8.4 NR sidelink communication, V2X sidelink communication and Ranging/Sidelink positioning related identities

The following identities are used for NR sidelink communication and SL-PRS transmission on shared SL-PRS resource pool:

• Source Layer-2 ID: Identifies the sender of the data in NR sidelink communication and/or SL-PRS transmission. The Source Layer-2 ID is 24 bits long and is split in the MAC layer into two bit strings:
• One bit string is the LSB part (8 bits) of Source Layer-2 ID and forwarded to physical layer of the sender. This identifies the source of the intended data and/or SL-PRS in sidelink control information and is used for filtering of packets at the physical layer of the receiver;
• Second bit string is the MSB part (16 bits) of the Source Layer-2 ID and is carried within the MAC header. This is used for filtering of packets at the MAC layer of the receiver.
• Destination Layer-2 ID: Identifies the target of the data in NR sidelink communication and/or SL-PRS transmission. For NR sidelink communication and SL-PRS transmission on shared SL-PRS resource pool, the Destination Layer-2 ID is 24 bits long and is split in the MAC layer into two bit strings:
• One bit string is the LSB part (16 bits) of Destination Layer-2 ID and forwarded to physical layer of the sender. This identifies the target of the intended data and/or SL-PRS in sidelink control information and is used for filtering of packets at the physical layer of the receiver;
• Second bit string is the MSB part (8 bits) of the Destination Layer-2 ID and is carried within the MAC header. This is used for filtering of packets at the MAC layer of the receiver.
• PC5 Link Identifier: Uniquely identifies the PC5 unicast link in a UE for the lifetime of the PC5 unicast link as specified in TS 23.287 [40]. The PC5 Link Identifier is used to indicate to upper layers the PC5 unicast link in which sidelink RLF was declared and corresponding PC5-RRC connection was released.

V2X sidelink communication related identities are specified in clause 8.3 of TS 36.300 [2].

The following identities are used for SL-PRS transmission on dedicated SL-PRS resource pool:

• Source ID: Identifies the sender of the SL-PRS transmission. The length of the identifier is either 12 or 24 bits, which is indicated in the RRC configuration. The source ID identifies the source of the intended SL-PRS in sidelink control information and is used for filtering at the MAC layer of the receiver;
• Destination ID: Identifies the target of the SL-PRS transmission. The length of the identifier is 24 bits. The Destination ID identifies the target of the intended SL-PRS in sidelink control information and is used for filtering at the MAC layer of the receiver.