Proportional Service Differentiation in Wireless LANs Using Spacing-based Channel Occupancy Regulation

In this paper, we propose Spacing-based Channel Occupancy Regulation (SCORE) MAC protocol for wireless LANs that provides proportional service differentiation in terms of normalized throughput. As shown by our system model and simulation study, SCORE provides consistent, scalable and adjustable proportional differentiation for any network size, any service class distribution, any node data rate and any packet size. Compared to state-of-the-art prioritized service differentiation schemes like Enhanced Distributed Coordination Function (EDCF), SCORE can quantitatively control the channel sharing between different service classes. Moreover, SCORE obtains significant performance improvements in terms of higher network throughput, higher transmission efficiency, lower medium access delay and lower delay jitter. Dr. Qi Xue is now a senior systems engineer with Qualcomm Inc. since Feb. 2005. Qi Xue is currently a Ph.D. candidate in the department of Electrical and Computer Engineering, University of Massachusetts at Amherst. He received his M.S. degree in Electrical and Information Engineering from Huazhong University of Science and Technology, China, in 2000. His research interests include protocol design and performance analysis in wireless networks. Weibo Gong received his Ph.D degree from Harvard University in 1987, and have been with the Dept. of Electrical and Computer Engineering, University of Massachusetts, Amherst since then. He is also an adjunct professor in the Dept. of Computer Science at the same campus. His major research interests include control and systems methods in communication networks, network security, and network modeling and analysis. He is a receipient of the IEEE Transactions on Automatic Control’s George Axelby Outstanding paper award, an IEEE Fellow, and the Program Committee Chair for the 43rd IEEE Conference on Decision and Control. Aura Ganz received her B.Sc, M.Sc and Ph.D degrees in Computer Science from the Technion in Israel. She is currently an associate professor and Director of the Multimedia Networks Laboratory at the ECE Department, University of Massachusetts at Amherst. She has experience in topics related to all strata of networking technology, from work related to topics in the network infrastructure development to advanced user-space application development for mobile clients. The research results are validated by a combination of analytical, simulation and prototyping tools. She has published a book “Multimedia Wireless Networks: Technologies, Standards and QoS” (Prentice Hall) and authored over one hundred and fifty peer reviewed publications. Dr. Ganz is a senior member of IEEE     

Enhancement of a WLAN-Based Internet Service

A wireless LAN (WLAN)-based Internet service, called NESPOT, of Korea Telecom (KT), the biggest telecommunication and Internet service company in Korea, has been operational since early 2002. As the numbers of subscribers and deployed access points (APs) increase, KT has been endeavoring to improve its service quality as well as the network management. In this paper, we introduce a joint effort between Seoul National University (SNU) and KT to achieve it. We have been addressing two major issues as part of the joint project thus far: (1) a unified WLAN management/maintenance tool; and (2) real-time traffic support enhancement. We present our on-going efforts as well as some preliminary results. Some issues, which need further attention for the future NESPOT service enhancement, are also introduced.The work reported in this paper was financed and supported by KT. Any opinions, findings, and conclusions or recommendations expressed in this publication are those of the authors and do not necessarily reflect the views of KT. Youngkyu Choi is an M.S. candidate in the department of electrical engineering at Seoul National University (SNU), Seoul, Korea. He received his B.S. with honors in electrical engineering from SNU in 2002. He has a lot of project experiences related with system software development. His current research interests are the design of MAC layer from distributed system to centralized cellular system, resource management in next-generation (4G) cellular system, and mathematical analysis of system performance. He had served in the Korean Army for 3 years from 1998. Sekyu Park is a research staff at the Multimedia & Wireless Networking Lab. (MWNL), Seoul National University (SNU), Seoul, Korea. Before joining MWNL in September 2003, he was with MMC Technology, Seoul, Korea as a Research Staff for five years. His current research interests are in the area of wireless/mobile networks and embedded OS. Sunghyun Choi is an assistant professor at the School of Electrical Engineering, Seoul National University (SNU), Seoul, Korea. Before joining SNU in September 2002, he was with Philips Research USA, Briarcliff Manor, New York, USA as a Senior Member Research Staff and a project leader for three years. He received his B.S. (summa cum laude) and M.S. degrees in electrical engineering from Korea Advanced Institute of Science and Technology (KAIST) in 1992 and 1994, respectively, and received Ph.D. at the Department of Electrical Engineering and Computer Science, The University of Michigan, Ann Arbor in September, 1999. His current research interests are in the area of wireless/mobile networks with emphasis on the QoS guarantee and adaptation, resource management, wireless LAN and PAN, next-generation mobile networks, data link layer protocols, and connection and mobility management. He authored/coauthored over 45 technical papers and book chapters in the areas of wireless/mobile networks and communications. He is the technical program co-chair for ACM International Workshop on Wireless Mobile Applications and Services on WLAN Hotspots (WMASH’2004). He is currently serving on program committees of a number of leading wireless and networking conferences including IEEE INFOCOM, IEEE GLOBECOM, and IEEE VTC. He is also a guest co-editor for a special issue on “Emerging WLAN Applications and Technologies” of Wiley Wireless Communications and Mobile Computing Journal. He is an active participant and contributor of the IEEE 802.11 WLAN standardization committee. Dr. Choi was a recipient of the Korea Foundation for Advanced Studies Scholarship and the Korean Government Overseas Scholarship during 1997–1999 and 1994–1997, respectively. Go Woon Lee is a researcher at Service Development Laboratory, Korea Telecom (KT), Seoul, Korea. She received her B.S. degrees in computer science and material engineering from Korea Advanced Institute of Science and Technology (KAIST) in 1995. She was with Microsoft Korea R&D Group as a research staff in 1995. She received M.S. degree in information & communication from Kwang-Ju Institute of Science and Technology (K-JIST) in 1998. Her current research interests are in the area of wireless/mobile networks with emphasis on data link layer protocols, remote diagnosis, and wireless service management. Jaehwan Lee is a researcher at Korea Telecom (KT), Seoul, Korea. He received his B.S. and M.S. degrees in electrical engineering from Seoul National University (SNU) in 1998 and 2000, respectively. His master’s research was about estimation theory related to Global Positioning System (GPS) and image processing in robot soccer. His current research interest is to analyze and enhance the performance of wireless/mobile networks (IEEE 802.11, sensor networks and mobile ad-hoc networks) regarding QoS, energy-efficiency and high-throughput considering hand-off and inter-networking with heterogeneous networks. Before joining wireless LAN group in KT, he developed the Web-GIS (Geographical Information System) client-server system from 2000 to 2001. Hanwook Jung, Ph.D joined KT in 1985 and got his Ph.D degree with the company finalcial scholarship of KT from 1991 to 1996 at SUNY at Buffalo. His thesis is about “Wireless signal transmission over Fiber by subcarrier multiplexing” which is current heavily utilized for PCS and cellular repeater line. From 1985 to 1991, he had developed a Videotex service which is now known as Hitel. From 1996 to 1999, he developed 26GHz broadband wireless local loop system and contributed to get the license from the government. Since 1999, he has led a business model and service with wireless LAN. The KT Wi-Fi public service, “NESPOT” has 300,000 subscribers and 10,000 public hotspots. In 2003 he was promoted as an assistant vice president leading NESPOT research team to enhance KT’s broadband with 5,000,000 subscribers. His vision regarding next generation communications service is believed to be true by combining the broadband access and wireless technology including WiFi wireless LAN, UWB, and bluetooth in those areas such as wireless home-networking, device-to-device communications, and ubiqutous networking.This revised version was published online in August 2005 with a corrected cover date.     

