Ultra-Wideband Communication Systems: Technology and Applications

Ultra-wideband (UWB) signals are defined to have a band-width of at least 500 MHz and/or a relative bandwidth of more than 20%. A signal with such a large bandwidth has some very unique properties like resistance to small-scale fading, good resolution for ranging and geolocation, and resistance to narrow-band interference. These signals can be used for transmission of extremely high-speed data or low-rate data with a large spreading factor. UWB communications have been investigated since the early 1990s, following the pioneering work of Win and Scholtz at USC. A major milestone for UWB deployment was the decision of the frequency regulator in the USA, the FCC (Federal Communications Commission) to allow unlicensed operation of UWB transmission subject to certain restrictions in the emission mask of the power spectral density. In essence, the FCC allowed intentional emissions in the frequency band between 3.1 and 10.6 GHz with a power spectral density of −41.3 dBm/MHz. This value agreed with the already existing regulations for unintentional emissions from electronic devices in that frequency range. Regulations in other countries were much slower in the making. Japan allowed UWB transmissions in the 3.1–4.8 and 6–10 GHz bands only in late 2006. A key requirement of the Japanese regulations is that, for frequencies between 3.1–4.8 GHz, UWB transmitters must employ " detect and avoid. " In other words, it is the duty of a UWB transmitter to detect a possible victim device and cease transmissions that might disturb such a device. Until 2010, the band between 4.1 and 4.8 GHz is exempt from this DAA requirement. European regulations are scheduled to be issued in the next years and are anticipated to be similar to the Japanese regulations. High-speed communications based on UWB were originally envisioned by the IEEE 802.15.3 standardization group, which tried to establish a standard for short-range communications with rates in excess of 100 Mps. Though standardization within IEEE 802.15.3a failed, and the group ultimately dissolved, two major proposals for high-speed UWB communications emerged and were standardized by industry groups: multiband-OFDM (later-on adopted by the Wi-Media Alliance and the European Computer Manufacturing Association, as standard ECMA 369/369), and a direct-sequence CDMA approach adopted by the UWB Forum. Products based on UWB will soon appear on the market. The first application will be wireless USB (universal serial bus). The USB Implementers Forum (USB-IF) has introduced certified wireless USB based on the WiMedia multiband-OFDM radio platform. …