A Video Streaming System for Mobile Phones: Practice and Experience

This paper presents a case of video streaming system for mobile phone which has actually been implemented and deployed for commercial services in CDMA2000 1X cellular phone networks. As the computing environment and the network connection of cellular phones are significantly different from the wired desktop environment, the traditional desktop streaming method is not applicable. Therefore, a new architecture is required to suit the successfully streaming in the mobile phone environment. We have developed a very lightweight video player for use in mobile phone and the related authoring tool for the player. The streaming server has carefully been designed to provide high efficiency, reliability and scalability. Based on a specifically-designed suite of streaming protocol, the server employs an adaptive rate control mechanism which transmits the media packets appropriately into the network according to the change in network bandwidth.Hojung Cha is currently a professor in computer science at Yonsei University, Seoul, Korea. His research interests include multimedia computing system, multimedia communication networks, wireless and mobile communication systems and embedded system software. He received his B.S. and M.S. in computer engineering from Seoul National University, Korea, in 1985 and 1987, respectively. He received his Ph.D. in computer science from the University of Manchester, England, in 1991.Jongmin Lee is a Ph.D. candidiate in computer science at Yonsei University, Seoul, Korea. His research interests include wireless multimedia system, QoS architecture, multimedia communication networks. He received his B.S. and M.S. in computer science from Kwangwoon University in 1999 and 2001, respectively.Jongho Nang is a professor in the Department of Computer Science at Sogang University. He received his B.S. degree from Sogang University, Korea, in 1986 and M.S. and Ph.D. degree from KAIST, in 1988 and in 1992, respectively. His research interests are in the field of multimedia systems, digital video library, and Internet technologies. He is a member of KISS, ACM, and IEEE.Sung-Yong Park is an associate professor in the Department of Computer Science at Sogang University, Seoul, Korea. He received his B.S. degree in computer science from Sogang University, and both the M.S. and Ph.D. degrees in computer science from Syracuse University. From 1987 to 1992, he worked for LG Electronics, Korea, as a research engineer. From 1998 to 1999, he was a research scientist at Telcordia Technologies (formerly Bellcore) where he developed network management software for optical switches. His research interests include high performance distributed computing and systems, operating systems, and multimedia.Jin-Hwan Jeong received the B.S. and M.S. degrees in computer science from Korea University, Seoul, Korea, in 1997, and 1999, respectively. He is currently in Ph.D. course at Korea University. His research interests include video processing for thin devices, multimedia streaming and operating systems.Chuck Yoo received the B.S. degree in electronics engineering from Seoul National University, Seoul, Korea and the M.S. and Ph.D. in computer science in University of Michigan. He worked as a researcher in Sun Microsystems Lab. from 1990 to 1995. He joined the Computer Science and Enginnering Department, Korea University, Seoul, Korea in 1995, where he is currently a professor. His research interests include high performance network, multimedia streaming, and operating systems.Jin-Young Choi received the B.S. degree from Seoul National University, Seoul, Korea, in 1982, the M.S. degree from Drexel University in 1986, and the Ph.D. degree from University of Pennsylvania, in 1993. He is currently a professor of Computer Science and Engineering Department, Korea University, Seoul, Korea. His current research interests are in real-time computing, formal methods, programming languages, process algebras, security, software engineering, and protocol engineering.     

A Software-Hardware Co-Implementation of MPEG-4 Advanced Video Coding (AVC) Decoder with Block Level Pipelining

