MITSUBISHI ELECTRIC RESEARCH LABORATORIES http://www.merl.com Optimal and Suboptimal Linear Receivers for Impulse Radio UWB Systems S. Gezici, V. Poor, H. Kobayashi, A. Molisch TR2006-067 September 2006 Abstract The high time resolution of ultra-wideband (UWB) signals results in a large number of multipath components (MPCs) arriving at the receiver, which presents a source of diversity. In addition to this multipath diversity, there is also repetition diversity inherent in impulse radio (IR) UWB systems, since a number of pulses are transmitted for each information symbol. In order to make optimal use of both multipath and repetition diversity, the receiver needs to consider the optimal conbination of contributions from both different frames and different MPCs. In this overview paper, the optimal linear receiver for a given user in frequency-selective multiuser environment, which combines all the samples from the received signal according to the minimum mean square error (MMSE), criterion is studied. Due to the complexity of this optimal receiver, two suboptimal receivers with lower complexity are considered, optimal frame combining (OFC) and optimal multipath combining (OMC) receivers, which reduce computational complexity by suboptimal combining in the multipath diversity and repetition domains, respectively. Finally, a two-step MMSE algorithm which reduces complexity by performing MMSE combining in two steps is presented, and its optimality properties are discussed. Simulations are performed to compare the performance of different receivers. IEEE International Conference on Ultra-Wideband (ICUWB 2006) This work may not be copied or reproduced in whole or in part for any commercial purpose. Permission to copy in whole or in part without payment of fee is granted for nonprofit educational and research purposes provided that all such whole or partial copies include the following: a notice that such copying is by permission of Mitsubishi Electric Research Laboratories, Inc.; an acknowledgment of the authors and individual contributions to the work; and all applicable portions of the copyright notice. Copying, reproduction, or republishing for any other purpose shall require a license with payment of fee to Mitsubishi Electric Research Laboratories, Inc. All rights reserved. Copyright c  Mitsubishi Electric Research Laboratories, Inc., 2006 201 Broadway, Cambridge, Massachusetts 02139