Security Level: Call Re-estab Clarification Huawei RF Team www.huawei.com HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Call Re-estab Algorithm 1. When some call drop conditions are satisfied, RNC will send “RADIO LINK ACTIVATION COMMAND ” with IE “deactivate” to NodeB instead of sending “Iu Release Req” to CN. 3. So UE detects radio link is “out of sync”. And it will a. Try to re-select to a suitable cell; b. Send Cell Update to RNC indicates Radio Link failure on the suitable cell. Calldrop condtion is satisfied Iu Release Req RADIO LINK ACTIVATION COMMAND Shutdown the UE DL transmit power N313 T313 T313 Cell Update(RL Failure) T314+T302*N3 02 4. RNC will re-established the radio link with cell update confirmed. HUAWEI TECHNOLOGIES CO., LTD. CELL_B Huawei Confidential RL Setup Req RL Setup Rsp Xs+T302*N302 RL Del Req RL Del Rsp Cell Update Confirm Physical CH Reconfig CMP Page 2 Additional service mute time 2. Then NodeB will shut down UE’s DL transmit power. CELL_A Call Re-estab Success scenarios Faculative congestion (result to handover fail) Handover is not timely Highway High Speed Railway Shopping Malls Pass poor coverage region Tunnel Elevator Building keep the signal out HUAWEI TECHNOLOGIES CO., LTD. Indoor Corner Huawei Confidential Re-estab effect for user 1 Service Normal 2 3 Mute Mute RNC trigger call Re-estab RAN UE UE continual research suitable cell Call Re-estab active User 4 5 Normal UE trigger re-estab immediately Move and Wait Local or Peer can’t bear mute and released the call. Service Normal RAN UE Normal Mute RNC release call Call Re-estab don’t active User HUAWEI TECHNOLOGIES CO., LTD. UE continual research suitable cell Move and Repeat call(Every attempt is failed) Huawei Confidential User’s call attempt is successful. User’s tolerance time for mute Content is important and be willing to wait for suitable cell Hypersensitive for mute We have analysis many re-estab samples in live network and find 1. a. b. 2. Mute 5s Normal 8s Normal 11s Normal 14s Normal Normal UE find a suitable cell and complete call re-estab. Service interregnum time distributing after re-estab 21.6% 30% 34.8% RNC trigger call Re-estab Service More than 50% Re-estab is complete within 5s. About 90% Re-estab is complete within 8s. Notes: The data may be different between different areas. 2s Normal More than 55% user can put up with more than 5s More than 40% user can put up with more than 8s ~55% user can benefit from re-estab and continue service a. b. Content is not important or call will end Service UE ~45% user can’t tolerate mute and voluntary release call. Normal 9.2% 2.4% 2% Time Mute Mute UE UE continual search suitable cell. User tolerance time distributing Local or peer release the call during the procedure of re-estab. 26.9% 9.7% HUAWEI TECHNOLOGIES CO., LTD. 8.0% 14.2% Huawei Confidential 9.1% 1.9% Page 5 30.1% Normal Re-estab time Call Retrieve Procedure Delay Once a suitable cell appeared, UE trigger re-estab immediately. ~400ms User’s call attempt isn’t successful until a suitable cell has appeared. ~4s HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 6 Call Re-estab Solution Positive impact: 1. Call Re-estab can decrease the opportunity of call drop and increase KPI. 2. Call Re-estab can retrieve call quickly and improve user experience when user want to continue call. The following counter show the benefit. 备注:目前我们的Counter无法评估有多少用户从链路重建中获取了好处:VS.SuccRlReEst.CS, VS.RAB.Rel.CS.CNInit.AfterReEst不能直接减 Negative impact: Call Re-estab introduce more mute, and the additional mute time can be evaluated by the following counters in RAN18.1. VS.RLReEst.TotalTime.CS: Call Re-estab additional mute time VS.RLReEstTime.0.CS: The number of Call Re-estab which additional mute time is between 0s and 2s VS.RLReEstTime.1.CS: The number of Call Re-estab which additional mute time is between 2s and 5s VS.RLReEstTime.2.CS: The number of Call Re-estab which additional mute time is between 5s and 8s VS.RLReEstTime.3.CS: The number of Call Re-estab which additional mute time is between 8s and 11s VS.RLReEstTime.4.CS: The number of Call Re-estab which additional mute time is between 11s and 14s VS.RLReEstTime.5.CS: The number of Call Re-estab which additional mute time is more than14s 备注:这套指标只包含了链路重建成功时的统计(对应P5中的业务中断时延),没有包含P5中下面客户容忍时间的统计,也即链路重 建流程超时(从重建到流程超时额外引入的静音时间固定),链路重建过程中对端释放(从重建到对端释放额外引入静音时间不固 定),链路重建成功后不久本端或对端释放(从重建到成功后立刻释放额外引入的静音时间不固定)。有了这些指标就有了类似P5 结果,就可以给出优化建议(小区级或RNC级)。 HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential Page 7 Thank you www.huawei.com