On-Demand MPS Service
The invocation-related priority mechanisms for prioritized services are based on interaction with an Application Server and between the Application Server and the PCF over Rx/N5 interface (as described in 3GPP TS 23.228, clause 5.21 in the case of MPS using IMS).
Invocation-related mechanisms for Mobile Originations (for example, via SIP/IMS) are explained below:
-
PCF:
-
When an indication for a session arrives over the Rx/N5 interface and the UE does not have priority for the signaling QoS Flow, the PCF derives the ARP and 5QI parameters plus associated QoS characteristics as appropriate, as per the Service Provider policy (specified in clause 6.1.3.11 of 3GPP TS 23.503).
-
For MPS sessions, when establishing or modifying a QoS Flow as part of the session origination procedure, the PCF selects the ARP and 5QI parameters plus associated QoS characteristics as appropriate, to provide priority treatment to the QoS Flows.
-
When all active sessions to a particular DN are released and the UE is not configured for priority treatment to that particular PDU session, the PCF downgrades the IMS Signaling QoS Flows from appropriate settings of the ARP and 5QI parameters plus associated QoS characteristics as appropriate, to those entitled by the UE based on subscription.
-
Invocation-related mechanisms for Mobile Terminations (for example, via SIP/IMS) are explained below:
-
PCF: When an indication for a session arrives over the Rx/N5 interface, the mechanisms as described above for Mobile Originations are applied.
-
UPF: If an IP packet arrives at the UPF for a UE that is CM-IDLE, the UPF sends a "Data Notification" including the information to identify the QoS Flow for the DL data packet to the SMF (specified in clause 4.2.3.3 of 3GPP TS 23.502).
-
SMF: If a "Data Notification" message arrives at the SMF for a QoS Flow associated with an ARP priority level value for priority use, delivery of priority indication during the Paging procedure is provided by inclusion of the ARP in the N11 interface "N1N2MessageTransfer" message (specified in clause 4.2.3.3 of 3GPP TS 23.502).
-
AMF: If an "N1N2MessageTransfer" message arrives at the AMF containing an ARP priority level value for priority use, the AMF handles the request with priority and includes the "Paging Priority" IE in the N2 "Paging" message set to a value assigned to indicate that there is an IP packet at the UPF entitled to priority treatment (specified in clause 4.2.3.3 of 3GPP TS 23.502).
-
SMF: For a UE that is not configured for priority treatment, upon receiving the "N7 Session Management Policy Modification" message from the PCF with an ARP priority level for priority use, the SMF sends an "N1N2MessageTransfer" to update the ARP for the Signaling QoS Flows (specified in clause 4.3.3.2 of 3GPP TS 23.502).
-
AMF: Upon receiving the "N1N2MessageTransfer" message from the SMF with an ARP priority level for priority use, the AMF updates the ARP for the Signaling QoS Flows (specified in clause 4.3.3.2 of 3GPP TS 23.502).
-
(R)AN: Inclusion of the "Paging Priority" in the N2 "Paging" message triggers priority handling of paging in times of congestion at the (R)AN (specified in clause 4.2.3.3 of 3GPP TS 23.502).
Invocation-related mechanisms for the Priority PDU connectivity services:
-
PCF:
-
If the state of the Priority PDU connectivity services is modified from disabled to enabled, the QoS Flows controlled by the Priority PDU connectivity services are established/modified to have the service appropriate settings of the ARP and 5QI parameters plus associated QoS characteristics as appropriate, using the PDU Session Modification procedure (specified in clause 4.3.3 of 3GPP TS 23.502).
-
If the state of Priority PDU connectivity services is modified from enabled to disabled, the QoS Flows controlled by the Priority PDU connectivity services are modified from service appropriate settings of the ARP and 5QI parameters plus associated QoS characteristics as appropriate, to those entitled by the UE as per subscription, using the PDU Session Modification procedure (specified in clause 4.3.3 of 3GPP TS 23.502).
-