WHAT IS RANDOM ACCESS PHASE 3 ?

PHASE 3

In Phase 3 (or first scheduled UL transmission), the UE provides the network with a unique identifier in the message. It transmits on Uplink shared channel (UL-SCH) according to the grant contained in the RA Response. The type of UE identifier, e.g. C-RNTI, TMSI, IMSI or IMEI, depends on which extent the UE is already known in the network.

• In case of initial access, the message is an RRC Connection Request message.
• In case of non-initial access, (i.e. when the UE is already RRC Connected), the UE identifier is the Cell Radio Network Temporary Identifier (C-RNTI) and is signaled by the MAC layer.