Section: 16.9 Sidelink 16.9.1 General
Content: 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[ Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2 ]  [2]. Ranging/Sidelink positioning is specified in TS 38.305[ NG Radio Access Network (NG-RAN); Stage 2 functional specification of User Equipment (UE) positioning in NG-RAN ]  [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. Figure 16.9.1-1: NG-RAN Architecture supporting the PC5 interface 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.