We present a baseline MPEG-4 Advanced Video Coding (AVC) decoder based on the methodology of joint optimization of software and hardware. The software is first optimized with algorithm improvements for frame buffer management, boundary padding, content-aware inverse transform and context-based entropy decoding. The overall decoding throughput is further enhanced by pipelining the software and the dedicated hardware at macroblock level. The decoder is partitioned into the software and hardware modules according to the target frame rate and complexity profiles. The hardware acceleration modules include motion compensation, inverse transform and loop filtering. By comparing the optimized decoder with the committee reference decoder of Joint Video Team (JVT), the experimental results show improvement on the decoding throughput by 7 to 8 times. On an ARM966 board, the optimized software without hardware acceleration can achieve a decoding rate up to 5.9 frames per second (fps) for QCIF video source. The overall throughput is improved by another 27% to 7.4 fps on the average and up to 11.5 fps for slow motion video sequences. Finally, we provide a theoretical analysis of the ideal performance of the proposed decoder.Shih-Hao Wang was born in Tainan, Taiwan, R.O.C. in 1977. He received the M.S. degree in Electrical and Control Engineering from National Chiao Tung University, Hsinchu, Taiwan, in 2001, where he is currently working toward the Ph.D. degree in the Institute of Electronics.His research interests are video compression and VLSI implementation.Wen-Hsiao Peng was born in Hsin-Chu, Taiwan, Republic of China, in 1975. He received the B.S. and the M.S. degrees in Electrics Engineering from National Chiao-Tung University, Hsin-Chu, Taiwan, in 1997 and 1999respectively. During 2000–2001, he was an intern in Intel Microprocessor Research Lab, U.S.A. In 2002, he joined the Institute of Electronics of National Chiao-Tung University, where he is currently a Ph.D candidate. His major research interests include scalable video coding, video codec optimization and platform based architecture design for video compression applications. Since 2000, he has been working with video coding development and implementation. He has actively contributed to the development of MPEG-4 Fine Granularity Scalability (FGS) and MPEG-21 Scalable Video Coding (Now, MPEG-4 Part 10 AVC Amd.1).Yu-Wen Hereceived his Ph.D. degree in computer application from Tsinghua University in 2002. He was a lecture of the Department of Computer Science and Technology from 2002 to 2003 in Tsinghua University. In 2004, he joined Internet Media group of Microsoft Research Asia.His research interests include video coding, transmission and embedded multimedia application systems.Guan-yi Lin was born in Kaohsiung, Taiwan in 1981. He received the B.S. degree in Electronics Engineering from National Chiao Tung University, Hsinchu, Taiwan, in 2003, where he is currently working toward the M.S. degree in the Institute of Electronics.His research interests are video compression and communication systems design.Cheng-Yi Lin was born in Tainan, Taiwan in 1981. He received the B.S. degree in Electronics Engineering from National Chiao Tung University, Hsinchu, Taiwan, in 2003, where he is currently working toward the M.S. degree in the Institute of Electronics.His research interests are on-chip communication and testing.Shih-Chien Chang was born in Taichung, Taiwan in 1981. He received the B.S. degree in Electronics Engineering from National Chiao Tung University, Hsinchu, Taiwan, in 2003, where he is currently working toward the M.S. degree in the Institute of Electronics.His research interests are video compression and VLSI implementation.Chung-Neng Wang was born in PingTung, Taiwan, in 1972. He received the B.S. degree and Ph.D degree in computer science and information engineering from National Chiao-Tung University (NCTU), HsinChu, Taiwan in 1994 and 2003, respectively. He joined the faculty at National Chiao-Tung University in Taiwan, R.O.C in January 2003.Since 2001 he has actively participated in ISO’s Moving Picture Experts Group (MPEG) digital video coding standardization process. He has made more than 18 contributions to the MPEG committee over the past 4 years. He published over 23 technical journal and conference papers in the field of video and signal processing. His current research interests are video/image compression, motion estimation, video transcoding, and streaming.Tihao Chiangwas born in Cha-Yi, Taiwan, Republic of China, 1965. He received the B.S. degree in electrical engineering from the National Taiwan University, Taipei, Taiwan, in 1987, and the M.S. degree in electrical engineering from Columbia University in 1991. He received his Ph.D. degree in electrical engineering from Columbia University in 1995. In 1995, he joined David Sarnoff Research Center as a Member of Technical Staff. Later, he was promoted as a technology leader and a program manager at Sarnoff. While at Sarnoff, he led a team of researchers and developed an optimized MPEG-2 software encoder. For his work in the encoder and MPEG-4 areas, he received two Sarnoff achievement awards and three Sarnoff team awards.Since 1992 he has actively participated in ISO’s Moving Picture Experts Group (MPEG) digital video coding standardization process with particular focus on the scalability/compatibility issue. He is currently the co-editor of the part 7 on the MPEG-4 committee. He has made more than 90 contributions to the MPEG committee over the past 10 years. His main research interests are compatible/scalable video compression, stereoscopic video coding, and motion estimation. In September 1999, he joined the faculty at National Chiao-Tung University in Taiwan, R.O.C. Dr. Chiang is currently a senior member of IEEE and holder of 13 US patents and 30 European and worldwide patents. He was a co-recipient of the 2001 best paper award from the IEEE Transactions on Circuits and Systems for Video Technology. He published over 50 technical journal and conference papers in the field of video and signal processing.     

