Content for  TS 23.304  Word version:  19.1.0

PC5 DRX operations are supported to enable 5G ProSe-enabled UE power saving for the following functions:

• 5G ProSe Direct Discovery;
• Unicast, groupcast and broadcast mode 5G ProSe Direct Communication;
• 5G ProSe UE-to-Network Relay Discovery and 5G ProSe UE-to-Network Relay Communication;
• 5G ProSe UE-to-UE Relay Discovery and 5G ProSe UE-to-UE Relay Communication.

Support for PC5 DRX operations in the AS layer is specified in TS 38.300.

For 5G ProSe Direct Discovery, 5G ProSe UE-to-Network Relay Discovery and 5G ProSe UE-to-UE Relay Discovery when the UE is "not served by NG-RAN", the UE uses the provisioned default PC5 DRX configuration for PC5 DRX operation as specified in clause 5.1.2.1, clause 5.1.4.1 and clause 5.1.5.1, respectively.

The ProSe layer determines the respective ProSe services (i.e. ProSe identifiers) and derives the corresponding PC5 QoS parameters based on either the mapping of ProSe services (i.e. ProSe identifiers) to PC5 QoS parameters, or the ProSe Application Requirements for the ProSe services (i.e. ProSe identifiers) provided by the application layer. For broadcast and groupcast, the ProSe layer also determines the NR Tx Profile based on the mapping of ProSe services (i.e. ProSe identifiers) to NR Tx Profiles as described in clause 5.1.3.1. The ProSe layer passes the PC5 QoS parameters and destination Layer-2 ID to the AS layer as specified in clauses 6.4.1, 6.4.2 and 6.4.3. The ProSe layer also passes the corresponding NR Tx Profile to the AS layer, if the ProSe layer has determined the corresponding NR Tx Profile. For broadcast or groupcast, the ProSe layer maintains a list of all ProSe services (i.e. ProSe identifiers), i.e. activated ProSe services and/or ProSe services that the UE is interested for reception, for a given destination Layer-2 ID and determines the NR Tx Profile to be mapped for the respective ProSe service based on the configuration described in clause 5.1.3.1. Whenever the list of the ProSe services for a given destination Layer-2 ID changes, the ProSe layer updates the AS layer for the NR Tx Profiles information by providing all the mapped NR Tx Profiles to the AS layer for the given destination Layer-2 ID, e.g. when providing other information such as the destination Layer-2 ID, PC5 QoS parameters. For broadcast, the mapping from destination Layer-2 ID to NR Tx Profile is configured in the NG-RAN. The NG-RAN may derive the NR Tx Profile from the destination Layer-2 ID to perform the network scheduled operation mode, alignment of Uu DRX and PC5 DRX, etc. When the PC5 DRX operation is needed, the AS layer determines the PC5 DRX parameter values for 5G ProSe Direct Communication or 5G ProSe UE-to-Network Relay Communication over PC5 reference point, taking into account, e.g., PC5 QoS parameters and/or destination Layer-2 ID provided by the ProSe layer. For broadcast and groupcast, the UE enables the PC5 DRX based on the NR Tx Profile. For unicast mode 5G ProSe Direct Communication, 5G ProSe UE-to-Network Relay Communication and 5G ProSe UE-to-UE Relay Communication, two UEs may negotiate the PC5 DRX configuration in the AS layer and the PC5 DRX parameter values can be configured per pair of source and destination Layer-2 IDs in the AS layer. For transmitting and receiving Direct Communication Request messages, a default PC5 DRX configuration may be used (see TS 38.300). For broadcast and groupcast when the UE is "not served by NG-RAN", the UE uses the provisioned PC5 DRX configuration for PC5 DRX operation as specified in clause 5.1.3.1.

The 5G ProSe Layer-3 UE-to-UE Relay shall provide generic function that can relay any IP, Ethernet or Unstructured traffic. The 5G ProSe Layer-3 UE-to-UE Relay provides the functionality to support connectivity between 5G ProSe Layer-3 End UEs. A 5G ProSe Layer-3 UE-to-UE Relay and 5G ProSe Layer-3 End UEs can be located within NG-RAN coverage or outside of NG-RAN coverage. The type of traffic supported over PC5 reference point is indicated by the 5G ProSe Layer-3 UE-to-UE Relay e.g. using the corresponding RSC.

The 5G ProSe Layer-2 UE-to-UE Relay provides forwarding functionality that can relay any type of traffic over the PC5 link. The 5G ProSe Layer-2 UE-to-UE Relay provides the functionality to support connectivity between 5G ProSe Layer-2 End UEs. A 5G ProSe Layer-2 UE-to-UE Relay and 5G ProSe Layer-2 End UEs can be located within NG-RAN coverage or outside of NG-RAN coverage.

Multi-path communication uses one direct network communication path and one indirect network communication path with UE-to-Network Relay as illustrated in Figure 5.17.1-1, where path #1 shows the direct communication path via Uu and path #2 is shows the indirect communication path via 5G ProSe UE-to-Network Relay.

The indirect communication path may be via a 5G ProSe Layer-2 UE-to-Network Relay, or via a 5G ProSe Layer-3 UE-to-Network Relay with or without N3IWF.

A 5G ProSe Layer-3 Remote UE may access the network via a 5G ProSe Layer-3 UE-to-Network Relay with or without N3IWF. When a 5G ProSe Layer-3 Remote UE accesses the network via a 5G ProSe Layer-3 UE-to-Network Relay without N3IWF, the multi-path communication via direct Uu path and via the UE-to-Network Relay may be applied to the application traffic. When a 5G ProSe Layer-3 Remote UE accesses the network via a 5G ProSe Layer-3 UE-to-Network Relay with N3IWF, the Layer-3 Remote UE connection via Layer-3 UE-to-Network Relay with N3IWF is considered as "untrusted non-3GPP access to 5GC via N3IWF", therefore the multi-path communication can be achieved using MA PDU Session in ATSSS features specified in clause 5.32 of TS 23.501.