| A department research team is developing some first-ever models of a newly available wireless communications technology being touted for wireless video transmission in homes, jam-proof military communications, and other high-data-rate applications.
A Radar Technique for Wireless
Thanks to a 2002 change in Federal Communications Commission (FCC) regulations, ultra-wideband (UWB) techniques, first developed for radar, now can be used without special licenses at frequencies from 3.1-10.6 GHz. UWB employs narrow, short pulses (typically less than 1 nsec.) that are spread across a wide frequency spectrum.
More Data at Less Cost
UWB signals can transmit more data, using less power than previous wireless technologies and can penetrate walls, vegetation, and ground. UWB systems are expected to cost less than other systems and the commercial device market is estimated to exceed $2 billion by 2007.
Defining the Technology
To tap this potential, the wireless industry is working to define standards and researchers are delving into UWB channel limitations and performance and UWB relationship to existing technologies.
Funded by a $750,000 grant from the Defense Advanced Research Projects Agency (DARPA), the ECE team is developing UWB channel models for indoor and outdoor environments. "The channel has a tremendous impact on the efficiency of the system design," explained Michael Buehrer, a principal investigator on the project and expert in wireless communications. "Right now, we don't fully understand how the propagation of UWB signals will impact system design, and there is no consensus on how to model the UWB channel," he said.
Channel Models for Planning, Simulation
Tech's team is composed of experts in wireless communications, electromagnetics, antennas, and time-domain measurements. The team is developing two types of channel models for each environment: path-loss models for network planning purposes and small-scale channel models for simulation and receiver performance evaluation. The small-scale channel model includes the number and distribution of multiple paths, pulse distortion, delay spread, and arrival rates and clustering — all necessary for the design of UWB transmitters and receivers.
Extensive Measurement Support
The models are being built on data from a measuring campaign undertaken this past year with expertise from several laboratories. Using ECE's sub-nanosecond and wideband pulse propagation measurement systems, data was obtained in the time domain and frequency domain for indoor, outdoor and indoor-to-outdoor situations. The team is also studying the design and characterization of wideband antennas for UWB systems.
The extensive measured data has been critical to the project, explained Jeffrey Reed, a principal investigator and expert in wireless communications and signal processing. "Most research studies into UWB assume an ideal received pulse and ignore the distortion effects that are inevitable," he said. "Previous work in UWB has also assumed simple channel models. Our models will provide the research community with an intuitive view of the UWB propagation mechanism and help guide communications algorithm development."
Extending the Research
After completing the models, the team hopes to extend the research to developing new UWB antenna systems and hardware prototypes, designs, and UWB techniques. The team has received another grant to develop simulation tools for UWB and to start developing receiver designs.
Interdisciplinary Team
In addition to Buehrer and Reed, the research team includes Sedki Riad and Ahmad Saafai-Jazi, experts in time domain and RF measurements; William Davis, an expert in antennas and propagation; and and Dennis Sweeney, an expert in RF and time domain measurements; modeling, and simulation.
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