Sunday, April 15, 2007

Three Axes for IMS: #2 Multimedia Communication

As I wrote in the previous entry, I see three main axes around which the potential of IMS can be exploited.

After, fixed mobile convergence, the second one is Multimedia Communication.

Once again, the term is ambiguous, and I am not sure what was really meant when the name "IP Multimedia Subsystem" was initially cornered.

For some people with a classical telco culture, "multimedia" means more or less "voice and video telephony".

You already get closer to the truth if you consider that IMS is "multimedia" because it can support a variety of communication means, including, voice, video, messaging, and various enrichments of them.

My definition goes further and is directly derived from the SIP protocol and its session control capabilities.

Since its "capture" by the enterprise and telco domains, SIP has been wrongly labelled as a "VoIP" protocol. From the begining, the concept of SIP session was defined as a very generic rendez-vous mechanism. A SIP session can include any type of media and/or any type of application. You can set up a SIP session to play a game, watch a video, share a browsing experience with your friends, chat with them, or perform all of this in sequence or in parallel.

A SIP session therefore permits to share a service context between a user and an application, or between two or more users. Each service within the SIP session can use its own protocol(s), and SIP is just setting the framework for these protocols to be used between various endpoints until one of them decides to call it quits.

A SIP session can be re-negotiated at any time, as some media components can be added, removed or replaced at any time.

Here is a potential multimedia communication scenario: Mary receives a call set up request from Paul for a voice session. As she is currently sitting in a train, she answers that she prefers a chat session, which is then established. When leaving the train, she upgrades the session to voice so that she can speak while walking back home. Arrived at home, she transfers the ongoing session to her PC, and enriches it with a peer-to-peer game. After some time Paul decides to drop the voice component as he is losing and blames Mary's taunting comments for this. At the end of the game, they decide to share their web browsing and re-establish a voice component in order to jointly select on the web a restaurant for dinner.

Multimedia communication according to SIP is likely to revolutionize the way people communicate...unless SIP multimedia capabilities are never used to their full extent.

It is a fact that early IMS implementations totally ignore the multimedia capabilities of SIP. Whether the service is Push To Talk Over Cellular (kind of walkie-talkie for cellular handsets), VoIP, or Instant Messaging, the assumption is that a SIP session is composed of a unique medium negotiated at the begining of the session and valid until the end. Specific application servers have to be deployed in the network, which permit the SIP session to only include the medium specified for the service. While it is possible to extend the specification of the service to support one or more additional media, this will lead to the ad-hoc extension of the media support within the application server. An operator may therefore end up extending a push to talk server to support messaging, a messaging server to support voice, and a voice server to support gaming, without never truly supporting a multimedia communication experience, just "rich PoC", "rich messaging" or "rich voice" services.

For me there are three big challenges an operator will face regarding multimedia communication:
1) Deploy an IMS infrastructure which permits multimedia communication between IMS (and other SIP) endpoints.
2) Deploy applications that add value to the end-to-end multimedia experience of the users (thus making useful to have a network between them!).
3) Deploy applications which exploit the multimedia capabilities of SIP to provide the user with a unique and optimal service experience.

To be frank, at the moment the industry is still struggling with #1. However, it is a good sign that the Open Mobile Alliance (OMA) has started to work on the Converged IP Messaging (CPM) enabler, which tries to incorporate such a multimedia experience in the telco network.

Christophe

1 comment:

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