|
|
|
|
|
|
Below is UE protocol stack. Layer 3 signaling happen over Signaling Radio Bearers (SRB), User data transfer happen over Data Radio Bearers (DRB). In eNode B, Access stratum remain same, NAS signaling goes to S1AP and User data (IP packets) towards GTP-U.
Fig 1.4.2
Three SRBs are defined [36.331:4.2.2], SRB0 (meant for Common Control Signaling e.g. RRCConnectionRequest) and SRB1/SRB2 (Dedicated - UE associated - Layer 3 signaling). SRB1 is meant for RRC signaling (e.g. RRCConnectionReconfiguration) and SRB2 is for NAS signaling (e.g. EMM Security Mode Command thru RRC ULInformationTransfer, ESM Bearer Resource Allocation Request thru RRC DLInformationTransfer).
|
|
|
|
|
|
|
|
|
|
|
