The Subsystem Is the Message

1/27/2006 7:04 PM Eastern

In the not-too-distant future, Jane and Joe Cable Customer are at home watching their favorite TV show when an alert flashes on the TV screen. It’s an urgent text message from their 17-year-old son, sent from his cell phone. So Joe grabs the TV remote, pauses the live TV stream and opens the message.

It turns out Junior has bashed up the family’s Ford in a fender bender, and the police need Jane and Joe to come fill out paperwork at the crash scene.

Joe got the message because his cable provider had a network smart enough to know two things: that he had switched off his cell phone, and that he was watching TV on a fancy interactive set that could accept text messages. Thus, the network automatically forwarded the message.

Tech Spec
Internet Protocol Multimedia Subsystem (IMS)
What it is: A standard way for delivering signals to different devices in a network, so they can jointly deliver a service to a stationary or mobile user.
How it works: Moves and manages signals throughout the network so instructions on how to set up a data stream, how to monitor it and how to send any data from the session to the network’s billing system are relayed and acted upon.
Known problems with it: A complex standard, it can be difficult to implement if network gear manufacturers or carriers choose slightly different versions.
Why it’s important: If adhered to, any server or other computing device in a network can participate in the delivery of service, regardless of what kind of visual, aural or textual action or file is involved.
Who uses it: BellSouth and AT&T are now installing it in their networks; cable operators are testing the technology.
Why they use it: IMS will allow network providers to offer new services that blend TV, Internet and wireless communications, so customers can get their content any time, anywhere and with any device.


That ability to deliver content and communications across any network to any device is a real possibility with the rise of a technical architecture for delivering audio, video and text services to both mobile users and those “fixed” in place, such as at home or in the office.

This Internet Protocol Multimedia Subsystem likely will be used not just by cable system operators, but also by wireless and wired telephone companies who want to deliver services like those used by Joe, Jane and Junior.

“What really matters is eyeballs — that’s what really counts, with the ability to connect to a [personal digital assistant], to connect to a set-top box, to connect to any device that allows you to render a service to an end user relative to where they are, what they are using and what they need at that particular point in time,” said John Marinho, Lucent’s corporate strategic marketing vice president. “And it is those assets combined with IMS that really then represent a significant advantage for a service provider to go to market.”

A product of the cellular world, IMS is a signaling architecture — in geek-speak translation, that means it provides networks a set of instructions on how to direct signals between two points, be it a network server and a user or from user to user.

In IP networks, it sets up the connection and identifies the point of origin and destination. The subsystem also checks whether the sender and recipient are authorized users, monitors the transmission and then feeds data on the session to a carrier’s billing system.

An IMS network brain consists essentially of a subscriber directory server in the network operations center linked to intelligent services gateways that translate IP and telecom traffic from other provider networks. That distributed brain can also keep track of what device a subscriber has, and use that information to send a video or other multimedia stream that will fit that device’s display.

Moreover, the architecture allows multiple services such as voice or video-on-demand servers to share databases detailing who customers are, where they are and what devices they are using. That, in turn, could not only cut out duplicate databases but also allow operators to fuse two or more applications — such as voice and video — into sexier new service offerings.

Work is already under way at CableLabs Inc. to bring IMS into cable networks. The Louisville, Colo.-based research consortium has made the subsystem the core of its draft PacketCable 2.0 standard, set for release later this year.

The protocol was built originally for cellular wireless systems “and there were a lot of details that need to be tweaked or enhanced in order to support cable,” said Eric Rosenfeld, the CableLabs director of PacketCable architecture. “So we are basing PacketCable 2.0 off of IMS, but we are also doing a lot of work to ensure that it meets the needs of cable.”

Nor are the operators standing still. Time Warner Cable is backing the PacketCable 2.0 specification and is already testing the technology, with an IMS lab up and running in Herndon, Va.


What’s exciting to operators like Time Warner is IMS’s ability to deliver services that cross what are now network boundaries. A case in point is phone service that combines Wi-Fi and cellular wireless connections, offering customers a single phone for use in the house our elsewhere.

That’s a service Time Warner is eyeing, particularly given its involvement in the recently announced cable consortium with Sprint Nextel, aimed at delivering new cellular voice products.

But while much of the early applications will focus on voice, “the truth is, you can use that subsystem to converge any kind of services you want,” said Time Warner Cable chief technology officer Mike LaJoie.

Take video, for example. IMS could allow video clips to be funneled to a wireless handset from a Time Warner video server or Web site, or some other partner’s Web site, LaJoie said.

“Obviously, you are not going to send [a cell phone] a 3.75 Megabit-per-second video stream. It won’t work,” LaJoie said. “So somewhere in the middle of that, in that IMS core, you are going to have a service called transcode.”

That IMS-driven transcoder would automatically scale down the video file before firing it off to the customer. And it could make that adjustment for cell-phone or computer viewing, LaJoie added.


An application Lucent has already developed is an active phonebook. Displayed on a wireless phone, TV or computer screen, the active phonebook presents a list of contacts and their connection status —that is, whether they are logged onto a computer or cellular wireless network or watching interactive TV, and what device they are using.

Such applications may start showing up this year.

“From what we’re seeing with the market and working with customers, I think you’ll start to see a lot momentum gaining speed in the market throughout 2006,” Lucent’s Marinho said. “And then I think you’ll see full-scale commercialization of services in terms of things that are out there in stores and Web sites that you can buy and order, certainly by 2007.”

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