VoNR call setup — Mobile Originated (MO)

VoNR MO Call — IMS Signaling Chain

A VoNR Mobile Originated call involves both IMS signaling and 5GC QoS setup working in concert. The UE sends a SIP INVITE with an SDP offer to the P-CSCF, which forwards it through the IMS chain. The S-CSCF evaluates Initial Filter Criteria and invokes the TAS for supplementary service processing — checking call forwarding rules, applying caller ID settings, and similar telephony logic. After TAS processing, the S-CSCF routes the INVITE to the far-end IMS network. Simultaneously, the P-CSCF sends an Rx/N5 request to PCF to authorize dedicated voice QoS.