DOA Estimation of multipath clusters in WiMedia UWB systems

Ultra wideband (UWB) systems are expected to find widespread use in future short range applications. Increasing popularity of these devices will require management of occupied spectrum in spatial domain to keep the interference low. In UWB systems, one encounters many multipath components. By optimally forming beams in the direction of the principal multipath clusters, one can achieve optimum spectrum efficiency. The number of components would depend on the sampling rate as the number of resolvable components depends on it. Besides, many of the multipath components would be coming from the same cluster. The estimation of the Direction of Arrival (DOA) of these clusters is very useful to focus the transmit power in the optimum direction. A new algorithm, exploiting the known pilot signals of multiband UWB systems for estimation of DOA of clusters in the presence of inband interferers is proposed in this paper. By making use of a new matrix incorporating the cross correlation between the focused UWB signal and the known pilot signal of the transmitted data in each array element, one would be able to separate the multipath clusters from a single source. It is proven that the proposed new matrix would span the same subspace as the direction of arrival vectors and the eigen vectors corresponding to the zero eigen value of the product of this new matrix with its Hermitian would span the orthogonal compliment of the DOA subspace. Computer experiments are included to verify the performance of the proposed algorithm.