weather it is RRCConnection request or direct NAS message as ULInfotransfer?
TAU request is a NAS message and it will be piggybacked in RRC connection setup complete message just like other NAS messages are piggybacked in RRC connection setup complete. Once SRB2 is established, NAS message through SRB2 if NAS message is independent from RRC signalling. MSG3 will be RRC connection Request message.
TAU request can be periodic or event based. This will first require MME to page all eNBs serving the tracking area and the UE which is paged shall trigger a service request requiring establishment of rrcConnection again which implies it should be rrcConnectionRequest as MSG3 after successful RACH procedure.
Handover RACH will be initiated as Contention free, RNTI will be included in Mobility info. But while doing RACH What will be the RNTI value included in RAR? Will this be same as Mobility RNTI?
If no SR is configured at UE side, then IF UE triggeres RACH then what will be the MSG3 content? How ENB knows UE is triggering an RACH for UL grant?
If HO fails the UE will initiate contention based reestablishment and connect to some ENB, But target ENB have provided the contention free Rach preamble , at failure case how long ENB will hold this preamble because it has to release for other UE?
