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Which layer in eNB varifies Short-MACI sended by UE in Re-establishment message?

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What is content of Short-MACI and how it verified by Receiver? please explain?

posted Oct 14, 2016 by Suchakravarthi Sripathi

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2 Answers

+1 vote

Hi,

It is a 16 bit integer which is calculated based on the source cell security algorithm. It is used to verify the rrc-reestablishment message. This verification done at RRC layer.

answer Oct 14, 2016 by Jaganathan
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ShortMAC-I is the 16 least significant bits of calculated MAC-I. Usually when a RRC message is exchanged between UE and eNodeB it is integrity & ciphered protected. This protected message is transmitted over DCCH (Dedicated control channel).
In this particular RRC re-establishment, message is sent from UE to eNodeB over CCCH (common control channel). This common control channel is neither integrity protected nor the ciphered.

RRC at eNodeB receives un-protected and un-ciphered RRC Re-establishment Request message. After receiving this message, eNodeB first gets UE context from the received "Re-establish UE Identity" and then does verification of short-MAC-I.

MAC-I is calculated by using the stored Key RRCint, VarShortMAC-I message. In formula it can be written like
MAC- I = f(key, varShortMAC-I, count, bearer, direction). Here varShortMAC-I is prepared by using (current cellId, pci of source cell and C-RNTI of old cell). Other parameters like count, bearer and direction set to all 1.

answer Oct 15, 2016 by Rupam
Hi Rupam,

can you please provide me some specification reference to verify ShortMAC-I in eNodeB???
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