发Request-ACK表示会话已经接通,但在时间点15:44:19终端收到网络下发的BYE消息携带的失败原因为承载资源释放。导致一次未接通事件如下图：

(Reason: SIP;cause=503;text=\

继续通过PCAP包信令分析发现在时间点11:44:19, eNB主动进行拆链释放原因为无线链路失败UEContextReleaseRequest 。

Cause: radioNetwork (failure-in-radio-interface-procedure(26))

? 无线空口分析

主叫占用EARFCN:37900、PCI:390小区，终端发起SIP INVITE会话呼叫，服务器响应并回复终端SIP INVITE 100 Trying，网络侧发起QCI=1，EPS承载为7建立的语音业务，无线环境良好CRC-RSRC=-90dbm，CRC-SINR=12，在11:44:22 由于UE上行PUSCH功率较大，上行失步导致主叫掉话。

第 17 页 共 27 页

通过主被叫信令分析，主被叫UE接通后占用崔家大滩西侧微站LTE-1小区（EARFCN:37900、PCI:390）后，无线覆盖较好，但是UE上行的PUSCH TxPower却增大至22，上行失步2s后11:44:21重选至宏润建设集团LTE-8小区 (EARFCN:37900、PCI:7）进行RRC重建请求，重建请求拒绝后，UE收到网络侧下发的BYE Request消息，通过后台网管提取该小区子帧干扰情况，发现崔家大滩西侧微站LTE-1小区2、7子帧有强干扰，由于上行干扰失步导致掉话。 网元友好名:崔家大滩 607018 小区本地ID = 4 小区子帧号 = 1 小区上行底噪测量值

= {0,0,0,4,0,0,0,0,4,5,5,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,13} 小区上行通道总功率测量值(dBm) = {-94,-92,-127,-127,-127,-127,-127,-127,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0} 小区上行无用户通道总功率测量值(dBm)

= {-94,-92,-127,-127,-127,-127,-127,-127,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0} 小区子帧号 = 2 小区上行底噪测量值

= {24,24,24,25,24,23,23,22,20,18,19,21,20,17,19,21,20,20,22,21,20,19,19,21,20,21,21,20,18,19,20,20,19,20,18,21,19,20,21,22,21,20,21,19,21,23,22,21,23,22,22,22,20,20,21,20,19,18,19,19,20,19,20,19,20,20,20,22,20,20,20,19,19,20,21,20,19,20,20,19,22,22,21,21,19,20,20,21,21,19,19,19,21,20,21,21,20,20,20,21} 小区上行通道总功率测量值(dBm)

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= {-55,-53,-116,-116,-116,-116,-116,-116,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0} 小区上行无用户通道总功率测量值(dBm)

= {-81,-81,-116,-116,-116,-116,-116,-116,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0} 小区子帧号 = 6 小区上行底噪测量值

= {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,11,12,12,14,0,0,8,0,0} 小区上行通道总功率测量值(dBm)

= {-83,-85,-127,-127,-127,-127,-127,-127,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0} 小区上行无用户通道总功率测量值(dBm)

= {-79,-82,-127,-127,-127,-127,-127,-127,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0} 小区子帧号 = 7 小区上行底噪测量值

= {21,20,21,22,20,18,19,19,19,18,19,21,20,18,18,20,21,21,22,20,20,19,19,20,20,21,21,20,18,18,19,20,20,20,19,21,19,21,21,22,21,20,21,20,22,23,22,22,23,22,22,21,21,20,19,19,21,18,19,19,20,19,20,19,20,20,20,22,20,20,19,18,19,20,21,20,19,21,19,19,21,21,20,21,20,19,20,20,20,18,18,19,21,21,20,21,19,20,20,20} 小区上行通道总功率测量值(dBm)

= {-55,-53,-116,-116,-116,-116,-116,-116,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0} 小区上行无用户通道总功率测量值(dBm)

= {-54,-51,-116,-116,-116,-116,-116,-116,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 解决方案: D+F都新开站点，未及时修改帧头偏移。 4.3. 传输问题导致SIP-503 S1切换导致VoLTE掉话 问题现象：

兰州拉网测试过程中发现每次联通西固锅炉厂-3（PCI：255）向西固青少年活动中心-2（PCI：247）出现掉话，ENB给UE下发RRC connection Release，原因是Other。查看无线环境，均无质差，具体如下图：

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问题分析： X2切换问题分析：

结合大唐基站告警进行分析，发现西固锅炉厂基站和西固青少年活动中心基站SCTP链路故障，导致无法进行X2切换。

通过故障处理，联通西固锅炉厂和西固青少年活动中心SCTP链路恢复正常，进一步验证，X2切换正常（以下是炎强平台log），现场无掉话现象，问题暂时规避：

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