Is C_RNTI is mandatory in mobility control info

Question

Why we need c_rnti in mobility control info, because UE will get the CRNTI in target ENB RAR right ???

Answer 1

As per 3gop 36.331 c-rnti in mobility control info is mandatory. This could be because rach during HO can be contention based. So ue needs to tell c-rnti to eNb in msg3 to identify the ue context at eNb.

Comments

thank you for your answer, now i understood why it is included in mobility control info.  But why it is included in bot the case like contention based and contention free case.

Answer 2

In handover case, UE context is already created at target eNodeB, that's why Target cell sends the allocated C-RNTI to source and source cell in turn sends to UE in mobility control info IE.

When UE does RAR with the assigned preamble target eNodeB MAC maps the UE context and since all the contexts have already been created at target eNodeB handover becomes faster.
This is my understanding and interpretation of sending target eNodeB's C-RNTI in mobility control info.