Antennas and Propagation Measurement Techniques for UWB Radio

The progressive development of Ultra Wide Band (UWB) antennas and microelectronics allows for a wide range of future UWB radio communication applications. The paper focuses on testing and measuring various antennas and propagation aspects important in UWB radio. The ‘Delft approach’ of measuring UWB antennas using time-domain measurement techniques is explained including the diagnostics of antenna mismatch and wave scattering from the inside and the antennas environment. The approach is illustrated with measurements.The experimental time-domain set up allows instantaneous measurements up to 26GHz. After an overview of various UWB antennas some latest developments of a miniaturized antenna are reported. UWB channel measurements in ‘short-range radio’ illustrates that good insight in the propagation of short radar pulses can be obtained. Leo P. Ligthart was born in Rotterdam, the Netherlands, on September 15, 1946. He received an Engineer's degree (cum laude) and a Doctor of Technology degree from Delft University of Technology in 1969 and 1985, respectively. He is fellow of IEE and IEEE. He received Doctorates (honoris causa) at Moscow State Technical University of Civil Aviation in 1999 and Tomsk State University of Control Systems and Radioelectronics in 2001. He is academician of the Russian Academy of Transport. Since 1992, he has held the chair of Microwave Transmission, Radar and Remote Sensing in the Department of Electrical Engineering, Mathematics and Computer Science, Delft University of Technology. In 1994, he founded the International Research Center for Telecommunications and Radar (IRCTR) and is the director of IRCTR. Prof. Ligthart's principal areas of specialization include antennas and propagation, radar and remote sensing, but he has also been active in satellite, mobile and radio communications. He has published over 300 papers.     

Multi-VDD Testing for Analog Circuits

We present industrial results of a quiescent current testing technique suitable for RF testing. The operational method consists of ramping the power supply and of observing the corresponding quiescent current signatures. When the power supply is swept, all transistors are forced into various regions of operation. This has as advantage that the detection of faults is done for multiple supply voltages and corresponding quiescent currents, enhancing in this form the detectability of faults. We found that this method of structural testing yields fault coverage results comparable to functional RF tests making it a potential and attractive technique for production wafer testing due to its low cost, low testing times and low frequency requirements.José Pineda de Gyvez received the Ph.D. degree from the Eindhoven University of Technology. He is currently a principal scientist at Philips Research Laboratories, The Netherlands. Dr. Pineda was Associate Editor in IEEE Transactions on Circuits and Systems Part I and also Associate Editor for Technology in IEEE Transactions on Semiconductor Manufacturing. His research interests are in the general areas of design for manufacturability and analog signal processing.Guido Gronthoud received the electrical engineering degree from the Delft University in 1975. From 1976 to 1980 he worked at the Delft University on the design of Microwave systems. From 1980 he works with Philips. He has been working in the fields of circuit simulation and modelling for IC designs, CAD development for PCB design and electronic circuits and systems reliability. Since 1998 he is working on test innovation of digital and mixed-signal circuits. His interests are Defect Oriented Test, fault modeling and Process Related Test. He has authored and co-authored technical papers.     

A Centralized MAC Protocol for QoS Support in UWB-Based Wireless Networks

In this paper we introduce a novel MAC protocol that provides Quality of Service (QoS) support for multimedia traffic in UWB-based wireless local area networks. The proposed protocol allocates transmission opportunities to QoS and best effort traffic using a set of scheduling and resource control algorithms. The algorithms account for the UWB characteristics such as the co-existence of multiple simultaneous transmissions as well as the possibility of dynamically assigning the nodes' transmission rate and power. The simulation results show that the proposed protocol can provide QoS support while optimizing resource utilization. Yuechun Chu received her B.Sc. degree in electrical engineering from Shanghai University, China, in 1996 and M.Sc. degree in electrical engineering from University of Science and Technology of China in 1999. She is currently pursuing the Ph.D. degree in the department of electrical and computer engineering at the University of Massachusetts Amherst. Her research interests include MAC protocol design for UWB-based networks, wireless multimedia applications, and architectures and protocols for wireless networks with QoS guarantees. Aura Ganz is currently an Associate Professor and Director of the Multimedia Networks Laboratory at the ECE Department, University of Massachusetts at Amherst. She has experience in topics related to multimedia wireless networks, optical networks and ubiquitous computing. The research results are validated by a combination of analytical, simulation and prototyping tools. She has published a book “Multimedia Wireless Networks: Technologies, Standards and QoS” (Prentice Hall) and authored over one hundred and fifty peer reviewed publications. Dr. Ganz received her BSc, MSc and Ph.D degrees in Computer Science from the Technion in Israel.     

SOLONet: Sub-optimal location-aided overlay network for MANETs

Overlay networks have made it easy to implement multicast functionality in MANETs. Their flexibility to adapt to different environments has helped in their steady growth. Overlay multicast trees that are built using location information account for node mobility and have a low latency. However, the performance gains of such trees are offset by the overhead involved in distributing and maintaining precise location information. As the degree of (location) accuracy increases, the performance improves but the overhead required to store and broadcast this information also increases. In this paper, we present SOLONet, a design to build a sub-optimal location aided overlay multicast tree, where location updates of each member node are event based. Unlike several other approaches, SOLONet doesn’t require every packet to carry location information or each node maintain location information of every other node or carrying out expensive location broadcast for each node. Our simulation results indicate that SOLONet is scalable and its sub-optimal tree performs very similar to an overlay tree built by using precise location information. SOLONet strikes a good balance between the advantages of using location information (for building efficient overlay multicast trees) versus the cost of maintaining and distributing location information of every member nodes. Abhishek Patil received his BE degree in Electronics and Telecommunications Engineering from University of Mumbai (India) in 1999 and an MS in Electrical and Computer Engineering from Michigan State University in 2002. He finished his PhD in 2005 from the Department of Computer Science and Engineering at Michigan State University. He is a research engineer at Kiyon, Inc. located in San Diego, California. His research interests include wireless mesh networks, UWB, mobile ad hoc networks, application layer multicast, location-aware computing, RFIDs, and pervasive computing. Yunhao Liu received his BS degree in Automation Department from Tsinghua University, China, in 1995, and an MA degree in Beijing Foreign Studies University, China, in 1997, and an MS and a Ph.D. degree in Computer Science and Engineering at Michigan State University in 2003 and 2004, respectively. He is now an assistant professor in the Department of Computer Science at Hong Kong University of Science and Technology. His research interests include wireless sensor networks, peer-to-peer and grid computing, pervasive computing, and network security. He is a senior member of the IEEE Computer Society. Li Xiao received the BS and MS degrees in computer science from Northwestern Polytechnic University, China, and the PhD degree in computer science from the College of William and Mary in 2002. She is an assistant professor of computer science and engineering at Michigan State University. Her research interests are in the areas of distributed and Internet systems, overlay systems and applications, and sensor networks. She is a member of the ACM, the IEEE, the IEEE Computer Society, and IEEE Women in Engineering. Abdol-Hossein Esfahanian received his B.S. degree in Electrical Engineering and the M.S. degree in Computer, Information, and Control Engineering from the University of Michigan in 1975 and 1977 respectively, and the Ph.D. degree in Computer Science from Northwestern University in 1983. He was an Assistant Professor of Computer Science at Michigan State University from September 1983 to May 1990. Since June 1990, he has been an Associate Professor with the same department, and from August 1994 to May 2004, he was the Graduate Program Director. He was awarded ‘The 1998 Withrow Exceptional Service Award’, and ‘The 2005 Withrow Teaching Excellence Award’. Dr. Esfahanian has published articles in journals such as IEEE Transactions, NETWORKS, Discrete Applied Mathematic, Graph Theory, and Parallel and Distributed Computing. He was an Associate Editor of NETWORKS, from 1996 to 1999. He has been conducting research in applied graph theory, computer communications, and fault-tolerant computing. Lionel M. Ni earned his Ph.D. degree in electrical and computer engineering from Purdue University in 1980. He is Chair Professor and Head of Computer Science and Engineering Department of the Hong Kong University of Science and Technology. His research interests include wireless sensor networks, parallel architectures, distributed systems, high-speed networks, and pervasive computing. A fellow of IEEE, Dr. Ni has chaired many professional conferences and has received a number of awards for authoring outstanding papers.     

