The fact that UWB technology has been around for so many years and has been used for a wide variety of applications is a strong evidence of the viability and flex- ibility of the technology. The simple transmitter and receiver structures which are possible make this a powerful technology for low-complexity, low-cost commu- nications. As will be discussed in later chapters, the physical characteristics of the
signal also support location and tracking capabilities of UWB much more readily than in existing narrowerband technologies.
The severe restrictions on transmit power, allowing less than 0.5 mW maxi- mum power over the 7.5 GHz band in the FCC emission mask, have substantially limited the range of applications of UWB to short-distance high-data-rate, or low- data-rate, longer-distance applications. The great potential of UWB is to allow flexible transition between these two extremes without the need for substantial modifications to the transceiver. On the other hand, UWB technology emission masks outside the USA are still under discussion pending the outcome of compat- ibility studies with other radio services.
Whilst UWB is still the subject of significant debate, there is no doubt that the technology is capable of achieving very high data rates and is a viable alternative to existing technology for WPAN; short-range, high-data-rate communications; multimedia applications, and cable replacement. Much of the current debate cen- ters around which PHY layer(s) to adopt, development of a standard, and issues of coexistence and interference with other radio services.
At the time of writing, no standard exists for a MAC which has been specifi- cally developed for UWB which will support all of the unique advantages of UWB. The potential of UWB systems to offer flexible data rates, support coexistence, en- able large numbers of users and positioning services are critically dependent on the capabilities of the MAC.
Research is ongoing in industry and academic consortia including the IEEE, MBOA, and in European Union Projects such as PULSERS [22]. There is work ongoing in standardization bodies to adapt, optimize, and enhance existing MACs for use over UWB. Part of the reason for the slow progress in developing a flexible, comprehensive MAC specifically for UWB is due to the inherent complications of using a physical layer signal which is difficult to detect and difficult to synchronize for intended users. Efforts have been made to develop MACs which allow efficient operation for large numbers of devices. However, this work is still at an early stage.
Acknowledgments
The author would like to thank colleagues from CWC for input to this chapter. In particular, thanks to Matti H¨am¨al¨ainen and Jari Iinatti. The author would also like to thank colleagues from the Wireless World Research Forum (WWRF) Work- ing Group (Short Range Communications) for their input related to the regula- tory status section. In particular,thanks to Fr´ed´eric Lallemand and Guy Salingue. Thanks also to Therese Oppermann for careful proofreading.
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Ian Oppermann: Department of Electrical and Information Engineering, University of Oulu, FIN-90014, Finland