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Introduction to the Issue on Signal Processing in Heterogeneous Networks for Future Broadband Wireless Systems
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ITH THE increase in data traffic driven by a new generation of wireless devices, data is expected to overwhelm cellular network capacity in the next few years. Heterogeneous networks are a comprehensive approach to provide high cellular network capacity. A generalization of the conventional macrocell cellular architecture, heterogeneous networks combine architectural features such as small cellular access points (picocells and femtocells), low-power fixed relays, and distributed antennas. Heterogeneous networks are expected to achieve higher data rates and better coverage by exploiting spatial reuse, at the same time retaining the seamless connectivity and mobility of cellular networks. The successful deployment of heterogeneous networks will require new advances in signal processing, especially in distributed algorithms and optimization. One of the main challenges is interference management. For example, scalable algorithms in the form of beamforming or precoding, equalization, scheduling, and feedback are needed to align, avoid, or otherwise deal with the interference. In many settings, heterogeneous networks will require development of decentralized algorithms and autonomous operation of the nodes, because of the delays and overhead in the backhaul connections between the nodes. Cognitive signal processing techniques become more practical, where the macrocell can be viewed as the primary user and the second-tier network connections as secondary users. Novel approaches for channel estimation and limited feedback techniques considering the interference-limited characteristics of heterogeneous networks will become important. Other important challenges include coexistence, resource and energy management, femtocell/picocell access control, synchronization, practical relaying strategies, and self-organized network design. In the end, six papers were selected for inclusion in the special issue. The first two papers are on the topic of interference alignment, which is an interference management technique. The paper “Blind Interference Alignment” establishes that under a particular block fading models, when certain users experience smaller coherence time/bandwidth than others, it is possible to achieve the degrees of freedom using a transmission technique that does not employ channel state information, called blind interference alignment. The paper “Retrospective Interference Alignment over Interference Networks” explores the idea of achieving interference alignment with delayed channel state information at the transmitter in interference channel, especially where cooperation among transmitters is not allowed. Digital Object Identifier 10.1109/JSTSP.2012.2190541
The next paper “Block Modulation for Interference Management in Heterogeneous Wireless Networks” proposes and studies the interference cancelling block modulation (ICBM) technique for interference mitigation in heterogeneous networks. It introduces redundancy in the form of an outer code in the modulation alphabet, where rank deficiency of the covariance matrix of interference from other ICBM transmissions enables interference mitigation. The paper “Fundamentals of Inter-cell Overhead Signaling in Heterogeneous Cellular Networks” develops a framework for quantifying the overhead in signaling associated with coordination between cells. The paper “Sum-Rate Maximization in Distributed-Antenna Heterogeneous MIMO Downlinks: Application to Measured Channels” considers multiuser MIMO precoding under a variety of practical power constraints, including per-antenna power constraints, and evaluates the performance using measured channels. Finally the paper “On the Expanded Region of Picocells in Heterogeneous Networks” derives the range expansion bias value that is required to achieve a desired coverage for a picocell base station and macrocell-picocell cooperative scheduling strategies for interference mitigation in downlink/uplink. We received many papers in response to the call for papers of this special issue. Based on relevance and fit for the special issue, many high-quality papers could not be included. We would like to thank all the authors who submitted their manuscripts to this issue. We would also like to thank the reviewers who lent their precious time to evaluate papers for the issue. Finally, we hope that the wide range of papers in this special issue spurns the future development of heterogeneous networking solutions within the signal processing community.
ROBERT W. HEATH, JR., Lead Guest Editor Department of Electrical and Computer Engineering The University of Texas at Austin Austin, TX 78712-0240 (e-mail:
[email protected])
MEROUANE DEBBAH, Guest Editor Supelec 91190 Gif-sur-Yvette, France (e-mail:
[email protected])
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ERIK G. LARSSON, Guest Editor Linköping University 581 83 Linköping, Sweden (e-mail:
[email protected])
HARISH VISWANATHAN, Guest Editor Alcatel-Lucent Bell Labs Murray Hill, NJ 07974 USA (e-mail:
[email protected])
DONG IN KIM, Guest Editor Sungkyunkwan University Suwon 440-746, Korea (e-mail:
[email protected])
˙ISMAIL GÜVENÇ, Guest Editor DOCOMO Innovations, Inc. Palo Alto, CA USA (e-mail:
[email protected])
Robert W. Heath, Jr. (S’96–M’01–SM’06-F’11) received the Ph.D. degree in electrical engineering from Stanford University, Stanford, CA. Since January 2002, he has been with the Department of Electrical and Computer Engineering, University of Texas at Austin, where he is currently an Associate Professor and Director of the Wireless Networking and Communications Group. He is also President and CEO of MIMO Wireless, Inc., and Chief Innovation Officer at Kuma Signals LLC. Dr. Heath was a coauthor of best student paper awards at several conferences. He was corecipient of the 2010 EURASIP Journal on Wireless Communications and Networking Best Paper Award. He is the recipient of the David and Doris Lybarger Endowed Faculty Fellowship in Engineering, a licensed Amateur Radio Operator, and is a registered Professional Engineer in Texas.
