A MIMO-OFDM Testbed for Wireless Local Area Networks

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A MIMO-OFDM Testbed for Wireless Local Area Networks Albert Guillén i Fàbregas,1 Maxime Guillaud,2 Dirk T. M. Slock,2 Giuseppe Caire,3 Karine Gosse,4 Stéphanie Rouquette,4 Alexandre Ribeiro Dias,4 Philippe Bernardin,4 Xavier Miet,4 Jean-Marc Conrat,5 Yann Toutain,6 Alain Peden,7 and Zaiqing Li7 1 Institute

for Telecommunications Research, University of South Australia, SPRI Building, Mawson Lakes Boulevard, Mawson Lakes, SA 5095, Australia 2 Eurécom Institute, 2229 Route des Crêtes, 06904 Sophia Antipolis, France 3 Electrical Engineering Department, University of Southern California, 3740 McClintock Avenue, Los Angeles, CA 90089, USA 4 Motorola Labs, Centre de Recherche de Motorola, Espace Technologique Saint-Aubin, 91193 Gif-sur-Yvette, France 5 France Telecom R&D, 3 avenue des Usines, 90007 Belfort, France 6 Antennessa, avenue la Perouse, 29280 Plouzane, France 7 École Nationale Supérieure des Télécommunications de Bretagne, Technopôle Brest-Iroise, 29238 Brest, France Received 15 December 2004; Revised 11 May 2005; Accepted 21 June 2005 We describe the design steps and final implementation of a MIMO OFDM prototype platform developed to enhance the performance of wireless LAN standards such as HiperLAN/2 and 802.11, using multiple transmit and multiple receive antennas. We first describe the channel measurement campaign used to characterize the indoor operational propagation environment, and analyze the influence of the channel on code design through a ray-tracing channel simulator. We also comment on some antenna and RF issues which are of importance for the final realization of the testbed. Multiple coding, decoding, and channel estimation strategies are discussed and their respective performance-complexity trade-offs are evaluated over the realistic channel obtained from the propagation studies. Finally, we present the design methodology, including cross-validation of the Matlab, C++, and VHDL components, and the final demonstrator architecture. We highlight the increased measured performance of the MIMO testbed over the single-antenna system. Copyright © 2006 Albert Guillén i Fàbregas et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

1.

INTRODUCTION

Future wireless communication networks will need to support extremely high data rates in order to meet the rapidly growing demand for broadband applications such as highquality audio and video. Existing wireless communication technologies cannot efficiently support broadband data rates, due to their sensitivity to fading. Multiple antennas have recently emerged as a key technology in wireless communication systems for increasing both data rates and system performance. Ever since the landmark results by Telatar [1] and Foschini and Gans [2], there has been a growing interest in developing practical transmission schemes that exploit the extra spatial dimension to achieve reliable communication over