7.2.1 Overview

24.5543GPPProximity-services (ProSe) in 5G System (5GS) protocol aspectsRelease 17Stage 3TS

This clause describes the PC5 signalling protocol procedures between two UEs for one-to-one (i.e., unicast) mode of ProSe direct communication. The following PC5 signalling protocol procedures are defined:

a) 5G ProSe direct link establishment;

b) 5G ProSe direct link modification;

c) 5G ProSe direct link release;

d) 5G ProSe direct link identifier update;

e) 5G ProSe direct link keep-alive;

f) 5G ProSe direct link security mode control;

g) 5G ProSe direct link re-keying; and

h) 5G ProSe direct link authentication.

Each 5G ProSe direct link is associated with a 5G ProSe direct link context. For 5G ProSe UE-to-network relay, the 5G ProSe direct link context includes:

a) user info ID and layer-2 ID of 5G ProSe remote UE;

b) user info ID and layer-2 ID of 5G ProSe UE-to-network relay UE;

c) relay service code; and

d) in the case of 5G ProSe Layer-3 UE-to-network relay, the network layer protocol and the information about PC5 QoS flow(s).

The 5G ProSe direct link context shall be created during a 5G ProSe direct link establishment procedure, be updated accordingly after a 5G ProSe direct link modification procedure or 5G ProSe direct link identifier update procedure and be deleted during the 5G ProSe direct link release procedure or during a local release of 5G ProSe direct link as specified in clause 7.2.