A Hybrid Error Recovery scheme for Scalable Video Transmission over 3G Cellular Broadcast Networks

The cdma2000 1xEV-DO mobile communication system provides broadcast and multicast services (BCMCS) to meet an increasing demand for multimedia data services. But the servicing of video streams over a BCMCS network faces a challenge from the unreliable and error-prone nature of the radio channel. BCMCS uses Reed-Solomon coding integrated with the MAC protocol for error recovery. We show that this is not effective for mobiles moving at the edge of service area, where the channel condition is bad, resulting in significantly lower video quality. To improve the playback quality of an MPEG-4 FGS (fine granularity scalability) video stream, we propose a hybrid error recovery scheme incorporating a packet scheduler, which uses slots saved by reducing the Reed-Solomon coding overhead. Packets to be retransmitted are prioritized by a utility function which reduces the packet error-rate in the application layer within a fixed retransmission budget by considering of the map of the error control block at each mobile node. Our error recovery scheme also uses the characteristics of MPEG-4 FGS to improve the video quality even for a slow-moving mobile which is experiencing a high error-rate in the physical channel because of error bursts. Kyungtae Kang received B.S. (1999) and M.S. (2001) degrees in computer engineering from Seoul National University, Korea. He received Ph.D. degree in Dept. of Electrical Engineering and Computer Science from Seoul National University, Korea in 2007. He is a member of IEEE and IEICE. His research interests include packet scheduling, error control, QoS provision, and energy minimization issues in nextgeneration wireless/mobile networks. In particular, he is researching the performance and energy requirements of 3G cellular broadcast services such as BCMCS and MBMS. Yongwoo Cho received the Premedical Degree from the College of Medicine, University of Ulsan, in 1997, a B.S. degree in Computer Science from Korea National Open University in 2004, while he was an military service, and an M.S. degree in Electrical Engineering and Computer Science from Seoul National University in 2006. He has worked as a researcher in Dooin Corp. and as a general manager in Bluecord Technology, Inc. His primary interests include multimedia systems, digital broadcasting, next-generation wireless/mobile networks, error control, real-time computing, and low-power design. He is currently a Ph.D. student in the School of Electrical Engineering and Computer Science at Seoul National University. Heonshik Shin received the B.S. degree in applied physics from Seoul National University, Korea, in 1973. Since he received Ph.D. degree in computer engineering from the University of Texas at Austin in 1985, he has actively involved himself in researches of various topics, ranging from real-time computing and distributed computing to mobile systems and software. He is currently a professor of School of Computer Science and Engineering at Seoul National University.     

MANTIS OS: An Embedded Multithreaded Operating System for Wireless Micro Sensor Platforms

