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IP Multimedia Subsystem: IMS An IntroductionAbstract Telecom infrastructure trends are changing as they move to support the third generation of mobile networks (3G  ). These trend changes stem from the industry trying to meet the wants of customers, carriers and service providers, and network equipment provider. One primary goal as the telecom industry moves towards supporting 3G is the design and implementation of a central core network infrastructure capable of providing for all the desired blended services offered by today’s ever evolving multimedia applications that end users crave. To this end, IP Multimedia Subsystems (IMS) was developed and subsequently standardized for use as a way to move from the traditional infrastructure architecture of dedicated circuit-switched and packet-switched network cores for each service type to a single IP based core network capable of supporting the multitude of desired applications and services that the 3G mobile network has come to be expected to support. The hope of this paper is to provide an introduction to IP Multimedia Subsystem (News - Alert) (IMS).Changes in Telecom Trends Bring about IMS While most service providers usually offer multiple ways of accessing their services, all types of service generally fall into four major categories. The four common types of service access are fixed line, mobile, broadband, and Voice over IP which may use any number of communication mediums. These four types of service are constantly vying for a bigger piece of the market. As such, the current trends associated with these four types of service are steadily changing. As you can see from the below U.S. Telecom Market Projection (Figure 1), revenues from fixed line services are on a steady decline across the board in all revenue streams and are expected to continue to decline. (Warming, 2007). In contrast Mobile voice, mobile data, internet advertising, and TV Distribution revenue streams are steadily increasing, and are expected to continue to increase well into 2009 and possibly beyond. Fixed Line service providers are facing new challenges from low-cost providers, mobile provider and the ever increasing number of VoIP offerings. While profits for fixed voice and data are still relatively high, there is a steep downward trend in fixed line market share and profit margin because of increasing pressure from competing technology and low price offerings of this older technology medium. However fixed line providers do have the advantage of higher quality and reliability from in place tried and true networks. They are also constantly looking for ways to reduce their network costs and increase their revenue through new service offerings and technology. Mobile provider’s market share is steadily increases even though market penetration is already extremely high. In fact, in June of 2007 the total number of global mobile subscriptions reached the elusive 3 billion mark and is expected to reach 4 billion mobile subscriptions by 2009. (Ryan, 2007) The increase in the mobile market share is from strong growth in developing countries in Asia, Latin America, and Africa where mobile providers are opening new markets which are replacing fixed line providers. Most of mobile providers revenue and profits are still from voice, but new opportunities are on the rise from enhanced content such ring tones, wallpapers and games, and new services such as conferencing, streaming video and chat. The market shares of Broadband and VoIP service providers are also continuing to rise. This is from the proliferation of new technology which can deliver the bandwidth required for the ever increasing customer demand for more content and services. But growth is limited by the profit margin associated with installing end user infrastructure required for broadband and from VoIP’s quality and reliability shortfalls. Also the over all profit margin for broadband and VoIP are beginning to decline, as customer turnover is high and competition from new emerging providers is increasing. So what does all this mean? It means that service providers are always in search of more customers, ways to reduce costs, new service offerings for new and increased revenue streams, and a fast way to bring these new offerings to market. At the same time, Network Equipment Providers also want more customers, to reduce their costs, provide new products for new and increased revenue streams, and to provide highly compatible equipment to promote brand recognition and thus gain more market share. On the other hand, Customers are always in search of newer services which provide better value along with ease of use, increased mobility and freedom. With all these desires out there, it is easy to see why so many companies are pursing business models which embrace the all digital economy. Currently today, if end users want all the different bells and whistles of emerging services that are available, they have to have multiple service providers for their multiple devices, such as phone, PDA, PC/Laptop, IP phone, etc. But because of the market trends, IMS has been developed and promises to bring freedom and ease of use to end users where they can have any service anywhere with any carrier, without all the headaches of today. With this in mind, Network Equipment Providers have been investing in IMS development heavily since 2003, and in 2007 and 2008 the combined investment in IMS development is expected to top 4.5 billion. (Hewlett-Packard (News - Alert), 2006) At the same time number of new services offered are expected to go from the 3 or 4 new services a year offered in 2003 to as many as 10 new services a month by 2008. (Hewlett-Packard, 2006) What is IP Multimedia Subsystems (IMS)? First, IMS is not a protocol, but is an open-systems architecture which was defined by the 3rd Generation Partnership Project (3GPP) and supports a very broad range of IP-Based services, over existing circuit and packet switched networks which use wireless and/or fixed access technologies. (3GPP, 2007) IMS has been being defined in phases. The early phases focused specifically on the Global System for Mobile communications (GSM) evolution which is an open, digital cellular technology used for transmitting mobile voice and data services. (GSM, 2007) Subsequently each new release has increased the features and functionality while also expanding the scope of applicability beyond GSM. IMS is completely access independent, meaning