This procedure is used to establish an RRC connection to the network.
After this procedure SRB1 will be established.
This procedure is also used to transfer initial NAS dedicated information message from UE to Network.
Initiation
UE will initiate this procedure, when upper layers request for establishment of RRC Connection when UE in RRC_IDLE mode.
Actions related to transmission of RRCSetupRequest message
UE will set the contents of RRCSETUPRequest as below:
1. If upper layer has provided ue-Identity in 5G-S-TMSI, then set the ue-Identity to ng-5G-S-TMSI-Part1
2. else create a 39-bit random value in the range 0..239-1 and set the ue-Identity to this value;
3. set the establishmentCause in accordance with the information received from upper layers;
Reception of the RRCSetup by the UE
UE will perform below action upon reception of the RRCSetup:
if the RRCSetup is received in response to an RRCReestablishmentRequest; or RRCResumeRequest or RRCResumeRequest1,
-> then discard any stored UE Inactive AS context and suspendConfig;
-> discard any current AS security context including the KRRCenc key, the KRRCint key, the KUPint key and the KUPenc key;
-> release radio resources for all established RBs except SRB0, including release of the RLC entities, of the associated PDCP entities and of SDAP;
-> release the RRC configuration except for the default L1 parameter values, default MAC Cell Group configuration and CCCH configuration;
if the RRCSetup is received in response to an RRCResumeRequest, RRCResumeRequest1 or RRCSetupRequest:
-> enter RRC_CONNECTED;
-> stop the cell re-selection procedure;
-> consider the current cell to be the PCell;
-> set the content of RRCSetupComplete message as follows:
-> if upper layers provide a 5G-S-TMSI:
-> if the RRCSetup is received in response to an RRCSetupRequest:
-> set the ng-5G-S-TMSI-Value to ng-5G-S-TMSI-Part2;
-> else:
-> set the ng-5G-S-TMSI-Value to ng-5G-S-TMSI;
Source TS 38.331