5.22.2 Subscription-related Priority Mechanisms

Subscription-related mechanisms which are always applied:

• (R)AN: During initial Access Network RRC Connection Establishment procedure or RRC Connection Resume procedure, the Establishment Cause or Resume Cause, respectively is set to indicate that special treatment is to be applied by the (R)AN in the radio resource allocation as specified in clause 5.2 for 3GPP access.
• UDM: As defined in clause 5.2.3 of TS 23.502 [3], the UE subscription data in the UDM contains an MPS subscription indication (i.e. MPS priority indication and optionally MPS for Messaging indication) and an MCX subscription indication (i.e. MCX priority) for the UE that has subscription to MPS and MCX, respectively. The MPS priority, the MPS for Messaging indication and the MCX priority, if available, are provided to the AMF via the Registration or the UE Configuration Update procedure as defined in clause 4.2 of TS 23.502 [3]. The MPS for Messaging indication sets(enables)/clears(disables) the MPS priority treatment of Messaging service (i.e. SMS over NAS, SMS over IP and messaging over IMS are all controlled by one indication) for an MPS-subscribed UE. The MPS for Messaging indication is used in communications between NFs and network entities in the CN. The MPS for Messaging indication is not delivered to UE. The MPS for Messaging indication parameter may be provisioned by an AF via NEF as described in clause 4.15.6 of TS 23.502 [3].
• AMF: Following Access Network RRC Connection Establishment procedure, the receipt of the designated Establishment Cause (i.e. high priority access) by the AMF will result in priority handling of the "Initial UE Message" received as part of the Registration procedures of clause 4.2.2 of TS 23.502 [3]. If the AMF did not receive a designated Establishment Cause (i.e. high priority access), but when the AMF determines that there is a MPS priority (or MCX priority) in the UDM for that UE, the AMF shall provide priority handling for that UE at that time and shall provide the MPS priority (or MCX priority) to the UE via the Registration or the UE Configuration Update procedure, as defined in clause 4.2 of TS 23.502 [3]. In addition, certain exemptions to Control Plane Congestion and Overload Control are provided as specified in clause 5.19. For the MPS for Messaging indication, the AMF uses the parameter to determine the Message priority header related to SMS delivery and as described in clause 4.13 of TS 23.502 [3].

Subscription-related mechanisms which are conditionally applied:

• UE: When barring control parameters are broadcast by the RAN, access barring based on Access Identity(es) configured in the USIM, or provided by the network as part of the Registration or UE Configuration Update procedure and/or an Access Category, is applied prior to an initial upstream transmission (initial or resume) for the UE which provides a mechanism to limit transmissions from UEs categorized as non-prioritized, while allowing transmissions from UEs categorized as prioritized (such as MPS subscribed UEs), during the RRC Connection Establishment procedure and RRC Connection Resume procedure as specified in clause 5.2. A UE categorized as prioritized (e.g. MPS subscribed UEs), as specified in clause 5.16.5:
• in CM-IDLE state, uses a high priority Establishment Cause in the UE Triggered Service Request procedure; and
• in RRC_INACTIVE state, uses a high priority Resume Cause in the Connection Resume procedure.
• UDM: One or more ARP priority levels are assigned for prioritized or critical services. The ARP of the prioritized QoS Flows for each DN is set to an appropriate ARP priority level. The 5QI is from the standard value range as specified in clause 5.7.2.7. In addition, Priority Level may be configured for the standardized 5QIs and if configured, it overwrites the default value specified in the QoS characteristics Table 5.7.4-1.
• PCF: If the "IMS Signalling Priority" information is set for the subscriber in the UDR and the PCF modifies the ARP of the QoS Flow used for IMS signalling, for each DN which supports prioritized services leveraging on IMS signalling, to an appropriate ARP priority level assigned for that service.
• SMF/AMF: Based on the QoS parameters (e.g. ARPs, 5QI) of a PDU Session, the SMF may provide a PDU Session Priority to the AMF. The AMF stores the information for further PDU Session related priority handling (i.e. for determination of Message Priority header of subsequent message related to the PDU Session).

NOTE: For a UE with MPS subscription, the MPS priority per DN can be different (e.g. only certain specific DNs has MPS priority while other DNs have no MPS priority).