EECS CSPL SEMINAR SERIES
FALL TERM 1999
James Freebersyser
Dr. James A. Freebersyser
Program Officer, Communications and Networks
Office of Naval Research
Arlington, VA
freebej@onr.navy.mil
Thursday, November 18
4:30 - 5:30 P.M.
Room 1311 EECS
Future Research Directions in Ultrawideband (Impulse Radio)
Communications
Abstract-
Ultrawideband (UWB) communications also called impulse radio,
uses impulses
to communicate information rather than a continuous
sinusoid, as is the case
with conventional narrowband communications systems. The
name UWB is derived
from the greater than GHz spectral occupancy that results
when the impulse
widths are in the sub-nanosecond range. Information can be
modulated on the
impulses by, for example, pulse position modulation (PPM).
Code Division
Multiple Access (CDMA) techniques can be utilized by
time-hopping the
impulses in a manner similar to direct-sequence spread
spectrum systems. An
UWB communication system has many advantages: the ability to
do very fine
time resolution results in precise (cm) ranging; the large
coherence
bandwidth results in the ability to resolve multiple paths
and reduce
multipath interference; the low transmit duty cycle
operation results in
greatly reduced power consumption; and, the removal of mixed
signal
processing results in less expensive single chip radios.
However, UWB
systems do have drawbacks, such as the potential for longer
initial link
synchronization times compared to narrowband systems, and
limited range and
building/foliage penetration due to the high frequency
content of the
signal. Some of the possible applications for UWB
communications systems
include: wireless end-user information distribution; RF tags
for geolocation
of equipment, parts and people; and, distributed unmanned
sensor networks.
Most significantly, UWB systems, if operated as FCC part 15
devices, have
the potential to operate without the channelized frequency
allocations that
currently exist. Many areas of UWB communications are either
unexplored, not
well understood, or both. Examples of future research areas
in UWB that will
be discussed include channel measurement and modeling,
antennas, circuits,
waveform and receiver design, communications and information
theory, and UWB
communications system design tools.
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