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14 June 2022

Will voice be as challenging to implement in 5G as 4G? 

One of the surprising things about the mobile broadband market in 4G and 5G is how important cellular voice has remained. Not in revenue terms – most mobile operators include voice virtually for free in their service bundles, and usage has declined in the face of Internet voice applications. But abandoning voice altogether has proved far more difficult than many expected in 4G, and the number of examples of successful data-only mobile services is vanishingly small.  


Operators had to undergo the challenging migration to Voice over LTE (VoLTE), as the circuit-switched 2G and 3G networks were replaced with IP architectures (or live with the inefficiencies of circuit-switched fallback). They have tried to add value to voice services with adoption of Rich Communications Services (RCS) or add-on applications, but in general, voice has proved the app that contributes least to KPIs, but that remains essential to the consumer proposition. 


Will it be different in 5G? The migration to Voice over 5G NR (VoNR) should be less difficult than that to VoLTE, since the essential underpinnings, in the IP Multimedia Subsystem (IMS), will be in place. But there are few signs that operators will be able to give up on voice in the 5G era. 


Indeed, financial analysts at New Street Research speculate that voice is already causing problems for Dish Network, as it races to switch on its 5G-only services, with an FCC mandate to cover 20% of the US population by June 14.  


“Our understanding is that making 5G Standalone voice services (VoNR) work seamlessly has proven challenging for the industry at large,” the New Street analysts wrote in a client note last week. “While VoNR is working for Dish in Las Vegas, our sense is that it has been tough to optimize it in other markets, and specifically, to accomplish seamless hand-offs between VoNR on Dish’s network and VoLTE on either AT&T or T-Mobile’s network when a customer moves beyond Dish’s network coverage and onto the MVNOs’.” 


This echoes the problems that many operators found when implementing VoLTE – and are still finding, since only about one-third of MNOs have yet deployed the 4G voice service, which requires the IMS, a complex piece of software. In many cases, it was optimizing VoLTE to deliver the same quality of service as circuit-switched voice, or even VoIP apps such as WhatsApp, that proved difficult. 


New Street thinks Dish will continue to rely on its MVNO and roaming arrangements with T-Mobile and AT&T for voice services, even within the areas it manages to cover with 5G by June 14, to give itself more time for the optimization exercise. Dish chairman Charlie Ergen said last month that the initial 5G offerings would be “for data”, and also acknowledged that 5G would be “less robust at the outset” than he had hoped. 


“Based on our read of Dish’s commitment to offer ‘5G Broadband Service’, it seems unlikely to us that Dish will be considered to have failed to achieve 20% coverage if they rely on the MVNOs for voice services within that coverage at the outset, while only using their own network for broadband services,” New Street wrote. “Still, if complaints about Dish meeting its commitments arise, we suspect they will be about this issue, rather than about whether the network covers 20% of the population.” 

Another analyst, Roger Entner of Recon Analytics, told FierceWireless that VoNR “doesn’t work right now … there’s a lot of chatter in the vendor community that part of it is the latency,” and that accelerator cards are not available yet. 


However, Dish’s Sidd Chenumolu, VP of technology development, said that the company has rolled out VoNR, and that it will be relatively easy to introduce other voice calling services, such as Microsoft Teams, on top of its network, if customers demand this. 


The New Street analysts believe that even T-Mobile USA is still relying only on VoLTE for voice, even though it is one of the few operators in the world to have deployed a 5G Standalone core on a nationwide basis. This highlights how challenging it is to implement voice services to the required quality of service. However, TMO itself recently said it did now offer VoNR in parts of two markets, though acknowledged it is rolling out this service cautiously. 


It has launched VoNR in districts of Portland, Oregon, and Salt Lake City, Utah, but its VP of device engineering, Grant Castle, warned: “It’s going to be super not-exciting. If we do this right, people will notice exactly no differences.” In other words, the challenge is to maintain the same quality of experience on VoNR as on VoLTE, not to introduce new bells and whistles in the first instance.  


Last week, TMO’s CTO Neville Ray told an investor conference that “VoNR is tough” because “voice is not very data app-like” but needs a fully consistent quality of connection with no dropped packets. It also needs to support requirements for E-911 emergency calls and location accuracy.  


“Voice is a surprisingly demanding application and it requires optimization on the phone, the radio network, the core network and everything in between,” Castle concurred. 


TMO has worked on testing and optimizing VoNR with its two RAN and core suppliers, Ericsson and Nokia, and two device-side partners, Qualcomm for chips and Samsung for smartphones. Portland is a Nokia market and Salt Lake City is an Ericsson market.  


Last week, T-Mobile filed a heavily-redacted status update with the FCC to update the regulator about its progress in complying with the conditions of its merger with Sprint. For instance, it is required to cover 55% of the USA’s rural population with its midband 5G by April 2023, but the update only says it is “just under its three-year milestone requirement”. It also says that 45% of TMO’s postpaid subscribers now use a 5G handset, and 5G traffic on its network increased sixfold between April 2021 and April 2022, accounting for over half of all its traffic now.