The MANTIS MultimodAl system for NeTworks of In-situ wireless Sensors provides a new multithreaded cross-platform embedded operating system for wireless sensor networks. As sensor networks accommodate increasingly complex tasks such as compression/aggregation and signal processing, preemptive multithreading in the MANTIS sensor OS (MOS) enables micro sensor nodes to natively interleave complex tasks with time-sensitive tasks, thereby mitigating the bounded buffer producer-consumer problem. To achieve memory efficiency, MOS is implemented in a lightweight RAM footprint that fits in less than 500 bytes of memory, including kernel, scheduler, and network stack. To achieve energy efficiency, the MOS power-efficient scheduler sleeps the microcontroller after all active threads have called the MOS sleep() function, reducing current consumption to the μA range. A key MOS design feature is flexibility in the form of cross-platform support and testing across PCs, PDAs, and different micro sensor platforms. Another key MOS design feature is support for remote management of in-situ sensors via dynamic reprogramming and remote login. Shah Bhatti is a Ph.D. student in Computer Science at the University of Colorado at Boulder. He also works as a Senior Program Manager in the R&D Lab for Imaging and Printing Group (IPG) at Hewlett Packard in Boise, Idaho. He has participated as a panelist in workshops on Integrated Architecture for Manufacturing and Component-Based Software Engineering, at IJCAI ‘89 and ICSE ‘98, respectively. Hewlett Packard has filed several patents on his behalf. He received an MSCS and an MBA from the University of Colorado, an MSCE from NTU and a BSCS from Wichita State University. His research interests include power management, operating system design and efficient models for wireless sensor networks. James Carlson is a Ph.D. student in Computer Science at the University of Colorado at Boulder. He received his Bachelor’s degree from Hampshire College in 1997. His research is supported by the BP Visualization Center at CU-Boulder. His research interests include computer graphics, 3D visualization, and sensor-enabled computer-human user interfaces. Hui Dai is a Ph.D. student in Computer Science at the University of Colorado at Boulder. He received his B.E. from the University of Science and Technology, China in 2000, and received has M.S. in Computer Science from the University of Colorado at Boulder in 2002. He has been co-leading the development of the MANTIS OS. His research interests include system design for wireless sensor networks, time synchronization, distributed systems and mobile computing. Jing Deng is a Ph.D. student in Computer Science at the University of Colorado at Boulder. He received his B.E. from Univeristy of Electronic Science and Technology of China in 1993, and his M.E from Institute of Computing Technology, Chinese Academy of Science in 1996. He has published four papers on security wireless sensor networks and is preparing a book chapter on security, privacy, and fault tolerance in sensor networks. His research interests include wireless security, secure network routing, and security for sensor networks. Jeff Rose is an M.S. student in Computer Science at the University of Colorado at Boulder. He received his B.S. in Computer Science from the University of Colorado at Boulder in 2003. He has been co-leading the development of the MANTIS operating system. His research interests include data-driven routing in sensor networks. Anmol Sheth is a Ph.D. student in Computer Science at the University of Colorado at Boulder. He received his B.S. in Computer Science from the University of Pune, India in 2001. His research interests include MAC layer protocol design, energy-efficient wireless communication, and adapting communications to mobility. Brian Shucker is a Ph.D. student in Computer Science at the University of Colorado at Boulder. He received his B.S. in Computer Science from the University of Arizona in 2001, and his M.S. in Computer Science from the University of Colorado at Boulder in December 2003. He has been co-leading the development of the MANTIS operating system. His research interests in wireless sensor networks include operating systems design, communication networking, and robotic sensor networks. Charles Gruenwald is an undergraduate student in Computer Science at the University of Colorado at Boulder. He joined the MANTIS research group in Fall 2003 as an undergraduate researcher. Adam Torgerson is an undergraduate student in Computer Science at the University of Colorado at Boulder. He joined the MANTIS research group in Fall 2003 as an undergraduate researcher. Richard Han joined the Department of Computer Science at the University of Colorado at Boulder in August 2001 as an Assistant Professor, Prof. Han leads the MANTIS wireless sensor networking research project, http://mantis.cs.colorado.edu. He has served on numerous technical program committees for conferences and workshops in the field of wireless sensor networks. He received a National Science Foundation CAREER Award in 2002 and IBM Faculty Awards in 2002 and 2003. He was a Research Staff Member at IBM’s Thomas J. Watson Research Center in Hawthorne, New York from 1997-2001. He received his Ph.D. in Electrical Engineering from the University of California at Berkeley in 1997, and his B.S. in Electrical Engineering with distinction from Stanford University in 1989. His research interests include systems design for sensor networks, secure wireless sensor networks, wireless networking, and sensor-enabled user interfaces.This revised version was published online in August 2005 with a corrected cover date.     

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.     

