Establishing an RRC connection in LTE typically involves the following steps:
- UE initiates a session to the eNodeB using a random RA-RNTI.
- eNodeB assigns a C-RNTI and sends timing adjustment to the UE.
- UE adjusts the the timing and requests an RRC Connection Setup via the UL-SCH channel.
- The eNodeB sends the RRC Connection Setup to the UE on the DL-SCH channel. This message sets up the SRB. DRB may also be established at this point.
- Finally, the UE acknowledges the message with RRC Connection Complete message.
The messages in the RRC Connection Setup are described in the following presentation.