December 8, 2023

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What is VoNR (Voice over New Radio) under 5G cellphone network?

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What is VoNR (Voice over New Radio) under 5G cellphone network?


What is VoNR (Voice over New Radio) under 5G cellphone network?

Like 4G, 5G continues the voice solution based on the IMS architecture.

The voice carried on the 4G LTE network is called VoLTE, and the voice carried on the 5G NR network is called VoNR.


The application of VoNR transmission technology can not only shorten the time for establishing a telephone call connection, but also greatly improve the connection success rate and reduce possible interruptions during the call.

In addition, it can maintain a stable and high-speed 5G data connection during the call, so that the gaming and video experience will not be affected by the slow network speed.


What is VoNR (Voice over New Radio) under 5G cellphone network?


Although the growing demand for data services is the main driving force behind the evolution of mobile communication networks to 5G, voice services are still an integral part.


In the early stage of 5G deployment, the 5GNR network has not yet formed a comprehensive coverage.

In order to avoid the poor user experience caused by frequent voice switching between 5G and 4G, the 5G SA network voice generally adopts the EPS fullback scheme.

However, under this scheme, when a terminal working on the 5G network initiates a voice call or has an incoming voice call, the network switches the 5G terminal to the 4G network through the switching process, and provides voice services through the VoLTE technology of the 4G network, so it will reduce the network speed, which affects the user experience.


With the large-scale deployment of 5G networks, 5GNR forms continuous coverage, and 5G voice uses the VoNR solution.

Because VoNR directly carries IMS voice services from 5GS end-to-end, the establishment time of voice calls is shorter, the voice quality is better, and users can enjoy the smooth 5G network speed while making voice calls, and the user experience is greatly improved.


VoNR (Voice over New Radio)

VoNR (Voice over New Radio) is an IP Multimedia System (IMS)-based voice call service that uses 5G networks for Internet Protocol (IP) voice processing.

Mobile voice is a legacy service that will continue to exist in every generation of mobile communications.

Let’s take a brief look at how VoNR is implemented.


5G mobile networks will provide two main types of voice services:

Carrier-grade voice service, with strict QoS support, carrier-grade voice service, with strict QoS support, not part of Voice over Public Internet New Radio (VoNR) or Vo5G.


OTT voice services:

will continue to exist in 5G networks and will continue to be provided through mobile Internet access on a best-effort basis using net neutrality (e.g. WeChat, WhatsApp, Skype, etc.).


3GPP has specified 5G to use 4G voice/video communication architecture, and still provides voice/video communication services based on IMS. You may notice that VoLTE and VoNR are different access modes for IMS (IP Multimedia Subsystem) voice/video communication services.


The evolution to 5G VoNR is divided into 3 steps as follows:

  • Double Wiring (EN-DC)
  • EPS falls
  • NR voice

What is VoNR (Voice over New Radio) under 5G cellphone network?

Source: Ericsson


1. Double Wiring (EN-DC)

  • This is the first choice for providing voice services:
  • Voice over LTE when using NR as a profile enhancement.
  • There is an option to stop data on NR during a call to ensure sufficient uplink power for voice over LTE at the cell edge.

What is VoNR (Voice over New Radio) under 5G cellphone network?



2. EPS fallback

  • NR transmits data, but falls back to LTE (for voice and data) when making or receiving calls:
  • NR based profiles can be recreated after EPS-FB (with ENDC).
  • EPC and 5GC with N26 interworking function and reserve IP address in 5GC.
  • EPC fallback can be triggered when the UE initiates an IMS voice call when the UE is connected to the 5G core network using New Radio (NR). It requires the 5G core network to have connectivity to the IMS.
  • The fallback procedure uses EUTRA to move the UE onto the 4G core network, so the 4G core network also has connectivity to the IMS, so the voice call setup can be done.

What is VoNR (Voice over New Radio) under 5G cellphone network?

EPS fallback


3. NR voice solution

  • When 5G is mature enough:
  • NR carries both voice and data
  • NR for voice coverage
  • Seamless switching between 5G and 4G (and WiFi)
  • There is no handoff/fallback from 5G to CS.


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