Content for  TS 24.501  Word version:  19.0.0

The purpose of the 5G ProSe remote UE report procedure is for a UE acting as a 5G ProSe layer-3 UE-to-network UE relay to notify the network that a 5G ProSe remote UE is connected to the 5G ProSe layer-3 UE-to-network relay UE or disconnected from the 5G ProSe layer-3 UE-to-network relay UE as specified in TS 23.304. The UE does not initiate the remote UE report procedure if the timer T3396 is running. The UE does not initiate the remote UE report procedure if the timer T3584 is running. The UE does not initiate the remote UE report procedure if the timer T3585 is running.

In order to initiate the 5G ProSe remote UE report procedure, the UE shall create a REMOTE UE REPORT message. The UE shall include information of newly connected or disconnected 5G ProSe remote UEs to the network in the REMOTE UE REPORT message by setting the values of the Remote UE context connected IE or the Remote UE context disconnected IE to the 5G ProSe remote UE identities that are being connected or disconnected, respectively. The UE shall set the Remote UE ID with:

1. the UP-PRUK ID of the 5G ProSe remote UE, if the security for 5G ProSe communication via 5G ProSe UE-to-network relay is performed over user plane as specified in TS 33.503;
2. the CP-PRUK ID of the 5G ProSe remote UE, if the security for 5G ProSe communication via 5G ProSe UE-to-network relay is performed over control plane as specified in TS 33.503; or
3. the PEI of the 5G ProSe remote UE, if the RSC is specific for emergency services as specified in TS 24.554, and the 5G ProSe remote UE is identified by a PEI.

If the UE sets the Remote UE ID with the PRUK ID of the 5G ProSe remote UE and the UP-PRUK ID is in 64-bit string format, the UE shall include the HPLMN ID of the 5G ProSe remote UE. If the UE allocated an IPv4 address to a 5G ProSe remote UE and enabled UDP usage to the 5G ProSe remote UE, the UE shall include in the REMOTE UE REPORT message the UDP port range assigned to the 5G ProSe remote UE in the NAT function of 5G ProSe layer-3 UE-to-network relay. If the UE allocated an IPv4 address to a 5G ProSe remote UE and enabled TCP usage to the 5G ProSe remote UE, the UE shall include in the REMOTE UE REPORT message the TCP port range assigned to the 5G ProSe remote UE in the NAT function of 5G ProSe layer-3 UE-to-network relay. The UE shall set the PDU session ID IE to the value of the PDU session associated with the 5G ProSe remote UE connected to the 5G ProSe layer-3 UE-to-network relay UE or disconnected from the 5G ProSe layer-3 UE-to-network relay UE. The UE shall allocate a PTI value currently not used and shall set the PTI IE of the REMOTE UE REPORT message to the allocated PTI value. The UE shall transport the REMOTE UE REPORT message and the PDU session ID, using the NAS transport procedure as specified in subclause 5.4.5, and the UE shall start timer T3586 (see example in Figure 6.6.2.2.1).

Upon receipt of the REMOTE UE REPORT message, the SMF shall send a REMOTE UE REPORT RESPONSE message to the UE. The SMF shall include the PTI from the REMOTE UE REPORT message. The SMF shall set the EAP message IE to an EAP-success message or an EAP-failure message to be sent to the 5G ProSe layer-3 remote UE if the EAP-success message or the EAP-failure message is received from the DN. Upon receipt of the REMOTE UE REPORT RESPONSE message, the UE shall stop timer T3586 and enter the state PROCEDURE TRANSACTION INACTIVE.

The following abnormal cases can be identified:

1. Expiry of timer T3586:
   On the first expiry of the timer T3586, the UE shall resend the REMOTE UE REPORT message and shall reset and restart timer T3586. This retransmission is repeated two times, i.e. on the third expiry of timer T3586, the UE shall abort the procedure and release any resources for this procedure.
2. Collision of network-requested PDU session release procedure and remote UE report procedure:
   If the UE receives a PDU SESSION RELEASE COMMAND message during the remote UE report procedure, and the PDU session indicated in the PDU SESSION RELEASE COMMAND message is the PDU session ID that the UE had indicated in the REMOTE UE REPORT message, the UE shall abort the remote UE report procedure and proceed with the network-requested PDU session release procedure.
3. Collision of remote UE report procedure and N1 NAS signalling connection release:
   The UE may immediately retransmit the REMOTE UE REPORT message and stop, reset and restart timer T3586, if following conditions apply:
   1. the original REMOTE UE REPORT was initiated over an existing N1 NAS signalling connection; and
   2. the previous transmission of the REMOTE UE REPORT message was not initiated due to timer T3586 expiry.

The following abnormal cases have been identified:

1. Collision of network-requested PDU session release procedure and remote UE report procedure:
   If the SMF receives a REMOTE UE REPORT message during a network-requested PDU session release procedure, and the PDU session indicated in the PDU SESSION RELEASE COMMAND message is the PDU session ID that is in the REMOTE UE REPORT message, the SMF shall abort the remote UE report procedure and proceed with the network-requested PDU session release procedure.
2. PDU session inactive for the received PDU session identity:
   If the PDU session ID in the REMOTE UE REPORT message belongs to any PDU session in state PDU SESSION INACTIVE in the SMF, the SMF shall send the 5GSM STATUS message to the UE with the 5GSM cause #43 "Invalid PDU session identity".