Wayne Cutler, Technical Director, explains how the GSMA’s Networks Working Group is helping the mobile industry harness the full benefits of VoLTE (Voice over Long Term Evolution).
As the global mobile industry embraces 4G and increasingly 5G, voice calls can benefit from the same IP-based technologies as video and other data-based services. For mobile network operators (MNOs), the move away from dedicated circuit-switched voice calls is driving economies of scope and scale, reducing costs and paving the way to switch off 2G and 3G networks.
But this industry-wide shift is far from complete. While there are 735 4G networks operating across the world, only 388 of these enable users to make voice calls via VoLTE – the industry standard for voice communications over 4G networks. There are now more than 2,500 VoLTE capable devices, with a few hundred further devices being launched each year. With so many devices and networks, one-to-one testing is simply not feasible in all cases, particularly as many MVNOs also support VoLTE.
As a result, many devices fall back to legacy circuit-switched networks to make voice calls, increasing operators’ costs and making it harder for them to streamline their network operations. If these legacy networks aren’t available, a device that doesn’t support VoLTE cannot obtain an operator-provided voice service, which in a worst-case scenario, may not being able to make an emergency call.
At the root of this issue is a lack of interoperability between devices and networks. The original VoLTE standard, which is based on the IP multimedia subsystem (IMS), allows for many different deployment permutations and options, complicating life for both network operators and device makers. This led to some handset makers resorting to blocking usage of the technology on unknown/untrusted networks on the basis that they can’t be sure their customers would have a good experience. In addition, even when a device supports VoLTE on a home network, it may not support the technology when roaming on to another network due to a lack of a VoLTE roaming agreement. Globally, only 275 MNO networks support VoLTE roaming.
Cutting through the complexity
In the GSMA’s Networks Group, we are addressing these issues by helping operators and device makers to narrow down the implementation options and create more consistency across VoLTE deployments. There are only about 50 IMS parameters, but they allow for multiple different settings, so there are hundreds of potential configurations to support an IMS-based service, such as VoLTE. Still, many of the different network settings are very similar and can be consolidated without any material difference to the functionality.
In 2021, the GSMA defined six standard service-based IMS configuration profiles for mobile operators to adopt. Two years later, we rationalised these six profiles to two – P#4 and P#6. P#6 is a superset of P#4 (i.e. it adds VoWiFi). The GSMA recommends mobile operators adopt P#4 or P#6, and that device makers support P#6 and allow VoLTE on any network.
In response to industry concerns raised in 2022 regarding the availability and interoperability of IMS emergency calls, the GSMA established a Board Level Task Force (TF) to address the emergency calling issue. The TF has endorsed P#4 or P#6 for VoLTE interoperability.
To employ VoLTE on networks that predate these measures, devices can consult the GSMA NSX Database to see how a specific network has configured VoLTE and then adjust their settings accordingly.
As one-to-one testing is often not feasible, the GSMA Networks Group also runs a VoLTE testing service and informs device makers of accredited networks and vice versa. Device makers are then encouraged to engage with accredited networks to enable VoLTE.
Through these measures, the Networks Group is breaking the testing logjam and enabling our members to finally realise the many benefits of IP-based communications.
For more on this topic, watch our latest LinkedIn Live webinar on VoLTE Challenges where Wayne Cutler, GSMA shared next generation work on VoLTE, covering specs, emergency service challenges, and how testing led to the Interoperability service. Miguel Monforte Nicolas from OXIO gave an operator view, highlighting how interoperability testing supported smoother deployment and collaboration with device makers.
Get involved
If you’re a GSMA Member and interested in collaborating on this topic, please join the most relevant working groups for you on Member Gateway.