Your guide to enabling voice services in 5G networks

Recently, we published a new series of guides to help service providers navigate their evolution to a cloud-native 5G Core. A key milestone on this journey to a 5G network is enabling 5G voice services. We all know that 5G enables faster, low latency mobile broadband data and new services, but we mustn’t forget about voice services. A 5G smartphone is still a phone, so everyone expects to be able to make and receive voice calls, like they have always done. Most users are unaware of what happens behind the scenes in a mobile network, and of course, they don’t need to know. However, service providers need to consider how to deploy mobile voice services during their 5G network launch. So why is this seemingly basic service something you still need to spend time and effort on?

Why voice services are still important in 5G networks

When 2G networks were built, they were purpose-built to handle mobile voice calls, as that was the first service used on mobile phones. Later, mobile data traffic capabilities were introduced in 2G and 3G mobile networks. Back then, voice services were circuit-switched. Today in 4G, we have migrated the networks to deliver packet-switched voice services. One of the reasons is that packet-switched networks enables more advanced services beyond voice and SMS. Examples of these services include the one-number voice service enabling voice calls on several of your personal devices such as your smartphone, smartwatch and smart speaker. Other examples include IP messaging, video communication, and enterprise voice services with collaboration capabilities. In 5G, the voice service is also packet-switched, and the service should have equal or better quality than in 4G to satisfy users. A 5G smartphone will not connect to a mobile network unless voice support is available, so enabling this is a must.  

Why are there special requirements when designing mobile networks so they can handle voice calls? The main reason is that the mobile voice service is by nature a real-time critical service. If you talk to another person, you’ll soon be annoyed if there’s the slightest delay or interruption in the call, as normal human conversations don’t work that way. If a few mobile data packets are delayed a second or two when you send an e-mail or surf on the web, no one will notice. Video streaming services on your mobile phone buffer the content, but you can’t do that with a voice call, as that would add a disturbing delay. There are also still several radio access networks used in parallel today, spanning from 2G to 5G, so to enable seamless and high-quality voice calls across these radio accesses require intricate network design. Ensuring voice calls are treated as a prioritized real-time critical service – in combination with the large amounts of mobile data traffic sent over different network accesses – is one of the main reasons why there are special requirements for designing the network so it can handle mobile voice services.

With 5G, it’s possible to build even more advanced voice and communication services than in 4G, for example, by adding Augmented Reality on top of a call, improving video calling quality, or enabling interactive calling (a new service standardized for 5G). In the future, there will be even more futuristic services, such as hologram communication. These are real-time critical services, which require high quality everywhere in a mobile network to ensure a good user experience. There are also new business opportunities to build dedicated 5G networks in, for example, factories, hospitals, mines or other businesses which require critical 5G low-latency broadband data services in combination with voice and communication services.  

Leverage VoLTE for 5G voice

So, what do you need to do in your mobile network to enable 5G voice?

Actually, you’re better off once you have already deployed voice in 4G networks (VoLTE or voice over LTE), as the same infrastructure for telephony services, IMS (IP Multimedia Subsystem), will also be used to enable 5G voice. The big undertaking is done when voice services are migrated from circuit-switched 2G and 3G networks to packet-switched 4G networks. As 5G is also a packet-switched technology, you have already come far in your voice deployment project for 5G.

Figure 1: Several industry evolutions happening at the same time that affect mobile voice service deployments

As you can see in the figure above, there are several evolutions happening in the industry simultaneously which affect how mobile voice services are deployed in mobile networks.

• Radio access network evolution: This is what puts the foundation for how you also need to evolve the voice service from circuit-switched (2G and 3G) to 4G and 5G voice.
• Cloud infrastructure evolution: This is a major transformation throughout the whole core network, and this journey has a different pace for different solutions and products. The end game is a more TCO-efficient and service agile cloud-native network.
• End-user voice service evolution: The big technical network migration step is between circuit-switched voice (voice and SMS over 2G and 3G) and packet-switched voice services in 4G and 5G networks. This transition is what enables service providers to offer more valuable and advanced voice and communication services for consumers, enterprises and industries.

These are overall industry evolutions which happen with different speeds in different markets, and this is also one of the reasons voice migration may seem cumbersome, as there are several network evolutions going on in parallel, and each one may be a big undertaking on its own. You need to consider all these aspects on the journey towards enabling 5G voice, depending on how fast and far you have come on your journey to building nationwide 5G radio coverage, and how quickly you’re evolving to cloud-based networks.

As voice services require end-to-end 5G network support, to enable the high-quality voice service experience for mobile devices, you also need to consider the whole network chain: with IMS, 5G core and 5G radio access networks. This also includes testing the 5G end-to-end network towards all kinds of voice-capable 5G devices, so everything works together. The network must also handle interworking towards 4G, 3G or 2G networks in case users move out of 5G coverage (for example seamless voice handover when you move between cells and access technologies).

There are several aspects to consider when enabling voice services in 5G networks, and this will be a gradual evolution, that’s largely determined by 5G radio network coverage as well as availability of devices. There are three solutions to enabling voice calls on 5G devices: Dual Connectivity, Evolved Packet System (EPS) Fallback, and Voice over New Radio (NR). The same IMS can be used in all solutions, requiring only a software upgrade to support EPS Fallback and Voice over NR in the 5G system.

If you want to learn more about how the radio access network evolution and cloud infrastructure evolution for IMS affects 5G voice, read our comprehensive guide “5G voice – A guide to enabling 5G voice services in mobile networks”

Want to know more?

This post is part of our guide to building a cloud-native 5G Core blog post series, where we outline six strategic areas that form the foundation for a cloud-native core network capable of unleashing the full potential of 5G. Investing time in these topics will make you better equipped to plan, deploy and manage your new network for business success. 

Continue reading the complete guide to dig deeper into each of its topic areas.

Read the previous articles of the series: ​

Building a cloud native 5G Core: the guide series

Your guide to building a cloud native infrastructure for 5G

Your guide to evolving to 5G Core with full efficiency

Your guide to 5G network automation and zero touch

You guide to transforming network operations on the journey to 5G

Your guide to end-to-end security when introducing 5G core

Read more about Network automation

Read more about Core network