Standards Watch: IMS Could Be the Key to Wireless-Wireline Convergence

Carriers want to enable users to engage in a voice call that seamlessly migrates into a mobile call with the same device as the user roams from house to car to work. They also want to add to that session the ability to simultaneously transmit a text message, picture or video from the same device in the same session. However, the complexity of managing balances, brokering services and the inherent authorizing, provisioning, charging and billing that must ensue makes true quad play a daunting proposition.

The key to enabling those types of services is a common standard or roadmap; however, some confusion surrounds IMS (IP multimedia subsystem), as many hardware, billing and OSS vendors are claiming to be "IM-compliant" when in fact no real standard exists as of yet.

Unlike with TCP/IP, or Parlay or GSM or SIP, there is no IMS governing body possessing a unified set of protocols and equipment that "compliant" companies must use.

Rather, IMS has emerged as a way to incorporate all the influential wireless and wireline protocols and standards—and most importantly philosophy—for how to swap out and swap in pieces to ultimately achieve a service- and customer-oriented set of converged services.

While Parlay, SIP, Diameter, Radius, H.323 and a host of other standards have been tweaked here and there to fill IP voice, data and multimedia "voids," there exists no one particular standard for creating an IP-centric view for controlling end points of an IP network at this point in time, nor may there ever be.

What has happened, however, under the auspices of 3GPP (with overlapping members of the IETF, GSMA and ITU), IMS is evolving as a roadmap for how network elements in an architecture will interface and interoperate to enable simultaneous use of different media in the same session, or in multiple sessions.

Rather than having hardwired functions for something like prepay, where IN vendors supply tightly integrated protocols and hardware to support balance management or session management, rating and other functions, IMS defines the various components and establishes many layers of control. IMS defines a service layer to enable applications and services; a transport layer to provide access to different access networks (cellular, fixed line, cable, etc.); and a control layer based on SIP to enable services and applications to operate across multiple access networks.

Because functions are defined at the service control layer in IMS, this environment introduces a level of control that has generated a lot of appeal for manufacturers.

The control layer exists above the network as we know it—the switches, routers and OSS—and the service layer above that. Utilizing the softswitch technology at the control layer, the network is supposed to enable better control of sessions, as well as control over unwanted Internet telephony traffic (such as Skype). On top of the control layer is the service layer, which resides at the IMS IP-based core.

Because IMS defines the interfaces between the control, service and transport layers, all interfaces among IMS "compliant" vendors will be much simpler. The element of differentiation will be in how vendors populate those three layers.

In fact, IMS grew out of backlash from the hodgepodge of applications and network elements that service providers had to grapple with during integration efforts. What IMS has done is force manufacturers to the table to agree on what pieces and components must be decoupled and opened up so that interfacing to key elements and components would be drastically simplified. That means a more unified view by manufacturers, and for the billing and OSS vendors that must interact with their network elements.

Although it is true that each hardware vendor is coming up with its own PowerPoint version of the IMS architecture, the purpose is more to demonstrate the framework with each vendor's flavor of elements in the picture. Unlike other evolving standards, the IMS concept remains surprisingly consistent.

"If you remove the logos from the PowerPoint presentations, the philosophy is truly consistent, which means good things for vendors like us and for the service providers overall," says CSG's Will Rotch, CTO of the Americas. Because IMS promulgates decoupling of elements, billing vendors can more readily interface with components of the overall architecture, making it easier to move billing to the application layer.

"IMS forces manufacturers to separate out session and balance management into a control layer—rather than develop proprietary functions—that enables billing vendors to create modular solutions built around SOA concepts. That means billing vendors have a decoupled place to plug in, so we can be more real-time," says Rotch. "Billing can now become a service in and of itself, as billing, in essence, will run like a service, with authorization, charging and rating all running as low-latency services within the IMS architecture."