Progressive meshes transmission over a wired-to-wireless network

The evolution of mobile network and the popularization of mobile devices; the demand for multimedia services and 3D graphics applications on limited resource devices is more contemporary. Most of the works on multimedia transmission are focused on bit errors and packet losses due to the fading channel environment of a wireless network. Error resilient multimedia is significant research topic which can be adapted to the different conditions in a wireless environment. The current solutions in transmission of multimedia across different networks include some type of transcoder where the source is partially or fully decoded, and re-encoded to suit the network conditions. This paper introduces a flexible progressive coding framework for 3D meshes, which can be adapted to the different conditions imposed by wired and wireless channels at the bitstream level. By avoiding the computationally complex steps of transcoding between networks, could deteriorate decoded model quality. The framework also allows refined degradation of model quality when the network conditions are poor due to congestion or deep fades. Xiaonan Luo, male, born in Feb. 1963 in Jiangxi Province, China, Ph. D., completed his post-doctorate training in Mar. 1995. He is a professor and Ph. D. advisor of the School of Information Science and Technology, and the Chairman of Computer Application Institute of Sun Yat-sen University. His current interests are in mobile graphics transmission and 3D geometric simulation methods. He enjoys the government special allowance granted by the State Council of China. He won the National Science & Technology Progress Prize awarded by the Ministry of Science and Technology of China and the National Natural Science Funds granted by the National Nature Science Foundation of China. Guifeng Zheng, male, born in Jan. 1977 in Guangdong Province, China, Ph. D., received his Ph.D. degree from Sun Yat-sen University in 2005. He is currently an research assistant in the Computer Application Institute of Sun Yat-sen University. His research interests span the areas of wireless networks and mobile graphics computing.     

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.     

A Practical Cross-Layer Mechanism For Fairness in 802.11 Networks

Many companies, organizations and communities are providing wireless hotspots that provide networking access using 802.11b wireless networks. Since wireless networks are more sensitive to variations in bandwidth and environmental interference than wired networks, most networks support a number of transmission rates that have different error and bandwidth properties. Access points can communicate with multiple clients running at different rates, but this leads to unfair bandwidth allocation. If an access point communicates with a mix of clients using both 1 Mb/s and 11 Mb/s transmission rates, the faster clients are effectively throttled to 1 Mb/s as well. This happens because the 802.11 MAC protocol approximate “station fairness”, with each station given an equal chance to access the media. We provide a solution to provide “rate proportional fairness”, where the 11 Mb/s stations receive more bandwidth than the 1 Mb/s stations. Unlike previous solutions to this problem, our mechanism is easy to implement, works with common operating systems and requires no change to the MAC protocol or the stations. Joseph Dunn received an M.S. in computer science from the University of Colorado at Boulder in 2003, and B. S. in coputer science and mathematics from the University of Arizona in 2001. His research interests are in the general area of computer systems, primarily focusing on security and scalability in distributed systems. He is currently working on his Ph.D. in computer science from the University of Colorado at Boulder. Michael Neufeld received a Ph.D. in Computer Science from the University of Colorado at Boulder in December of 2004, having previously received an M.S. in Computer Science from the University of Colorado at Boulder in 2000 and an A.B. in Computer Science from Princeton University in 1993. His research interests are in the general area of computer system, specifically concentrating on wireless networking, software defind/cognitive radio, and streerable antennas. He is currently a postdoc in the Computer Science department at the University of Calorado at Boulder pursuing research related to software defined radio and new MAC protocols for steerable phase array antennas. Anmol Sheth is a Ph.D. student in Computer Science at the University of Colorado at Boulder. He received his B.S. in Computer Science from the University of Pune, India in 2001. He has been co-leading the development of the MANTIS operating system. He has co-authored three papers include MAC layer protocol design, energy-efficient wireless communication, and adapting communications to mobility. Dirk Grunwald received his Ph.D. from the University of Illinois in 1989 and joined the University of Colorado the same year. His work addresses research and teaching in the broad area of “computer systems”, which includes computer architecture, operating systems, networks, and storage systems. His interests also include issues in pervasive computing, novel computing models, and enjoying the mountains. He is currently an Associate Professor in the Department of Computer Science and in Electrical and Computer Engineering and is also the Director of the Colorado Center for Information Storage. John Bennett is a Professor of Computer Science with a joint appointment in Electrical and Computer Engineering at the University of Colorado at Boulder. He also serves as Associate Dean for Education in the College of Engineering and Applied Science. He joined the CU-Boulder faculty in 2000, after serving on the faculty of Rice University for 11 years. While at Rice, Bennett pioneered a course in engineering design for both engineering and non-engineering students that has been emulated at several universities and high schools. In addition to other teaching awards, Bennett received the Keck Foundation National Award for Engineering Teaching Excellence for his work on this course. Bennett received his Ph.D. in 1988 from the University of Washington. Prior to completing his doctoral studies, he was a U.S. Naval Officer for several years and founded and served as President of Pacific Mountain Research, Inc., where he supervised the design and development of a number of commercial computing systems. Bennett's primary research interests are broadly focused in the area of distributed systems, and more narrowly in distributed information management and distributed robotic macrosensors.     

