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LTE: Why presence of Tracking Area Identity (TAI) and E-UTRAN CGI (ECGI) IEs is mandatory in Uplink NAS Transport ?

+5 votes
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Uplink NAS transport message is used between eNodeB and MME to pass NAS messages between UE and MME transparently.
Since eNodeB has already communicated TAI and E-CGI as part of "Initial UE message" and MME knows current serving (cell and tai ) of UE then why both IEs are mandatory in Uplink NAS transport. I think it should be optional and it should be included in the message when there is a change in serving (cell or tai or both).

posted May 16, 2018 by Vimal Kumar Mishra

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