The principles for conveying roaming and access restriction info for EN-DC are described in TS 36.300. For MR-DC with 5GC, SCG (re)selection at the SN is based on roaming and access restriction information in SN. If roaming and access restriction information is not available at the SN, the SN shall consider that there is no restriction for SCG (re)selection. Therefore, MN needs to convey the up-to-date roaming and access restriction information to SN via XnAP messages.

E-UTRAN and NG-RAN aspects of network sharing are specified in TS 36.300 and TS 38.300.

Usage of the Subscriber Profile ID for RAT/Frequency Priority (SPID) and the Additional RRM Policy Index (ARPI) in E-UTRAN is specified in TS 36.300 and applies to EN-DC. Therefore, the MN needs to convey the up-to-date ARPI/SPID information to the SN via X2AP messages.

In-Device Coexistence (IDC) solution as described in TS 36.300 is extended to address EN-DC operation. Only FDM solution, where the list of NR carriers suffering from IDC problems is signalled in IDC indication, is supported in this version of the specifications. The requirement on RRM/RLM/CSI measurements in different phases of IDC interference defined in TS 36.300 is applicable except that for NR serving cell, the requirements in TS 38.133 and TS 38.101-1, TS 38.101-2, TS 38.101-3 apply.

NR Sidelink Communication, V2X Sidelink Communication and NR Sidelink Discovery cannot be configured in MR-DC in this release.

The MN stores and correlates the UE History Information from MN and SN(s) as long as the UE stays in MR-DC, forwards UE History Information and optional UE History Information from the UE to its connected SNs. The resulting information is then used by SN for dual-connectivity operation. The SN is in charge of collecting SCG UE history information and providing the collected information to the MN. If the UE stays in a PSCell for a duration exceeding the maximum value of the Time Stay parameter, the SN may store the PSCell information with consecutive entries using the same PSCell identity. The total stay time in this PSCell is the sum of stay time for all consecutive PSCell with the same identity. The SN shall provide the collected SCG UE history information, if available, to the MN in the following procedures:

• the SN Release, and SN initiated SN Change procedures
• the MN initiated SN Modification procedure if requested by the MN in this procedure
• the SN initiated SN modification procedure upon PSCell change if subscribed in the SN Addition procedure

When the target NG-RAN node receives the SCG UHI from the source NG-RAN node via Handover Request message for CHO, the target NG-RAN node updates the time UE stayed in cell of the latest PSCell entry (i.e. the source PSCell) when the UE successfully accesses to a candidate cell of the target NG-RAN node. The updated value of the time UE stayed in the source PSCell is equal to the value received from the source NG-RAN node during the Handover Preparation plus the time from receiving Handover Request message from the source NG-RAN node to receiving RRC Reconfiguration Complete message from the UE.