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JPL's Wireless Communication Reference WebsiteChapter: Network Concepts and Standards. Section: Wireless Broadband Multimedia Communication. |
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,
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.