end users can access the services using any existing medium such as WIFI, UMTS , CMDA, TDMA, Private line, or DSL/Cable. (Camarillo and García-Martín, 2006) IMS was standardized by 3GPP and is based on Session Initiation Protocol (News - Alert) (SIP) as defined in RFC 3261. (IETF, 2007) From this the 3rd Generation Partnership Project 2 made IMS standard to interface with legacy CDMA networks. (3GPP2, 2007) The ETSI (News - Alert) TISPAN and ITU-T standardized the next generation network which is a FMC network. (ETSI, 2007) The OMA created standards for E2E services such as PoC. The IETF created the Internet protocols standards which IMS uses and since SIP is also at the heart of the internet this allows for IP end to end meaning Applications and services can be supported seamlessly across all networks.IMS: the Primary Difference is in the Architecture The primary difference between legacy networks and IMS networks lies in the architectures. In most legacy networks, each type of service requires its own dedicated vertical stovepipe or silo, and each is designed to support only one access-scenario. (See Figure 2) This means all network layers have to be provided for each service provided such as web services, mobile phone, video conferencing, and VOIP. (Cisco, 2006) However with IMS, a horizontal layered architecture is used, which enables providers to re-use their existing applications and hardware. (Cisco, 2006) In the horizontal architecture a new service can be implemented without having to focus on a certain access network since the only differentiation is made on the client side in which end-device is used to access the service. So What Does All This Mean To End Users? IMS promises that in the not to distant future users will be able to access a broad range of multimedia services seamlessly anywhere and at anytime. The idea being that in end users will be able to combine video, pictures, and music across all electronic communication mediums. Examples of what IMS hopes to bring to the world are: • Being able to start a voice call from a land line phone and transfer it to a mobile for the drive to work completely seamlessly across multiple carriers if necessary. • Sending/Receiving a multimedia message on a mobile PDA device and transferring it to a TV or PC to view later. • Ordering a video on demand sporting event by TV and transferring it to a wireless PDA to watch while checking the burgers and dogs on the barbeque outside. • But the real kicker is that all of the above will be able to be done with a single account, on a single log-in with multiple devices over any number of access networks so that each providers charges for their services used by the end user are billed on one single bill. Examples of IMS impacting the world can already be seen. The entertainment industry has already embraced the use of mobile devices and numerous subscription based music services are available by end users. The use of Global Positioning Systems (GPS) and other navigation services are on the rise as well as the use of mobile web capable devices such as PDA’s and mobile phones. However in the past, end users had to choose a specific carrier to use and thus were limited by what services that particular carrier offered or they had to use multiple vendors/carriers and multiple similar devices. However with IMS end users will be able to access a broad range of multimedia services seamlessly from anywhere and anytime using any IMS accessible carrier. Final Thoughts Even with all that IMS currently offers and hopes to offer in the future, there are still areas of concern. The architecture of IMS networks are much more complex than legacy networks and thus a larger concern for carriers in regards to maintenance and implementation. The quality of service standards over what potentially could be multiple carriers’ network are an area still being addressed. The continued cooperation of the many standardisation groups such as IETF and 3GPP are cause for concern, especially in areas of overlap. The lack of maturity in the SIP and IMS architectures make them unable to guarantee full functionality of all IP applications across all networks, yet. Finally, the end terminal complexity could become more of an issue, especially for less technical end user, if user intervention is needed by the end user in order to upgrade access devices for new services desired. But even with these areas of concern, the gains from the use of IP Multimedia Subsystems and its ability to provide at the very least a bridge to the next generation network, make it the best choice for carriers. References Camarillo, Gonzalo, & García-Martín, Miguel-Angel. (2006). The 3G IP Multimedia Subsystem (IMS): Merging the Internet and the Cellular Worlds, Second Edition. West Sussex, England: John Wiley & Sons LTD. Cisco. (2006). In Supporting the IP Multimedia Subsystem for Mobile, Wireline, and Cable Providers. Retrieved June 5th, 2007 from http://www.cisco.com/en/US/netsol/ns733/networking_solutions_white_paper0900aecd 80395cb0.shtml. ETSI. (2007). In Defining the Next Generation Network. Retrieved June 4th, 2007 from http://www.etsi.org/tispan/tispan.htm. GSM, (2007). In What is GSM? Retrieved June 4th, 2007 from http://www.gsm.org/technology/what.shtml. Hewlett-Packard. (2006). In IP Multimedia Services Charging. Retrieved June 5th, 2007 from http://h71028.www7.hp.com/ERC/downloads/4AA0-3817ENW.pdf. IETF. (2007). In RFC 3261. Retrieved June 5th, 2007 from http://www.ietf.org/rfc/rfc3261.txt?number=3261. Ryan, Emmet. (2007). In Global Mobile Subscriptions Hit 3bn. Retrieved July, 16, 2007 from http://www.enn.ie/article/64654.html. Warming, Torben. (2007). In Cablelabs Summit, 3’07. Retrieved June 10th, 2007 from http://www.cablelabs.com/conferences_public/VF2007/downloads/warming.ppt. 3GPP. (2007). In 3rd Generation Partnership Project. Retrieved June 10th, 2007 from http://www.3GPP.org. 3GPP2. (2007). In 3rd Generation Partnership Project 2. Retrieved June 10th, 2007 from http://www.3GPP2.org ------------------------------------------------------ About the Author Mr. Daniel Johnson is a Sr. WAN Network Analysis Consultant Engineer with Verizonbusiness in Cary, NC. Mr. Johnson currently holds a Bachelors of Science in Internetworking Technology and has over 15 years experience in the IT Industry. He is currently pursing a Master's of Science in Industrial Technology with concentrations in Computer Network Management and Internetworking Security at East Carolina University. |