Merouane Debbah (S’00-M’02–SM’08) received the M.Sc. and Ph.D. degrees from the Ecole Normale Supérieure de Cachan, Paris, France. He worked for Motorola Labs (Saclay, France) from 1999 to 2002 and the Vienna Research Center for Telecommunications (Vienna, Austria) from 2002 to 2003. He then joined the Mobile Communications Department of the Institut Eurecom (Sophia Antipolis, France) as an Assistant Professor. Since 2007, he has been a Full Professor at Supelec, Gif-sur-Yvette, France, holder of the Alcatel-Lucent Chair on Flexible Radio. Dr. Debbah is an Associate Editor for the IEEE TRANSACTIONS ON SIGNAL PROCESSING. He is the recipient of the “Mario Boella” prize award in 2005, the 2007 General Symposium IEEE GLOBECOM Best Paper Award, the Wi-Opt 2009 Best Paper Award, the 2010 Newcom++ Best Paper Award as well as the Valuetools 2007, Valuetools 2008 and CrownCom2009 Best Student Paper Awards. He is a WWRF fellow. In 2011, he received the IEEE/SEE Glavieux Prize Award.
Erik G. Larsson (M’02–SM’11) received the Ph.D. degree from Uppsala University, Uppsala, Sweden. He has been a Professor and Head of the Division for Communication Systems in the Department of Electrical Engineering (ISY), Linkoping University (LiU), Linkoping, Sweden, since 2007. He has previously held academic positions at the Royal Institute of Technology (KTH), Stockholm, Sweden, the University of Florida, and George Washington University. His main professional interests are within the areas of wireless communications and signal processing. He has published some 80 journal papers on these topics, he is coauthor of the textbook Space-Time Block Coding for Wireless Communications (Cambridge University Press, 2003) and he holds ten patents. Prof. Larsson is an Associate Editor for the IEEE TRANSACTIONS ON COMMUNICATIONS and Technical Chair of the Asilomar Conference on Signals, Systems, and Computers 2012.
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Dong In Kim (S’89–M’91–SM’02) received the Ph.D. degree in electrical engineering from the University of Southern California, Los Angeles, in 1990. From 2002 to 2007, he was a tenured Professor in the School of Engineering Science, Simon Fraser University, Canada. Since 2007, he has been with Sungkyunkwan University (SKKU), Suwon, Korea, where he is a Professor in the School of Information and Communication Engineering. His current research interests include wireless cellular, relay networks, and cross-layer design. Dr. Kim has served as an Editor and Area Editor for Cross-Layer Design and Optimization for the IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS from 2002 to 2011, and also served as Co-Editor-in-Chief for the Journal of Communications and Networks from 2008 to 2011. He is currently an Editor for Spread Spectrum Transmission and Access for the IEEE TRANSACTIONS ON COMMUNICATIONS and Founding Editor-in-Chief for the IEEE WIRELESS COMMUNICATIONS LETTERS in 2012.
Harish Viswanathan (S’93–M’97–SM’03) received the B.Tech. degree from the Department of Electrical Engineering, Indian Institute of Technology, Chennai, and the M.S. and Ph.D. degrees from the School of Electrical Engineering, Cornell University, Ithaca, NY, in 1995 and 1997, respectively. Since joining Alcatel-Lucent Bell Labs, Murray Hill, NJ, in October 1997, he has worked on multiple antenna technology for cellular wireless networks, network optimization, mesh networking, and mobility management protocols. He is currently an advisor to the Corporate CTO, Bell Labs. His current interests include optimizing video over cellular wireless and machine-to-machine communications.
˙ Ismail Güvenç (M’06– SM’10) received the Ph.D. degree in electrical engineering from University of South Florida, Tampa, FL, in 2006 (with outstanding dissertation award). He was with Mitsubishi Electric Research Labs, Cambridge, MA, in 2005, and since June 2006, he has been with DOCOMO Innovations, Inc., Palo Alto, CA, working as a Research Engineer. His recent research interests include heterogeneous wireless networks and future radio access beyond 4G wireless systems. He has published more than 60 conference and journal papers and several standardization contributions. He coauthored/coedited three books for Cambridge University Press. He holds eight U.S. patents, and has another 15 pending U.S. patent applications. Dr. Güvenç is an editor for the IEEE COMMUNICATIONS LETTERS and IEEE WIRELESS COMMUNICATIONS LETTERS, and was a guest editor for two special issue journals on heterogeneous networks.
