Special issue: Adaptive antennas and MIMO systems (2002)

‘Space is the final frontier’ has taken on a new meaning in today's wireless communications world. Exploiting the spatial dimension by means of smart antennas or multiple-input-multiple-output (MIMO) systems promises big increases in system performance and capacity. To achieve the full benefits of such systems, a wide variety of problems, ranging from channel modeling and measurements to multiple-access scheduling must be treated. This special issue presents tutorial, survey, and original contributions in the design, performance analysis, and computer evaluation of adaptive antennas and MIMO systems. The opening paper by Yu and Ottersten describes MIMO channel modeling. As MIMO systems have become more popular, channel models that are suitable for system simulations have become a necessity. The authors give a classification of available models, distinguishing between ‘physical’ and ‘nonphysical’ models. The former approach describes the distribution of scatterers and/or angles of arrival and departure of the electromagnetic waves. The latter approach uses the correlation matrix between the signals at the different antenna elements. Comparisons with measurement campaigns are given, and an extensive literature list provides access to all details of to all details of the different models. In the tutorial paper ‘A moment generating function (MGF)-based approach for performance evaluation of space-time coded communication systems’, Simon starts by describing the concept of transmit diversity. He then reviews the Alamouti space-time technique with and without trellis-coded modulation. Next he considers the more general space-time trellis-coded modulation for an arbitrary number of transmit and receive antennas. In both cases, the emphasis is to show that the MGF-based approach can be used to accurately evaluate the performance of the space-time schemes under consideration for both fast and slow fading channels. The paper by Ma and Giannakis focuses on linear complex field (LCF) codes which have the advantage of boosting the performance of single- and multiple-antenna fading channels without rate loss. Along with the performance and capacity analysis, the paper presents systematic guidelines for constructing LCF encoders. The paper also discusses the merits of LCF space-time coded multi-antenna systems which provide ample flexibility in designing schemes that optimize the typical performance-rate-complexity tradeoffs encountered in wireless applications. The paper by González-López et al. treats space–time receivers for the GSM system and their performance in subway tunnels. The GSM system is by far the most widely used wireless system throughout the world, and users have become accustomed to being able to call from virtually anywhere. Subways are one of the remaining challenges, although network providers and subway operators have teamed up in recent years to provide coverage underground. The paper covers both the aspects of channel modeling of the wireless channel, and the design of algorithms to exploit multiple antennas. In addition to surveying turbo space–time schemes, the paper by Cui et al. introduces new turbo space–time codes for QPSK and 8-PSK. These new turbo codes, termed turbo multiple antenna coded modulations (turbo-MACM), use an iterative decoding scheme based on the BCJR-MAP algorithm. The performance of this new family of codes is studied and is compared to the performance of conventional space–time codes. The paper by Li et al. discusses channel estimation and interference suppression for space–time coding. The paper looks at (two-antenna) space–time block coding, in particular the Alamouti scheme, which is popular because of its relative simplicity, and has been adopted for the 3G standard. The authors first discuss the channel estimation, as this forms the basis for the detection process. Then, the symbol detection, with special emphasis on interference suppression, is discussed. Finally, Affes and Mermelstein propose a new blind coherent spatio-temporal receiver for orthogonal Walsh-modulated CDMA systems. The blind receiver is based on a typical decision-directed adaptive technique. When some degree of coherent processing is desired, the receiver capitalizes on a decision feedback adaptive channel identification scheme. The paper also looks into fully coherent blind receivers in which the correlation structure of Walsh sequences is exploited as a reference signal. Overall the paper compares a wide range of alternatives and the presented results can be very useful as design guidelines for CDMA2000-based systems. Mohamed-Slim Alouini received the ‘Diplome d'Ingenieur’ degree from the Ecole Nationale Superieure des Telecommunications (TELECOM Paris), Paris, France, and the ‘Diplome d'Etudes Approfondies (D.E.A.)’ degree in Electronics from the University of Pierre & Marie Curie (Paris VI), Paris, both in 1993. He then received the M.S.E.E. degree from the Georgia Institute of Technology (Georgia Tech), Atlanta, GA, U.S.A., in 1995, and the Ph.D. degree in electrical engineering from the California Institute of Technology (Caltech), Pasadena, CA, U.S.A., in 1998. Since then he has been with the Department of Electrical and Computer Engineering at the University of Minnesota, Minneapolis, where his current research interests include statistical modeling of multipath fading channels, adaptive and hierarchical modulation techniques, diversity and MIMO systems, interference mitigation techniques, multi-hop communication systems, and digital communication over fading channels. Dr. Alouini has published several journal and conference papers on the above subjects and he is a co-author of the recent Wiley textbook ‘Digital Communication over Fading Channels’. He is a recipient of a National Semiconductor Graduate Fellowship Award, the Charles Wilts Prize for outstanding independent research leading to a Ph.D. degree in electrical engineering at Caltech, and co-recipient of the 1999 Prize Paper Award of the IEEE Vehicular Technology Conference (VTC'99-Fall), Amsterdam, The Netherlands, for his work on the performance evaluation of diversity systems. He was awarded a 1999 CAREER Award from the National Science Foundation, a McKnight Land-Grant Professorship by the Board of Regents of the University of Minnesota in 2001, and a Best Instructor Award by the Institute of Technology Student Board at the University of Minnesota in 2001 and 2002. Andreas F. Molisch received the Dipl. Ing., Dr. techn., and habilitation degrees from the Technical University Vienna, Austria, in 1990, 1994, and 1999, respectively. He is currently with Mitsubishi Electric Research Labs, Murray Hill, NJ, U.S.A., and Lund University, Lund, Sweden. Previously, he was with the Institut fuer Nachrichtentechnik und Hochfrequenztechnik (INTHFT) of the TU Vienna, the FTW Research Center for Telecommunications Vienna, and the Wireless Systems Research Department at AT&T Laboratories—Research in Middletown, NJ. He has done research in the areas of SAW filters, radiative transfer in atomic vapors, atomic line filters, and base station antennas. His current research interests are the measurement and modelling of mobile radio channels, MIMO systems, smart antennas, and ultrawideband wireless systems. Dr. Molisch has authored, co-authored or edited two books, five book chapters, some 50 journal papers, and numerous conference contributions. He is a senior member of IEEE, editor of the IEEE Transactions on Wireless Communications, vice-chairman of URSI Commission C, and chairman of the COST273 group on MIMO channel modeling. He received the GiT prize of the Austrian electrical engineering society in 1991, the Kardinal Innitzer prize in 1999, and an INGVAR award of the Swedish Strategic Research Foundation in 2001. Reinaldo A. Valenzuela obtained his Bachelor of Science from University of Chile and his Ph.D. from the Imperial College of Science and Technology of the University of London, U.K. At Bell Laboratories, he studied indoor microwave propagation and modeling, packet reservation multiple access for wireless systems and optical WDM networks. He became Manager, Voice Research Department, at Motorola Codex, involved in the implementation integrated voice and data packet systems. On returning to Bell Laboratories he led a multi-disciplinary team to create a software tool for Wireless System Engineering (WiSE), now in widespread use in Lucent Technologies. He received the Distinguished Member of Technical Staff award and is Director of the Wireless Communications Research Department. He is interested in microwave propagation measurements and models, intelligent antennas, third generation wireless system and space time systems achieving high capacities using transmit and receive antenna arrays. He has published over eighty papers and has twelve patents. He is a Fellow of the IEEE. He is editor for the IEEE Transactions on Communications and the IEEE Transactions on Wireless.