Relay sensor placement in wireless sensor networks

This paper addresses the following relay sensor placement problem: given the set of duty sensors in the plane and the upper bound of the transmission range, compute the minimum number of relay sensors such that the induced topology by all sensors is globally connected. This problem is motivated by practically considering the tradeoff among performance, lifetime, and cost when designing sensor networks. In our study, this problem is modelled by a NP-hard network optimization problem named Steiner Minimum Tree with Minimum number of Steiner Points and bounded edge length (SMT-MSP). In this paper, we propose two approximate algorithms, and conduct detailed performance analysis. The first algorithm has a performance ratio of 3 and the second has a performance ratio of 2.5. Xiuzhen Cheng is an Assistant Professor in the Department of Computer Science at the George Washington University. She received her MS and PhD degrees in Computer Science from the University of Minnesota - Twin Cities in 2000 and 2002, respectively. Her current research interests include Wireless and Mobile Computing, Sensor Networks, Wireless Security, Statistical Pattern Recognition, Approximation Algorithm Design and Analysis, and Computational Medicine. She is an editor for the International Journal on Ad Hoc and Ubiquitous Computing and the International Journal of Sensor Networks. Dr. Cheng is a member of IEEE and ACM. She received the National Science Foundation CAREER Award in 2004. Ding-Zhu Du received his M.S. degree in 1982 from Institute of Applied Mathematics, Chinese Academy of Sciences, and his Ph.D. degree in 1985 from the University of California at Santa Barbara. He worked at Mathematical Sciences Research Institutea, Berkeley in 1985-86, at MIT in 1986-87, and at Princeton University in 1990-91. He was an associate-professor/professor at Department of Computer Science and Engineering, University of Minnesota in 1991-2005, a professor at City University of Hong Kong in 1998-1999, a research professor at Institute of Applied Mathematics, Chinese Academy of Sciences in 1987-2002, and a Program Director at National Science Foundation of USA in 2002-2005. Currently, he is a professor at Department of Computer Science, University of Texas at Dallas and the Dean of Science at Xi’an Jiaotong University. His research interests include design and analysis of algorithms for combinatorial optimization problems in communication networks and bioinformatics. He has published more than 140 journal papers and 10 written books. He is the editor-in-chief of Journal of Combinatorial Optimization and book series on Network Theory and Applications. He is also in editorial boards of more than 15 journals. Lusheng Wang received his PhD degree from McMaster University in 1995. He is an associate professor at City University of Hong Kong. His research interests include networks, algorithms and Bioinformatics. He is a member of IEEE and IEEE Computer Society. Baogang Xu received his PhD degree from Shandong University in 1997. He is a professor at Nanjing Normal University. His research interests include graph theory and algorithms on graphs.     

Provisioning link layer proportional service differentiation in wireless networks with smart antennas

In this paper, we present a collision free MAC protocol for wireless networks with smart antennas that provides proportional service differentiation to various classes of traffic based on their respective bandwidth demand. The proposed protocol works for diverse physical parameters such as number of interfaces at each node, number of communication frequencies, and antenna beamwidth. To the best of our knowledge, this is the first work that provides link layer differentiated services for wireless networks with smart antennas and explores the influence of the physical parameters and network topology on the performance of the MAC layer. Ashish Deopura received his B.Tech degree in Electrical Engineering from the Indian Institute of Technology Delhi, India, in 2003, and he received his M.S. degree in Computer Systems Engineering from the University of Massachusetts Amherst, in 2005. He currently works as a Modeling Engineer for OPNET Technologies located in Bethesda, MD Professor Aura Ganz is the director of the Multimedia Networking Laboratory at the University of Massachusetts at Amherst. She has authored more than 170 journal and conference papers in the areas of multimedia wireless networks, ubiquitous computing, telemedicine, and security. She is a co-author of the book: “Multimedia Wireless Networks”, Prentice Hall, 2003. Some of her recent assignments include: general co-chair of the IEEE UWBNETS workshop, general co-chair of the IEEE BROADMED workshop, general co-chair of the Massachusetts 3rd Annual R&D Conference, keynote speaker at the NSF sponsored workshop in Mobile Computing, and invited speaker at Personal and Local Wireless Network Solutions conference, and Motorola’s Wireless Communications Futures Forum, Wireless Local Area Networks Conference. She has a PhD, MSc and BSc in Computer Science from the Technion in Israel. More details can be found at: dvd1.ecs.umass.edu/wireless.     

Smooth handoff with enhanced packet buffering-and-forwarding in wireless/mobile networks

Packet buffering-and-forwarding is a simple mechanism and has been widely used to provide seamless handoffs in many wireless/mobile networks. However, some undesirable side effects of this mechanism, if not managed appropriately, can easily diminish its effectiveness in providing seamless inter-cell transitions during a handoff. We first examine these side effects and show how inappropriate buffer management by a mobility agent could affect the TCP performance. The throughput of TCP is then studied with special emphasis on the effects of a handoff. We then propose a Last-Come-First-Drop (LCFD) buffer management policy (to be employed by mobility agents) and post-handoff acknowledgement suppression (to be used by mobile nodes) to improvement the TCP performance. Our enhancements are backward compatible and suitable for the gradual/incremental deployment. By deriving an analytical model and conducting numerical analysis, we show that our scheme can improve the TCP throughput up to 30%. Finally, we conduct the ns-2-based simulation to confirm these numerical results, and demonstrate the applicability of the analytic model for predicting TCP throughput in other handoff schemes. Chun-Ting Chou is currently a senior member research staff in Philips Research North America, Briarcliff Manor, New York. He received both the B.S. and M.S. degrees in Electrical Engineering from National Taiwan University in 1995 and 1997, respectively. He received the Ph.D. degree in Electrical Engineering and Computer Science from the University of Michigan, Ann Arbor, in 2004. He is actively involved in standardization of WiMedia Ultra-Wide Band (UWB) Wireless PANs, IEEE 802.15.3c high-speed wireless PANs and IEEE 802.15.5 meshed Wireless PANs. His current research interests include quality of service (QoS), MAC protocols for UWB Wireless PANs, 60-GHz wireless PANs using directional antennas, meshed wireless LANs and PANs, and spectrum agile and cooperative communication. Kang G. Shin is the Kevin and Nancy O’Connor Professor of Computer Science and Founding Director of the Real-Time Computing Laboratory in the Department of Electrical Engineering and Computer Science, The University of Michigan, Ann Arbor, Michigan. His current research focuses on QoS-sensitive networking and computing as well as on embedded real-time OS, middleware and applications, all with emphasis on timeliness and dependability. He has supervised the completion of 54 PhD theses, and authored/coauthored around 630 technical papers and numerous book chapters in the areas of distributed real-time computing and control, computer networking, fault-tolerant computing, and intelligent manufacturing. He has co-authored (jointly with C. M. Krishna) a textbook “Real-Time Systems,” McGraw Hill, 1997. He has received a number of best paper awards, including the IEEE Communications Society William R. Bennett Prize Paper Award in 2003, the Best Paper Award from the IWQoS’03 in 2003, and an Outstanding IEEE Transactions of Automatic Control Paper Award in 1987. He has also coauthored papers with his students which received the Best Student Paper Awards from the 1996 IEEE Real-Time Technology and Application Symposium, and the 2000 UNSENIX Technical Conference. He has also received several institutional awards, including the Research Excellence Award in 1989, Outstanding Achievement Award in 1999, Service Excellence Award in 2000, Distinguished Faculty Achievement Award in 2001, and Stephen Attwood Award in 2004 from The University of Michigan; a Distinguished Alumni Award of the College of Engineering, Seoul National University in 2002; and 2003 IEEE RTC Technical Achievement Award. He received the B.S. degree in Electronics Engineering from Seoul National University, Seoul, Korea in 1970, and both the M.S. and Ph.D degrees in Electrical Engineering from Cornell University, Ithaca, New York in 1976 and 1978, respectively. From 1978 to 1982 he was on the faculty of Rensselaer Polytechnic Institute, Troy, New York. He has held visiting positions at the U.S. Airforce Flight Dynamics Laboratory, AT &T Bell Laboratories, Computer Science Division within the Department of Electrical Engineering and Computer Science at UC Berkeley, and International Computer Science Institute, Berkeley, CA, IBM T. J. Watson Research Center, Software Engineering Institute at Carnegie Mellon University, and HP Research Laboratories. He also chaired the Computer Science and Engineering Division, EECS Department, The University of Michigan for three years beginning January 1991. He is Fellow of IEEE and ACM, and member of the Korean Academy of Engineering, is serving as the General Chair for the 3rd ACM/USENIX International Conference on Mobile Systems, Applications, and Services (MobiSys’05), was the General Chair of the 2000 IEEE Real-Time Technology and Applications Symposium, the Program Chair of the 1986 IEEE Real-Time Systems Symposium (RTSS), the General Chair of the 1987 RTSS, the Guest Editor of the 1987 August special issue of IEEE Transactions on Computers on Real-Time Systems, a Program Co-Chair for the 1992 International Conference on Parallel Processing, and served numerous technical program committees. He also chaired the IEEE Technical Committee on Real-Time Systems during 1991--93, was a Distinguished Visitor of the Computer Society of the IEEE, an Editor of IEEE Trans. on Parallel and Distributed Computing, and an Area Editor ofInternational Journal of Time-Critical Computing Systems,Computer Networks, and ACM Transactions on Embedded Systems.     

