The purpose of this procedure is to, under the control of the network, transfer a connection between the UE and another Radio Access Network (e.g. E-UTRAN) to NR.
The handover to NR procedure applies when SRBs, possibly in combination with DRBs, are established in another RAT. Handover from E-UTRA to NR applies only after integrity has been activated in E-UTRA.
The RAN using another RAT initiates the handover to NR procedure, in accordance with the specifications applicable for the other RAT, by sending the RRCReconfiguration message via the radio access technology from which the inter-RAT handover is performed.
The network applies the procedure as follows:
to activate ciphering, possibly using NULL algorithm, if not yet activated in the other RAT;
The network initiates the mobility from NR procedure to a UE in RRC_CONNECTED, possibly in response to a MeasurementReport or an MCGFailureInformation message, by sending a MobilityFromNRCommand message. The network applies the procedure as follows:
the procedure is initiated only when AS security has been activated, and SRB2 with at least one DRB or multicast MRB are setup and not suspended;
the procedure is not initiated if any DAPS bearer is configured;
if there is a protocol error in the inter RAT information included in the MobilityFromNRCommand message, causing the UE to fail the procedure according to the specifications applicable for the target RAT: