A Location-Aware Routing Protocol for the Bluetooth Scatternet

Bluetooth is a most promising technology for the wireless personal area networks and its specification describes how to build a piconet. Though the construction of scatternet from the piconets is left out in the specification, some of the existing solutions discuss the scatternet formation issues and routing schemes. Routing in a scatternet, that has more number of hops and relay nodes increases the difficulties of scheduling and consumes the bandwidth and power resources and thereby impacts on the performance of the entire network. In this paper, a novel routing protocol (LARP) for the Bluetooth scatternet is proposed, which reduces the hop counts between the source and the destination and reconstructs the routes dynamically using the location information of the Bluetooth devices. Besides, a hybrid location-aware routing protocol (HLARP) is proposed to construct the shortest routes among the devices with or without having the location information and degenerate the routing schemes without having any location information. Experimental results show that our protocols are efficient enough to construct the shortest routing paths and to minimize the transmission delay, bandwidth and power consumption as compared to the other protocols that we have considered. Chih-Yung Chang received the Ph.D. degree in Computer Science and Information Engineering from National Central University, Taiwan, in 1995. He joined the faculty of the Department of Computer and Information Science at Aletheia University, Taiwan, as an Assistant Professor in 1997. He was the Chair of the Department of Computer and Information Science, Aletheia University, from August 2000 to July 2002. He is currently an Associate Professor of Department of Computer Science and Information Engineering at Tamkang University, Taiwan. Dr. Chang served as an Associate Guest Editor of Journal of Internet Technology (JIT, 2004), Journal of Mobile Multimedia (JMM, 2005), and a member of Editorial Board of Tamsui Oxford Journal of Mathematical Sciences (2001--2005). He was an Area Chair of IEEE AINA'2005, Vice Chair of IEEE WisCom 2005 and EUC 2005, Track Chair (Learning Technology in Education Track) of IEEE ITRE'2005, Program Co-Chair of MNSA'2005, Workshop Co-Chair of INA'2005, MSEAT'2003, MSEAT'2004, Publication Chair of MSEAT'2005, and the Program Committee Member of USW'2005, WASN'2005, and the 11th Mobile Computing Workshop. Dr. Chang is a member of the IEEE Computer Society, Communication Society and IEICE society. His current research interests include wireless sensor networks, mobile learning, Bluetooth radio systems, Ad Hoc wireless networks, and mobile computing. Prasan Kumar Sahoo got his Master degree in Mathematics from Utkal University, India. He did his M.Tech. degree in Computer Science from Indian Institute of Technology (IIT), Kharagpur, India and received his Ph.D in Mathematics from Utkal University, India in April, 2002. He joined in the Software Research Center, National Central University, Taiwan and currently working as an Assistant Professor, in the department of Information Management, Vanung University, Taiwan, since 2003. He was the Program Committee Member of MSEAT'2004, MSEAT'2005, WASA'2006, and IEEE AHUC'2006. His research interests include the coverage problems, modeling and performance analysis of wireless sensor network and Bluetooth technology. Shih-Chieh Lee received the B.S. degree in Computer Science and Information Engineering from Tamkang University, Taiwan, in 1997. Since 2003 he has been a Ph.D. Students in Department of Computer Science and Information Engineering, Tamkang University. His research interests are wireless sensor networks, Ad Hoc wireless networks, and mobile/wireless computing.     

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.     

A Credit-Based On-Demand QoS Routing Protocol Over Bluetooth WPANs

The quality-of-service (QoS) communication that supports mobile applications to guarantee bandwidth utilization is an important issue for Bluetooth wireless personal area networks (WPANs). In this paper, we address the problem of on-demand QoS routing with interpiconet scheduling in Bluetooth WPANs. A credit-based QoS (CQ) routing protocol is developed which considers different Bluetooth packet types, because different types of Bluetooth packets have different bandwidth utilization levels. This work improves the bandwidth utilization of Bluetooth scatternets by providing a new interpiconet scheduling scheme. This paper mainly proposes a centralized algorithm to improve the bandwidth utilization for the on-demand QoS routing protocol. The centralized algorithm incurs the scalability problem. To alleviate the scalability problem, a distributed algorithm is also investigated in this work. The performance analysis illustrates that our credit-based QoS routing protocol achieves enhanced performance compared to existing QoS routing protocols.This work was supported by the National Science Council of the Republic of China under grant nos. NSC-92-2213-E-194-022 and NSC-93-2213-E-194-028. Yuh-Shyan Chen received the B.S. degree in computer science from Tamkang University, Taiwan, Republic of China, in June 1988 and the M.S. and Ph.D. degrees in Computer Science and Information Engineering from the National Central University, Taiwan, Republic of China, in June 1991 and January 1996, respectively. He joined the faculty of Department of Computer Science and Information Engineering at Chung-Hua University, Taiwan, Republic of China, as an associate professor in February 1996. He joined the Department of Statistic, National Taipei University in August 2000, and joined the Department of Computer Science and Information Engineering, National Chung Cheng University in August 2002. Dr. Chen served as Co-Editors-in-Chief of International Journal of Ad Hoc and Ubiquitous Computing (IJAHUC), Editorial Board Member of Telecommunication System Journal, International Journal of Internet Protocol Technology (IJIPT) and The Journal of Information, Technology and Society (JITAS). He also served as Guest Editor of Telecommunication Systems, special issue on “Wireless Sensor Networks” (2004), and Guest Editor of Journal of Internet Technology, special issue on “Wireless Internet Applications and Systems” (2002) and special issue on “Wireless Ad Hoc Network and Sensor Networks” (2004). He was a Vice Co-Chair, Wireless IP Symposium of WirelressCOM2005, USA (2005) and a Workshop Co-Chair of the 2001 Mobile Computing Workshop, Taiwan. Dr. Chen also served as IASTED Technical Committee on Telecommunications for 2002–2005, WSEAS International Scientific Committee Member (from 2004), Program Committee Member of IEEE ICPP'2003, IEEE ICDCS'2004, IEEE ICPADS'2001, ICCCN'2001–2005, MSN'2005, IASTED CCN'2002–2005, IASTED CSA'2004–2005, IASTED NCS'2005, and MSEAT'2003–2005. His paper wins the 2001 IEEE 15th ICOIN-15 Best Paper Award. Dr. Chen was a recipient of the 2005 Young Scholar Research Award given by National Chung Cheng University to four young faculty members, 2005. His recent research topics include mobile ad-hoc network, wireless sensor network, mobile learning system, and 4G system. Dr. Chen is a member of the IEEE Computer Society, IEICE Society, and Phi Tau Phi Society. Keng-Shau Liu received the M.S. degree in Computer Science and Information Engineering from National Chung Cheng University, Taiwan, Republic of China, in July 2004. His research includes wireless LAN, Bluetooth, and mobile learning.     

The Coverage Problem in a Wireless Sensor Network

One of the fundamental issues in sensor networks is the coverage problem, which reflects how well a sensor network is monitored or tracked by sensors. In this paper, we formulate this problem as a decision problem, whose goal is to determine whether every point in the service area of the sensor network is covered by at least k sensors, where k is a given parameter. The sensing ranges of sensors can be unit disks or non-unit disks. We present polynomial-time algorithms, in terms of the number of sensors, that can be easily translated to distributed protocols. The result is a generalization of some earlier results where only k = 1 is assumed. Applications of the result include determining insufficiently covered areas in a sensor network, enhancing fault-tolerant capability in hostile regions, and conserving energies of redundant sensors in a randomly deployed network. Our solutions can be easily translated to distributed protocols to solve the coverage problem.A preliminary version of this paper has appeared in the Workshop on Wireless Sensor Networks and Applications, 2003, San Diego, CA, USA. Chi-Fu Huang received his B.S. and M.S. degrees both in Computer Science and Information Engineering from the Feng-Chia University and the National Central University in 1999 and 2001, respectively. He obtained his Ph.D. in the Department of Computer Science and Information Engineering from the National Chiao-Tung University in September of 2004. He is currently a Research Assistant Professor at the Department of Computer Science and Information Engineering, National Chiao-Tung University, Taiwan. His research interests include wireless communication and mobile computing, especially in ad hoc and sensor networks. Yu-Chee Tseng received his B.S. and M.S. degrees in Computer Science from the National Taiwan University and the National Tsing-Hua University in 1985 and 1987, respectively. He worked for the D-LINK Inc. as an engineer in 1990. He obtained his Ph.D. in Computer and Information Science from the Ohio State University in January of 1994. He was an Associate Professor at the Chung-Hua University (1994–1996) and at the National Central University (1996–1999), and a Full Professor at the National Central University (1999–2000). Since 2000, he has been a Full Professor at the Department of Computer Science and Information Engineering, National Chiao-Tung University, Taiwan. Dr. Tseng served as a Program Chair in the Wireless Networks and Mobile Computing Workshop, 2000 and 2001, as a Vice Program Chair in the Int’l Conf. on Distributed Computing Systems (ICDCS), 2004, as a Vice Program Chair in the IEEE Int’l Conf. on Mobile Ad-hoc and Sensor Systems (MASS), 2004, as an Associate Editor for The Computer Journal, as a Guest Editor for ACM Wireless Networks special issue on “Advances in Mobile and Wireless Systems”, as a Guest Editor for IEEE Transactions on Computers special on “Wireless Internet”, as a Guest Editor for Journal of Internet Technology special issue on “Wireless Internet: Applications and Systems”, as a Guest Editor for Wireless Communications and Mobile Computing special issue on “Research in Ad Hoc Networking, Smart Sensing, and Pervasive Computing”, as an Editor for Journal of Information Science and Engineering, as a Guest Editor for Telecommunication Systems special issue on “Wireless Sensor Networks”, and as a Guest Editor for Journal of Information Science and Engineering special issue on “Mobile Computing”. He is a two-time recipient of the Outstanding Research Award, National Science Council, ROC, in 2001–2002 and 2003–2005, and a recipient of the Best Paper Award in Int’l Conf. on Parallel Processing, 2003. Several of his papers have been chosen as Selected/Distinguished Papers in international conferences. He has guided students to participate in several national programming contests and received several awards. His research interests include mobile computing, wireless communication, network security, and parallel and distributed computing. Dr. Tseng is a member of ACM and a Senior Member of IEEE.This revised version was published online in August 2005 with a corrected cover date.     

An On-Demand Routing Protocol with Backtracking for Mobile Ad Hoc Networks

A mobile ad hoc network (MANET) is characterized by multi-hop wireless links and frequent node mobility. Communication between non-neighboring nodes requires a multi-hop routing protocol to establish a route. But, the route often breaks due to mobility. The source must rediscover a new route for delivering the data packets. This wastes the resources that are limited in MANET. In this paper, a new on-demand routing protocol is proposed, named on-demand routing protocol with backtracking (ORB), for multi-hop mobile ad hoc networks. We use the multiple routes and cache data technique to reduce the rediscovery times and overhead. After executing the route discovery phase, we find out a set of nodes, named checkpoint, which has the multiple routes to the destination. When a checkpoint node receives a data packet, it caches this data packet in its buffer within a specific time period. When a node detects a broken route during the data packets delivery or receives an error packet, it will either recover the broken route or reply the error packet to the source. If a node can not forward the data packet to the next node, it replies an error packet to the source. This packet is backtracking to search a checkpoint to redeliver the data packet to the destination along other alternate routes. The main advantage of ORB is to reduce the flooding search times, maybe just delay and cost while a route has broken. The experimental results show that the proposed scheme can increase the performance of delivery but reduce the overhead efficiently comparing with that of AODV based routing protocols. Hua-Wen Tsai received the B.S. degree in Information Management from Chang Jung Christian University, Taiwan, in June 1998 and the M.B.A. degree in Business and Operations Management from Chang Jung Christian University, Taiwan, in June 2001. Since September 2001, he has been working towards the Ph.D. degree and currently is a doctoral candidate in the Department of Computer Science and Information Engineering, National Cheng Kung University, Taiwan. His research interests include wireless communication, ad hoc networks, and sensor networks. Tzung-Shi Chen received the B.S. degree in Computer Science and Information Engineering from Tamkang University, Taiwan, in June 1989 and the Ph.D. degree in Computer Science and Information Engineering from National Central University, Taiwan, in June 1994. He joined the faculty of the Department of Information Management, Chung Jung University, Tainan, Taiwan, as an Associate Professor in June 1996. Since November 2002, he has become a Full Professor at the Department of Information Management, Chung Jung University, Tainan, Taiwan. He was a visiting scholar at the Department of Computer Science, University of Illinois at Urbana-Champaign, USA, from June to September 2001. He was the chairman of the Department of Information Management at Chung Jung University from August 2000 to July 2003. Since August 2004, he has become a Full Professor at the Department of Information and Learning Technology, National University of Tainan, Tainan, Taiwan. Currently, he is the chairman of the Department of Information and Learning Technology, National University of Tainan. He co-received the best paper award of 2001 IEEE ICOIN-15. His current research interests include mobile computing and wireless networks, mobile learning, data mining, and pervasive computing. Dr. Chen is a member of the IEEE Computer Society. Chih-Ping Chu received the B.S. degree in agricultural chemistry from National Chung Hsing University, Taiwan, the M.S. degree in computer science from the University of California, Riverside, and the Ph.D. degree in computer science from Louisiana State University. He is currently a Professor in the Department of Computer Science and Information Engineering of National Cheng Kung University, Taiwan. His current research interests include parallel computing, parallel processing, component-based software development, and internet computing.     

