In this proposal a complete study of fundamental issues, both experimental and analytical, in ultra-wideband (UWB) radio is presented. The proposed work involves a strong interaction between experimental and analytical components, so that experimentally derived models can be used to design optimized algorithms, which can in turn be tested. For this purpose, radio, video, and test equipment is requested to complement existing facilities in the ultra-wideband radio lab (UltRa Lab). This equipment will be used for closely related research projects that support the development of fully mobile indoor video communication systems. The motivating wireless technology is spread-spectrum impulse radio which alleviates multipath problems, but must coexist in the same spectrum with signals in the frequency range from roughly 500 MHz to 2 GHz. The experiments are aimed at (1) quantifying the ability of different radio systems to coexist in the same band without mutually interfering, (2) quantifying the distortion properties of ultra-wideband antennas and propagation environments, and (3) measuring the effects of indoor radio performance anomalies on video transmissions. The equipment requested includes anechoic chamber components, a flexible software video compression system, high quality LANs that can be utilized in both the video and radio interference experiments, and a bit error-rate tester and other components necessary for interference and coexistence tests. These experiments will result in a database of channel measurements, which characterize propagation, antenna, and interference effects. The database will be used to extract statistical models which, in turn, will be used to develop algorithms for receiver signal processing and video rate control. This process of experimentation, model extraction, and algorithm development will be iterated throughout the duration of the requested support. Each of these experiments is briefly described below.
(1) Interference Rejection and Coexistence Experiments and Analysis (Scholtz and Chugg). This experimental work will explore the ability of impulse radio with power spectrum thinly spread roughly from 500 MHz to 2 GHz to coexist over short range channels with the myriad of other electronic systems in that broad spectrum. This effort will test coexistence with LANs, cordless phones, microwave ovens, wireless TV links, etc. The processing gain of the spread-spectrum techniques employed in the impulse radio will be checked and the dynamic range of current impulse radios will be tested. These experiments will determine the direction of research efforts on impulse radio implementation.
(2) Characterization of ultra-wideband antennas and propagation environment (Prata, Chugg, Scholtz). The experimental work to be carried out in the controlled environment of an anechoic chamber supports the characterization of ultra-wideband antennas for impulse radio, and the characterization of narrower-band antennas to evaluate their ability to receive/reject impulses. This environment will be used to evaluate new UWB antenna designs that provide more robust spatial coverage, better pulse shaping characteristics, polarization diversity, and to study the propagation of UWB signals through different kinds of materials. The equipment purchased under this grant is destined for an anechoic chamber atleast 15' (w) x 15' (h) x 30' (l) to be constructed in the near future (architectural work on the building containing this chamber is beginning now).
(3) Experiments with Software-Compressed Asynchronous Video over UWB Wireless Links (Ortega, Chugg). Two stages are planned in the experimental work with robust asynchronous video transmission. In a first stage, laptops and wireless LAN equipment will be used to test techniques, which are currently under study for rate control over a time varying channel. All video functions (compression, rate control, error correction, retransmission, etc.) will be implemented in software. In a second stage the algorithms will be adapted to operate over an experimental impulse radio link. At that point the results from the initial stage will be incorporated and also changes needed for the particular transmission conditions of impulse radio will be implemented.
Each of the student researchers supported under the requested funding will be involved in all three of these aspects. This research will be further supported by the UltRa Lab infrastructure, which has been developed recently under the support of NSF and through the Integrated Media System Center ERC and our industrial sponsors. The infrastructure includes laboratory space, equipment, a team of undergraduate merit scholars to assist in laboratory procedures, and access to circuit and semiconductor process expertise from both USC collaborators and industrial partners. The research described in this proposal is a portion of the fundamental investigations required to develop and demonstrate UWB indoor radio multimedia systems (complementary investigations into integrated circuit design are also necessary, but are not part of the research proposed herein). The original equipment budget for this proposal has been revised to reflect equipment acquisitions from other sources and no other proposals for this work are currently pending.
