We are currently experiencing a rise of interest in mobile operator VoIP services as carriers move to protect their voice revenues from the likes of Skype. The reason for this rise is almost certainly tied to the imminent global roll out of LTE. AT&T has announced a service named Call International and Telefonica has announced TuME. Even T-Mobile’s Bobsled service would come into the category, although it’s definitely a unique experiment.

To accomplish these moves into VoIP, AT&T outsourced the service to 8×8, Telefonica is using a completely separate infrastructure via Jajah, and Bobsled’s service is built on the Vivox platform. The point is – none of these is actually IMS based.

Why would an operator want to offer their own second line service? It’s simply a case of “if you can’t beat ‘em, join ‘em”. OTT VoIP providers like Skype are starting to cut into mobile voice revenues, particularly international direct dial. Operators are left with three options:

  1. try to block it
  2. lower the IDD rates across the board
  3. offer a similar/competing product

There are two basic routes open to operators – primary or second line VoIP service. The current trend is for a second line. This is largely down to technical hurdles – more of which later, but simply put, creating a second line is more manageable.

At Mobile World Congress 2012, Kineto Wireless announced Smart VoIP, a second line service which uses the operator’s existing infrastructure rather than relying on outsourced components. Second line services such as Skype, Call International, and Bobsled, are where the user still has a primary mobile service/number (running over GSM most likely), and an OTT VoIP App is adding a second identity (requiring a separate user/password or phone number). The second line identity is only available when the App is running.

LTE, however, holds the promise of primary line services – naturally these are more attractive to consumers. Unfortunately for carriers, there are some significant hurdles to overcome with primary line. It uses IMS/SIP, but of course, any SIP/IMS gear the operator bought for services at the end of the last decade is likely to be hopelessly out of date.

One very difficult part is session continuity between the existing 2G/3G circuit voice core network and this new IMS/SIP VoIP core network. Imagine the user starts a call over LTE, the call is anchored in IMS-land. LTE coverage fades, now the network needs to figure out how to pass the call into a circuit voice session over 2G/3G. First is the technical complexity of switching from LTE to 2G/3G, then comes the complexity of changing from a VoIP session to circuit, and then comes handing the ‘context’ of the call from one call manage (IMS) to another (circuit voice MSC).

The evolution from 2G to 3G only had 1/3 the challenge of VoLTE/LTE. It needed to hand a call from one radio resource (2G) to another (3G). However, both calls were circuit, and they were both anchored in the same circuit MSC. Recall how long it took to get handover from 3G to 2G? Years. And radio handover is arguably the easiest part.

This is a part of the complexity VoLGA addressed. VoLGA took the operator’s existing circuit voice service from the MSC and delivered it to an LTE phone as a VoIP session. The call remained anchored in the same MSC, and was still a circuit session. All that needed to happen was radio resource handover.

I think LTE, and LTE devices, will be a game changer as other companies jump into OTT. Could AT&T put their OTT VoIP product on a Verizon LTE phone? Well, the jury’s out. The future is bright, but it is still a long way off. For a while, FMC and the single contact number seemed inevitable, but that did not come to pass. It could be that a single line ‘primary’ VoIP service becomes a modern day FMC.