CHF and PCF Integration for Service Request Procedures

This section describes the CHF and PCF integration for service request procedures.

SMF processes the received SM Context Update Request to update N3 tunnel path state from Idle to Active or Active to Idle. SMF performs the following steps:

  1. When UE is in CM-Idle state at AMF, which is Active to Idle mode—Based on the configuration, SMF updates UPF for N3 tunnel state to drop or buffer by sending the N4 session mode request. Based on charging configuration, SMF receives a usage report. Based on the Charging Triggers that qualify during session creation, SMF sends the N40 Charging Update request.

  2. When UE is in CM-Connected state at AMF, which implies SMF receives UE-requested Procedures to change the subscriber N3 Tunnel Path from Idle to Active State—SMF receives the updated user location and UE time zone in the SM Context Update Request. SMF sends the N4 Session Modification Request to UPF to update the DL tunnel details of gNB. Based on charging configuration, SMF receives a usage report. Based on the Charging Triggers that qualify during session creation, SMF sends the N40 Charging Update request.

  3. When the N3 Tunnel is unavailable for the Network Service Request Triggers, which implies that UE is in CM-Idle state at AMF—SMF initiates the Network Service Request Procedures for AMF to initiate Paging toward the end user. Then, AMF begins the UE Service Request Procedures to configure the N3 Tunnel as specified in Step 2.