One of the greatest frustrations in my career has been the struggle for acceptance and commercial deployments of IMS (IP Multi-media Subsystem) in telecom networks. I started work on the ALU version of IMS with our software release 0.1, 0.2 and 0.3 – which were never intended to see the light of day beyond a lab. But we wanted to get the full requirements process engaged and the development team initialized in the right frame of mind. This was late 2002, when I was director of systems architecture and engineering in Lucent’s Mobile Applications Services Delivery. The initial IMS standards (Rel 5) from 3GPP had barely had time to dry, and had already started significant enhancement/revisions (still occurring). Yet many of us shared the strong conviction that moving voice services from the very optimized, but inflexible implementation that was then common in 2G technologies (and beginning initial deployments in 3G) would be the pathway to an explosion of new services and applications offered by mobile network operators, taking advantage of these new high speed mobile data networks that 3G enabled. We all remember what happened to the wireline ISPs (Internet service providers),.. They had been reduced to only providing a “simple” point to multipoint IP data transport service for a fixed monthly fee, but with constant demand for higher speed (bandwidth) and capacity (data volume). Where was the money for future network investment going to come from, if not from an explosion of new services/applications? How would mobile operators make money once the inevitable influx of these non-operator (aka over-the-top) applications started coming available over mobile networks? Well, at the time, IMS was our answer!
Ten years later, and no 3G network that I know of has implemented IMS as a replacement for its voice core network. Yes, there have been a few supplemental voice services (e.g. push to talk), and several video or other data services implemented using IMS. I worked on a couple of those… None that I know of were commercially successful; though I’m glad the RCS effort continues to show some progress! Using 4G/LTE technology, MetroPCS is still the only US mobile operator with a commercial Voice over LTE implementation using IMS (not ALU’s). And that implementation may not survive the pending acquisition by T-Mobile (sounds vaguely familiar to another wireless IMS implementation that I worked on…). Verizon’s VoLTE implementation has yet to launch, nor any offering from AT&T.
So where is today’s largest IMS commercial implementation? It’s in wireline voice networks, e.g. over 2 million subscribers on just one US implementation. It is most ironic that the first two releases of the IMS standards didn’t include significant support for these wireline networks!! And we’re still waiting for that explosion of mobile operator applications… Oh, wait, I just received notification of some new appls for my iPhone… …uh!