While high speed data services are the driving factor in the development of 5G, traditional voice and video communications remain an important part of network operator services.

December 2021 – As of October 1, 2021, China Mobile requires all 5G enabled mobile phones to support voice services over 5G NR (VoNR). Accordingly, the network operator has announced corresponding audio quality test cases. China Mobile relies on the R&S CMX500 radio communication tester from Rohde & Schwarz for 5G VoNR test verification, and the first acceptance tests have already been performed.

 While high speed data services are the driving factor in the development of 5G, traditional voice and video communications remain an important part of network operator services. However, the voice business model has undergone tremendous changes between 2G and 5G. In 2G and 3G networks, voice was carried through the circuit switched domain (CS), while data services were carried through the packet switched domain (PS). As of 4G, voice services were based on IP multimedia subsystem (IMS) architecture, and have continued to evolve from there.

 The current deployment of 5G standalone (SA) networks is paving the way for high-quality 5G voice over New Radio. The enhanced voice service (EVS) codec used by VoNR focuses on high-quality multimedia services. The service has wider audio bandwidth, a higher sampling rate, a better quantization level and higher definition. These features enable 5G applications based on low latency, ultra-high definition voice communications such as remote collaboration, virtual reality (VR), remote surgery and mission-critical communications, and significantly improve the voice quality and thus the user experience.

 Rohde & Schwarz and China Mobile jointly performed 2G/3G/4G audio quality testing with the R&S CMW500 wideband radio communication tester, and the companies are now continuing this collaboration with 5G VoNR audio quality test cases using the R&S CMX500 5G radio communication tester. Rohde & Schwarz also coordinated VoNR test cases such as IMS, SIP protocol and emergency call tests with chip manufacturers and terminal manufacturers earlier this year, which can now be leveraged for the China Mobile VoNR acceptance tests.

 With the technology behind VoNR being similar to voice over LTE (VoLTE), the IMS is the voice service enabler that uses the 5G core and needs to be thoroughly tested. However, testing voice services in 5G also includes VoLTE aspects for the non-standalone (NSA) and EPS fall-back scenarios, which enable the handover from NR to LTE when 5G coverage is limited.

 The test setup for 5G voice and video applications includes the R&S CMX500 5G radio communication tester, which supports LTE and 5G NR devices and is used for network-independent signalling testing. The internal IMS server of the R&S CMX500 provides virtual UE emulation and an audio loopback mode for fast and simple VoNR functional testing. The setup can be extended with an audio analyser for electrical audio performance measurements and a dummy head with an artificial ear and mouth for high-quality acoustic tests in line with 3GPP and ETSI audio measurements.