Security Level:
Call Re-estab Clarification
Huawei RF Team
www.huawei.com
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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.
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CELL_B
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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
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Indoor
Corner
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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
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UE continual research suitable cell
Move and Repeat call(Every attempt is failed)
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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%
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8.0%
14.2%
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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
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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）。
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Thank you
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