JPL's Wireless Communication Reference Website

Chapter: Network Concepts and Standards. Section: Wireless Broadband Multimedia Communication.

WIRELESS BROADBAND MULTIMEDIA COMMUNICATIONS

Contributed by Ramjee Prasad and Luis M. Correia
Edited by Jean-Paul Linnartz

Wireless Broadband Multimedia Communication Systems (WBMCSs). WMCS, provide data rates higher than 2 Mb/s and up to 155 Mb/s. The aim of the Wireless Broadband Multimedia Communication Systems (WBMCS) is to provide its users a means of radio access to broadband multimedia supported on customer premises networks or offered directly by public fixed networks. WBMCS will provide a mobile (or at least movable) nonwired extension to wired networks for information rates exceeding 2 Mbps with applications foreseen in wireless Local Area Network (LAN) or mobile broadband systems. Thus, WBMCS will be a wireless extension to the B-ISDN (Broadband Integrated Services Digital Networks). It will be achieved with the transparent transmission of ATM (Asynchronous Transmission Mode) cells.

Research and development of WBMCS is in progress in North America, Europe and Japan in the micr wave and millimeter wave bands in order to accommodate the necessary bandwidth. The research in the field of WBMCS has drawn a lot of attention because of the increasing role of multimedia and computer applications in communications. There is a major thrust on three research areas, namely,

In short, WBMCS will provide novel multimedia and video mobile communication services, also related to WCPN (Wireless Customer Premises Network) and WILL (Wireless In Local Loop) broadband.

To implement the wireless broadband multimedia communication systems, the following challenges must be considered:

Multimedia and computer communications are playing an increasing role in today's society, creating new challenges to those working in the development of telecommunications systems. Besides that, telecommunications means more and more to establish links between or to non-wired terminals. Thus, the pressure for non-wired systems to cope with increasing data rates is enormous, and Wireless Broadband Multimedia Communication Systems (WBMCSs), those with data rates higher than 2 Mb/s, are emerging rapidly, even if at this moment applications for very high transmission rates do not exist.

Several WBMCSs are being foreseen for different users with different needs: they may accommodate data rates ranging between 2 Mb/s and 155 Mb/s; terminals can be mobile (moving while communicating) or portable (static while communicating), and moving speeds can be as high as the one of a fast train; users may, or may not, be allowed to use more than one channel if their application requires so; the system bandwidth may be fixed, or dynamically allocated according to the user's needs; communication between terminals may be done directly or must go through a base station; possibility of usage of ATM technology; and so on. Many other cases can be listed as making the difference between various perspectives of a WBMCS, but two major approaches are emerging: WLANs directed to communications between computers, from which HIPERLAN and IEEE 802.11 are examples, and MBS (Mobile Broadband System) intended as a cellular system providing full mobility to B-ISDN users.

The different requirements imposed by the various approaches to WBMCSs have consequences on system design and development. The trade-offs between maximum flexibility on one hand and complexity and cost on the other hand are always difficult to decide, since they will have an impact not only on the initial deployment of a system, but also on its future evolution and market acceptance (GSM can be looked as a good example of a system which has been foreseen to accommodate additional services and capacities to those initially offered, and the fact that operators are already implementing Phase 2+ is the proof of that fact). This means that many decisions have to be done concerning the several WBMCSs that will appear in the market; for HIPERLAN for example, those decisions are taken, since the system will be commercialized in the very near future, but for other systems there are still many aspects to be decided. Of course this depends on what are the applications intend to be supported by the systems, and if these applications are targeted to the mass market or only to some niche ones: the former (from which mobile phones are a good example) will certainly include WLANs, since the expansion of personal computers will dictate this application as one of great success in WBMCSs; the latter will possibly have TV broadcasters among their users (to establish links between HDTV cameras and the central control room).

Not only market aspects are at stake in the development and deployment of WBMCSs, but also many technical challenges are posed as well. The transmission of such high data rates via radio in a mobile environment creates additional difficulties, compared to the existing systems; these difficulties are augmented by the fact that frequencies higher than UHF are needed to support the corresponding bandwidths, thus pushing mobile technology challenges (size and weight among other things) to frequencies where these aspects were not much considered up to now. However, additional challenges are posed to those involved in the development of WBMCSs: in today's world, where consumers are getting the habit of using a communications system that is available in different places (the roaming capability of GSM is the example, since users can make and receive phone calls in an increasing number of countries world-wide), or of being able of exchanging information between different systems (the exchange of files between different computer applications and systems is the example in this case), it does not make sense to consider systems for the future that offer a high data rate but that do not support these capabilities to some extent.

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