Scheduling for time-division based shared channel allocation for UMTS

The Universal Mobile Telecommunications System (UMTS) adopts the WCDMA technology as the radio access interface to provide variable transmission rate services. There are four classes of connections identified in UMTS, which are the conversational, streaming, interactive, and background connections. To efficiently utilize radio bandwidth, the shared channel approach is proposed to deliver the packets for the interactive and background connections. This paper proposes a “Shared-Channel Assignment and Scheduling” (SCAS) algorithm to periodically allocate shared channels to serve interactive and background connections. We conduct formal mathematical proofs and simulation experiments to investigate the performance of the SCAS algorithm. We formally prove that with SCAS, a shared channel can be fully utilized (i.e., the utilization of a shared channel can be up to 100%) to serve the interactive connections. Our analysis indicates that compared with the previously proposed shared channel allocation and scheduling algorithms, there are less computation and communication overheads introduced in the SCAS algorithm. The results of the simulation experiments indicate that it is preferred to set up the Transmission Time Interval (TTI; that is, the unit of time interval for shared channel allocation) smaller to optimize the performance of the SCAS algorithm, including the shared channel utilization and the average waiting time of a connection before getting transmission service. A preliminary version [11] of this work has been accepted by IEEE Wireless Communications and Networking Conference 2004. This paper is an extension of the proposed algorithm, and simulation and analysis are conducted to investigate the performance of the proposed algorithm. Chai-Hien Gan was born in Malaysia in 1971. He received his BS degree in computer science from Tamkang University in 1994, Taipei County, Taiwan, and both his MS. and Ph.D. degrees in computer science and information engineering from National Taiwan University, Taipei, Taiwan, in 1996 and 2005, respectively. Since March 2005, he has been a Research Assistant Professor in Department of Computer Science, National Chiao Tung University, R.O.C. His current research interests include wireless mesh networks, mobile computing, personal communications services, and wireless Internet. Phone Lin received his BSCSIE degree and Ph.D. degree from National Chiao Tung University, Taiwan, R.O.C. in 1996 and 2001, respectively. From August 2001 to July 2004, he was an Assistant Professor in Department of CSIE and Graduate Institute of Graduate of Networking and Multimedia, National Taiwan University, R.O.C. Since August 2004, he has been an Associate Professor in Department of CSIE and Graduate Institute Graduate of Networking and Multimedia, National Taiwan University, R.O.C. His current research interests include personal communications services, wireless Internet, and performance modeling. Dr. Lin is an Associate Editor for IEEE Transactions on Vehicular Technology, Editor for IEEE Wireless Communications special issue on Mobility and Resource Management and a Guest Editor for ACM/Springer MONET special issue on Wireless Broad Access. He is also an Associate Editorial Member for the WCMC Journal. P. Lin’s email and website addresses are plin@csie.ntu.edu.tw and http://www.csie.ntu.edu.tw/~plin, respectively. Nei-Chiung Perng is presently a Ph.D. student in the Department of Computer Science and Information Engineering, National Taiwan University. He received his Bachelor and Master degrees in the Department of Computer and Information Science, National Chiao Tung University in 1999 and 2001, respectively. His research interests include real-time systems and scheduling algorithms. Tei-Wei Kuo received B.S.E. degree in computer science and information engineering from National Taiwan University in Taipei, Taiwan, in 1986. He received the M.S. and Ph.D. degrees in computer sciences from the University of Texas at Austin in 1990 and 1994, respectively. He is currently a Professor and the Chairman of the Department of Computer Science and Information Engineering of the National Taiwan University, Taiwan, ROC. He was an Associate Professor in the Department of Computer Science and Information Engineering of the National Chung Cheng University, Taiwan, ROC, from August 1994 to July 2000. Dr. Kuo is a senior member of the IEEE computer society. His research interest includes embedded systems, real-time process scheduling, real-time operating systems, and real-time databases. He has over 100 technical papers published or been accepted in international journals and conferences and has a book “Real-Time Database Systems: Architecture and Techniques” published by Kluwer Academic Publishers (ISBN 0-7923-7218-2, USA). He is the Program Co-Chair of IEEE 7th Real-Time Technology and Applications Symposium, 2001, and an associate editor of the Journal of Real-Time Systems since 1998. He is an executive committee member of the IEEE Technical Committee on Real-Time Systems in 2005 and the steering committee chair of IEEE RTCSA’05. Dr. Kuo has consulted for government and industry on problems in various real-time and embedded systems designs. Dr. Kuo received several research awards in Taiwan, including the Distinguished Research Award from the ROC National Science Council in 2003 and the Young Scholar Research Award from Academia Sinica, Taiwan, ROC, in 2001. Ching-Chi Hsu was born in Taipei, Taiwan in 1949. He received his BS degree in physics from National Tsing Hwa. University in 1971, Hsishu, Taiwan, and both his MS. and Ph.D. degrees in computer engineering from EE department of National Taiwan University, Taipei, Taiwan, in 1975 and 1982, respectively. In 1977, he joined the faculty of the Department of Computer Science and Information Engineering at National Taiwan University and became an associate professor in 1982. During the years between 1987 and 2002, he was first engaged as a professor and became the chairman of the department. During his tenure in National Taiwan University, Dr. Hsu was a visiting scholar of Computer Science Department, Stanford University from 1984 to 1985. After serving in National Taiwan University for over 25 years, Dr. Hsu had left and was promoted as the president of Kai Nan University in 2002. Starting from February 2004, Dr. Hsu has been the executive vice president of the Institute for Information Industry in which he is mainly in charge of accelerating the growth of information industry in the whole nation. His research interests include distributed processing of data and knowledge, mobile computing and wireless networks.     

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     

Energy-Efficient Data Caching and Prefetching for Mobile Devices Based on Utility

