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LTE: How does integrity verification is performed by receiving PDCP entity ?

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What are the steps involved to do integrity verification ?

posted Dec 18, 2013 by Harshita

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1 Answer

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PDCP layer performs integrity protection and verification based on the role. I mean when PDCP entity works as a transmitter, it does integrity protection of upper layer SDU coming over SRB1 and SRB2 of an UE. When PDCP transmitting entity receives a packet, it prepares PDCP Control plane data pdu. For the format of PDCP control plane data pdu, please check 36.323 spec. PDCP layer calculates 32 bits long MAC-I from RRC integrity key and values of variables COUNT, BEARER ID and , DIRECTION.

At the receiver side, PDCP layer calculates X-MAC based on input parameters i.e RRC Integrity key, COUNT, BEARER ID and DIRECTION. If the calculated X-MAC corresponds to the received MAC-I, Integrity protection is verified successfully.

answer Dec 18, 2013 by Vimal Kumar Mishra
Thanks for your quick reply. But I have a related question. How PDCP receiver entity knows that for which of the bearer (SRB1 or SRB2) data is received. Since SRB1 and SRB2 both would have different bearer Id and it is one of the necessary parameter to do integrity verification.
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