCH PHYSICAL INFORMATION 不断下发物理消息。。。。
5 Layer 3 Uplink 18:37:55.664 FACCH HANDOVER FAILURE 6 Handover Fail 18:37:55.664
原因解释：车行至室内覆盖泄漏区，出现瞬间强信号，手机发起切换，但是当系统下发物理消息时，手机已走出室内覆盖区，手机不能正常收到物理信息，造成切换失败。