5.3.24 WUS assistance

A UE supporting reception of WUS assistance information indicates its capability for reception of WUS assistance information during registration procedure (see 3GPP TS 23.501 [8]). The UE supporting WUS assistance information may include its UE paging probability information in the Requested WUS assistance information IE in the REGISTRATION REQUEST message (see 3GPP TS 23.501 [8]). The UE shall not include its UE paging probability information during:

• a registration procedure for initial registration for emergency services (see clause 5.5.1.2);
• a registration procedure for initial registration for initiating an emergency PDU session (see clause 5.5.1.2);
• a registration procedure for mobility and periodic registration update (see clause 5.5.1.3) for initiating an emergency PDU session if the UE is in the state 5GMM-REGISTERED.ATTEMPTING-REGISTRATION-UPDATE; or
• a registration procedure for mobility and periodic registration update (see clause 5.5.1.3) when the UE has an emergency PDU session established.

The UE and the network may negotiate the UE paging probability information during a registration procedure when the UE does not have an emergency PDU session. The UE paging probability information is an assistance information used to determine the WUS group for paging UE (see 3GPP TS 23.501 [8], 3GPP TS 36.300 [25B]).

NOTE 1: The determination of UE paging probability information is up to UE implementation.

If a UE supporting WUS assistance information did not receive the Negotiated WUS assistance information IE during the last registration procedure due to an active emergency PDU session over 3GPP access, the UE shall initiate a registration procedure for mobility and periodic registration update to request WUS assistance information after the emergency PDU session is released over 3GPP access.

If the UE does not have an emergency PDU session and the network accepts the use of the WUS assistance information for the UE, the network determines the negotiated UE paging probability information for the UE based on the requested UE paging probability information, if any, local configuration or previous statistical information for the UE, and then indicates the negotiated UE paging probability information in the Negotiated WUS assistance information IE to the UE in the REGISTRATION ACCEPT message. The network shall store the negotiated UE paging probability information in the 5GMM context of the UE for paging.

The UE shall use WUS assistance information only if the UE received the Negotiated WUS assistance information IE during the last registration procedure. If the UE did not receive the Negotiated WUS assistance information IE during the last registration procedure, the UE shall delete any existing WUS assistance information received from the network.

If the network did not accept the request to use WUS assistance information, the network shall delete the stored negotiated UE paging probability information for the UE, if available.

When an emergency PDU session is successfully established after the UE received the Negotiated WUS assistance information IE during the last registration procedure, the UE and the AMF shall not use WUS assistance information until:

• the successful completion of the PDU session release procedure of the emergency PDU session;
• the UE receives WUS assistance information during a registration procedure with PDU session status IE or upon successful completion of a service request procedure, if the UE or the network locally releases the emergency PDU session; or
• the successful completion of the handover of the emergency PDU session to non-3GPP access.

NOTE 2: WUS assistance is not supported by NR connected to 5GCN.