Guest Editorial Energy-Efficient Wireless Communications - IEEE Xplore

IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS, VOL. 29, NO. 8, SEPTEMBER 2011

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Guest Editorial Energy-Efficient Wireless Communications I. I NTRODUCTION

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HE EXPLOSIVE growth and widespread application of high rate multimedia wireless communication has prompted waves of research and standard development activities. While semiconductor processing speed has been increasing exponentially, doubling almost every two years, processor power consumption also continues to grow by 150% every two years. Energy efficiency, therefore, is becoming an increasingly important factor for battery-driven wireless mobile communication. Moreover, wireless communication systems, as a whole, are also facing a serious challenge as the total energy consumed by networked devices as well as the CO2 emissions resulting from their manufacturing and operation increase significantly. In the case of unattended sensor networks (e.g., for environmental monitoring, border surveillance, etc.), replacing batteries can be difficult, and extending the lifetime of nodes and networks becomes critical. Finding radio networking solutions that greatly improve energy-efficiency, therefore, not only benefits the global environment but also makes commercial sense for wireless system operators. In addition, we have to recognize that being connected to the internet is becoming crucial in corner of the planet, for economic, educational, as well as political reasons. Increasingly, for a large number of remote sites, internet connectivity can only be achieved by means of wireless communications, often with limited local access to energy resources. Hence, for enabling the connected world of the future with fair broadband access to the internet, energy efficient wireless communications is a crucial global economic and political goal. This special issue is therefore, timely and provides a comprehensive coverage of this important topic, bringing together state-of-the-art research results and industrial applications for energy-efficient wireless communications. It includes 21 original papers spanning a broad spectrum of topics relevant to energy-efficient communications.

II. OVERVIEW OF PAPERS There are many ways to improve energy efficiency in wireless communications. Network topologies play a key role in determining the power required for communication. Therefore, the focus of power efficiency improvement schemes can differ substantially across different network topologies. The papers in this special issue cover topologies ranging from wide-area cellular networks to short range sensor networks. For example, Digital Object Identifier 10.1109/JSAC.2011.110901

while the paper by Fransecso, Anastasi, Conti, Das and Neri, develops cross-layer techniques for optimizing power efficiency in short range 802.15.4 based sensor networks, the paper by Son, Kim, Yi, and Krishamachari, optimizes base station operation and association rules to tradeoff delay and energy efficiency in cellular systems. Additionally, network topologies based on relay architectures have shown to be effective in bridging the power efficiency gap between long and short range communications by using multi-hop communication to substantially lower the transmission power required. Several papers in this category address theoretical improvements as well as protocol enhancements for relay-based networks. The paper by C. Chen, Star and S. Chen, develops theoretical analysis characterizing energy-bandwidth tradeoff for MIMO multi-hop networks. The paper by Qi, Hoshyar, Imran and Tafazolli improves power efficiency by improving relay-based Hybrid ARQ mechanisms while papers by Wang, Vandendorpe and by Liu, Zhang, Yao and Fang employ radio-resource management (RRM) and medium access control (MAC) schemes for improving power efficiency in relay networks. While reducing the useful power required for information transmission is important for improving device energy efficiency, a significant proportion of a device’s energy consumption comprises power consumed in overhead communication and in the device electronics. Several papers aim to optimize protocols that prolong inactive or low power states for devices and efficiently manage active to inactive transitions to lower power consumption. The paper by Wu, C. Chen and M. Chen, develops efficient wakeup and sleep schedule in clustered adhoc networks, while papers by Guha, Basu, Chau and Gibbens and by Azad, Alouf, Altman, Borkar, and Paschos focus on optimizing sleep protocols. Wang, Tsai, Maciocco, Tai, and Wu develop traffic shaping techniques so as to prolong the time a device can spend in the sleep state. A. P. Azad also analyzes the power saving sleep protocols in WiMAX using a queuing theory framework. Finally, Marinkovic and Popovici develop an efficient implementation of a wakeup receiver designed for Body Area Networks. Other papers in this special issue improve algorithmic efficiency of device functions to lower the processing power required. The papers by Pei, Liang, Teh and Li, and by F. Fazel, M. Fazel and M. Stojanovic improve sensing strategies to improve energy efficiency. Cohen and Leshem improve the detection algorithm in wireless sensor networks to lower the transmission power required. In a novel application, Xu, Gu, Wang, Xing, Cheung and Ng, develop population dependent transmit power settings for RFID readers to reduce power consumption and minimize collisions in the system.

