Steps in 5G SA VONR Call flow:
5G VONR (Voice over New Radio) call flow involves establishing a voice call using 5G technology. It relies on the 5G standalone (SA) architecture and combines Radio Resource Control (RRC) messages with Session Initiation Protocol (SIP) messages to provide an end-to-end connection for voice calls.
1️⃣ ?☎️ User A wants to call User B: User A initiates a voice call to User B using their 5G-enabled smartphones.
2️⃣ ?? RRC Connection: User A’s phone establishes an RRC connection by sending an RRC Connection Request (IE: UE Identity) and receiving an RRC Connection Setup (IE: ConfiguredGrantConfig) message from the network.
3️⃣ ?? NAS Registration: User A’s phone registers with the 5G network by sending a Registration Request (IE: SUPI, PEI) and receiving a Registration Accept (IE: 5G-GUTI) message from the network.
4️⃣ ?? PDU Session Establishment: User A’s device sends a PDU Session Establishment Request (IE: SSC mode, DNN) to the 5G core network, which responds with a PDU Session Establishment Accept (IE: PDU address, QoS rules).
5️⃣ ?? Call setup: User A’s phone sends a SIP INVITE (IE: SDP, called number) to User B through the 5G network. The network forwards the SIP INVITE to User B’s device.
6️⃣ ?? Alerting: User B’s phone sends a SIP 180 Ringing message (IE: SDP, alerting pattern) back to User A’s device through the 5G network, indicating that User B’s phone is ringing.
7️⃣ ??️ Call answer: When User B answers the call, their device sends a SIP 200 OK message (IE: SDP, selected codec) to User A’s phone via the 5G network, indicating that the call has been accepted.
8️⃣ ?? Call confirmation: User A’s phone sends a SIP ACK message (IE: selected codec, media path) to User B’s device through the 5G network, confirming that the call is established.
9️⃣ ?️? Ongoing call: User A and User B can now talk over the 5G VONR call, with voice data transmitted over the established media path.
? ?❌ Call termination: When the call is finished, either User A or User B sends a SIP BYE message (IE: call duration, reason) through the 5G network, and the other party responds with a SIP 200 OK message, indicating that the call has been terminated.
1️⃣1️⃣ ?? RRC Connection Release: After the call is terminated, User A’s phone releases the RRC connection by sending an RRC Connection Release (IE: Release Cause) message to the network, and the network responds with an RRC Connection Release Complete message.