In mobile computing environments, vital resources like battery power and wireless channel bandwidth impose significant challenges in ubiquitous information access. In this paper, we propose a novel energy and bandwidth efficient data caching mechanism, called GreedyDual Least Utility (GD-LU), that enhances dynamic data availability while maintaining consistency. The proposed utility-based caching mechanism considers several characteristics of mobile distributed systems, such as connection-disconnection, mobility handoff, data update and user request patterns to achieve significant energy savings in mobile devices. We develop an analytical model for energy consumption of mobile devices in a dynamic data environment. Based on the utility function derived from the analytical model, we propose algorithms for cache replacement and passive prefetching of data objects. Our comprehensive simulation experiments demonstrate that the proposed caching mechanism achieves more than 10% energy saving and near-optimal performance tradeoff between access latency and energy consumption. Huaping Shen received his M.S. and B.S. degrees in computer science from Fudan University, China, in 2001 and 1998, respectively. He is currently a Ph.D. student in the Department of Computer Science and Engineering at the University of Texas at Arlington. His research interests include data management in mobile networks, mobile computing, peer-to-peer networks, and pervasive computing. Mohan Kumar is an Associate Professor in Computer Science and Engineering at the University of Texas at Arlington. His current research interests are in pervasive computing, wireless networks and mobility, active networks, mobile agents, and distributed computing. Recently, he has developed or co-developed algorithms for active-network based routing and multicasting in wireless networks and caching prefetching in mobile distributed computing. He has published over 90 articles in refereed journals and conference proceedings and supervised Masters and doctoral theses in the areas of pervasive computing, caching/prefetching, active networks, wireless networks and mobility, and scheduling in distributed systems. Kumar is on the editorial board of The Computer Journal and he has guest edited special issues of several leading international journals including MONET and WINET issues and the IEEE Transactions on Computers. He is a co-founder of the IEEE International Conference on pervasive computing and communications (PerCom)—served as the program chair for PerCom 2003, and is the vice general chair for PerCom 2004. He has also served in the technical program committees of numerous international conferences/workshops. He is a senior member of the IEEE. Mohan Kumar obtained his PhD (1992) and MTech (1985) degrees from the Indian Institute of Science and the BE (1982) from Bangalore University in India. Prior to joining The University of Texas at Arlington in 2001, he held faculty positions at the Curtin University of Technology, Perth, Australia (1992–2000), The Indian Institute of Science (1986-1992), and Bangalore University (1985–1986). Dr. Sajal K. Das is currently a Professor of Computer Science and Engineering and also the Founding Director of the Center for Research in Wireless Mobility and Networking (CReWMaN) at the University of Texas at Arlington (UTA). Prior to 1999, he was a professor of Computer Science at the University of North Texas (UNT), Denton where he founded the Center for Research in Wireless Computing (CReW) in 1997, and also served as the Director of the Center for Research in Parallel and Distributed Computing (CRPDC) during 1995–97. Dr. Das is a recipient of the UNT Student Association’s Honor Professor Award in 1991 and 1997 for best teaching and scholarly research; UNT’s Developing Scholars Award in 1996 for outstanding research; UTA’s Outstanding Faculty Research Award in Computer Science in 2001 and 2003; and the UTA College of Engineering Research Excellence Award in 2003. An internationally-known computer scientist, he has visited numerous universities, research organizations, government and industry labs worldwide for collaborative research and invited seminar talks. He is also frequently invited as a keynote speaker at international conferences and symposia.Dr. Das’ current research interests include resource and mobility management in wireless networks, mobile and pervasive computing, wireless multimedia and QoS provisioning, sensor networks, mobile internet architectures and protocols, parallel processing, grid computing, performance modeling and simulation. He has published over 250 research papers in these areas, directed numerous industry and government funded projects, and holds four US patents in wireless mobile networks. He received the Best Paper Awards in the 5th Annual ACM International Conference on Mobile Computing and Networking (MobiCom’99), 16th International Conference on Information Networking (ICOIN-16), 3rd ACM International Workshop on Modeling, Analysis and Simulation of Wireless and Mobile Systems (MSWiM 2000), and 11th ACM/IEEE International Workshop on Parallel and Distributed Simulation (PADS’97). Dr. Das serves on the Editorial Boards of IEEE Transactions on Mobile Computing, ACM/Kluwer Wireless Networks, Parallel Processing Letters, Journal of Parallel Algorithms and Applications. He served as General Chair of IEEE PerCom 2004, MASCOTS’02 ACM WoWMoM 2000-02; General Vice Chair of IEEE PerCom 2003, ACM MobiCom-2000 and IEEE HiPC 2000-01; Program Chair of IWDC 2002, WoWMoM 1998-99; TPC Vice Chair of ICPADS 2002; and as TPC member of numerous IEEE and ACM conferences. He is Vice Chair of the IEEE TCPP and TCCC Executive Committees and on the Advisory Boards of several cutting-edge companies.Dr. Sajal K. Das received B.S. degree in 1983 from Calcutta University, M.S. degree in 1984 from Indian Institute of Science, Bangalore, and Ph.D. degree in 1988 from the University of Central Florida, Orlando, all in Computer Science. Zhijun Wang received the M.S degree in Electrical Engineering from Pennsylvania State University, University Park, PA, 2001. He is working toward the Ph.D. degree in Computer Science and Engineering Department at the University of Texas at Arlington. His current research interests include data management in mobile networks and peer-to-peer networks, mobile computing and networking processors.This revised version was published online in August 2005 with a corrected cover date.     

Scheduling Sleeping Nodes in High Density Cluster-based Sensor Networks

In order to conserve battery power in very dense sensor networks, some sensor nodes may be put into the sleep state while other sensor nodes remain active for the sensing and communication tasks. In this paper, we study the node sleep scheduling problem in the context of clustered sensor networks. We propose and analyze the Linear Distance-based Scheduling (LDS) technique for sleeping in each cluster. The LDS scheme selects a sensor node to sleep with higher probability when it is farther away from the cluster head. We analyze the energy consumption, the sensing coverage property, and the network lifetime of the proposed LDS scheme. The performance of the LDS scheme is compared with that of the conventional Randomized Scheduling (RS) scheme. It is shown that the LDS scheme yields more energy savings while maintaining a similar sensing coverage as the RS scheme for sensor clusters. Therefore, the LDS scheme results in a longer network lifetime than the RS scheme. Jing Deng received the B.E. and M.E. degrees in Electronic Engineering from Tsinghua University, Beijing, P. R. China, in 1994 and 1997, respectively, and the Ph.D. degree in Electrical and Computer Engineering from Cornell University, Ithaca, NY, in 2002. Dr. Deng is an assistant professor in the Department of Computer Science at the University of New Orleans. From 2002 to 2004, he visited the CASE center and the Department of Electrical Engineering and Computer Science at Syracuse University, Syracuse, NY as a research assistant professor, supported by the Syracuse University Prototypical Research in Information Assurance (SUPRIA) program. He was a teaching assistant from 1998 to 1999 and a research assistant from 1999 to 2002 in the School of Electrical and Computer Engineering at Cornell University. His interests include mobile ad hoc networks, wireless sensor networks, wireless network security, energy efficient wireless networks, and information assurance. Wendi B. Heinzelman is an assistant professor in the Department of Electrical and Computer Engineering at the University of Rochester. She received a B.S. degree in Electrical Engineering from Cornell University in 1995 and M.S. and Ph.D. degrees in Electrical Engineering and Computer Science from MIT in 1997 and 2000 respectively. Her current research interests lie in the areas of wireless communications and networking, mobile computing, and multimedia communication. Dr. Heinzelman received the NSF Career award in 2005 for her work on cross-layer optimizations for wireless sensor networks, and she received the ONR Young Investigator award in 2005 for her research on balancing resource utilization in wireless sensor networks. Dr. Heinzelman was co-chair of the 1st Workshop on Broadband Advanced Sensor Networks (BaseNets '04), and she is a member of Sigma Xi, the IEEE, and the ACM. Yunghsiang S. Han was born in Taipei, Taiwan, on April 24, 1962. He received the B.S. and M.S. degrees in electrical engineering from the National Tsing Hua University, Hsinchu, Taiwan, in 1984 and 1986, respectively, and the Ph.D. degree from the School of Computer and Information Science, Syracuse University, Syracuse, NY, in 1993. From 1986 to 1988 he was a lecturer at Ming-Hsin Engineering College, Hsinchu, Taiwan. He was a teaching assistant from 1989 to 1992 and from 1992 to 1993 a research associate in the School of Computer and Information Science, Syracuse University. From 1993 to 1997 he was an Associate Professor in the Department of Electronic Engineering at Hua Fan College of Humanities and Technology, Taipei Hsien, Taiwan. From 1997 to 2004 he was with the Department of Computer Science and Information Engineering at National Chi Nan University, Nantou, Taiwan. He was promoted to Full Professor in 1998. From June to October 2001 he was a visiting scholar in the Department of Electrical Engineering at University of Hawaii at Manoa, HI, and from September 2002 to January 2004 he was the SUPRIA visiting research scholar in the Department of Electrical Engineering and Computer Science and CASE center at Syracuse University, NY. He is now with the Graduate Institute of Communication Engineering at National Taipei University, Taipei, Taiwan. His research interests are in wireless networks, security, and error-control coding. Dr. Han is a winner of 1994 Syracuse University Doctoral Prize. Pramod K. Varshney was born in Allahabad, India on July 1, 1952. He received the B.S. degree in electrical engineering and computer science (with highest honors), and the M.S. and Ph.D. degrees in electrical engineering from the University of Illinois at Urbana-Champaign in 1972, 1974, and 1976 respectively. Since 1976 he has been with Syracuse University, Syracuse, NY where he is currently a Professor of Electrical Engineering and Computer Science and the Research Director of the New York State Center for Advanced Technology in Computer Applications and Software Engineering. His current research interests are in distributed sensor networks and data fusion, detection and estimation theory, wireless communications, intelligent systems, signal and image processing, and remote sensing he has published extensively. He is the author of Distributed Detection and Data Fusion, published by Springer-Verlag in 1997 and has co-edited two other books. Dr. Varshney is a member of Tau Beta Pi and is the recipient of the 1981 ASEE Dow Outstanding Young Faculty Award. He was elected to the grade of Fellow of the IEEE in 1997 for his contributions in the area of distributed detection and data fusion. In 2000, he received the Third Millennium Medal from the IEEE and Chancellor's Citation for exceptional academic achievement at Syracuse University. He serves as a distinguished lecturer for the AES society of the IEEE. He is on the editorial board Information Fusion. He was the President of International Society of Information Fusion during 2001.     

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.     

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.     

Implementation and performance evaluation for a ubiquitous and unified multimedia messaging platform

As networking technology advances, more advanced message services are provided. Users may have one or more different message accounts and devices. Before sending messages, the sender must make sure which message service the receipt currently uses. Any misjudgement may delay the time when the messages are received. To make users be able to receive messages anytime and anywhere with any kind of devices, we propose a Ubiquitous and Unified Multimedia Messaging (UMM) platform. The UMM platform integrates different message services and provides a more efficient way for message delivery. Our design does not modify the existing protocols of message services and need not involve the network operators. An analytical model is proposed to evaluate the performance of the implemented platform. Our study shows that with a large number of message services the user subscribes and long message processing time in the network, the delayed message probability can be limited within 1.5%. This performance is considered satisfactory. This paper is an extension of the work that has won the second place of the Mobile Hero contest sponsored by Industrial Development Bureau of Ministry of Economic Affairs, Taiwan, R.O.C., and was awarded USD 15,000. Phone Lin (M’02-SM’06) received his BSCSIE degree and Ph.D. degree from National Chiao Tung University, Taiwan, R.O.C. in 1996 and 2001, respectively. From August 2001 to July 2004, he was an Assistant Professor in Department of Computer Science and Information Engineering (CSIE), National Taiwan University, R.O.C. Since August 2004, he has been an Associate Professor in Department of CSIE and in Graduate Institute of Networking and Multimedia, National Taiwan University, R.O.C. His current research interests include personal communications services, wireless Internet, and performance modeling. Dr. Lin is an Associate Editor for IEEE Transactions on Vehicular Technology, a Guest Editor for IEEE Wireless Communications special issue on Mobility and Resource Management, and a Guest Editor for ACM/Springer MONET special issue on Wireless Broad Access. He is also an Associate Editorial Member for the WCMC Journal. Dr. Lin has received many research awards. He was a recipient of Research Award for Young Researchers from Pan Wen-Yuan Foundation in Taiwan in 2004, a recipient of K. T. Li Young Researcher Award honored by ACM Taipei Chapter in 2004, a recipient of Wu Ta You Memorial Award of National Science Council (NSC) in Taiwan in 2005, a recipient of Fu Suu-Nien Award of NTU in 2005 for his research achievements. Dr. Lin is listed in WHO’S WHO IN SCIENCE AND ENGINEERING(R) in 2006. Dr. Lin is a Senior Member, IEEE. P. Lin’s email and website addresses are plin@csie.ntu.edu.tw and respectively. Shan-Hung Wu received the B.S. degree from Department of Information Management, National Central University, Jhongli, Taiwan, and M.S. degree from Department of Computer Science and Information, National Taiwan University, Taipei, Taiwan. He is currently a Ph.D. candidate at Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan. His research interests include distributed data management, pervasive computing, wireless and sensor networks, and performance modeling. Chung-Min Chen is Director of Telcordia Applied Research Center in Taiwan. His research interests span across areas in distributed computing, data engineering, telecommunication and network management. He received a Ph.D. in Computer Science from the University of Maryland, College Park and a B.S. in Computer Science and Information Engineering from National Taiwan University. Ching-Feng Liang received M.S. degree in electronic engineering from National Taiwan University of Science & Technology (NTUST) in 1993 and joined the Information & Communication Laboratory (ICL) of Industrial Technology Research Institute (ITRI) as an engineer. Liang has led more than 10 projects of Taiwan Ministry of Economic Affairs (MoEA) to study and develop the technologies of mobile network and services including GPRS/3G core network, WLAN/Cellular interworking and number portability service. Liang received the ITRI Award in 2005 and the Outstanding Project Award of Taiwan MoEA in 2003. Liang is currently the manager of the Core Network Department of ICL/ITRI.     

QoS-driven asynchronous uplink subchannel allocation algorithms for space-time OFDM-CDMA systems in wireless networks

