Andrew Seybold: Intro to IMS--Simplifying the network


We are hearing a lot about IMS these days, but what is it? Most of you probably know that IMS stands for Internet Protocol Multimedia Subsystem, and perhaps you know it is intended to replace the wireless network operator's current complex back-end architecture with simpler architecture based on routers and IP soft switches. Today's wireless networks grew up using massive hardwired switches based on SS7 (Signaling System 7), which was invented by AT&T to replace its older switching systems already in use.

If you look at diagrams of most wireless networks today, you will see that in addition to a large number of MSCs (Mobile Switching Subsystem), over time a number of servers have been added for a variety of additional functionality including SMS, IM, MMS and other forms of voice and data services. The problem with these wireless network back-ends is that they have grown up piece-meal over time and have become extremely complex. Another problem is the large number of touch points,or different connections to the outside world's wired and wireless systems, that have been added over the years.

The idea of IMS is to simplify all of these connections and, over time, replace SS7 switches and other hardware components with IP components where most of the work is done in software. While numerous IMS systems are under construction, many of them got their start when 3G data services were added to the networks. Airvana, a Massachusetts company, has been pioneering in this area for a many years, AT&T, is building an IMS system based on Alcatel-Lucent technology and systems around the world are coming on line.

Even though the IMS standard was adapted for wireless by the 3GPP (3rd Generation Partnership Program) and the 3GPP2 (the CDMA version of the standards organization), there are still many differences between IMS systems being deployed. In some cases, the network operator finds out that the equipment it is installing has some proprietary components embedded in it. As with any standard, vendors want a marketing advantage.

Although IMS was updated for wireless by the 3GPP, there are still a number of issues that make “standardIMS less than optimal for many wireless networks. There is the issue of IMS being designed to handle SIP (Session Initiation Protocol) applications but not doing an optimal job with non-SIP applications (the bulk of what is being used today). Another issue is that “standard IMS still has what some consider to be too many touch points to external networks and not enough security across the network to defend against rogue devices or content.
These issues are currently being addressed in both the 3GPP and the 3GPP2 thanks to the leadership of Verizon Wireless and a consortium of companies that have reviewed the specifications and made additional recommendations. The result will be a more secure version of IMS with a single touch point to trusted sources beyond the network and a more secure network that could be disengaged from the rest of the worlds networks if there were a massive denial of service or other disruption on the wired Internet or elsewhere.

Everyone in the industry believes that IMS, or at least IP in the network back-end, is the ultimate goal. We also know that all of the new wireless technologies including WiMAX, UMB and LTE are being designed to embrace IP from devices through the entire network back-end. The results will be long time coming though, as there are a number of issues yet to be resolved. If you look at a diagram of a typical IMS back-end, you will see that it has grown to be almost as complex as today’s hard switch systems, and then there is the issue of a network dumping SS7 switching, which is still carried on the books and being depreciated.

All of this will work itself out. What are the benefits for wireless network operators? They range from a better, easier-to-manage network, to less capital expense and less operating expenses. The resulting benefit is that wireless network operators will be able to deliver voice and data services less expensively in the future.

What does this mean for end users? Over the long term, as the cost to deliver voice and data across the networks declines, the cost of using voice and data should also decline. Finally, because we will, at some point, live in an all-IP world, we will have more flexibility to access other networks, different content and a new set of services these systems will enable.

Like any new technology upgrade, conversion to IMS will occur slower than has been predicted and there will be bumps along the way. But once we get there, wireless networks will be more efficient, and services to the customer base will be more plentiful and less expensive.

Andrew M. Seybold is an authority on technology and trends shaping the world of wireless mobility. A respected analyst, consultant, commentator, author and active participant in industry trade organizations, his views have influenced strategies and shaped initiatives for telecom, mobile computing and wireless industry leaders worldwide.

Note from editor: Learn more about IMS and it's potential at IMS 2007 Sept. 19-20 in Washington, D.C. Hosted by FierceMarkets, this event delves into the technical and business aspects of deploying IMS. Here's a link to the agenda.

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