IMS for Mobile Operators

I will try to dedicate a series of posts to analyze how I think IMS is perceived by different types of operators.

I will first focus on mobile operators, as this is a world I have known for years. I will then speak about fixed operators, and finally about operators that have both fixed and mobile organizations. Unfortunately I have too little knowledge about cable operators to dare saying anything about them.

IMS was an invention of the mobile industry, as its standadization started as early as 2000 in 3GPP (with initial work started the year before in the AT&T Wireless -led 3G.IP initiative).

The positioning of IMS in the cellular world cannot be voice-centric, for the simple reason that 3GPP specified a softswitch architecture as part of 3GPP R4, which permits to support VoIP within the mobile core network while keeping circuit-switched channels on the cellular access. Many mobile operators have deployed or are currently deploying this new architecture, and this is not to replace it with IMS in the next few years.

This is why, from the begining, 3GPP defined IMS as a network initially for "new multimedia services" and then, years later, to eventually replace the circuit-switched core network and therefore support legacy services as well (at least those that still make sense at the time).

An issue is that 3GPP never came up with a clear definition or list of such "multimedia services" (though it could be rightly argued that this was not the role of 3GPP to do it), and little progress has been made to this respect in the last years.

There are other important handicaps for using IMS in a mobile context:
- Current cellular access cannot efficiently support real time media over IP (e.g. conversational voice or video)
- Mobile handsets are still closed devices, and introducing openness and innovation into them is a slow and difficult process.

A consequence is that mobile operators will try to think of IMS in terms of "innovative services". However, the telco industry has shown so far little proficiency in creating innovative IMS services, and even when it does it faces the challenge to implement the relevant support for these services in mobile handsets and in application servers.

Push To Talk Over Cellular (PoC) was the first mobile IMS service to appear. The idea was to adapt a successful enterprise group walkie talkie service implemented on a circuit-switched network to the residential mass market and IMS. PoC has the (technical) advantage of relying on talk bursts instead of real time bidirectional voice. From a business perspective, the results are mixed, to say the least.

Then came so-called combinational or rich voice services, which try to combine a voice call established using the circuit-switched network with a data session over IMS. The approach permits to address the cellular voice over IMS problem, by integrating circuit-switched voice with non real time IMS services. It requires mobile handsets able to concurrently use circuit-switched and packet-switched sessions, with a client that transparently combines them for the end user. This approach led to "Push To X" services, permitting for instance to send pictures or to stream a unidirectional video during a voice call. Whether they are successful or not, such services are certainly not enough to support a convincing IMS business case.

IMS Messaging might deliver very interesting services for mobile operators, but this part of IMS/SIP standardization is not totally mature (at least from an implementation perspective), and in the meantime operators tend to directly support Internet IM integration (e.g. Google, Yahoo). The positioning of IMS Messaging with legacy SMS and MMS (with risks of cannibalization) is also an issue to consider. On the other hand, and unless I am mistaken, the positioning of IMS messaging with the pre-IMS mobile IM standard called OMA IMPS (formerly Wireless Village) is currently being addressed by this latter finally not taking off.

IMS Presence might also be very interesting, but presence is an enabler more than a service, and interesting applications of this enabler have not spread too much in the public sphere. A related issue associated to presence is that few know what the real potential of this enabler is, as many still associate it only to Instant Messaging or the basic indication of the ability/willingness of a user to communicate.

One of the latest trends for mobile operators is to link IMS to...VoIP, but not through cellular access. Voice over IMS is possible for dual mode mobile handsets making use of WiFi. IMS may therefore be used to provide VoIP services on WLANs, more especially for enterprises or for residential customers at home or in hotspots. In this area, IMS can be seen as the long-term solution while UMA is more a tactical alternative.

There is no question that IMS is part of the normal mobile evolution roadmap for mobile operators. However, their main problem is to decide when it makes sense to start deploying IMS, and with which services they should start. This is a reason why most mobile operators are still in an exploration phase.

Christophe