James Freebersyser

Dr. James A. Freebersyser

Program Officer, Communications and Networks

Office of Naval Research

Arlington, VA

Thursday, November 18
4:30 - 5:30 P.M.
Room 1311 EECS

Future Research Directions in Ultrawideband (Impulse Radio) Communications

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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