LTE attach and default bearer setup flow

LTE Attach and Default Bearer Setup

This call flow describes the signaling involved in LTE attach and default bearer setup. The sequence diagram covers the following phases:

1. Random Access Procedure: The UE uses a slotted aloha procedure to access the eNodeB. The UE sends a preamble on a random access channel, the network replies with corrected timing and resource assignments.
2. RRC Connection Establishment: The UE and the eNodeB then interact to establish a Signaling Radio Bearer (SRB). The SRB will be used for the signaling between the eNodeB and the UE.
3. Attach and Authentication: The UE now registers with the Core Network. Session contexts are set up at the MME and the Serving Gateway. This step also results in the authentication of the UE and the Network.
4. Default Radio Bearer Setup: Finally, the default bearer for data transfer is established. Default bearer session is established at the UE, eNodeB, MME, Serving GW and PDN Gateway. User data is exchanged once the default bearer is set up.

The sequence diagram also contains links to access further details about the messages. Click on the messages with blue titles for details about the message.

RRC Connection, LTE Attach and Default Radio Bearer Setup