IMS is a label that has started springing up all over the telecom industry, whether on individual products, or as vendor systems platforms or interoperability programs. It’s the acronym for IP Multimedia Subsystem, and it is very, very important – a big vision of the future of telecommunications hangs on it. It’s also very, very complicated and pretty abstract.

This tutorial aims to resolve some of that unfortunate conjunction by providing a quick and easy guide to some questions that are frequently asked about IMS. In the report's initial form, answers to a number of basic questions are given, one per page. But the idea is that readers can ask further questions on the message board attached to this article. If you want to send a private message, please email us, and include "IMS Guide" in the subject field. Frequently posed questions will be answered by adding pages to this report.

For a basic understanding of IMS, here are the key starting points:

• IMS started as a technology for 3G mobile networks (under the auspices of the 3rd Generation Partnership Project (3GPP)), but it is now spreading to next-generation wireline networks and is going to be a key to fixed/mobile convergence. It builds on the Session Initiation Protocol (SIP), which has emerged as the crucial technology for controlling communications in IP-based next-generation networks (NGNs).
  
  
• IMS is about services and applications, enabling telcos, mobile operators, and other service providers to offer rich multimedia services across both next-generation packet-switched and (within obvious limits) traditional circuit-switched networks. It is standards-based and uses open interfaces and functional components that can be assembled flexibly into hardware and software systems to support real-time interactive services and applications.
  
  
• IMS will have a major impact on the telecom industry – including telcos, mobile operators, service providers, vendors, and others – because it will lead to new business models and opportunities, and (hopefully) lower costs through standards-based procurement. It simultaneously lets network owners derive added value from their networks, while opening these networks to third parties (including enterprise customers) to develop and offer enhanced and tailored services and applications of their own. The full exploitation of mass-market broadband will depend on it.
  
  
• The basic set of standards for IMS implementation were released in 2004, and the first implementations are in hand or planned. Both the International Telecommunication Union (ITU) and the European Telecommunications Standards Institute (ETSI) are heavily involved, and IMS standards are still developing to fill in the inevitable gaps and to add new capabilities. However, IMS is still untested in real-life major carrier networks, and its widescale implementation is some years away.

Support for IMS even at this early stage in its development seems to be fairly hard-nosed, if the results of a poll taken during the Light Reading Webinar on which some of this report is based – IMS: A Blueprint for Fixed-Mobile Convergence – are typical:

• Just over 40% of respondents thought that the most important catalyst for IMS deployment was the service providers’ need to create a more flexible environment for the deployment of applications.
• 18% thought it was service providers’ need to create a converged fixed and mobile network.
• 17% thought it was service providers’ need to deploy blended or combinational multimedia applications.

In other words, a large majority in favor of pragmatic flexibility, rather than any fancy and/or more futuristic possibilities.

Here's a hyperlinked list of the questions and answers in this report:

• What Is IMS?
  A unified service architecture for all networks
  
  
• Why Is It Important?
  It's life after the bit-pipe
  
  
• What Is the State of Standards?
  Work in progress, but solid results
  
  
• How Does IMS Work?
  Very abstractly
  
  
• Are There Issues With the Technology?
  It's still early days
  
  
• What Does IMS Mean for Legacy Circuit-Switched Networks?
  Higher revenues if telcos are smart
  
  
• What Can IMS Be Used For?
  Everything from tailored applications to the next big thing
  
  
• Who Would Deploy IMS?
  Just about everyone could be interested, one way or another
  
  
• Acronyms
  There are a lot
  
  

This report is based partly on material drawn from various Light Reading resources, including:

Archived Webinar on IMS:

• IMS: A Blueprint for Fixed Mobile Convergence moderated by Graham Finnie, Senior Analyst, Heavy Reading, and sponsored by Convedia Corp., IBM Corp. (NYSE: IBM), NexTone Communications Inc., and Tekelec Inc. (Nasdaq: TKLC).
  
  

Paid research reports on IMS:

• IMS: The Heart of Wireless & Wireline Convergence, by Gabriel Brown, Chief Analyst, Insider Research Services
• Fixed-Mobile Convergence Reality Check, by Graham Finnie, Senior Analyst, Heavy Reading
  
  

Light Reading news analysis on IMS:

• Asian Heavyweights Tackle FMC
• Fixed/Mobile Convergence Ramps Up
• ETSI Drives Convergence Standard
• Ericsson Demos IMS
• IMS Could Push Carriers Toward VOIP
• IMS Tops 3GSM Agenda

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To learn more about IMS, check out the coming Light Reading Live! conference:

IMS: Blueprint for Fixed-Mobile Convergence
at The Sheraton Hotel (Buckhead) in Atlanta, on Wednesday, March 30, 2005

• For more information, click here.
  
• To register, click here.
  
  

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— Tim Hills is a freelance telecommunications writer and journalist