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Several papers in this issue also consider transmission protocols that utilize energy harvesting through clever use of transmission protocols or the channel environment. The paper by Wang, Wu, Han, Yang, and Liu uses channel reciprocity to echo back a received signal in order to maximize the use of multi-path diversity in the channel to lower power requirements. G. Morabitos paper encodes information between transmission events on the timing channel to save transmission power. Antelipi, Biyikoglu and Erkal, as well as Ozel, Tutuncuoglu, Yang, Ulukus and Yener, focus on optimizing scheduling and transmission policies to improve system performance with energy harvesting nodes. Finally, the paper by Grover, Woyach and Sahai develops theory to understand tradeoffs between coded and uncoded systems when both transmit and decoding power are considered together. ACKNOWLEDGMENT We received a very large number of submissions and many good quality papers could not be accepted. The guest editors would like to thank the authors for their submissions and the reviewers for their high quality reviews. We would also like to express our great gratitude to Liying Li, Richard Fritzsche, and Laurel Greenidge who have provided significant help and support throughout the whole process. Geoffrey Ye Li, Guest Editor Georgia Institute of Technology, Georgia, USA Shugong Xu, Guest Editor Huawei Technologies Co., Shanghai, China Ananthram Swami, Guest Editor Army Research Lab., Maryland, USA Nageen Himayat, Guest Editor Intel Corporation, Santa Clara, California, USA Gerhard Fettweis, Guest Editor Technische Universit¨at Dresden, Dresden, Germany Gunnar Karlsson, J-SAC Board Representative

Geoffrey Y. Li received his B.S.E. and M.S.E. degrees in 1983 and 1986, respectively, from the Department of Wireless Engineering, Nanjing Institute of Technology, Nanjing, China, and his Ph.D. degree in 1994 from the Department of Electrical Engineering, Auburn University, Alabama. He was a Teaching Assistant and then a Lecturer with Southeast University, Nanjing, China, from 1986 to 1991, a Research and Teaching Assistant with Auburn University, Alabama, from 1991 to 1994, and a Post-Doctoral Research Associate with the University of Maryland at College Park, Maryland, from 1994 to 1996. He was with AT&T Labs—Research at Red Bank, New Jersey, as a Senior and then a Principal Technical Staff Member from 1996 to 2000. Since 2000, he has been with the School of Electrical and Computer Engineering at Georgia Institute of Technology as an Associate and then a Full Professor. He is also holding the Cheung Kong Scholar title at the University of Electronic Science and Technology of China since March 2006. His general research interests include statistical signal processing and telecommunications, with emphasis on OFDM and MIMO techniques, crosslayer optimization, and signal processing issues in cognitive radios. In these areas, he has published over 200 papers in refereed journals or conferences and two books, 20 of which are with over 100 Google citations. He has over 20 patents granted or filed. He once served or is currently serving as an editor, a member of editorial board, and a guest editor for over 10 technical journals. He organized and chaired many international conferences, including technical program vice-chair of IEEE ICC03 and co-chair of IEEE SPARC11. He has been awarded an IEEE Fellow for his contributions to signal processing for wireless communications since 2006, selected as a Distinguished Lecturer for 2009–2010 by IEEE Communications Society, and won 2010 IEEE Communications Society Stephen O. Rice Prize Paper Award in the field of communications theory.

