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LTE: How does eNodeB identify for which UE rrc re-establishment request message is received ?

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LTE: How does eNodeB identify for which UE rrc re-establishment request message is received ?
posted Sep 3, 2016 by Vikram Singh

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1 Answer

+2 votes

Hi Vikram,
eNodeB can know each UE based (after first RRC Connection made in network) on ue-Identity.

More info about RRC Connection Reestablishment for more clarification:------
RRC Connection Reestablishment Request Message

Direction: UE => E-UTRAN
Signalling Radio Bearer: SRB0
RLC Mode: TM
Logical Channel: CCCH
Transport Channel: UL-SCH

IEs in RRC CONNECTION REESTABLISHMENT REQUEST message are given below:

ue-Identity: UE identity is included to retrieve UE context and to facilitate contention resolution by lower layers. The UE Identity shall be set as follows:
Set the C-RNTI to the C-RNTI used in the source PCell (In case of handover and mobility from E-UTRA failure) or used in the PCell in which the trigger for the re-establishment occurred (other cases);
Set the physCellId to the physical cell identity of the source PCell (handover and mobility from E-UTRA failure) or of the PCell in which the trigger for the re-establishment occurred (other cases);
Set the shortMAC-I to the 16 least significant bits of the calculated MAC-I
reestablishmentCause: This IE indicates the failure cause that triggered the re-establishment procedure and shall be set as follows:
If the re-establishment procedure was initiated due to reconfiguration failure (the UE is unable to comply with the reconfiguration sent in RRC CONNECTION RECONFIGURATION), then set the reestablishmentCause to the value 'reconfigurationFailure';
If the re-establishment procedure was initiated due to handover failure (intra-LTE handover failure or inter-RAT mobility from EUTRA failure) then, set the reestablishmentCause to the value 'handoverFailure'
Set the reestablishmentCause to the value 'otherFailure' if the re-establishment procedure was triggered due other causes than indicated in cases 1 and 2

answer Sep 3, 2016 by Sivakumar.d
Similar Questions
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 ?

+1 vote

Usually, I always saw when UE sends "S-TMSI" in RRC connection Request message then it definitely sends "Registered MME Information " in RRC Connection Setup Complete message.

I am looking for a scenario on which UE sends "Random number" in RRC Connection Request message and "Registered MME Information" in RRC Connection Setup Complete message.

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