B.2 Transition from Idle Mode to UTRA RRC Connected Mode

25.3313GPPProtocol specificationRadio Resource Control (RRC)Release 17TS

The transition to the UTRA RRC Connected Mode from the Idle Mode can only be initiated by the UE by transmitting a request for an RRC Connection. The event is triggered either by a paging request from the network or by a request from upper layers in the UE.

When the UE receives a message from the network that confirms the RRC connection establishment, the UE enters the CELL_FACH or CELL_DCH state of UTRA RRC Connected Mode.

In the case of a failure to establish the RRC Connection the UE goes back to Idle Mode. Possible causes are radio link failure, a received reject response from the network or lack of response from the network (timeout).

B.2.1 Transitions for Emergency Calls

Refer to [4] for all states and procedures referred to in this subclause. When UE leaves idle mode from state Camped on any cell in order to make an emergency call, moving to state Connected mode (emergency calls only), the UE shall attempt to access the current serving cell. If the access attempt to the serving cell fails the UE shall use the Cell Reselection procedure. If no acceptable cell is found, the UE shall use the Any cell selection. When returning to idle mode, the UE shall use the procedure Cell selection when leaving connected mode in order to find an acceptable cell to camp on, state Camped on any cell.