Voice over New Radio (VoNR) allows your calls to stay entirely on the 5G highway, utilizing the 5G Standalone (SA) core for a smoother, more efficient ride.

Benefits:

• Sharper Sound: VoNR leverages a more advanced audio codec, meaning your voice calls will sound richer and clearer, almost indistinguishable from face-to-face conversations.

• Faster Connections: Gone are the days of waiting for your call to connect. The lower latency of 5G allows for near-instantaneous call setup, eliminating those frustrating delays.

• Seamless Handoffs: Imagine being on a call while switching between Wi-Fi and cellular data. With VoNR, these handoffs become seamless, preventing dropped calls and ensuring uninterrupted conversations.

• A Platform for Innovation: VoNR paves the way for future voice applications. Imagine integrating real-time translation or voice assistants directly into your calls – the possibilities are endless.

Components:

• User Equipment (UE):  a.k.a. 5G smartphone.
• gNB (Next Generation Node B): The new 5G cell tower UE connects to.
• 5G Core (5GC): The brain of the 5G network, handling core functionalities.
• IMS (IP Multimedia Subsystem): The switch behind voice and multimedia services.

High Level Call Flow:

• Registration and Capability Exchange :The flow begins with the UE registering with the 5GC. This registration includes information about the UE’s VoNR capabilities, which the 5GC verifies.
• PDU Session Establishment: The UE initiates a call by sending a “PDU Session Establishment Request” to the 5GC. This request specifies the need for a dedicated data path for voice traffic. The 5GC analyzes the request and configures a PDU session with specific QoS (Quality of Service) parameters to ensure smooth voice delivery.
• Voiceover NR (RRC Connection Setup): gNB to establishes an RRC (Radio Resource Control) connection with the UE. This connection creates a dedicated radio channel for transmitting and receiving voice data.
• SIP Signaling and Media Flow: The UE initiates Session Initiation Protocol (SIP) signaling with the IMS. This communication establishes the call, negotiates codecs for voice compression, and exchanges information about the participants.
• Conversational Voice: Once the SIP negotiation is complete, the media flow begins. Encoded voice packets travel between the UE and the IMS core over the established PDU session.
• Call Management and Mobility: Throughout the call, the UE and the 5GC communicate using signaling messages to manage the call (e.g., hold, mute). Additionally, if the UE moves between gNBs during the call, a handover procedure ensures seamless handoff of the VoNR session while maintaining the call connection.
• Call Termination: The call concludes with SIP tear-down procedures, where the participants are notified and the resources are released.

While this is a simplified view, the signaling flow involves various messages and protocols like NAS (Non-Access Stratum) messages for control plane communication between the UE and the 5GC, and NG-RAN (Next Generation Radio Access Network) signaling for radio resource management between the UE and the gNB.

VoNR signaling flows represent a complex choreography ensuring the smooth delivery of voice calls over the 5G network. As the technology matures, further advancements like integration with network slicing and edge computing hold the potential to further enhance voice quality and unlock innovative voice applications in the 5G era.