Private Authentication Techniques for the Global Mobility Network

Numerous authentication approaches have been proposed recently for the global mobility network (GLOMONET), which provides mobile users with global roaming services. In these authentication schemes, the home network operators can easily obtain the authentication key and wiretap the confidentiality between the roaming user and the visited network. This investigation provides a solution of authentication techniques for GLOMONET in order to prevent this weakness from happening and presents a secure authentication protocol for roaming services. In addition, a round-efficient version of the same authentication protocol is presented. Comparing with other related approaches, the proposed authentication protocol involves fewer messages and rounds in communication. Tian-Fu Lee was born in Tainan, Taiwan, ROC, in 1969. He received his B.S. degree in Applied Mathematics from National Chung Hsing University, Taiwan, in 1992, and his M.S. degree in Computer Science and Information Engineering from National Chung Cheng University, Taiwan, in 1998. He works as a lecturer in Leader University and pursues his Ph.D. degree at Department of Computer Science and Information Engineering, National Cheng Kung University, Taiwan. His research interests include cryptography and network security. Chi-Chao Chang received the BS degree in Microbiology from Soochow University in 1990 and the MS degree in Computer Science from State University of New York at Albany in 1992. He is currently working as an instructor in Chang Jung Christian University and a graduate student in National Cheng Kung University. His research interests are information security, mobile agent systems, anonymous digital signatures and quantum cryptography. Tzonelih Hwang was born in Tainan, Taiwan, in March 1958. He received his undergraduate degree from National Cheng Kung University, Tainan, Taiwan, in 1980, and the M.S. and Ph.D. degrees in Computer Science from the University of Southwestern Louisiana, USA, in 1988. He is presently a professor in Department of Computer Science and Information Engineering, National Cheng Kung University. His research interests include cryptology, network security, and coding theory.     

