deployment of new communication technologies and services in both wireless and wired communication sys- tems. Third-generation (3G) wireless cellular ...
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GUEST EDITORIAL
ADVANCES IN SIGNAL PROCESSING FOR WIRELESS AND WIRED COMMUNICATIONS
Mehmet Keskinoz
R
Sedat O ¨ lcer
Hamid R. Sadjadpour
ecent years have witnessed impressive growth in the deployment of new communication technologies and services in both wireless and wired communication systems. Third-generation (3G) wireless cellular systems; wireless personal, local, and metropolitan area networks (802.11 [WiFi], 802.15, 802.16 [WiMAX], etc.); emerging wireless sensor networks; and ADSL2+ and VDSL2-based digital subscriber lines are but a few examples. Other technologies are being developed that will pave the way for future services or extensions of existing services, based, for example, on fourth-generation cellular systems, cognitive radio systems, pervasive wireless sensor networks, power line communication systems, and so on. Multi-input multioutput (MIMO) communications have started to be extended to encompass multi-user communications. Orthogonal frequency-division multiplexing (OFDM) in MIMO systems is another example of future communication devices. In all these applications, signal processing is a key technology enabler. Indeed, signal processing for communications has been an extremely active field in the past few years, fueled not only by the explosive growth of wireless and wired services and applications, but also by the progress in very large-scale integration (VLSI) technology, enabling the implementation of highly complex signal processing algorithms in both hardware and software. Systemon-a-chip architectures now allow a further level of integration and design efficiency. The goal of this Feature Topic is to cover recent advances in the theory and applications of signal processing techniques for data communication systems. Given the space limitations, it was not possible to touch on all new developments, but we are confident that the articles selected convey the essential concepts behind some of the key advances in state-of-the-art communications systems, and delineate trends for future applications and directions for research. The advantages of MIMO systems combined with coding and automatic repeat request (ARQ) techniques are investigated in “Exploiting Diversity for Wireless Systems via MIMO Hybrid ARQ.” In this first article the authors focus on exploring the benefits of ARQ systems incorpo-
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rating forward error correction in retransmission of packets while taking into account the degrees of freedom provided by multiple antennas at the transmitter and receiver sides. Various receiver architectures based on this approach are described, along with the bit error rate performance of these systems. The combination of ultra-wideband (UWB) in OFDM systems for communication devices with multiple antennas is explored in the next article, entitled “Precoding in OFDM-Based Multi-Antenna Ultra-Wideband Systems.” A main challenge is to design robust systems. This objective is achieved by utilizing techniques such as precoding methods for multiple antennas. As UWB devices require strict transmit power constraints, the design of precoders for these systems requires special attention. The focus of this article is to introduce precoders that are suitable for UWB OFDM-based multiple-antenna devices. Advanced signal processing techniques to enhance the performance of already developed 3G wideband code-division multiple access (WCDMA) receivers are proposed and analyzed in “Signal Processing Advances for 3G WCDMA: From Rake Receivers to Blind Techniques.” The authors focus on two techniques to improve 3G WCDMA receiver performance: the optimal joint multiuser detection for long-code WCDMA by using fast inversion based on the state-space approach and semi-blind channel-estimation techniques to realize rate-efficient transmission. For high-speed wireless communications over frequency-selective channels, equalization techniques with low complexity become important and are investigated in “Designing Low-Complexity Equalizers for Wireless Systems.” Its authors first summarize the complexity and performance and diversity orders obtained by linear and decision feedback equalizers. Toward developing low-complexity equalizers, an overview of the lattice reduction technique and first VLSI implementation results are also included. In “The 4th Generation Broadband Concept,” the authors address the next — and probably last — DSL technology beyond the VDSL family that is starting to ramp up. This next-generation DSL realizes the so-called fiber-
IEEE Communications Magazine • January 2009
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GUEST EDITORIAL to-the-curb or -building scenario, which, because of the widespread deployment of DSL technologies in the past 15 years, can now be envisioned and described more realistically than when it was first heralded many years ago. Through proper combination of advanced signal processing and dynamic spectrum management techniques, this last-drop DSL technology will offer customers unprecedented data rates on the order of a few gigabits per second. The readily available, ubiquitous power line network turns out to be a harsh communication channel if highspeed data communications must be overlaid on its original function of AC power distribution. High-data-rate communications over power lines thus requires sophisticated yet robust signal processing techniques. In “Multirate Signal Processing Techniques for High-Speed Communication over Power Lines,” the authors provide a survey of wavelet filter banks and multirate systems that promise the robustness and flexibility needed to operate under the adverse noise and distortion conditions of PLC systems. Future directions in the application of wavelet filter banks for PLC are also discussed. We hope readers will find these articles useful, not only for highlighting recent developments but also for inspiring their own work. We thank all authors and reviewers for contributing their time and effort to this set of articles. The lack of space prevented us from including many good papers that were also submitted. We thank the former Editor-in-Chief of IEEE Communications Magazine, Prof. Thomas Chen, for his support in making this Feature Topic a reality. Also, we are grateful to the current Editorin-Chief, Dr. Nim. K. Cheung, for his support and guidance in all phases of preparing this Feature Topic.