Minimum energy transmission scheduling subject to deadline constraints

We consider the problem of transmission scheduling of data over a wireless fading channel with hard deadline constraints. Our system consists of N users, each with a fixed amount of data that must be served by a common deadline. Given that, for each user, the channel fade state determines the throughput per unit of energy expended, our objective is to minimize the overall expected energy consumption while satisfying the deadline constraint. We consider both a linear and a strictly convex rate-power curve and obtain optimal solutions, based on dynamic programming (DP), and tractable approximate heuristics in both cases. For the special non-fading channel case with convex rate-power curve, an optimal solution is obtained based on the Shortest Path formulation. In the case of a linear rate-power curve, our DP solution has a nice “threshold” form; while for the convex rate-power curve we are able to obtain a heuristic algorithm with comparable performance with that of the optimal scheduling scheme. Alessandro Tarello received his M.Sc. and Ph.D. degrees in Electrical and Communication Engineering from Politecnico di Torino, Torino, Italy, in 2002 and 2006 respectively. He currently holds a Postdoctoral position at Politecnico di Torino. He visited the Laboratory for Information and Decision Systems at MIT, Cambridge, MA, USA, in 2004 and 2005. During Summer 2005 he also visited the Jet Propulsion Laboratory, Pasadena, CA, USA. He received the best student paper award at the Third International Symposium on Modeling and Optimization in Mobile, Ad-Hoc and Wireless Networks (WiOPT’05). His research interests are in the fields of stochastic and fluid models for performance evaluation of packet networks and optimization techniques for wireless and ad-hoc networks. Jun Sun received his B.S. degree in Computer Engineering from University of Florida in 1997 and his M.S. in Electrical Engineering from Massachusetts Institute of Technology in 2002. He is currently a Ph.D. student in the Laboratory for Information and Decision Systems at MIT. His research interest is on communication networks with emphasis on satellite and wireless networks. Murtaza Zafer received his B.Tech degree in Electrical Engineering from the Indian Institute of Technology (IIT), Madras, India, in 2001 and his M.S. degree in Electrical Engineering and Computer Science from the Massachusetts Institute of Technology (MIT), MA, USA, in 2003. Currently, he is pursuing his doctoral studies at the Laboratory for Information and Decision Systems (LIDS) in the department of Electrical Engineering and Computer Science at MIT. He spent the summer of 2004 at the Mathematical Sciences Research center, Bell Laboratories and the summer of 2003 at Qualcomm, Inc. His research interests lie in queueing theory, information theory, control and optimization theory and its applications to wireless communication networks. He is the co-recipient of the best Student Paper award at WiOpt, 2005. He also received the Siemens (India) and Philips (India) award for academic excellence. Eytan Modiano received his B.S. degree in Electrical Engineering and Computer Science from the University of Connecticut at Storrs in 1986 and his M.S. and PhD degrees, both in Electrical Engineering, from the University of Maryland, College Park, MD, in 1989 and 1992 respectively. He was a Naval Research Laboratory Fellow between 1987 and 1992 and a National Research Council Post Doctoral Fellow during 1992–1993. Between 1993 and 1999 he was with MIT Lincoln Laboratory where he was the project leader for MIT Lincoln Laboratory’s Next Generation Internet (NGI) project. Since 1999 he has been on the faculty at MIT; where he is presently an Associate Professor. His research is on communication networks and protocols with emphasis on satellite, wireless, and optical networks. He is currently an Associate Editor for Communication Networks for IEEE Transactions on Information Theory and for The International Journal of Satellite Communications. He had served as a guest editor for IEEE JSAC special issue on WDM network architectures; the Computer Networks Journal special issue on Broadband Internet Access; the Journal of Communications and Networks special issue on Wireless Ad-Hoc Networks; and for IEEE Journal of Lightwave Technology special issue on Optical Networks. He is the Technical Program co-chair for Wiopt 2006, IEEE Infocom 2007, and ACM MobiHoc 2007.     

