20.2.1 X2-CP Functions

36.3003GPPEvolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN)Overall descriptionRelease 17Stage 2TS

The X2AP protocol supports the following functions:

– Intra LTE-Access-System Mobility Support for UE in ECM-CONNECTED:

– Context transfer from source eNB to target eNB;

– Control of user plane tunnels between source eNB and target eNB;

– Handover cancellation.

– Support of DC for UE in ECM-CONNECTED:

– Establishment, Modification and Release of a UE context at the SeNB;

– Control of user plane tunnels between MeNB and SeNB for a specific UE for split bearer and data forwarding;

– Provision of the TNL information of the S1 user plane tunnels for SCG bearers.

– Support of EN-DC for UE in ECM-CONNECTED:

– Establishment, Modification and Release of a UE context at the SgNB;

– Control of user plane tunnels between MeNB and SgNB for a specific UE for split bearer, SCG split bearer and data forwarding;

– Provision of the TNL information of the S1 user plane tunnels for SCG bearers and SCG split bearers.

– Support of inter-eNB UE Context Resume:

– Retrieval of UE context for a UE which attempts to resume its RRC connection in an eNB different from where the RRC connection was suspended.

– Load Management;

– General X2 management and error handling functions:

– Error indication;

– Setting up the X2;

– Resetting the X2;

– Updating the X2 configuration data;

– X2 Release;

– X2AP Message Transfer;

– Registration;

– X2 Removal.

– Mobility failure event notification and information exchange in support of handover settings negotiation;

– Energy Saving. This function allows decreasing energy consumption by enabling indication of cell activation/deactivation.

– Support of cell resource coordination between eNB and en-gNB.

– Support of UE Radio Capability ID Mapping between eNB and en-gNB.