Ultrawideband (UWB) is viewed by some as the next great wireless technology. Its appeal is enormous, with the promise of massive data rates for low transmitter power levels and long battery life. Of course, those >investing in more traditional "narrowband" wireless applications, including Bluetooth, GPS, PCS, and WLANs, view ultrawideband as the Federal Communications Commission's (FCC's) greatest mistake.
UWB transmitters and receivers operate over broad segments of bandwidth using short, low-power pulses. The time position of these pulses represents the modulation or information carried by the pulse train. In theory, although the pulses occupy broad portions of (occupied) bandwidth, they are transmitted at such low power levels as to be negligible to other receivers in that spectrum. At least that is the finding of the FCC, which approved last year the license-free use of UWB technology for short-range commercial applications. (The technology has been in used by the military and government agencies for some time, for a variety of applications including ground-penetrating radars and through-wall imaging systems). The FCC legalized about 7 GHz worth of "free spectrum" (between 3.1 and 10.0 GHz) for UWB designers, permitting the marketing and operation of certain types of new products based on UWB technology.
The UWB lobby, which includes companies such as Time Domain Corp. (Huntsville, AL, www.timedomain.com/) and XtremeSpectrum (Vienna, VA, www.xtremespectrum.com/), persuaded the FCC that UWB transmissions would not affect the operation devices with co-located frequencies, such as cellular telephones and wireless local area networks (WLANs). Developers and operators of Global Positioning Systems (GPS), in particular, were wary of the potential interference offered by UWB transmitters. To safeguard against interference, the FCC has mandated that UWB transmissions be limited in output power (according to frequency) so as not to exceed other "non-intentional" radiators such as computers and microwave ovens that might be found in those co-located bands. The FCC also requires compliance of all out-of-band emissions, and requires FCC compliance of any UWB product prior to gaining approval for commercial sale.
Time Domain ==> http://lists.planetee.com/cgi-bin3/DM/y/eA0CWyaL0Gth0BAuI0AC XtremeSprectrum >==> http://lists.planetee.com/cgi-bin3/DM/y/eA0CWyaL0Gth0BAuJ0AD
With that said, the rush to adopt UWB technology has been slow at best. Almost a year ago, XtremeSpectrum launched the first commercial products based on UWB technology, the Trinity chip set (see Microwaves & RF, July 2002, p. 98). Consisting of four integrated circuits (ICs), the chips combine to transmit data at rates to 100 Mb/s using low-power pulses generally concentrated from about 3 to 10 GHz. When first demonstrating the chip set, the company broadcast six video streams simultaneously to six separate flat-panel displays using a single UWB connection. These transmissions co-existed with an IEEE 802.11b 2.4-GHz WLAN, a 2-45-GHz wireless oven, a cellular/PCS telephone, and a cordless telephone, with interference in either direction. The company recently announced its collaboration with Motorola's Semiconductor Products Sector as part of Motorola's support for the use of UWB technology in the IEEE 802.15.3a alternate physical layer standard for wireless personal area networks (WPANs).
Another leader in the technology, Time Domain Corp., now offers a full UWB evaluation kit to help engineers better understand the technology. The PulseON 200 evaluation kit includes two of the company's UWB radios (the first commercial product to be granted FCC compliance according to FCC Part 15, 517, 15.209 regulations), a dedicated microprocessor for embedded applications development, a power supply, biphase pulse modulator, antenna, and several software tools. The kit operates over a 3.2-GHz bandwidth centered at 4.7 GHz with -11.5-dBm effective isotropic radiated power (EIRP) and pulse repetition frequency of 9.6 MHz. It can achieve data rates ranging from 75 kb/s to 9.6 Mb/s.
As with most "novel" technologies, several companies must take the lead before others follow. UWB technology might be best helped by the adoption of solid standards for 802.15 WPANs. After all, WLAN technology (at 2.4 >GHz) was stalled for several years while the IEEE 802.11 committee debated over data limits and other factors (before finally expanding the WLAN standard into additional secondary standards).
One of those companies hoping for a leadership position is Focus Enhancements of Campbell, CA (www.focusenhancements.com/). Well known to those working in video signal-processing, the company holds a variety of patents, including for several scan converters. Its video chips have been funded by major communications firms, including Intel and Microsoft. The company sees great potential for the use of UWB technology in wireless transmission of digital video, noting that data rates to 500 Mb/s and higher should be possible over short distances (10 m). By scaling and optimizing the technology, through a process the firm calls "soft-tailoring," Focus hopes to offer UWB-based wireless home video systems capable of transmitting 200 Mb/s over distances of 25 m. The company targets the use of omnidirectional antennas, increased packet sizes, and forward error correction (FER).
Focus Enhancements ==> http://lists.planetee.com/cgi-bin3/DM/y/eA0CWyaL0Gth0BAuK0AE
The use of UWB technology for routine transmission of voice or data can likely be accomplished with the fraction of the power of traditional, competing transmitter/receiver technologies. But competing with "entrenched" technologies may not be the best demonstration of UWB's capabilities. Perhaps it will be highly visible applications like wireless digital video terminals and home media gateways that finally display some of the enormous potential of UWB technology.
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