In order to support the diverse Quality of Service (QoS) requirements for differentiated data applications in broadband wireless networks, advanced techniques such as space-time coding (STC) and orthogonal frequency division multiplexing (OFDM) are implemented at the physical layer. However, the employment of such techniques evidently affects the subchannel-allocation algorithms at the medium access control (MAC) layer. In this paper, we propose the QoS-driven cross-layer subchannel-allocation algorithms for data transmissions over asynchronous uplink space-time OFDM-CDMA wireless networks. We mainly focus on QoS requirements of maximizing the best-effort throughput and proportional bandwidth fairness, while minimizing the upper-bound of scheduling delay. Our extensive simulations show that the proposed infrastructure and algorithms can achieve high bandwidth fairness and system throughput while reducing scheduling delay over wireless networks. Xi Zhang (S’89-SM’98) received the B.S. and M.S. degrees from Xidian University, Xi’an, China, the M.S. degree from Lehigh University, Bethlehem, PA, all in electrical engineering and computer science, and the Ph.D. degree in electrical engineering and computer science (Electrical Engineering—Systems) from The University of Michigan, Ann Arbor, USA. He is currently an Assistant Professor and the Founding Director of the Networking and Information Systems Laboratory, Department of Electrical and Computer Engineering, Texas A&M University, College Station, Texas, USA. He was an Assistant Professor and the Founding Director of the Division of Computer Systems Engineering, Department of Electrical Engineering and Computer Science, Beijing Information Technology Engineering Institute, Beijing, China, from 1984 to 1989. He was a Research Fellow with the School of Electrical Engineering, University of Technology, Sydney, Australia, and the Department of Electrical and Computer Engineering, James Cook University, Queensland, Australia, under a Fellowship from the Chinese National Commission of Education. He worked as a Summer Intern with the Networks and Distributed Systems Research Department, Bell Laboratories, Murray Hills, NJ, and with AT&T Laboratories Research, Florham Park, NJ, in 1997. He has published more than 80 technical papers. His current research interests focus on the areas of wireless networks and communications, mobile computing, cross-layer designs and optimizations for QoS guarantees over mobile wireless networks, wireless sensor and Ad Hoc networks, wireless and wireline network security, network protocols design and modeling for QoS guarantees over multicast (and unicast) wireless (and wireline) networks, statistical communications theory, random signal processing, and distributed computer-control systems. Dr. Zhang received the U.S. National Science Foundation CAREER Award in 2004 for his research in the areas of mobile wireless and multicast networking and systems. He is currently serving as an Editor for the IEEE Transactions on Wireless Communications, an Associated Editor for the IEEE Transactions on Vehicular Technology, and and Associated Editor for the IEEE Communications Letters, and is also currently serving as a Guest Editor for the IEEE Wireless Communications Magazine for the Special Issues of “Next Generation of CDMA vs. OFDMA for 4G Wireless Applications”. He has served or is serving as the Panelist on the U.S. National Science Foundation Research-Proposal Review Panel in 2004, the WiFi-Hotspots/WLAN and QoS Panelist at the IEEE QShine 2004, as the Symposium Chair for the IEEE International Cross-Layer Designs and Protocols Symposium within the IEEE International Wireless Communications and Mobile Computing Conference (IWCMC) 2006, the Technical Program Committee Co-Chair for the IEEE IWCMC 2006, the Poster Chair for the IEEE QShine 2006, the Publicity Co-Chair for the IEEE WirelessCom 2005, and as the Technical Program Committee members for IEEE GLOBECOM, IEEE ICC, IEEE WCNC, IEEE VTC, IEEE QShine, IEEE WoWMoM, IEEE WirelessCom, and IEEE EIT. He is a Senior Member of the IEEE and a member of the Association for Computing Machinery (ACM). Jia Tang (S’03) received the B.S. degree in electrical engineering from Xi’an Jiaotong University, Xi’an, China, in 2001. He is currently a Research Assistant working towards the Ph.D. degree in the Networking and Information Systems Laboratory, Department of Electrical and Computer Engineering, Texas A&M University, College Station, Texas, USA. His research interests include mobile wireless communications and networks, with emphasis on cross-layer design and optimizations, wireless quality-of-service (QoS) provisioning for mobile multimedia networks, wireless diversity techniques, and wireless resource allocation. Mr. Tang received the Fouraker Graduate Research Fellowship Award from the Department of Electrical and Computer Engineering, Texas A&M University in 2005.     

A Relay-Based MAC Protocol for Multi-Rate and Multi-Range Infrastructure Wireless LANs

Auto rate adaptation mechanisms have been proposed to improve the throughput in wireless local area networks with IEEE 802.11a/b/g standards that can support multiple data rate at the physical layer. However, even with the capability of transmitting multi-packets with multi-rate IEEE 802.11 PHY, a mobile host near the fringe of the Access-Point's (AP's) transmission range still needs to adopt a low-level modulation to cope with the lower signal-to-noise ratio (SNR), Thus, it can not obtain a data rate as high as that of a host near AP in most cases. According to the characteristics of modulation schemes, the highest data rate between a pair of mobile hosts will be inversely proportional with the transmission distance. Considering these factors, we here demonstrate a Relay-Based Adaptive Auto Rate (RAAR) protocol that can find a suitable relay node for data transmission between transmitter and receiver, and can dynamically adjust its modulation scheme to achieve the maximal throughput of a node according to the transmission distance and the channel condition. The basic concept is that the best modulation schemes are adaptively used by a wireless station to transmit an uplink data frame, according to the path loss condition between the station itself and a relay node, and that between the relay node and AP, thus delivering data at a higher overall data rate. Evaluation results show that this scheme provides significant throughput improvement for nodes located at the fringe of the AP's transmission range, thus remarkably improving overall system performance. Jain-Shing Liu was born in Taipei, Taiwan, in 1970. He received the Ph.D. degree in Department of Computer and Information Science, National Chiao Tung University, Hsinchu, Taiwan. He is currently with the faculty of the Department of Computer Science and Information Management, Providence University, Taichung, Taiwan 433, ROC. His research interests include wireless communication protocol design, performance analysis and modeling, personal communication networks, and distributed simulation. Dr. Liu is a member of IEEE and IEICE. Chunhung Richard Lin was born in Kaohsiung, Taiwan. He received the B.S. and M.S. degrees from the Department of Computer Science and Information Engineering, National Taiwan University, in 1987 and 1989, respectively, and the Ph.D. degree from Computer Science Department, University of California, Los Angeles (UCLA), in 1996. Dr. Lin joined National Chung Cheng University in Taiwan in 1996. Since August 2000, he has been with the Department of Computer Science and Engineering, National Sun Yat-Sen University, Kaohsiung, Taiwan. His research interests include the design and control of personal communication networks, protocol design and implementation for differentiated/integrated services in mobile wireless networks, mobile Internet, distributed simulation, and embedded operating system design and implementation. His email address is: lin@cse.nsysu.edu.tw. Dr. Lin is an ACM member. He received the 2001 Junior Professor Research Award from National Sun Yat-Sen University and the 2000 Investigative Research Award from the Pan Wen Yuan Foundation, Taiwan, ROC.     

Repacking on Demand for Hierarchical Cellular Networks

In mobile telecommunications operation, radio channels are scarce resources and should be carefully assigned. One possibility is to deploy the hierarchical cellular network (HCN). This paper studies a HCN channel assignment scheme called repacking on demand (RoD). RoD was originally proposed for wireless local loop networks. We expend this work to accommodate mobile HCN. A simulation model is proposed to study the performance of HCN with RoD and some previously proposed schemes. Our study quantitatively indicates that RoD may significantly outperform the previous proposed schemes. Hsien-Ming Tsai was born in Tainan, Taiwan, R.O.C., in 1973. He received the double B.S. degrees in Computer Science & Information Engineering (CSIE) and Communication Engineering, the M.S. degree in CSIE, and the Ph.D. degree in CSIE from National Chiao-Tung University (NCTU), Taiwan, in 1996, 1997, and 2002, respectively. He is currently a research specialist in Quanta Research Institute, Quanta Computer Inc. His research interests are in the areas of cellular protocols (UMTS/GPRS/GSM/DECT), cellular multimedia (MPEG-4 Audio/Speech), and embedded systems. He is an IEEE member. 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. Yung-Chun Lin was born in Kaohsiung, Taiwan, R.O.C., in 1978. He received the B.S. and M.S. degrees in Computer Science and Information Engineering (CSIE) from National Chiao-Tung University (NCTU), Taiwan, in 2001, 2003, respectively. He is currently pursuing the Ph.D. degree in CSIE. His research interests include design and analysis of a personal communications services network, the cellular protocols (UMTS/GPRS/GSM), and mobile computing. Yi-Bing Lin received his BSEE degree from National Cheng Kung University in 1983, and his Ph.D. degree in Computer Science from the University of Washington in 1990. From 1990 to 1995, he was with the Applied Research Area at Bell Communications Research (Bellcore), Morristown, NJ. In 1995, he was appointed as a professor of Department of Computer Science and Information Engineering (CSIE), National Chiao Tung University (NCTU). In 1996, he was appointed as Deputy Director of Microelectronics and Information Systems Research Center, NCTU. During 1997-1999, he was elected as Chairman of CSIE, NCTU. His current research interests include design and analysis of personal communications services network, mobile computing, distributed simulation, and performance modeling. Dr. Lin has published over 150 journal articles and more than 200 conference papers. Lin is an Adjunct Research Fellow of Academia Sinica, and is Chair Professor of Providence University. Lin serves as consultant of many telecommunications companies including FarEasTone and Chung Hwa Telecom. Lin is an IEEE Fellow and an ACM Fellow.     

