UWB Set to Challenge Radio Rules

The FCC's approval of Freescale's UWB chip set opens doors to capability and conflict.

With this months approval by the Federal Communications Commission of an Ultra-Wideband chip set, device designers and users can enjoy new options for robust, high-bandwidth wireless connections with minimal power consumption.

The XS110 chip set, now available in sample quantities from Freescale Semiconductor Inc., enables a claimed data rate of 110M bps over distances of 10 meters; the company also claims bit-error rates on the order of 1 in a billion at a power draw of three-quarters of a watt. (Full specifications are at www.freescale.com/files/

Freescales announcement calls the XS110 the first FCC-approved UWB chip set. This is not strictly correct—a chip set from Time Domain Corp., of Huntsville, Ala., was certified in September 2002. However, Time Domains offerings have so far focused on data rates of less than 10M bps, with applications in high-reliability communications and high-resolution radar and other somewhat-exotic realms.

Freescale does appear to be first out of the gate with a package aimed at mainstream consumer and enterprise desires for wireless connectivity in personal networks and LANs, with bandwidth sufficient for the most demanding multimedia data streams.

/zimages/6/28571.gifClick here to read about the ongoing UWB standards battle.

UWB radio technology is so different from prevailing radio practice that it almost seems like an entirely new engineering discipline. Conventional radio techniques treat bands of radio frequencies as almost the equivalent of real estate. The assumption thats built into almost all current radio equipment, and into national and international regulations, is that spectrum must be viewed as a collection of channels. Any given channel, within a vicinity whose size depends on a combination of frequency range and transmitter power, can be used for only one task at a time.

Some channels are quite narrow—for example, those used by radioteletype transmissions—while others, such as TV broadcasts, are much wider. An amateur radio operator using Morse code can occupy as little as 80Hz of spectrum. On the other hand, a U.S.-standard HDTV signal needs an 8MHz swath—enough to accommodate several tens of thousands of Morse code conversations, even if empty guard bands are left between adjacent pairs of signals.

To think of this in everyday terms, the conventional spectrum allocation process is like passing out differently colored filters with matching sets of colored eyeglasses to every person or group that wants to use flashlights. If only one group of cooperating parties illuminates objects of interest with a particular shade of red and only their glasses allow that single color to pass, then they can focus attention on any desired part of an otherwise-darkened landscape—without being distracted by anyone elses interests.

If no one is using an assigned color at any given time, thats just too bad. No one else sees any more than they would under worst-case conditions of all channels being active. Multiple user groups could agree to share a single channel, taking turns in the same way that multiple parties using handheld radios say "over" to indicate that its someone elses turn to talk, but parties have a strong motive to acquire spectrum rights based on their expectation of worst-case need. Economists cringe at the resulting inefficiencies, with a scarce resource winding up overpriced and underused.

Next page: UWB techniques defy common sense.