Subspace Analysis of Indoor UWB Channels
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Subspace Analysis of Indoor UWB Channels Aawatif Menouni Hayar Mobile Communications Laboratory, Institut Eur´ecom, 06904 Sophia Antipolis Cedex, France Email: [email protected]
Raymond Knopp Mobile Communications Laboratory, Institut Eur´ecom, 06904 Sophia Antipolis Cedex, France Email: [email protected]
Rachid Saadane UFR SysCom2, Facult´e des Sciences, Universit´e Mohammed V-Agdal, Rabat, Morocco Email: [email protected] Received 7 October 2003; Revised 13 June 2004 This work aims at characterizing the second-order statistics of indoor ultra-wideband (UWB) channels using channel sounding techniques. We present measurement results for different scenarios conducted in a laboratory setting at Institut Eur´ecom. These are based on an eigendecomposition of the channel autocovariance matrix, which allows for the analysis of the growth in the number of significant degrees of freedom of the channel process as a function of the signaling bandwidth as well as the statistical correlation between different propagation paths. We show empirical eigenvalue distributions as a function of the signal bandwidth for both line-of-sight and non-line-of-sight situations. Furthermore, we give examples where paths from different propagation clusters (possibly arising from reflection or diffraction) show strong statistical dependence. Keywords and phrases: indoor UWB channel measurements, subspace analysis, number of degrees of freedom.
1.
INTRODUCTION
The use of ultra-wideband (UWB) signaling techniques are being considered for short-range indoor communications, primarily for next-generation high-bit-rate wireless personal area networks (WPANs). Initial work in this direction was carried out by Scholtz [1, 2], using the most common form of signaling based on short-term impulses, where information is carried in their position. Such techniques, as well as others, are being considered in the standardization process of the IEEE 802.15.3a WPAN proposal (see http://grouper.ieee.org). At the same time, regulatory aspects are quickly being defined by the FCC. The expected bandwidths of these systems are of the order of one GHz, which has significant implications both for systems design and implementation. The goal of this work is to determine the result of these extremely large system bandwidths on the second-order statistics of the propagation channel as it is seen by the underlying system. We are primarily interested in assessing the growth in degrees of freedom (DoFs) needed to characterize the channel as a function of the system bandwidth. Other measurements studies on the UWB propagation channel are appearing in [3, 4, 5, 6] for instance. This work
is complementary in the sense that we use a state-of-the-art wideband measurement equipment to determine the growth of the number of significant free DoFs of the propagation channel as a function of the signaling bandwidth, based on subspace techniques. The number of significant DoF is related both to the number of resolvable multipath components and to the diversity order or richness of the in
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