VoLTE – Complexity, Complexity, Complexity

Filed in LTE, Roaming by on October 27, 2016 0 Comments

A lot has been written about the imminent rise of Voice over LTE (VoLTE) and the impact it could have on the customer experience. But many questions still remain in the minds of mobile operators relating to the necessity of even launching and supporting international VoLTE.

Specifically, what is VoLTE’s real global potential? How should operators deal with the whole complexity of providing VoLTE-based services in a global environment? And last but not least, what real and radical impact will VoLTE have on their business models going forward?

My first post in a three-part series on this topic will outline my views on the different complexities that come with offering and supporting international VoLTE termination, roaming and service mashup.

Complexity – national and international termination
Offering and supporting true global VoLTE is not as simple as it seems, as it is dependent on a list of factors, which are themselves dependent on which network, country and region you are in or communicating with.

First, it is dependent on the introduction of the VoLTE technology within an operator’s network at each end of the call – and this may impact interconnections that are both national and international.

In addition, it is also impacted by the uptake of VoLTE-enabled smartphones in each network, both on the originating and terminating side of the call.

Finally, it is reliant on the level of interoperability between VoLTE networks. Because VoLTE is a complex standard that has been implemented with different options in different networks, it is not necessarily a simple task to interconnect with other operators. Within a country, this is obviously worth resolving, but internationally with all the variants of signaling and codecs that you may encounter, there are many problems to overcome.

Now it is obvious that all these events will not take place at the same speed in all networks, which means operators and carriers will be faced with a complex variety of VoLTE call-termination scenarios, with the need to support breakout to a non-VoLTE environment for many years to come. Some of these scenarios that will need to be supported include:

  • End-to-end VoLTE calls
  • Calls initiated on VoLTE terminating on fixed lines and vice versa
  • Calls initiated on VoLTE and terminating on a non-VoLTE mobile device in an LTE network and vice versa
  • Calls between VoLTE-equipped devices and 2G/3G networks.

To add to this complexity, as I mentioned above, even though domestic interconnect issues have been resolved, it is far from clear that an international VoLTE call can be successfully terminated on a VoLTE device in a distant country. In my opinion, there will be a two-year lag between the national and international VoLTE termination capabilities being established.

On that basis then, there are two keys to success for operators and carriers wanting to successfully offer or support VoLTE for their international calls for some time to come:

  1. Evolved call-routing capabilities: The operator or carrier will have to acquire the ability to route (and maybe even charge) the call according to its specificity (end-to-end or non-end-to-end VoLTE), by identifying if a call is both originating and terminating on a VoLTE-enabled handset and network. Routing to the correct distant network is obviously key, so the support of ENUM for number portability becomes another factor.
  2. Network interworking: Finding a good partner – with an IPX network – that is able to handle the interworking challenges on your behalf and resolve both signaling and transcoding issues as they arise in real time.

Complexity – roaming
So far I have only mentioned the complexity of the VoLTE termination environment, both national and international. But one can imagine the complexity of supporting VoLTE calls when in a roaming environment.

Until now, no single solution has been agreed upon by the GSMA when it comes to supporting VoLTE roaming, as each has its pros and cons. But to make something complex very simple, mobile operators and carriers are faced with the following options:

  1. Local breakout or RAVEL (Roaming Architecture for Voice over IMS with Local Breakout): In this case, the signaling associated with the call is routed via the home network to provide evolved features and capabilities that the visited network can offer, with the final media path being routed by that visited network.
  2. Home routing: In this case, both the signaling and the media associated with the call is routed back to the home network as a data connection, and neither the visited network or IPX provider is aware that this is a VoLTE roaming call.


With the case of local breakout, which is closer to what is presently used for 3G calls, comes the risk of losing many benefits attached to a VoLTE call, such as end-to-end quality, service mashup and some availability of more innovative end-user-specific value-added offerings, if the signaling necessary to provide enhanced services is not fully supported.

On the other hand, with the home routing option comes the benefit of not only being able to control the call from start to finish but also of being able to send the call back to the home network using IPX transport or data roaming, and therefore circumventing the roaming rate system. However, calls to other phones in the visited network are potentially routed around the world twice!

Both options come with their set of complexities (both in terms of technology and business models), benefits and downfalls for operators and carriers, and the jury is still out on which option will be the preferred one. Therefore, IPX providers that are in the middle of this equation have to prepare themselves to support both options and their complexities.

Complexity – moving from voice to video
Looking to the future, some of the more exciting opportunities that will come from VoLTE is the possible transition between voice, video and messaging within a single session. I will not go into the technical challenges of enabling this evolution in this post, but I will discuss some of its business model complexities.

By definition, a VoLTE call (like VoIP calling) just generates a stream of data packets and, for purists, it should probably not really be charged per minute. However, for obvious reasons, operators and carriers want to extend the lifespan of the voice-per-minute model as long as they can. Some, however, are starting to question this philosophy and are considering the possibility of using a capacity or data volume business model to support VoLTE. This represents a complete paradigm shift compared with what we have known and loved in the voice business since its inception.

But the case for continuing to support a per-minute business model diminishes with the introduction of in-session transition between voice, video, messaging and file sharing.

While it’s clearly technically possible to track how a specific session has evolved from voice to video and perhaps back to voice, there is currently no agreed-upon commercial model for how that should be charged. The complexity that operators and carriers then face is that if they have 400 directly connected termination providers, and if each has a view on how a video call should be compensated, the processes and systems in place to quote, rate, and settle charges need to be immensely flexible to handle all the potential variants.

There is an opportunity here for more innovative service providers and carriers that are willing to take the step toward a converged voice and data pricing model. Mobile data hubs, for example, that have never had an extensive voice offer, and therefore have nothing to lose, could charge for their IPX network component of VoLTE termination using a capacity pricing model, and simply pass through the different ways that the termination is being charged. Their aim is to build volume and increasingly additional value-added services on top to monetize their customer relationships.

To a large extent, the IP voice service still remains separate from “data” service solely because of the termination charging mechanisms used. But perhaps this VoLTE feature will be the one that finally puts the nail in the coffin of the per-minute voice charging model.

But as I often say, from complexity comes great opportunity. To this end, the next post in my series will address the true opportunity that VoLTE offers to innovative operators and carriers that are ready to take the leap into the new voice world.

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About the Author ()

Isabelle is President and Founder of HOT TELECOM, one of the most innovative and creative telecom research and consulting companies in the industry. HOT TELECOM has been supporting Tier 1 and Tier 2 operators on a global basis for over 14 years, particularly in the international and wholesale areas. Most recently, Isabelle has been working with many of the world's global wholesalers and service providers to help them define their transformation strategy. She has published a number of articles and reports on the subject and has spoken at numerous conferences to share her views on the future of the wholesale business. Isabelle holds a bachelor’s degree in engineering and an MBA in finance, and she has over 20 years of experience.

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