16.9.1 General

In this clause, an overview of NR sidelink communication and how NG-RAN supports NR sidelink communication, V2X sidelink communication and Ranging/Sidelink positioning is given. V2X sidelink communication is specified in TS 36.300 [2]. Ranging/Sidelink positioning is specified in TS 38.305 [42].

The NG-RAN architecture supports the PC5 interface as illustrated in Figure 16.9.1-1. Sidelink transmission and reception over the PC5 interface are supported when the UE is inside NG-RAN coverage, irrespective of which RRC state the UE is in, and when the UE is outside NG-RAN coverage.

Support of V2X services via the PC5 interface can be provided by NR sidelink communication and/or V2X sidelink communication. NR sidelink communication may be used to support other services than V2X services.

NR sidelink communication can support one of three types of transmission modes for a pair of a Source Layer-2 ID and a Destination Layer-2 ID in the AS:

• Unicast transmission, characterized by:
• Support of one PC5-RRC connection between peer UEs for the pair;
• Transmission and reception of control information and user traffic between peer UEs in sidelink;
• Support of sidelink HARQ feedback;
• Support of sidelink transmit power control;
• Support of RLC AM;
• Detection of radio link failure for the PC5-RRC connection.
• Groupcast transmission, characterized by:
• Transmission and reception of user traffic among UEs belonging to a group in sidelink;
• Support of sidelink HARQ feedback.
• Broadcast transmission, characterized by:
• Transmission and reception of user traffic among UEs in sidelink.