HISNs: Distributed gateways for application-level integration of heterogeneous wireless networks

Integration of different kinds of wireless networks to provide people seamless and continuous network access services is a major issue in the B3G network. In this paper, we propose and implement a novel Heterogeneous network Integration Support Node design (HISN) and a distributed HISN network architecture for the integration of heterogeneous networks, under which the Session Mobility, Personal Mobility, and Terminal Mobility for mobile users can be maintained through the Session Management mechanism. Thus, the HISN node can serve as an agent for the user to access Internet services independent of underlying communication infrastructure. Our design is transparent to the bearer networks and the deployment of the HISN network does not need to involve the operators of the heterogeneous wireless networks. This paper is an extension of the work that won the championship of the Mobile Hero contest sponsored by Industrial Development Bureau of Ministry of Economic Affairs, Taiwan, R.O.C., and was awarded USD 30,000. The work of Lin, Chang and Cheng was supported in part by the National Science Council (NSC), R.O.C, under the contract number NSC94-2213-E-002-083 and NSC94-2213-E-002-090, and NSC 94-2627-E-002-001, Ministry of Economic Affairs (MOEA), R.O.C., under contract number 93-EC-17-A-05-S1-0017, the Computer and Communications Researches Labs/Industrial Technology Research Institute (CCL/ITRL), Chunghwa Telecom Labs, Telcordia Applied Research Center, Taiwan Network Information Center (TWNIC), and Microsoft Corporation, Taiwan. The work of Fang was supported in part by the US National Science Foundation Faculty Early Career Development Award under grant ANI-0093241 and US National Science Foundation under grant DBI-0529012. Phone Lin (M’02-SM’06) received his BSCSIE degree and Ph.D. degree from National Chiao Tung University, Taiwan, R.O.C. in 1996 and 2001, respectively. From August 2001 to July 2004, he was an Assistant Professor in Department of Computer Science and Information Engineering (CSIE), National Taiwan University, R.O.C. Since August 2004, he has been an Associate Professor in Department of CSIE and Graduate Institute of Networking and Multimedia, National Taiwan University, R.O.C. His current research interests include personal communications services, wireless Internet, and performance modeling. Dr. Lin is an Associate Editor for IEEE Transactions on Vehicular Technology, a Guest Editor for IEEE Wireless Communications special issue on Mobility and Resource Management, and a Guest Editor for ACM/Springer MONET special issue on Wireless Broad Access. He is also an Associate Editorial Member for the WCMC Journal. P. Lin’s email and website addresses are plin@csie.ntu.edu.tw and http://www.csie.ntu.edu.tw/∼plin, respectively. Huan-Ming Chang received the BSCSIE degree and Master CSIE degree from National Taiwan University, R.O.C. in 2003 and 2005, respectively. His current research interest includes wireless Internet. H.-M. Chang’s email address is r91114@csie.ntu.edu.tw. Yuguang Fang received a Ph.D. degree in Systems and Control Engineering from Case Western Reserve University in January 1994, and a Ph.D. degree in Electrical Engineering from Boston University in May 1997. From June 1997 to July 1998, he was a Visiting Assistant Professor in Department of Electrical Engineering at the University of Texas at Dallas. From July 1998 to May 2000, he was an Assistant Professor in the Department of Electrical and Computer Engineering at New Jersey Institute of Technology. In May 2000, he joined the Department of Electrical and Computer Engineering at University of Florida where he got the early promotion to Associate Professor with tenure in August 2003 and to Full Professor in August 2005. He has published over 180 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 is currently serving as an Editor for many journals including IEEE Transactions on Communications, IEEE Transactions on Wireless Communications, IEEE Transactions on Mobile Computing, and ACM Wireless Networks. He is also actively participating in conference organization such as the Program Vice-Chair for IEEE INFOCOM’2005, Program Co-Chair for the Global Internet and Next Generation Networks Symposium in IEEE Globecom’2004 and the Program Vice Chair for 2000 IEEE Wireless Communications and Networking Conference (WCNC’2000). Shin-Ming Cheng received the BSCSIE degree in 2000 from National Taiwan University, Taiwan, R.O.C., where he is currently working toward the Ph.D. degree in the Department of Computer Science and Information Engineering, National Taiwan University. His current research interests include mobile computing, personal communications services, and wireless Internet. S.-M. Cheng’s email and website addresses are shimi@pcs.csie.ntu.edu.tw and http://www.pcs.csie.ntu.edu.tw/∼shimi, respectively.     

Cross-layer radio resource allocation in packet CDMA wireless mobile networks

An efficient radio resource allocation scheme is crucial for guaranteeing the quality of service (QoS) requirements and fully utilizing the scarce radio resources in wireless mobile networks. Most of previous studies of radio resource allocation in traditional wireless networks concentrates on network layer connection blocking probability QoS. In this paper, we show that physical layer techniques and QoS have significant impacts on network layer QoS. We use a concept of cross-layer effective bandwidth to measure the unified radio resource usage taking into account both physical layer linear minimum-mean square error (LMMSE) receivers and varying statistical characteristics of the packet traffic in code devision multiple access (CDMA) networks. We demonstrate the similarity between traditional circuit-switched networks and packet CDMA networks, which enables rich theories developed in traditional wireless mobile networks to be used in packet CDMA networks. Moreover, since both physical layer signal-to-interference ratio (SIR) QoS and network layer connection blocking probability QoS are considered simultaneously, we can explore the tradeoff between physical layer QoS and network layer QoS in packet CDMA networks. This work is supported by Natural Science and Engineering Research Council of Canada. Please address all correspondence to Professor Vikram Krishnamurthy at the above address. Fei Yu received the Ph.D. degree in electrical engineering from the University of British Columbia in 2003. From 2002 to 2004, he was with Ericsson (in Lund, Sweden), where he worked on the research and development of dual mode UMTS/GPRS handsets. From 2005, he has been working in Silicon Valley at a start-up, where he conducts research and development in the areas of advanced wireless communication technologies and new standards. After completing the PhD, he has been a research associate in the Department of Electrical and Computer Engineering at the University of British Columbia. His research interests include cross-layer optimization, QoS provisioning and security in wireless networks. Vikram Krishnamurthy (S’90-M’91-SM’99-F’05) was born in 1966. He received his bachelor’s degree from the University of Auckland, New Zealand in 1988, and Ph.D. from the Australian National University, Canberra, in 1992. Since 2002, he has been a professor and Canada Research Chair at the Department of Electrical Engineering, University of British Columbia, Vancouver, Canada. Prior to this he was a chaired professor at the Department of Electrical and Electronic Engineering, University of Melbourne, Australia. His research interests span several areas including ion channels and nanobiology, stochastic scheduling and control, statistical signal processing and wireless telecommunications. Dr. Krishnamurthy has served as associate editor for IEEE Transactions on Signal Processing, IEEE Transactions Aerospace and Electronic Systems, IEEE Transactions Nanobioscience, IEEE Transactions Circuits and Systems II, Systems and Control Letters and European Journal of Applied Signal Processing. He was guest editor of a special issue of IEEE Transactions on NanoBioScience, March 2005 on bio-nanotubes.     

