VoNR (Voice over New Radio) is the 3GPP-standardised mechanism for delivering voice calls over a 5G New Radio air interface on a 5G Standalone (5G SA) network, using the IP Multimedia Subsystem (IMS). It is defined from 3GPP Release 15. It uses the same IMS architecture as VoLTE but replaces the 4G EPC with the 5G Core (5GC) and supports the EVS codec for audio quality up to 20 kHz.
VoNR is not a completely new standard. It is the evolution of VoLTE onto the 5G air interface and 5G Core. The IMS – the IP Multimedia Subsystem that handles SIP signalling, call routing, and supplementary services – is identical. The same P-CSCF, S-CSCF, TAS, and HSS elements serve both VoLTE and VoNR calls. The key differences are in the radio access network and the core network.
A 5G network architecture where both the radio (gNB/NR) and the core (5GC – 5G Core) are 5G. The 5GC uses a service-based architecture (SBA) and replaces the 4G EPC entirely. VoNR requires 5G SA. It does not work on 5G NSA (Non-Standalone), which uses the 4G EPC and therefore falls back to VoLTE for voice.
| Component | VoLTE (4G) | VoNR (5G SA) |
|---|---|---|
| Radio access | LTE (eNodeB / E-UTRAN) | 5G NR (gNB / NG-RAN) |
| Core network | EPC (MME, SGW, PGW) | 5GC (AMF, SMF, UPF) |
| QoS model | EPS bearers with QCI | QoS flows with 5QI |
| Voice QoS identifier | QCI 1 (GBR bearer) | 5QI 1 (GBR flow) |
| Signalling protocol | SIP via IMS | SIP via IMS (unchanged) |
| Primary voice codec | AMR-WB (HD Voice) | EVS (super-WB / fullband) |
| Audio range | 50 Hz – 7 kHz | 50 Hz – 20 kHz (EVS fullband) |
| IMS elements | P-CSCF, S-CSCF, TAS, HSS | Identical – same IMS |
| Network slicing | Not supported | Voice on dedicated network slice |
| Latency | Typically 50-100ms one-way | Lower – 5G NR URLLC capable |
The majority of UK 5G deployments launched in 2019-2022 are 5G Non-Standalone (NSA). In NSA, the 5G NR radio is an additional carrier attached to the 4G LTE anchor, and all core network functions – including voice – remain with the 4G EPC and IMS. A VoNR call on a 5G NSA network is impossible; the device falls back to VoLTE on the LTE bearer.
VoNR requires the 5G Core (5GC) because the 5GC natively integrates with the IMS using the N5 interface and supports QoS flows with 5QI identifiers. The 4G EPC does not have this integration path for 5G NR.
VoNR is defined from 3GPP Release 15. The GSMA has produced equivalent interoperability profiles for VoNR as it did for VoLTE (IR.92 equivalent for 5G voice). The core IMS specifications – TS 23.228, TS 24.229 – apply to both VoLTE and VoNR with 5G-specific additions in the Release 15 and later versions.
VoNR shares the entire IMS architecture with VoLTE. If you are new to IMS voice technology, start with the VoLTE reference at voltesim.co.uk. The IMS elements (P-CSCF, S-CSCF, TAS, SIP call setup, QoS bearers, ISIM provisioning) all carry over to VoNR.