The big problem for VoLTE...

... is that there are at least 10 completely separate problems for VoLTE.

I've long said that VoLTE is a good idea in principle (ie having a standardised "plain vanilla" carrier telephony service for wireless IP networks). Over six years ago, I predicted this was necessary, but would face many practical difficulties, so getting started ASAP was important, even on old HSPA networks before LTE.

It took years before fixed VoIP worked well. It was invented around 1997, but it was a least 7 years later that it even started to be reliable on enterprise Gigabit Ethernet LANs, where the CIO was free to use whatever equipment and QoS tools were needed. The first carrier broadband VoIP was launched by Softbank Yahoo in Japan in 2002. Twelve years later, we're still at less than 30% replacement of global circuit PSTN today.

The idea that adding not just cellular and mobility, but a completely new radio, RAN & EPC architecture to the mix would make 4G VoIP any quicker to launch/deploy/adopt is wishful thinking of the highest order.

And so it goes.

I keep getting pitched by vendors with solutions to bits of the VoLTE puzzle I hadn't even realised existed. Yesterday was the turn of Stoke, talking about latency inside routers and gateways from packets having multiple hops between functional blades doing DPI, encryption, routing and so on. Apparently the impact on small packets (step forward, voice calls) is particularly bad. I'm not a router-architecture specialist, but it sounds plausible. Apparently it's also a problem that will get worse as NSA-inspired paranoia inspires telcos to put harder crypto in various bits of their IMS/voice networks in future. 2048bit-wrangling won't be quick or easy, especially if it needs to be done sequentially with all the other functions in the chassis.

I'm just adding that to the ever-growing list of serious obstacles that VoLTE faces in actually getting to widespread launch and adoption.

An incomplete list of VoLTE's problems, some technical & some non-technical, includes:

- LTE coverage & capacity being good enough (including indoors)
- LTE backhaul being good enough
- SR-VCC not working very well
- Handset availability
- Handset battery life
- Handset client UI
- The need for some sort of IMS platform & all that entails
- Roaming- 911 / 999 / 112 emergency calling
- Internal VoLTE network security (vs hacking, DDoS etc)
- Integration with billing & OSS & support systems
- Multiple layers of QoS mechanisms, from the radio to the core
- DIAMETER to handle all the signalling from all of the above bits & pieces
- Making all the "furniture" like ringtones & voicemail work OK
- API exposure platforms if needed
- Handoff back to 2G/3G circuit (& coverage, RF etc etc)
- The normal interop issues between vendors' & OEMs' gear
- How does a VoLTE MVNO work, exactly? (Anyone heard of one? No, me neither)

Oh, and if fixed-VoIP is anything to go by, we'll probably be dealing with a host of new & exciting acoustic failure modes that require a black-belt network & device media-engine ninja to diagnose.

Most of these issues are completely orthogonal to each other - and are being fixed by vendors who are probably mutually unaware of the existence of each other, or each other's problems. The likelihood of inter-dependence is probably high. All the fun new stuff coming down the 4G/5G pipeline like coordinated multi-point networks, small cell overlays, carrier aggregation & so forth probably won't help either.

Meanwhile, in most advanced markets there is now flat or declining demand for vanilla telephony (& revenues/profit associated with it), even in perfectly-working GSM guise. Except where previous high prices & elasticity means a bit of latent demand still lurking, usage minutes are going to fall in future. And no, so-called "HD" voice won't make a blind bit of difference - it's available for 3G already, if it mattered that much ,and it doesn't.

In other words, VoLTE is now very late, with new problems emerging all the time, which are likely to be ever more expensive to fix. It's serving a declining market for a 120-year old product that consumers are starting to desert and dislike. It's based on a clunky, expensive and complex application platform (IMS) which isn't fit for the 21st century's communications trends. And all the old networks & CS systems will need to be kept in place for at least a decade (maybe two) in most countries, adding to the overall OPEX.

Not pretty.

And in other news, I've had inbound calls on both FaceTime Audio and Skype on my LTE iPhone in the last couple of days. Both needed a couple of seconds juggling with the UI to unlock the screen & answer the call, but seemed to work fine (with HD & optional video, obviously) once they got going. And I'm not even going to mention WebRTC's inevitable rise over the next couple of years.

I'm sure we'll hear lots about VoLTE in Barcelona. But as of yesterday there were 268 LTE networks operating in 100 countries (source: GSA), yet I count only 4 "proper" VoLTE (3 Korean telcos + MetroPCS) launches and a couple of press-release face-savers. That's a big enough red flag.

So, how many more "big problems" still need to be fixed for VoLTE? That's the problem. We don't know. And worse, most of the problem-solvers don't even know each other. I wouldn't want to be a vendor dependent on this space, as you're relying on many many other peoples' ingenuity rather than your own. I'd be investigating alternative sources of business too.