Ultra-Wideband Source Localization Using a Particle-Swarm-Optimized Capon Estimator from a Frequency-Dependent Channel M
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Ultra-Wideband Source Localization Using a Particle-Swarm-Optimized Capon Estimator from a Frequency-Dependent Channel Modeling Viewpoint Yifan Chen Positioning and Wireless Technology Centre, Nanyang Technological University, 50 Nanyang Drive, Research TechnoPlaza, BoderX Block, Singapore 637553 Email: [email protected]
Vimal K. Dubey Positioning and Wireless Technology Centre, Nanyang Technological University, 50 Nanyang Drive, Research TechnoPlaza, BoderX Block, Singapore 637553 Email: [email protected] Received 22 June 2004; Revised 21 September 2004; Recommended for Publication by Petar Djuric We introduce a realistic frequency-dependent channel model for ultra-wideband (UWB) communication systems and develop a generalized broadband Capon spatial spectrum estimator for localization of multiple incoherently distributed scattering clusters. The proposed estimator is able to address the three crucial features of practical UWB impulse propagation: presence of local scattering for multiple incoherently distributed clusters, wideband array signals, and frequency-dependent dispersive effects. The particle-swarm optimization, which is a recently invented high-performance optimizer based on the movement and intelligence of swarms, is then implemented to perform a multidimensional parameter search to jointly estimate the source central angles, the polynomial regression coefficients for angle spreads, and the frequency-dependence of various clusters. Numerical experiments are also carried out to examine the performance of the algorithm under various environments and model mismatches. Keywords and phrases: array processing, UWB channel modeling, broadband Capon estimator, particle-swarm optimization, multidimensional search.
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INTRODUCTION
The emerging ultra-wideband (UWB) technology demands much research effort to achieve improved operational capabilities and cost-effective system solutions for broad commercial and military applications [1]. Theoretical study in the area of signal modeling and signal processing is thus essential for the development and performance analysis of practical UWB systems. Despite that a large volume of literature has been devoted to handle problems like source localization and sidelobe reduction for the narrowband case, fundamental differences exist between the classical array signal processing techniques, pertaining to the incidence of narrowband signals, and the problem of interest here, where the signals have large fractional bandwidth [2, 3, 4, 5]. UWB system is at present defined by the Federal Communications Commission (FCC) as any wireless transmission scheme that occupies a large fractional bandwidth over 20%, or more than 500 MHz of absolute bandwidth. Recent
UWB indoor channel measurements showed that physical paths were clustered around transmit/receive directions and each cluster corresponded to a major path to the receiver [5, 6, 7, 8]. Arrivals within clusters are likely the result of closely associated objects that are part of a very similar group of paths to the receiver (
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