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Abnormal CS MT call during LTE testHUAWEI TECHNOLOGIES CO., LTD.Huawei confidentialAbnormal CS MT pushed UE drop to 3G frequently

UE was frequently pushed to 3G by CS MT call during idle mode GUL reselection test in Cluster 1.There were totally 9 CS MT calls cause UE drop to 3G which cause the test result couldnt reflect the real situation.

Page #Page #Huawei ConfidentialAbnormal CS MT during drive test

But all these 9 MT calls looked not like real calls:All of them are Aborted by CN 4 seconds after the Security Mode Complete. This kind of Abort cause MT CSFB call fail due to not reach the alerting procedure.Since UE didnt received the Setup message, so we couldnt see the MO number.From Drive Test team feedback, it is happening in all clusters randomly.And since the call didnt succeed in 3G, so fast return didnt trigger to push UE back to LTE in time but only wait background 3G data release then reselect to LTE. Thus user may complain why I drop to 3G even in LTE good coverage areaAbout 4S after security procedure, UE received Abort from CN to cancel the procedure.Page #Page #Huawei ConfidentialMT case in Senayan City Space walk test for the event

Page #Page #Huawei ConfidentialMT case in Senayan City Space walk test for the event

CS paging and the Abort message are from CS core (MSC).Need MSC help to do joint trace to locate this issue to explore: What trigger these MT call to the test number. Why CN always send abort message to UE to cancel the call before it setup.Page #Page #Huawei ConfidentialThank youwww.huawei.com