IMS Telephony – the long term plan for many operators, but still many years out.
VoLGA – by far the best interim solution for voice and SMS over LTE.
Then below the line, we have:
CS Fallback – a train wreck of a specification. Any operator who spends just 1 hour evaluating CSFB will realize it can not and should not ever be deployed; a technology with no visible supporters. Literally a "step backward" for LTE.
Fast Track voice over LTE – this NSN sponsored approach, announced with some fanfare a couple weeks back, has no visible support outside of NSN.
Maviner/Acme Packet – as reported by Unstrung, this approach is similar to NSN. It’s too early to say where this will fall out, but we decided to file it ‘below the line’.
So what’s the common thread? Why are there now five different approaches to voice over LTE?
I think there are two key points:
First, while everyone acknowledges that IMS Telephony is the long term, four solutions have been proposed solely to provide a transition towards that end. I think it’s clear IMS still has a ways to go.
Second, VoLGA, along with Fast Track and the Maviner/Acme Solution, have all been developed after CSFB. If CSFB was adequate, there would be no need for these alternatives. The one thing which unites them all is that CSFB is doomed.