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When S-TMSI or IMSI included in paging UE identity within paging message?

+2 votes
When S-TMSI or IMSI included in paging UE identity within paging message?
posted Dec 12, 2014 by Gnanendra Reddy

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2 Answers

+1 vote

I was just thinking the scenario and sharing thoughts. Once the UE gets handed over from source enodeb to target enodeb with MME relocation, target MME shall send paging message to UE with IMSI since S-TMSI was allocated by source MME and will be invalid at target MME. S-TMSI is a combination or MMEC+ M-TMSI, reason being, I am thinking this may the scenario when MME sends paging message to UE with IMSI.

It is just my thought, there may be other scenarios as well in which MME prefer IMSI in paging message. Looking for others to respond.

answer Dec 12, 2014 by Vikram Singh
thank you vikram
+1 vote

In normal scenario S-TMSI is used to page the UE?

when valid S-TMSI is not available due to a network failure then UE can be paged using IMSI.

answer Dec 13, 2014 by Veer Pal Singh Yadav
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+2 votes

It may be an easy question but still I have some doubt.
How RRC Connection setup procedure gets impacted with the presence of "S-TMSI" as an UE-Identity within the RRC Connection Request message ?
Note: RRC Connection request message can carry either 5 bytes long (S-TMSI) or 5 bytes long random value.

0 votes

RRC Connection Request message carries "Initial UE identity" which is just 5 bytes long identifier. Why does so many information elements send within the "Re-establish UE-Identity" like C-RNTI, physcellId etc ?

+3 votes

PagingUE-Identity ::= CHOICE {
imsi IMSI,

As pagingUE identity should contain any one of these in paging message so how MME decides which one to send, though for security purpose MME prefers t-o send send S-TMSI but in which scenarion MME wil use imsi as paging ue identity.

+1 vote

When UE sends GUTI/STMSI to MME and what all massages are involved?

0 votes

ue send s-tmsi in place of ue id in rrc con req, will s-TMSI remain same in case of HO also ?

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