High Performance Wireless Switch Protocol for IEEE 802.11 Wireless Networks

All mobile stations (STAs) in IEEE 802.11 infrastructure wireless local area networks (IWLAN) are coordinated by an access point (AP). Within the 2.4 GHz unlicensed industry, science, and medicine (ISM) band defined in the IEEE 802.11 2.4 GHz physical layer (PHY) specifications, three channels are available for concurrently transferring data packets at the coverage area of an AP. In most of small/medium enterprises or home environments, an AP with one selected channel is sufficient for covering whole service area, but this implies that the radio resources for the remaining two channels are wasted. In order to overcome the drawback, we propose a new and simple media access control (MAC) protocol, named wireless switch protocol (WSP), for increasing the throughput of IEEE 802.11 IWLAN network to support high quality multimedia traffic. This is achieved by allowing any pair of STAs in IWLAN to exchange data packets in one of other idle channels after their handshake with each other in the common channel controlled by AP. Simulation results show that the total network throughput of WSP depends on the time taken by channel switching, and on the ‘Intranet’ and ‘Internet’ traffic distribution, where the Intranet and Internet mean data transmission between STAs in IWLAN and between the STA and wired host, respectively. When all data packets are Intranet traffic and the traffic load is heavy, the ratio of Goodput for the proposed WSP to that of IEEE 802.11 standard approximates 400%. In the worse case of all Internet traffic, the proposed WSP still obtains the similar throughput as that of IEEE 802.11 standard.Jenhui Chen was born on October 12, 1971 in Taipei, Taiwan, Republic of China. He received the Bachelor’s and Ph.D. degree in Computer Science and Information Engineering (CSIE) from Tamkang University in 1998 and 2003, respectively. In the Spring of 2003, he joined the faculty of Computer Science and Information Engineering Department at Chang Gung University and served as the Assistant Professor. He occupies the supervisor of Network Department in the Information Center, Chang Gung University. Dr. Chen once served the reviewer of IEEE Transactions on Wireless Communications, ACM/Kluwer Mobile Networks and Applications (MONET), and Journal of Information Science and Engineering. His main research interests include design, analysis, and implementation of communication and network protocols, wireless networks, milibots, and artificial intelligence. He is a member of ACM and IEEE.Ai-Chun Pang was born in Hsinchu, Taiwan, R.O.C., in 1973. She received the B.S., M.S. and Ph.D. degrees in Computer Science and Information Engineering from National Chiao Tung University (NCTU) in 1996, 1998 and 2002, respectively. She joined the Department of Computer Science and Information Engineering, National Taiwan University (NTU), Taipei, Taiwan, as an Assistant Professor in 2002. Her research interests include design and analysis of personal communications services network, mobile computing, voice over IP, and performance modeling.Shiann-Tsong Sheu received his B.S. degree in Applied Mathematics from National Chung Hsing University in 1990, and obtained his Ph.D. degree in Computer Science from National Tsing Hua University in May of 1995. From 1995 to 2002, he was an Associate Professor at the Department of Electrical Engineering, Tamkang University. Since Feb. 2002, he has become a Professor at the Department of Electrical Engineering, Tamkang University. Dr. Sheu received the outstanding young researcher award by the IEEE Communication Society Asia Pacific Board in 2002. His research interests include next-generation wireless communication, WDM networks and intelligent control algorithms.Hsueh-Wen Tseng received his B.S. degree in electrical engineering from Tamkang University, Taipei country, Taiwan, in 2001 and M.S. degree in electrical engineering from National Taiwan University of Science and Technology, Taipei, Taiwan, in 2003. He is currently pursuing the Ph. D. degree at the Department of Computer Science and Information Engineering, National Taiwan University, Taipei, Taiwan. His research interests include design, analysis and implementation of network protocols and wireless communications.     

Multi-User Ultra-Wide Band Communication System Based on Modified Gegenbauer and Hermite Functions

In this paper a multi-user communication system based on ultra-wide band (UWB) technology is studied. UWB uses very short pulses, so that the spectrum of the emitted signals may spread over several GHz. In order to implement multi-user communication, the emitted signal must be modulated. One modulation scheme for UWB communications is to use analog waveforms to modulate the data. In this study, orthogonal waveforms called modified Gegenbauer functions are introduced as basis functions for the pulse shape and compared to the previously proposed modified Hermite functions. It is shown that Gegenbauer functions offer better performance for multi-user UWB communications. Fouzia Elbahhar was born in 1975. She received the M.S. and Ph.D. degrees from the University of Valenciennes (France) in 2000 and 2004, respectively. She is actually employed as Research Asistant at this university. She is especially involved in Ultra Wide Band technology. Her primary interest is in systems dedicated to land transportation for communications, like vehicle to vehicle telecommunication. Atika Rivenq-Menhaj was born in 1970. She received her Diploma of Engineering and the M.S. degree in 1993 and then her Ph.D. degree in 1996, from the University of Valenciennes (France). She actually is Assistant Professor in electronics at this university. Her primary interest is in signal processing applied to intelligent transportation systems and telecommunication systems. Jean-Michel Rouvaen was born in 1947. He received his M.S. degree in 1968 and his Ph.D. degree in 1971, from the University of Valenciennes (France). He is now Professor of electronics at ENSIAME, an engineering school of university of Valenciennes. His primary interests are in signal processing, nonlinear phenomena and telecommunications.     

Update Propagation Algorithms for Supporting Disconnected Write in Mobile Wireless Systems with Data Broadcasting Capability

We develop and analyze algorithms for propagating updates by mobile hosts in wireless client–server environments that support disconnected write operations, with the goal of minimizing the tuning time for update propagation to the server. These algorithms allow a mobile host to update cached data objects while disconnected and propagate the updates to the server upon reconnection for conflict resolutions. We investigate two algorithms applicable to mobile systems in which invalidation reports/data can be broadcast to mobile hosts periodically. We show that there exists an optimal broadcasting period under which the tuning time is minimized for update propagations. We perform a comparative analysis between these two update propagation algorithms that rely on broadcasting data and an algorithm that does not, and identify conditions under which an algorithm should be applied to reduce the total tuning time for update propagation by the mobile user to save the valuable battery power and avoid high communication cost. For real-time applications, we address the tradeoff between tuning time and access time with the goal to select the best update propagation algorithm that can minimize the tuning time while satisfying the imposed real-time deadline constraint. The analysis result is applicable to file/data objects that mobile users may need to modify while on the move. Ing-Ray Chen received the BS degree from the National Taiwan University, Taipei, Taiwan, and the MS and PhD degrees in computer science from the University of Houston. He is currently an associate professor in the Department of Computer Science at Virginia Tech. His research interests include mobile computing, pervasive computing, multimedia, distributed systems, real-time intelligent systems, and reliability and performance analysis. Dr. Chen has served on the program committee of numerous conferences, including as program chair for 29th IEEE Annual International Computer Software and Application Conference in 2005, 14th IEEE International Conference on Tools with Artificial Intelligence in 2002, and 3rd IEEE Symposium on Application-Specific Systems and Software Engineering Technology in 2000. Dr. Chen currently serves as an Associate Editor for IEEE Transactions on Knowledge and Data Engineering, The Computer Journal, and International Journal on Artificial Intelligence Tools. He is a member of the IEEE/CS and ACM. Ngoc Anh Phan received her Bachelor of Science degree from Moscow Technical University of Communication and Computer Science in 1997, and a Master of Science degree in Computer Science from Virginia Polytechnic Institute and State University (Virginia Tech) in 1999. She is currently a Ph.D student at Virginia Tech and a Senior Software Engineer at America Online Inc. Her research interests include wireless communications, data management, sensor networks, fault tolerance, and mobile computing. I-Ling Yen received her BS degree from Tsing-Hua University, Taiwan, and her MS and PhD degrees in Computer Science from the University of Houston. She is currently an Associate Professor of Computer Science at the University of Texas at Dallas. Dr. Yen's research interests are in distributed systems, fault-tolerant computing, self-stabilization algorithms, and security. She has served as program co-chair for the 1997 IEEE High Assurance Systems Engineering Workshop, the 1999 IEEE Symposium on Application-Specific Systems and Software Engineering Technology, and the 1999 Annual IEEE International Conference on Computer Software and Applications Conference. Dr. Yen is a member of the IEEE/CS.     

