For a UE in RRC_CONNECTED, the BWPs configured by a serving cell may overlap in the frequency domain with the BWPs configured for other UEs by other cells within a carrier. Multiple SSBs may also be transmitted within the frequency span of a carrier used by the serving cell. However, from the UE perspective, each serving cell is associated to at most a single SSB. Figure B.2-1 below describes a scenario with multiple SSBs in a carrier, identifying two different cells (NCGI = 5, associated to SSB1, and NCGI = 6, associated to SSB3) with overlapping BWPs, and where RRM measurements can be configured to be performed by the UE on each of the available SSBs, i.e. SSB1, SSB2, SSB3 and SSB4.
The I-RNTI provides the new NG-RAN node a reference to the UE context in the old NG-RAN node. How the new NG-RAN node is able to resolve the old NG-RAN ID from the I-RNTI is a matter of proper configuration in the old and new NG-RAN node.
Table C-1 below provides some typical partitioning of a 40bit I-RNTI, assuming the following content:
UE specific reference: reference to the UE context within a logical NG-RAN node;
NG-RAN node address index: information to identify the NG-RAN node that has allocated the UE specific part;
PLMN-specific information: information supporting network sharing deployments, providing an index to the PLMN ID part of the Global NG-RAN node identifier.
Each NG-RAN node serving a cell identified by a Cell Identity associated with either a subset of PLMNs, or a subset of SNPNs, or a subset of PNI-NPNs is connected to another NG-RAN node via a single Xn-C interface instance.
Each Xn-C interface instance is setup and removed individually.
Xn-C interface instances terminating at NG-RAN nodes which share the same physical radio resources may share the same signalling transport resources. If this option is applied:
Non-UE associated signalling is associated to an Xn-C interface instance by including an Interface Instance Indication in the XnAP message;
Node related, non-UE associated Xn-C interface signalling may provide information destined for multiple logical nodes in a single XnAP procedure instance once the Xn-C interface instance is setup;
A UE associated signalling connection is associated to an Xn-C interface instance by allocating values for the corresponding NG-RAN node UE XnAP IDs so that they can be mapped to that Xn-C interface instance.