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.     

Theoretical Analysis and Performance of NC-PRMA Protocol for Multichannel Wireless Networks

In this paper, we analyze the effect of duplexing schemes on the throughput and the average packet dropping probability of a new multichannel wireless access protocol which allows for non-collision packet reservation multiple access with multiple channel (NC-PRMA/MC). N _C equal-capacity, orthogonal, traffic channels are shared by M mobile users on the uplink. Transmission attempts on the uplink are made by using time-frequency signaling in every frame, which enables transmission attempts of mobile users to be conveyed to the base station without collisions. Two kinds of duplexing schemes, frequency division duplexing and shared time division duplexing, are considered in the performance analysis. Using a discrete-time Markov chain analysis, we derive the analytic expressions for the average per channel throughput and the average packet dropping probability. Computer simulation results verify the analysis. Analytical evaluation and computer simulation show that NC-PRMA/MC with shared time division duplexing improves the channel capacity, which approaches the theoretical upper bound. Jenn-Kaie Lain born in Taiwan, R.O.C., in 1973. He received the B.E. degree in engineering science from the National Cheng Kung University, Tainan, Taiwan, R.O.C., and the Ph.D. degree in electrical engineering from the National Chung Cheng University, Chiayi, R.O.C., in 1995 and 2001, respectively. Since August 2001, he joined the faculty of Department of Computer Science and Information Engineering at Shu-Te University, Kaohsiung, Taiwan, R.O.C., as an Assistant Professor. He has been on the Faculty at National Yunlin University of Science and Technology, Yunlin, Taiwan, R.O.C., since August 2002 and currently holds the position of Assistant Professor in the Institute of Electronic and Information Engineering. His current research interest is in the field of coding and modulation as well as efficient receiver designs for broadband wireless communications. Jyh-HorngWen received his B.S. degree in Electronic Engineering from the National Chiao Tung University, Hsing-Chu, Taiwan, in 1979 and the Ph.D. degree in Electrical Engineering from the National Taiwan University, Taipei, in 1990. From 1981 to 1983, he was a Research Assistant with the Telecommunication Laboratory, Ministry of Transportation and Communications, Chung-Li, Taiwan. From 1983 to 1991, he was a Research Assistant with the Institute of Nuclear Energy Research, Taoyun, Taiwan. Since February 1991, he has been with the Institute of Electrical Engineering, National Chung Cheng University, Chia-Yi, Taiwan, first as an Associate Professor and, since 2000, as a Professor. He was also the Managing Director of the Center for Telecommunication Research, National Chung Cheng University, from Aug. 2000 to July 2004. Currently, he is also the Dean of General Affairs, National Chi Nan University. He is an Associate Editor of the Journal of the Chinese Grey System Association. His current research interests include computer communication networks, cellular mobile communications, personal communications, spread-spectrum techniques, wireless broadband systems, and gray theory. Prof.Wen is a member of the IEEE Communication Society, the IEEE Vehicular Technology Society, the International Association of Science and Technology for Development,the Chinese Grey System Association, and the Chinese Institute of Electrical Engineering.     

1-V bulk-driven CMOS analog programmable winner-takes-all circuit

In this paper, a 1-V bulk-driven analog winner-takes-all circuit with programmable k-winners capability is proposed. By presetting a set of binary bits, the desired k-winners-take-all or k-losers-take-all function is programmable. The proposed upward-and-downward searching greatly improves the response time. The chip has been fabricated with a 0.25-μm CMOS technology. Simulated results show that the response time of the winner-takes-all circuit is 50 μs under 5-mV identified resolution. The input range is approximately to be rail-to-rail. This work was in part supported by the Chip Implementation Center and the MOE Program of Promoting Academic Excellence of Universities under the Grant EX-93-E-FA09-5-4. Yu-Cherng Hung was born in Changhua, Taiwan, R.O.C., in 1964. He received the M. S. degree in electronics engineering from the National Chiao Tung University, Hsinchu, Taiwan, R.O.C., in 1992, and the Ph.D. degree in electrical engineering from National Cheng Kung University, Tainan, Taiwan, R.O.C., in 2004. From Dec. 1986 to Jan. 2005, he was with the Division of Computer/Information, Chinese Petroleum Corp., Taiwan. He is currently an Assistant Professor with the Department of Electronic Engineering, National Chin-Yi Institute of Technology, Taiwan, R.O.C. His main research interests include analog circuit design, low-voltage VLSI design, and neural network applications. Dr. Hung is a Member of Phi Tau Phi Honorary Scholastic Society, IEEE, and the Institute of Electronics, Information, and Communications Engineers (IEICE). Bin-Da Liu received the Ph.D. degrees in electrical engineering from the National Cheng Kung University, Tainan, Taiwan, R.O.C., in 1983. Since 1977, he has been on the faculty of the National Cheng Kung University, where he is currently a Distinguished Professor in the Department of Electrical Engineering and the Director of the SoC Research Center. During 1983–1984, he was a Visiting Assistant Professor in the Department of Computer Science, University of Illinois at Urbana-Champaign. During 1988–1992, he was the Director of Electrical Laboratories, National Cheng Kung University. He was the Associate Chair of the Electrical Engineering Department during 1996–1999 and the Chair during 1999–2002. Since 1995, he has been a Consultant of the Chip Implementation Center, National Applied Research Laboratories, Hsinchu, Taiwan. He has published more than 200 technical papers. He also contributed chapters in the book Neural Networks and Systolic Array Design (D. Zhang Ed. Singapore: World Scientific, 2002) and the book Accuracy Improvements in Linguistic Fuzzy Modeling (J. Casillas, O. Cordón, F. Herrera, and L. Magdalena Eds. Heidelberg, Germany: Springer-Verlag, 2003). His current research interests include low power circuit, neural network circuit, CMAC neural network, analog neural network architecture, design of programmable cellular neural networks, and very large-scale integration implementation of fuzzy/neural circuits and audio/video signal processors. Dr. Liu is a Fellow of IEEE and the Vice President of Region 10, IEEE Circuits and Systems Society. He served as a CAS Associate Editor of IEEE Circuits and Devices Magazine and an Associate Editor of IEEE Transactions on Circuits and Systems I: Regular Papers. He is serving as an Associate Editor of IEEE Transactions on Very Large Scale Integration (VLSI) Systems. Chung-Yang Tsai was born in Mian-Li, Taiwan, R.O.C. He received the B.S. and M.S. degrees both in electrical engineering from the National Cheng Kung University, Tainan, Taiwan, R.O.C., in 2001 and 2003, respectively. His research interests include very large-scale integration design and signal processing.