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What is the use of S-TMSI for eNodeB ?

+1 vote
What is the use of S-TMSI for eNodeB ?
posted Sep 12, 2013 by Ganesh Kumar

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1 Answer

+1 vote

S-TMSI is sent by UE when It was earlier attached to Core network. It is not necessary that Ue will send S-TMSI in rrcConnectionRequest message. S-TMSI is derived from GUTI {PLMN + MMEGI + MMEC + TMSI). S-TMSI is combination of two parts {MMEC + TMSI}. GUTI is an optional assignment from MME to UE.It's used only to avoid UE identity enquiry messages like (Ue identity request and response) messages. when it is send by Ue in rrcConnectionRequest message. eNodeB fetch MMEC and forward InitialUeMessage to appropriate MME.

answer Sep 12, 2013 by Vimal Kumar Mishra
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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

Why do use IMSI for calculating the Paging Frame(PF) and not S-TMSI?

PF= SFN mod T = (T div N ) * (UE_ID mod N)

Where UE_ID= IMSI mod 1024.

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 ?

+1 vote

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