There is some concern that UWB devices will interfere with radio services
and GPS operation. Because of this, the U.S. FCC regulation of the commercial
use of UWB technology is accompanied by a list of strict standards for use and
device compliance.
Groups as diverse as the Air Transport Association of
America, Nortel, Nokia, and Qualcomm have lobbied against the proposal to
broaden the use of UWB. These groups claim that UWB will interfere with GPS
frequencies, as well as other public safety and air safety wireless networks,
cellular PCS systems, and some satellite services. At this time, related
testing has not been conclusive.
Because the UWB pulses employ the same
frequencies as traditional radio services, they can potentially interfere with
them. Marconi's spark-gap stations used a great deal of power, because
they needed to bridge great distances. In the current regulatory environment,
systems like Marconi's would be intolerable, because they would interfere
with almost every other radio technology. UWB communications systems operate at
power levels so low that they emit less radio energy as a by-product than a
laptop computer radiates. For example, a typical 200-microwatt UWB transmitter
radiates only 1/3000 of the average energy emitted by a conventional
600-milliwatt cellular phone.
Unlike traditional communications systems,
UWB wireless occupies a broad span of frequencies at very low power levels,
often below the noise floor of the existing signaling environment, as shown in
Figure
.
This
low-power output also means that UWB range is sharply restricted to distances
of 100 m (328 ft) or less, and sometimes as little as 10 m (32.8 ft).