The Voice of 5G & LTE for the Americas

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Voice Is More Important Than You Think

Chris Pearson, President, 5G Americas

February 2021 – By now, most everyone is well aware that people of different generations have different preferences for how they communicate. Boomers and Gen X grew up on voice calls and are used to them, but it’s become sort of a standard trope that Millennials and Gen Z avoid voice calls for various reasons. With so many different options like TikTok, Whatsapp, or Signal, communicating with each other has become a lush jungle of different choices that reflect who we are and our personal style.  As the COVID-19 pandemic has demonstrated, all forms of connecting with other people are important to our business and personal well-being.

You can use this thing for talking?

But what if I told you that voice calls dramatically increased in 2020? According to the Cellular Technology Industry Association (CTIA), “pandemic and stay-at-home protocols caused huge increases in wireless use, with a 24.3 percent increase in U.S. voice traffic and a 19.6 percent increase in U.S. data traffic”. Those numbers held up throughout last year, even as voice calling saw huge spikes during the COVID-19 lockdowns.

With many companies looking to continue work-from-home policies, this elevated level of voice calling may continue to reach a new normal.

It turns out that voice isn’t dead after all!

In 5G Americas’ latest white paper, The Future of Voice in Mobile Wireless Communications, we uncover the technical underpinnings of what makes voice calls work in 4G LTE and 5G systems. There are a lot of incredibly complex details that go into operating a voice network which doesn’t just run “over the top” (OTT) of an Internet connection. These types of voice networks have evolved from the old days of circuit-switched calling based on telephone lines, so they have been – and continue to be – integral to the reliability of important mission-critical functions like Emergency 9-1-1 systems.

OTT applications like those mentioned above are important, but you wouldn’t want to depend on them to necessarily address mission-critical voice calls because the quality of call experience could fluctuate quite a lot due to best efforts of having to compete with every other data bit on the Internet. These types of network latency can wreak havoc on both voice and video calls because communication is extremely sensitive to network latency. Even a few milliseconds of network latency can be noticeable on a call and is experienced as a delay between the callers.

Working from home means dealing with network latency.

You wouldn’t want your video call looking like a poorly-dubbed movie with lips moving, but terrible audio synchronization coming out, would you?

Instead, network operators have developed separate voice networks beginning with circuit-switched 2G and 3G networks, then switching over to packet-switched 4G Voice-Over-LTE (VoLTE) – and soon, with 5G VoNR (5G Voice-Over-New-Radio).  These are IMS-based (Internet Protocol Multimedia Systems) which keep the voice calls separate from the general Internet traffic which runs over other parts of core and radio access networks. Keeping voice traffic from standard Internet traffic provides an additional layer of resiliency.

The Future of Voice in Mobile Wireless Communications Figure 0 1: High Level Architecture of VoLTE versus VoNR

5G VoNR offers a compelling way for network operators to improve call quality and reduce operational costs.  This is because 5G VoNR will allow for voice calls to more efficiently use valuable network hardware and spectrum. With improved voice codecs, 5G VoNR can offer the same quality of voice from that of what you might hear on popular music applications, which goes far beyond just conversational voice quality. As more network operators launch their 5G standalone networks, it is reasonable to believe that consumers might begin to see 5G VoNR service towards the second half of 2021.

These types of upgrades to network operators’ IMS networks are codified in the Third Generation Partnership Project (3GPP) releases, which have defined LTE and 5G networks. In 3GPP Release 15 and 16, a solid foundation was created for the industry to offer commercial grade voice services over NR – and Release 17 could offer even more enhancements. The Future of Voice in Mobile Wireless Communications takes a deeper dive into all these enhancements and how they interact with the 5G network.

One important aspect about this evolution is that as 5G networks transition from non-standalone to standalone, Evolved Packet System Fallback (EPSFB) will provide a temporary solution, before it is replaced with a full 5G VoNR experience. Because 5G VoNR is modeled in many ways around similar concepts to how VoLTE was created, a template for this transition is already known, so there’s a logical way to evolve the systems. While EPSFB won’t perform as well as a full 5G VoNR system, it should provide for a smooth transition path for 5G networks.

The Future of Voice in Mobile Wireless Communications Table 4: Conclusion from NGMN study on EPS FB performance

In 3GPP Release 15, the full frameworks for both EPSFB and VoNR were defined, including two RAN procedures detailing how calls were to be handled. They are called ‘RRC Release with Redirect’ (RwR) and Handover (HO) – and each addresses how to route and manage the traffic as the 5G network is in transition. Release 16 provided additional enhancements to Handover performance and improved EPSFB call reliability, which of course, will no longer be necessary once full VoNR is achieved. More enhancements to these systems are expected in Release 17.

There are several factors that network operators need to consider as the wireless industry prepares for 5G VoNR. For instance, aside from the network architecture components, will they have right amount of spectrum to available for voice calling? What about the devices that consumers already own? Will enough of them be capable of making VoNR calls? How much will people be forced to upgrade their devices? Finally, what domestic roaming capabilities – what happens to a call if it needs to traverse onto another carrier’s network? And how will the voice call handle emergency services such as 9-1-1?

No time for Internet traffic congestion

Despite the challenges, 5G systems offer a great deal of flexibility in managing voice traffic, as well as improved interoperability and roaming capabilities. For instance, 5G introduces the concept of network slicing, where specific network resources such as routing, computation, and spectrum can be specifically delivered at the right amounts for the exact use case. Take for example a video call – it will require different kinds of network resources, more bandwidth, more spectrum, and probably a lot more computation to ensure the image quality looks good than will an audio call alone.

Aside from IMS systems, network slicing can be directly applied to Over-the-Top (OTT) and alternative voice solutions on 5G. Additionally, 5G networks will also offer a lot more support for both operator and virtual networks, as well as fine-tuning and flexibility for IMS voice service restrictions.

Hopefully, by now I’ve convinced you that there’s a lot more to voice calling than you ever imagined. There is a deep well of technology to mine here and if the COVID-19 lockdowns teach us anything – it’s that people need to maintain every channel of communication with each other. I think voice is going to be an important part of communication for a very long time. Sorry, Millennials and Gen Z, we old timers will still like to connect and communicate with our own voices!

-Chris

The Future of Voice in Mobile Wireless Communications

Find out more about voice communications are changing in LTE and 5G networks. What enhancements are underway? What challenges do network operators face - and what will that mean for voice callers.

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