Legitimate Skew Clock Routing with Buffer Insertion

In this paper, we propose a new quick and effective legitimate skew clock routing with buffer insertion algorithm. We analyze the optimal buffer position in the clock path, and conclude the sufficient condition and heuristic condition for buffer insertion in clock net. During the routing process, this algorithm integrates buffer insertion and node merging together, and performs them in parallel. Compared with the method of buffer insertion after zero skew clock routing, our method improves the maximal clock delay by at least 48%. Compared with legitimate skew clock routing algorithm with no buffer, this algorithm further decreases the total wire length and gets reductions from 42 to 82% in maximal clock delay. The experimental results show that our algorithm is quick and effective. Xinjie Wei received his B.Sc. degree in Computer Science from the PLA Nanjing Institute of Communications Engineering in 1993, and got M.S. degree in Computer Science from Xidian University in 1998. He is currently pursuing the Ph.D. degree at Tsinghua University. His research interests include computer network security, neural network and design automation for VLSI circuits and systems. And the major research attention is focused on VLSI physical design. Yici Cai received BSc degree in Electronic Engineering from Tsinghua University in 1983 and received in and MS degree in Computer Science & Technology from Tsinghua University in 1986, She has been an associate professor in the Department of Computer Science & Technology, Tsinghua University. Beijing, China. Her research interests include VLSI layout theory and algorithms. Meng Zhao has been an researcher in Semiconductor Industry Association of Beijing. She received her Bachelor of Engineering degree in Electronical Engineering from Tsinghua University, China, in 2000. She received her Master of Science degree in Computer Science from Tsinghua University, China, in 2003. Her research interests include VLSI design and CAD, Electronical material and device, VLSI verification and so on. Xianlong Hong graduated from Tsinghua University, Beijing, China in 1964. Since 1988, he has been a professor in the Department of Computer Science Technology, Tsinghua University. His research interests include VLSI layout algorithms and DA systems. He is the fellow of IEEE and the Senior Member of Chinese Institute of Electronics.     

On-demand diversity wireless relay networks

There has been much recent attention on using wireless relay networks to forward data from mobile nodes to a base station. This network architecture is motivated by performance improvements obtained by leveraging the highest quality links to a base station for data transfer. With the advent of agile radios it is possible to improve the performance of relay networks through intelligent frequency assignments. First, it is beneficial if the links of the relay network are orthogonal with respect to each other so that simultaneous transmission on all links is possible. Second, diversity can be added to hops in the relay network to reduce error rates. In this paper we present algorithms for forming such relay networks dynamically. The formation algorithms support intelligent frequency assignments and diversity setup. Our results show that algorithms that order the sequence in which nodes join a relay network carefully, achieve the highest amount of diversity and hence best performance. This research is supported in part by NSF grant CNS-0508114. JaeSheung Shin received the B.S. and M.S. degree in Computer Science and Engineering from DongGuk University, Korea, in 1991 and 1993, respectively. He is currently working toward the Ph.D. degree in Computer Science and Engineering at the Pennsylvania State University, University Park. He is a research assistant at the Networking and Security Research Center (NSRC). Prior to joining Pennsylvania State University, he was with Electronics and Telecommunications Research Institute (ETRI), Korea, since 1993. He worked on development of 2G and 3G wireless cellular core network elements. His research interests include mobility management and signaling for wireless cellular and routing and resource allocation for multi-radio multi-hop wireless cellular networks. Kyounghwan Lee received the B.S. degree in Electrical and Electronics Engineering from University of Seoul, Seoul, Korea, in 2000, and the M.S. degree in Information and Communication Engineering from Gwangju Institute of Science and Technology, Gwangju, Korea, in 2002. He is currently a Ph.D candidate at the Electrical Engineering department at the Pennsylvania State University and a research assistant at the Wireless Communications and Networking Laboratory (WCAN@PSU). His research interests include wireless communication theory and relay networks. E-mail: kxl251@psu.edu Aylin Yener received the B.S. degrees in Electrical and Electronics Engineering, and in Physics, from Bogazici University, Istanbul, Turkey, in 1991, and the M.S. and Ph.D. degrees in Electrical and Computer Engineering from Rutgers University, NJ, in 1994 and 2000, respectively. During her Ph.D. studies, she was with Wireless Information Network Laboratory (WINLAB) in the Department of Electrical and Computer Engineering at Rutgers University, NJ. Between fall 2000 and fall 2001, she was with the Electrical Engineering and Computer Science Department at Lehigh University, PA, where she was a P.C. Rossin assistant professor. Currently, she is with the Electrical Engineering department at the Pennsylvania State University, University Park, PA, as an assistant professor. Dr. Yener is a recipient of the NSF CAREER award in 2003. She is an associate editor of the IEEE Transactions on Wireless Communications. Dr. Yener’s research interests include performance enhancement of multiuser systems, wireless communication theory and wireless networking. Thomas F. La Porta received his B.S.E.E. and M.S.E.E. degrees from The Cooper Union, New York, NY, and his Ph.D. degree in Electrical Engineering from Columbia University, New York, NY. He joined the Computer Science and Engineering Department at Penn State in 2002 as a Full Professor. He is the Director of the Networking Research Center at Penn State. Prior to joining Penn State, Dr. La Porta was with Bell Laboratories since 1986. He was the Director of the Mobile Networking Research Department in Bell Laboratories, Lucent Technologies. He is an IEEE Fellow and Bell Labs Fellow. Dr. La Porta was the founding Editor-in-Chief of the IEEE Transactions on Mobile Computing. He has published over 50 technical papers and holds 25 patents.     

Efficient Timing Budget Management for Accuracy Improvement in a Collaborative Object Tracking System

This paper presents the idea of managing the comprising computations of an application performed by an embedded networked system. An efficient algorithm for exploiting the timing slack of building blocks of the application is proposed. The slack of blocks can be utilized by replacing them with slower but cheaper, i.e. better, modules and by assigning the computations to the proper resources. Thus, our approach manages the comprising computations and system resources and can indirectly assist the realtime scheduling of computations on system resources. This is performed without compromising the timing constraints of the application and can lead to significant improvements in power dissipation, computation accuracy or other metrics of the application domain. Our algorithm is well-suited for arbitrary tree computations. Moreover, it delivers solutions that are desirably close to the optimal solution. Experimental results for a number of object tracking applications implemented in an networked system with embedded computation resources, exhibit a significant amount of slack utilization. Soheil Ghiasi received his B.S. from Sharif University of Technology, Tehran, Iran in 1998, and his M.S. and Ph.D. in Computer Science from the University of California, Los Angeles in 2002 and 2004, respectively. Currently, he is an assistant professor in the department of electrical and computer engineering at the University of California, Davis. His research interests include different aspects of Embedded and Reconfigurable system design. Elaheh Bozorgzadeh received the B.S. degree in Electrical Engineering from Sharif University of Technology, Iran in 1998, M.S. degree in Computer Engineering from Northwestern University in 2000, and Ph.D. degree in Computer Science from the University of California, Los Angeles, in 2003. She is currently as assistant professor in the Department of Computer Science at the University of California, Irvine. Her research interest includes VLSI CAD, design automation for embedded systems, and reconfigurable computing. She is a member of ACM and IEEE. Karlene Nguyen received her B.S. and M.S. from University of California, Los Angeles in 2001 and 2003, respectively. She has been working with Prof. Majid Sarrafzadeh for her M.S. degree. Her research interests include embedded hardware and software design. Majid Sarrafzadeh received his B.S., M.S. and Ph.D. in 1982, 1984, and 1987 respectively from the University of Illinois at Urbana-Champaign in Electrical and Computer Engineering. He joined Northwestern University as an Assistant Professor in 1987. In 2000, he joined the Computer Science Department at University of California at Los Angeles (UCLA). His recent research interests lie in the area of Embedded and Reconfigurable Computing, VLSI CAD, and design and analysis of algorithms. Dr. Sarrafzadeh is a Fellow of IEEE for his contribution to “Theory and Practice of VLSI Design.” He received an NSF Engineering Initiation award, two distinguished paper awards in ICCAD, and the best paper award in DAC. He has served on the technical program committee of numerous conferences in the area of VLSI Design and CAD, including ICCAD, DAC, EDAC, ISPD, FPGA, and DesignCon. He has served as committee chairs of a number of these conferences. He is on the executive committee/steering committee of several conferences such as ICCAD, ISPD, and ISQED. He is the program committee chair of ICCAD 2004. Professor Sarrafzadeh has published approximately 250 papers, is a co-editor of the book “Algorithmic Aspects of VLSI Layout” (1994 by World Scientific), and co-author of the book “An Introduction to VLSI Physical Design” (1996 by McGraw Hill). Dr. Sarrafzadeh is an Associate Editor of ACM Transaction on Design Automation (TODAES) and an Associate Editor of IEEE Transactions on Computer-Aided Design (TCAD) and ACM Transactions on design Automation (TODAES). Dr. Sarrafzadeh has collaborated with many industries in the past fifteen years including IBM, Motorola, and many CAD industries. He is the architect of the physical design subsystem of Monterey Design Systems main product. He is a co-founder of Hier Design, Inc.     

