16.12.5.6 Paging

When both L2 U2N Relay UE and L2 U2N Remote UE are in RRC IDLE or RRC INACTIVE, the L2 U2N Relay UE monitors paging occasions of its connected L2 U2N Remote UE(s). When a L2 U2N Relay UE needs to monitor paging for a L2 U2N Remote UE, the L2 U2N Relay UE should monitor all POs of the L2 U2N Remote UE.

When the intermediate L2 U2N Relay UE is in RRC_IDLE or RRC_INACTIVE, and the intermediate L2 U2N Relay UE exists in the same cell as the last L2 U2N Relay UE, the intermediate L2 U2N Relay UE can monitor paging via the Uu link for all the downstream UE(s) if the intermediate L2 U2N Relay UE hasn't requested paging monitoring to the parent UE.

When L2 U2N Relay UE is in RRC_CONNECTED and L2 U2N Remote UE(s) or child UE(s) is in RRC_IDLE or RRC_INACTIVE, there are two options for paging delivery:

• The L2 U2N Relay UE monitors POs of its connected L2 U2N Remote UE(s) or of all the downstream UE(s) if the active DL BWP of the L2 U2N Relay UE is configured with common search space including paging search space;
• The delivery of the L2 U2N Remote UE's paging or of all the downstream UE(s)’paging can be performed through a dedicated RRC message from the gNB to the L2 U2N Relay UE. The dedicated RRC message for delivering L2 U2N Remote UE paging to the RRC_CONNECTED L2 U2N Relay UE may contain one or more Remote UE IDs (5G-S-TMSI or I-RNTI).

It is up to network implementation to decide which of the above two options to use. The L2 U2N Relay UE in RRC_CONNECTED, if configured with paging search space, can determine whether to monitor POs for a L2 U2N Remote UE based on the indication within the PC5-RRC signalling received from the L2 U2N Remote UE.

The L2 U2N Remote UE in RRC_IDLE provides 5G-S-TMSI and UE specific DRX cycle (if configured by upper layer) to the L2 U2N Relay UE for requesting to perform PO monitoring. The L2 U2N Remote UE in RRC_INACTIVE provides the minimum value of two UE specific DRX cycles (if configured respectively by upper layer and NG-RAN), 5G-S-TMSI and I-RNTI to the L2 U2N Relay UE for PO monitoring. The L2 U2N intermediate Relay UE in RRC_IDLE or RRC_INACTIVE can provide the received information for paging monitoring from the child UE(s) to the parent UE. The L2 U2N Relay UE in RRC_CONNECTED can notify the L2 U2N Remote UE or all the downstream UE information (i.e. 5G-S-TMSI/I-RNTI) to the gNB via the SidelinkUEInformationNR message for paging delivery purpose. The L2 U2N Relay UE receives paging messages to check the 5G-S-TMSI/I-RNTI and sends relevant paging record to the L2 U2N Remote UE or child UE accordingly.

The L2 U2N Relay UE uses unicast signalling to send paging to the L2 U2N Remote UE via PC5.