Shugong Xu received a B.Sc. degree from Wuhan University, China, and his M.E. and Ph.D. from Huazhong University of Science and Technology (HUST), Wuhan, China, in 1990, 1993, and 1996, respectively. He is currently director of the Access Network Technology Research Department, principal scientist, and vice director of the Communication Laboratory, Huawei Corporate Research, and chief scientist on Wireless Access Technologies in the National Key Laboratory on Wireless technologies at Huawei. He leads green research in Huawei including the GREAT (Green Radio Excellence in Architecture and Technologies) project, which focuses on power-efficient solutions for wireless radio access networks. Prior to joining Huawei Technologies in 2008, he was with Sharp Laboratories of America as senior research scientist for seven years. Before starting his career in industrial research, he worked at universities including Tsinghua Univiersity, China, Michigan State University, as well as City College of New York (CCNY). In his over 18+ years of research on cutting edge research on wireless/mobile networking and communication, home networking and multimedia communications, he published more than 30 peerreviewed research papers as lead-author in top international conferences and journals, in which the most referenced one has over 900 Google Scholar citations. He holds more than 30 granted US patents or patent applications, of which technologies have been adopted in 802.11 and LTE standards, including the DRX protocol for power saving in LTE standard. Dr. Xu is a senior member of IEEE, a Concurrent Professor at HUST, and the Technical Committee co-chair of Green Touch consortium.


Ananthram Swami received the B.Tech. degree from IIT-Bombay; the M.S. degree from Rice University, and the Ph.D. degree from the University of Southern California (USC), all in Electrical Engineering. He has held positions with Unocal Corporation, USC, CS-3 and Malgudi Systems. He was a Statistical Consultant to the California Lottery, developed a Matlab-based toolbox for non-Gaussian signal processing, and has held visiting faculty positions at INP, Toulouse. He is currently ST, Network Science, at the US Army Research Laboratory (ARL) where his work is in the broad area of wireless communications, sensor and mobile ad hoc networks, and network science; He is an ARL Fellow and a Fellow of the IEEE. Dr. Swami is a member of the IEEE SPS Technical Committee (TC) on Sensor Array & Multi-channel systems, and serves on the Senior Editorial Board of the IEEE Journal on Selected Topics in Signal Processing. He was a tutorial speaker on “Networking Cognitive Radios for Dynamic Spectrum Access” at ICASSP 2008, DySpan 2008, MILCOM 2008, and for ICC 2010, and co-editor of the 2007 Wiley book “Wireless Sensor Networks: Signal Processing & Communications Perspectives”. He has co-organized four IEEE workshops related to signal processing and communications.

Nageen Himayat is a senior research scientist with Wireless Communications Labs at Intel Corporation. Her work focuses on algorithm development and system design for next generation wireless systems, including WiMAX and 3GPP-LTE family of standards. Her current research interests are in heterogeneous networking architectures, PHY-MAC cross layer design, energy-efficient design and MIMOOFDM techniques for wireless systems. Prior to joining Intel, Dr. Himayat has held positions with Lucent Technologies and General Instrument Corp. (presently Motorola Corp.), where she worked on standards and system development for broadband “last-mile” access. Dr. Himayat has authored numerous technical publications in academic journals, conferences and industry standards, as well has several patents pending. She obtained her B.S.E.E degree from Rice University, TX and her Ph.D. degree from the University of Pennsylvania, PA, in 1989 and 1994 respectively. She also holds an MBA degree from the Haas School of Business, University of California at Berkeley.

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Gerhard Fettweis earned his Ph.D. degree from Aachen University of Technololgy (RWTH) in 1990 under the supervision of H. Meyr. From 1990 to 1991, he was Visiting Scientist at the IBM Almaden Research Center in San Jose, CA, developing signal processing innovations for IBMs disk drive products. From 1991 to 1994, he was Scientist with TCSI Inc., Berkeley, CA, responsible for signal processor IC development projects for cellular phone chipsets. Since 1994 he is Vodafone Chair Professor at Technische UniversitŁt Dresden, Germany. Gerhard Fettweis has (co-)authored 500 publications and more than 25 patent families. He was TPC Chair of IEEE ICC 2009 (Dresden), and has organized many other events. Beyond receiving awards, as the Alcatel-Lucent Research Award, he is an IEEE Fellow. He has spun-out nine start-ups so far: Systemonic (now NXP), Radioplan (now Actix), Signalion, InCircuit, Dresden Silicon (now Signalion), Freedelity, RadioOpt, and Blue Wonder Communications (now Intel), and INRADIOS. At TU Dresden he setup a team of currently 20 companies from Asia/Europe/US sponsoring his research. As part of this activity he currently runs the largest cellular testbed for LTEadvanced technology in downtown Dresden.