A New Space-Time Multiple Trellis Coded Modulation Scheme Using Transmit Symbol Phase Rotation

Space-time multiple trellis coded modulation (ST-MTCM) has been introduced in order to achieve maximum transmit diversity gain and larger coding gain with the existence of parallel paths. In our previous research, we designed a new coded modulation scheme for ST-MTCM which simultaneously maximizes the coding gain and diversity gain utilizing Hadamard Matrix giving the maximum determinant. This scheme, however, cannot achieve full transmit rate. In this paper, we extend our research so as to achieve full rate transmission as well as maximum coding and diversity gain. In addition, Super-Orthogonal Space-Time Trellis Code (SO-STTC) is well known for its high coding gain, full diversity gain and full transmit rate. Even though our proposed scheme is essentially the same as SO-STTC, we show in this paper that our proposed code design is different from SO-STTC, and achieves better performance. Our proposed code design utilizes transmit symbol phase rotation at a certain time slot so as to avoid same path transition in trellis, which occurs with conventional SO-STTC scheme. We design codes with different way of phase rotation for different MPSK modulation scheme, and simulation results show the improvements of our proposed codes for MPSK modulation with different number of states. Susu Jiang was born in Jilin, China, in 1979. She received the B.E. and M.S. degrees in electrical and computer engineering from Yokohama National University, Yokohama, Japan, in 2001 and 2003, respectively. She is currently working toward the Ph.D. degree in electrical and computer engineering at Yokohama National University, Yokohama, Japan. Her research interests include space-time coding, channel coding in wireless communications, and information theory. She is a student member of the IEICE and IEEE. Ryuji Kohno received the Ph.D. degree from the University of Tokyo in 1984. Dr. Kohno is currently a Professor of the Division of Physics, Electrical and Computer Engineering, Yokohama National University. In his currier he was a director of Advanced Telecommunications Laboratory of SONY CSL during 1998–2002 and currently a director of UWB Technology institute of National Institute of Information and Communications Technology (NICT). In his academic activities, he was elected as a member of the Board of Governors of IEEE Information Theory (IT) Society in 2000 and 2003. He has played a role of an editor of the IEEE Transactions on IT, Communications, and Intelligent Transport Systems (ITS). He is a fellow of IEICE, vice-president of Engineering Sciences Society of IEICE and has been the Chairman of the IEICE Technical Committee on Spread Spectrum Technology, that on ITS, and that on Software Defined Radio (SDR). Prof. Kohno has contributed for organizing many international conferences, such as an chair-in honor of 2002 & 2003 International Conference of SDR (SDR'02 & SDR'03), a TPC co-chair of 2003 International Workshop on UWB Systems (IWUWBS'03), and a general co-chair of 2003 IEEE International Symposium on IT (ISIT'03), that of Joint UWBST&IWUWB'04 and so on. He was awarded IEICE Greatest Contribution Award and NTT DoCoMo Mobile Science Award in 1999 and 2002, respectively.     

Performance of a burst-frame-based CSMA/CA protocol: Analysis and enhancement

In this paper, we develop an analytical model to evaluate the delay performance of the burst-frame-based CSMA/CA protocol under unsaturated conditions, which has not been fully addressed in the literature. Our delay analysis is unique in that we consider the end-to-end packet delay, which is the duration from the epoch that a packet enters the queue at the MAC layer of the transmitter side to the epoch that the packet is successfully received at the receiver side. The analytical results give excellent agreement with the simulation results, which represents the accuracy of our analytical model. The results also provide important guideline on how to set the parameters of the burst assembly policy. Based on these results, we further develop an efficient adaptive burst assembly policy so as to optimize the throughput and delay performance of the burst-frame-based CSMA/CA protocol. Kejie Lu received the B.E. and M.E. degrees in Telecommunications Engineering from Beijing University of Posts and Telecommunications, Beijing, China, in 1994 and 1997, respectively. He received the Ph.D. degree in Electrical Engineering from the University of Texas at Dallas in 2003. In 2004 and 2005, he was a postdoctoral research associate in the Department of Electrical and Computer Engineering, University of Florida. Currently, he is an assistant professor in the Department of Electrical and Computer Engineering, University of Puerto Rico at Mayagüez. His research interests include architecture and protocols design for computer and communication networks, performance analysis, network security, and wireless communications. Jianfeng Wang received the B.E. and M.E. degrees in electrical engineering from Huazhong University of Science and Technology, China, in 1999 and 2002, respectively, and the Ph.D. degree in electrical engineering from University of Florida in 2006. From January 2006 to July 2006, he was a research intern in wireless standards and technology group, Intel Corporation. In October 2006, he joined Philips Research North America as a senior member research staff in wireless communications and networking department. He is engaged in research and standardization on wireless networks with emphasis on medium access control (MAC). Dapeng Wu received B.E. in Electrical Engineering from Huazhong University of Science and Technology, Wuhan, China, in 1990, M.E. in Electrical Engineering from Beijing University of Posts and Telecommunications, Beijing, China, in 1997, and Ph.D. in Electrical and Computer Engineering from Carnegie Mellon University, Pittsburgh, PA, in 2003. Since August 2003, he has been with Electrical and Computer Engineering Department at University of Florida, Gainesville, FL, as an Assistant Professor. His research interests are in the areas of networking, communications, multimedia, signal processing, and information and network security. He received the IEEE Circuits and Systems for Video Technology (CSVT) Transactions Best Paper Award for Year 2001, and the Best Paper Award in International Conference on Quality of Service in Heterogeneous Wired/Wireless Networks (QShine) 2006. Currently, he serves as the Editor-in-Chief of Journal of Advances in Multimedia, and an Associate Editor for IEEE Transactions on Wireless Communications, IEEE Transactions on Circuits and Systems for Video Technology, IEEE Transactions on Vehicular Technology, and International Journal of Ad Hoc and Ubiquitous Computing. He is also a guest-editor for IEEE Journal on Selected Areas in Communications (JSAC), Special Issue on Cross-layer Optimized Wireless Multimedia Communications. He served as Program Chair for IEEE/ACM First International Workshop on Broadband Wireless Services and Applications (BroadWISE 2004); and as a technical program committee member of over 30 conferences. He is Vice Chair of Mobile and wireless multimedia Interest Group (MobIG), Technical Committee on Multimedia Communications, IEEE Communications Society. He is a member of the Best Paper Award Committee, Technical Committee on Multimedia Communications, IEEE Communications Society. Yuguang Fang received a Ph.D. degree in Systems Engineering from Case Western Reserve University in January 1994 and a Ph.D. degree in Electrical Engineering from Boston University in May 1997. He was an assistant professor in the Department of Electrical and Computer Engineering at New Jersey Institute of Technology from July 1998 to May 2000. He then joined the Department of Electrical and Computer Engineering at University of Florida in May 2000 as an assistant professor and got an early promotion to an associate professor with tenure in August 2003 and to a full professor in August 2005. He has published over 200 papers in refereed professional journals and conferences. He received the National Science Foundation Faculty Early Career Award in 2001 and the Office of Naval Research Young Investigator Award in 2002. He has served on several editorial boards of technical journals including IEEE Transactions on Communications, IEEE Transactions on Wireless Communications, IEEE Transactions on Mobile Computing and ACM Wireless Networks. He have also been actively participating in professional conference organizations such as serving as The Steering Committee Co-Chair for QShine, the Technical Program Vice-Chair for IEEE INFOCOM’2005, Technical Program Symposium Co-Chair for IEEE Globecom’2004, and a member of Technical Program Committee for IEEE INFOCOM (1998, 2000, 2003–2007). He is a senior member of the IEEE.     

