UE-initiated EPS Call Release Procedure

The following figure shows the call flow for UE-initiated release of EPS call.

UE-initiated EPS Call Release Flow

The detach procedures for the EPS are defined in 3GPP 23.401, Section 5.3.8. When the UE is attached to E-UTRAN, the detach procedure remains the same as mentioned in the specified 3GPP section except for the following changes:

  • Any interaction towards PCRF (CCR-T), that is PCEF-initiated IP-CAN session between P-GW and PCRF, is replaced by Npcf_SMPolicyControl_Update Request from the SMF to the PCF. The parameters sent in this message follow a mapping from Delete Session Request contents in a way similar to the Create Session Request message for initial attach.

  • All Gy and Gz interface messages are replaced by Nchf_ConvergedCharging_Release service operations.

  • The user plane resources are removed using the N4 Session Release procedure towards the UPF.