Section: 5.22.2 Subscription-related Priority Mechanisms
Content: Subscription-related mechanisms which are always applied: - (R)AN: During initial Access Network Connection Establishment, the Establishment Cause 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[ Procedures for the 5G System (5GS) ]  [3], the UE subscription data in the UDM contains an MPS subscription indication (i.e. MPS priority) and an MCX subscription indication (i.e. MCX priority) for the UE that has subscription to MPS and MCX, respectively. The MPS priority 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[ Procedures for the 5G System (5GS) ]  [3]. - AMF: Following Access Network Connection Establishment, 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[ Procedures for the 5G System (5GS) ]  [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[ Procedures for the 5G System (5GS) ]  [3]. In addition, certain exemptions to Control Plane Congestion and Overload Control are provided as specified in clause 5.19. 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 and/or an Access Category is applied prior to an initial upstream transmission 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 as specified in clause 5.2. - 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: The "IMS Signalling Priority" information is set for the subscriber in the UDM, 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.