Effective Capacity-Based Quality of Service Measures for Wireless Networks

An important objective of next-generation wireless networks is to provide quality of service (QoS) guarantees. This requires a simple and efficient wireless channel model that can easily translate into connection-level QoS measures such as data rate, delay and delay-violation probability. To achieve this, in Wu and Negi (IEEE Trans. on Wireless Communications 2(4) (2003) 630–643), we developed a link-layer channel model termed effective capacity, for the setting of a single hop, constant-bit-rate arrivals, fluid traffic, and wireless channels with negligible propagation delay. In this paper, we apply the effective capacity technique to deriving QoS measures for more general situations, namely, (1) networks with multiple wireless links, (2) variable-bit-rate sources, (3) packetized traffic, and (4) wireless channels with non-negligible propagation delay. Dapeng Wu received B.E. in Electrical Engineering from Huazhong University of Science and Technology, Wuhan, China, in 1990, M.E. in Electrical Engineering from Beijing University of Posts and Telecommunications, Beijing, China, in 1997, and Ph.D. in Electrical and Computer Engineering from Carnegie Mellon University, Pittsburgh, PA, in 2003. From July 1997 to December 1999, he conducted graduate research at Polytechnic University, Brooklyn, New York. During the summers of 1998, 1999 and 2000, he conducted research at Fujitsu Laboratories of America, Sunnyvale, California, on architectures and traffic management algorithms in the Internet and wireless networks for multimedia applications. Since August 2003, he has been with Electrical and Computer Engineering Department at University of Florida, Gainesville, FL, as an Assistant Professor. His research interests are in the areas of networking, communications, multimedia, signal processing, and information and network security. He received the IEEE Circuits and Systems for Video Technology (CSVT) Transactions Best Paper Award for Year 2001. Currently, he is an Associate Editor for the IEEE Transactions on Vehicular Technology and Associate Editor for International Journal of Ad Hoc and Ubiquitous Computing. He served as Program Chair for IEEE/ACM First International Workshop on Broadband Wireless Services and Applications (BroadWISE 2004); and as TPC member of over 20 conferences such as IEEE INFOCOM'05, IEEE ICC'05, IEEE WCNC'05, and IEEE Globecom'04. He is Vice Chair of Mobile and wireless multimedia Interest Group (MobIG), Technical Committee on Multimedia Communications, IEEE Communications Society. He is a member of the Award Committee, Technical Committee on Multimedia Communications, IEEE Communications Society. He is also Director of Communications, IEEE Gainesville Section. Rohit Negi received the B.Tech. degree in Electrical Engineering from the Indian Institute of Technology, Bombay, India in 1995. He received the M.S. and Ph.D. degrees from Stanford University, CA, USA, in 1996 and 2000 respectively, both in Electrical Engineering. He has received the President of India Gold medal in 1995. Since 2000, he has been with the Electrical and Computer Engineering department at Carnegie Mellon University, Pittsburgh, PA, USA, where he is an Assistant Professor. His research interests include signal processing, coding for communications systems, information theory, networking, cross-layer optimization and sensor networks.     

Efficiency of Optimized Dynamic Test Flows for ADCs: Sensitivity to Specifications

The long and complex procedure to test ADCs constitutes an important issue in the context of mixed-signal testing. To lower the testing costs, we propose shorter but less selective test flows solely based on spectral analysis. This paper investigates the efficiency that can be achieved using this approach and studies the influence of the ADC specifications on the efficiency of the proposed dynamic-only test flows.Florence Azaïs received the Ph.D. degree in electrical engineering from the University of Montpellier, France in 1996. She is currently working in the Microelectronics department of the Laboratory of Computer Science, Robotics and Microelectronics of Montpellier (LIRMM) as a researcher of the National Council of Scientific Research (CNRS). Since 1993, she has been interested in the general domain of test and reliability of integrated circuits and systems. Her main research interests include fault modeling, analog and mixed-signal circuit testing, MEMS testing, reliability and failure analysis of integrated systems. She has authored or co-authored over 80 international papers on these topics. She also served as a member of the Program Committee of several international conferences (DATE, ICCD, ETS, IMSTW, LATW).Serge Bernard received the M.S. degree in Electrical Engineering from the University of Paris XI, France in 1998 and the Ph.D. degree in Electrical Engineering from the University of Montpellier, France in 2001. He is a researcher of the National Council of Scientific Research (CNRS) in the Microelectronics Department of the Laboratory of Computer Science, Robotics and Microelectronics of Montpellier (LIRMM). His main research interests include Test, Design-For-Testability and Built-In-Self-Test for mixed-signal circuits and Design-For-Reliability for medical application ICs.Yves Bertrand is a Professor at the University of Montpellier (France). He works at the Microelectronics Department of the Laboratoire dAutomatique, Robotique et Microélectronique de Montpellier (LIRMM). Previously, Yves Bertrand worked in the field of solid-state physics and published several papers, especially on the photoemission of the semiconductors under synchrotron radiation. He joins the LIRMM in 1988. His research interests are principally, Fault Modeling, Design-For-Test and Built-In Self-Test for digital and mixed-signal analog/digital Integrated Circuits. He is author or co-author of about 200 papers in the field of solid-state physics and microelectronics. He is presently responsible for the CRTC (Centre de Ressources de Test du CNFM), which is the Common Test Resources Center for the French and European Universities.Mariane Comte took her Master of Engineering and Master of Sciences degrees in microelectronics engineering at INPG, (Institut National Polytechnique de Grenoble, National Engineering University Institution of Grenoble), France, in 2000. She carried out her Ph.D. studies at LIRMM (Laboratoire dInformatique, de Robotique et de Microélectronique de Montpellier, Computer Sciences, Robotics and Microelectronics Laboratory of Montpellier), France, working on Analog-to-Digital Converter testing, and received Ph.D. degree in microelectronics from the University of Montpellier, France, in 2003. After a post-doctoral fellow position at the Computer Design and Test Laboratory of NAIST (Nara Institute of Science and Technology), Japan, where she investigated on the detection of Gate-Oxide Shorts in Domino Logic cells, she is currently working as an assistant professor at the University of Montpellier. Her fields of interest spread from analog and mixed-signal testing to defect modeling.Michel Renovell is head of the Microelectronics Department at LIRMM (Laboratory of Computer Science, Automation and Microelectronics of Montpellier). His research interests include: Fault modeling, Analog testing and FPGA testing. He is Vice-Chair of the IEEE TTTC (Test Technology Technical Committee). He is a member of the editorial board of JETTA and the editorial board of IEEE Design & Test. Michel has been General Chair of the International Mixed Signal Testing Workshop IMSTW2000, the Field Programmable Logic Conference FPL2002 and the European Test Symposium ETS2004.