Let me make a bold assumption: Even in 10 years from now, people will still use their mobile device to call each other. Many other forms of communicating with each other have sprung up over the years, SMS, eMail, instant messaging, Skype video calling, Facebook, etc. etc. And I am a heavy user of most of them. Before I call someone I usually prefer other forms of communication, less interrupting, less direct, less intrusive. But still, voice calls remain important to me and I don't see that change anytime soon. But how will I do voice calls in 10 years from now?
Shouldn't be too difficult to figure out, should it? Back in 2008 I wrote a full chapter in one of my books about mobile voice options in the future but which way it would go was still unclear. Now, four years later, I've revisited that chapter and I have come to the conclusion that there are even more options today and even less clarity of were it will go.
For the IMS supporters the way forward is clear. The VoLTE profile for IMS will be the ultimate solution in the future. The road, however, is long and thorny. CS-Fallback will be used by many to bridge the time until VoLTE can be introduced. Good luck with the longer call setup delays. Once VoLTE has launched, Single Radio Voice Call Continuity (SR-VCC) to a circuit switched channel will have to be used by many network operators until LTE networks are really ubiquitous. IMS, CS-fallback and SR-VCC including IMS centralized services, each system is a daunting task to introduce. CS-fallback might be the easiest one. But even here here, complexity should not be underestimated.
Then there is or was (who can say today) the VOLGA approach that reuses the Generic Access Network (GAN) approach to reuse everything of the existing circuit switched voice solution except the radio layer and send everything over IP, no matter whether it's Wi-Fi (as in GAN) or LTE (as in VOLGA). It's appeal is its incredible simplicity to implement, no new voice infrastructure but only a gateway box, no new billing system, the current one continues to be used for all subscribers, straight forward implementation in mobile devices with reuse of already existing GAN software, e.g. on Android devices. But it's not loved in the operator world so the best this solution can hope for is its reincarnation.
But perhaps even VOLGA is too much to do in the day and age of ever falling prices for voice minutes. So how about dual radio phones? One baseband for the data and one baseband for telephony. The HTC Thunderbird LTE smartphone sold by Verizon for example has gone this way. It's the first of its kind, so its bulky and power hungry. But look at early GSM or UMTS phones, they didn't win exactly prices for slimness or power efficiency. So there is reasonable hope that over time, even dual radio designs can become small and power efficient. But it would mean that "legacy" infrastructure would have to be kept and maintained indefinitely. Perhaps it has to be kept anyway to support those people just wanting a 10 Euro phone for voice and SMS. Yes, there will be fewer people in the future buying such phones but I predict it will still be a sizable group. And then there's all the M2M equipment in embedded systems and perhaps cars in the future with eCall in Europe. No way that in the next 15 years, the infrastructure required to communicate with those devices goes away. So perhaps dual radio will reign?
Or should perhaps Apple with Facetime or Microsoft with Skype become the standard voice and video solutions on PCs and mobile devices? Great, I can't call my friends with an iPhone anymore and vice versa. But perhaps Apple and Microsoft strike a deal and make a gateway between their worlds. I wouldn't count on it. Also, while networks are built like they are built today, especially in the US, over the top voice services will continue to be unreliable at best over mobile infrastructures and drop as soon as you run out of LTE or HSPA+ coverage. So I don't think that's going to be the ultimate answer either.
There's no single solution I look at today from which I would say, 'yes, I'm sure this will be the main telephony service in 10 years from now'. So perhaps a little bit of everything? Or will one of the solutions be able to overcome its weaknesses? From my point of view, the most difficult thing to predict in mobile today is how telephony will work in 10 years from now. Compared to that, everything else is a piece of cake.