Because mechanisms that tie to billing systems can be put directly in the path of a session, according to the IMS philosophy, billing systems can become "always-on" entities that process CDRs in the network immediately and base decisions on customer information in a matter of milliseconds, rather than days. That means billing becomes a pay-now, authorize-now, charge-now practice facilitated by a mechanism that sits next to the network. If there is a need to authorize a service, then the mechanism calls on the authorization service or the session management service, depending on what the user is buying.

That also means that pre-event or even mid-event authorization for online gaming among a group of people simultaneously playing, text messaging and talking could be possible.

Indeed, carriers no longer want the network-centric approach of just cutting customers off when balances run dry. Rather, usage-centric models would mean moving knowledge about the type of customer into the network itself, so that charging controls exist in the network and in-session decisions can be made.

"Just having really fast rating or charging is not the same thing," Rotch says. "This goes way beyond that, as you must now take customer data models and customer information and break them out into pieces so billing can be done in a truly service-oriented manner."

With billing, the charging will have to become more pervasive than has traditionally been the case. "If you have fixed and mobile users over the same backbone, you must figure out roaming with prepaid authorization, which requires [that] visited networks versus home networks be known, as well as the networks and applications delivering the multimedia/multisession applications," says Elisabeth Rainge, program director for next-generation OSS, billing and network management at IDC, which is assembling research to identify opportunities in IMS infrastructure and professional services. "Because the IMS control layer bridges the gap between network functionality and business and application management, there is now a focus on management around presence, location and messaging."

She notes that interest has grown about the charging part of the IMS standard, originally written by Amdocs, but now a focus for companies like Lucent, Alcatel, BEA, IBM, HP and Sun—all of which are working closely with OSS/BSS vendors.
"The focus in IMS initially was geared toward the wireless space, but we want to help emphasize the importance now of the wireline piece, because we see the convergence of voice, video, data, multimedia and now mobility as the killer app," says Mike Cooper, director of global marketing and strategy at Lucent Technologies' Convergence Core Solutions Group. Lucent has submitted more than 1,400 contributions to the IMS standard and has members who chair various committees. "The value of reducing the overhead in the network and placing emphasis on services architecture as opposed to physical architecture is something we really believe in," says John Scaldaferri, senior product manager at the Convergence Core Solutions Group.

As customers increasingly augment their fixed assets by buying into WiMax licenses, the concept of "lifestyle services" is growing. "It's the notion of bringing together independent applications so that shared assets—like buddy lists and family services—affect the lifestyle of customers," says Cooper. He notes the value of being able to call family members based on location, or to have access to work and personal lists regardless of where the person is located.

"If you are on a conference call," Scaldaferri says, "and you want to seamlessly move the session from your office to a boardroom so you can share data or video files with many people, and you want to email co-workers in the same session about meeting in the boardroom to look at the files, you need the type of session control facilitated by IMS."

While most IMS talk revolves around the core, handset problems at the edge are expected to be resolved as mobile handset manufacturers take interest in IMS. One such player is Motorola. "We recognize IMS as the most cost-effective way to launch new services, and to facilitate the creation of OSS/BSS mechanisms necessary to charge, provision and tear down," notes Venkat Eswara, senior marketing manager for Motorola. Because IMS is "scripted" to IP services, Eswara says, it will help define what interfaces to legacy and existing services are needed for pure packet services to interact with SMS and legacy services in general. "If a group is engaging in a real-time call and they want to send pictures or video to someone who is not present," he says, "then they need push-to-talk and push-to-view capabilities to do store-and-push simultaneous with the real-time sessions."

Another missing piece of the puzzle involves OSS: "In IP, service management can mean many things, which makes IMS challenging from an OSS perspective," says IDC's Rainge, referring to the lack of news about IMS in the OSS space. "Except for billing or charging vendors, I don't see OSS vendors taking a clear position today, because they are waiting for the network to be built and the products to come to market."

As that life cycle issue resolves itself, IMS is expected to become as important in the United States as it has been abroad, where GSM has expedited its acceptance.