BIOGRAPHIES MEHMET KESKINOZ [M’98] got his M.S and Ph.D. degrees from the Electrical and Computer Engineering Department of Carnegie Mellon University, Pittsburgh, Pennsylvania, in 1997 and 2001 respectively. In 2001 he joined the
IEEE Communications Magazine • January 2009
Electronics Engineering Program of Sabancı University, Istanbul, Turkey where he is now an associate professor. He is director of the Communication Theory and Technologies (CTT) Group. His research interests include signal processing for wired and wireless communications, UWB communications, multiband OFDM UWB systems, wireless mesh networks, magnetic and optical data storage systems, distributed detection and data fusion for wireless sensor networks, turbo and LDPC coding, synchronization, and digital watermarking. He is a recipient of a Turkish NSF Research grant for distributed detection in wireless sensor networks and a Career Award in wireless mesh networks in August 2005. He has been on the program/organizational committees of several international conferences and has served as a TPC member for many conferences, including IEEE ICC, GLOBECOM, and Intermag. He is a reviewer for IEEE Transactions on Wireless Communications, Transactions on Signal Processing, and Transactions on Magnetics. He is a member of the IEEE Communication Society, IEEE Signal Processing Society, and Optical Society of America. SEDAT ÖLCER [F’05] received a Diploma in electrical engineering and a Ph.D. degree from the Swiss Federal Institute of Technology, Lausanne (EPFL), Switzerland, in 1978 and 1982, respectively. From 1982 to 1984 he was a research associate at the Information Systems Laboratory of Stanford University, California, and Yale University, New Haven, Connecticut. In 1984 he joined the IBM Zurich Research Laboratory, Rueschlikon, Switzerland. His research interests are in digital communications, signal processing, and coding with applications to digital magnetic recording channels, and highspeed data communications for local area networking and network access. He has participated and contributed to the work of several standards bodies, and served as chair and co-chair for many conferences. He is currently a Technical Editor of IEEE Communications Magazine. HAMID R. SADJADPOUR received his B.S. and M.S. degrees from Sharif University of Technology with high honors, and his Ph.D. degree from the University of Southern California in 1986, 1988, and 1996, respectively. After graduation, he joined AT&T as a member of technical staff, later senior technical staff member, and finally principal member of technical staff at AT&T Laboratories, Florham Park, New Jersey, until 2001. In fall 2001 he joined the University of California, Santa Cruz, where he is now an associate professor. He has served as a Technical Program Committee member for numerous conferences and as Chair of the Communication Theory Symposium at WirelessCom ’05, and Chair of the Communication and Information Theory Symposium at IWCMC ’06, ’07, and ’08. He has also been a Guest Editor of Special Issues on Multicarrier Communications and Signal Processing in 2003 and Mobile Ad Hoc Networks in 2006 of EURASIP, and is currently Associate Editor of the Journal of Communications and Networks. He has more than 100 publications. His research interests include space-time signal processing, scaling laws for wireless ad hoc networks, performance analysis of ad hoc and sensor networks, and MAC and routing protocols for MANETs. He was a co-recipient of the International Symposium on Performance Evaluation of Computer and Telecommunication Systems (SPECTS) 2007 best paper award. He holds more than 13 patents, one of them accepted in spectrum management of the T1.E1.4 standard.
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