A randomized energy-conservation protocol for resilient sensor networks*

In this paper we present PEAS, a randomized energy-conservation protocol that seeks to build resilient sensor networks in the presence of frequent, unexpected node failures. PEAS extends the network lifetime by maintaining a necessary set of working nodes and turning off redundant ones, which wake up after randomized sleeping times and replace failed ones when needed. The fully localized operations of PEAS are based on each individual node's observation of its local environment but do not require per neighbor state at any node; this allows PEAS to scale to very dense node deployment. PEAS is highly robust against node failures due to its simple operations and randomized design; it also ensures asymptotic connectivity. Our simulations and analysis show that PEAS can maintain an adequate working node density in presence of as high as 38% node failures, and a roughly constant overhead of less than 1% of the total energy consumption under various deployment densities. It extends a sensor network's functioning time in linear proportional to the deployed sensor population. Fan Ye received his B.E. in Automatic Control in 1996 and M.S. in Computer Science in 1999, both from Tsinghua University, Beijing, China. He received his Ph.D. in Computer Science in 2004 from UCLA. He is currently with IBM Research. His research interests are in wireless networks, sensor networks and security. Honghai Zhang received his BS in Computer Science in 1998 from University of Science and Technology of China. He received his MS and Ph.D. in Computer Science from University of Illinois at Urbana-Champaign. He is currently with the Wireless Advanced Technology Lab of Lucent Technologies. His research interests are wireless networks, WiMAX, and VoIP over wireless networks. Songwu Lu received both his M.S. and Ph.D. from University of Illinois at Urbana-Champaign. He is currently an associate professor at UCLA Computer Science. He received NSF CAREER award in 2001. His research interests include wireless networking, mobile computing, wireless security, and computer networks. Lixia Zhang received her Ph.D in computer science from the Massachusetts Institute of Technology. She was a member of the research staff at the Xerox Palo Alto Research Center before joining the faculty of UCLA’s Computer Science Department in 1995. In the past she has served on the Internet Architecture Board, Co-Chair of IEEE Communication Society Internet Technical Committee, the editorial board for the IEEE/ACM Transactions on Networking, and technical program committees for many networking-related conferences including SIGCOMM and INFOCOM. Zhang is currently serving as the vice chair of ACM SIGCOMM. Jennifer C. Hou received the Ph.D. degree in Electrical Engineering and Computer Science from The University of Michigan, Ann Arbor in 1993 and is currently a professor in the Department of Computer Science at University of Illinois at Urbana Champaign (UIUC). Prior to joining UIUC, she has taught at Ohio State University and University of Wisconsin - Madison. Dr. Hou has worked in the the areas of network modeling and simualtion, wireless-enabled software infrastructure for assisted living, and capacity optimization in wireless networks. She was a recipient of an ACM Recognition of Service, a Cisco University Research Award, a Lumley Research Award from Ohio State University, and a NSF CAREER award. ^*A Shorter version of this paper appeared in ICDCS 2003.     

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.     

Cycle-Accurate Energy Measurement and Characterization of FPGAs

Field Programmable Gate Arrays (FPGAs) play many important roles, ranging from small glue logic replacement to System-on-Chip (SoC) designs. Nevertheless, FPGA vendors cannot accurately specify the power consumption of their products on device data sheets because the power consumption of FPGAs is strongly dependent on the target circuit, including resource utilization, logic partitioning, mapping, placement and routing. Although major CAD tools have started to report average power consumption under given transition activities, power-efficient FPGA design demands more detailed information about power consumption. In this paper, we introduce an in-house cycle-accurate FPGA energy measurement tool and energy characterization schemes spanning low-level to high-level design. This tool offers all the capabilities necessary to investigate the energy consumption of FPGAs for operation-based energy characterization, which is applicable to high-level and system-wide energy estimation. It also includes features for low-level energy characterization. We compare our tool with Xilinx XPower and demonstrate the state-machine-based energy characterization of an SDRAM controller.The RIACT at Seoul National University provide research facilities for this study. This work was partly supported by the Brain Korea 21 Project.Hyung Gyu Lee received the B.S. degree in Dept. of Computer Engineering from DongGuk University, in 1999, M.S. degree in School of Computer Science and Engineering from Seoul National University, Seoul, Korea, in 2001, and is currently working toward the Ph.D. degree at Seoul National University. His research interests include device-level energy measurement and characterization, system-level low power design and low-power FPGA design.KyungSoo Lee is a M.S. student at the School of Computer Science and Engineering, Seoul National University. He received the B.S. degree in the School of Computer Science and Engineering from Seoul National University, Seoul, Korea, in 2004. He is currently working on low-power systems and embedded systems for his M.S. degree.Yongseok Choi received the B.S. and M.S. degree in the School of Computer Science and Engineering from Seoul National University, Seoul, Korea, in 2000 and 2002, respectively. He is currently working toward the Ph.D. degree in the School of Computer Science and Engineering at Seoul National University. His research interests include embedded systems and low power systems.Naehyuck Chang received his B.S., M.S. and Ph.D. degrees all from Dept. of Control and Instrumentation Engineering, Seoul National University, Seoul, Korea, in 1989, 1992 and 1996, respectively. Since 1997, he has been with School of Computer Science and Engineering, Seoul National University and currently is an Associate Professor. His research interest includes system-level low-power design and embedded systems design.     

MAC Layer Admission Control and Priority Re-allocation for Handling QoS Guarantees in Non-cooperative Wireless LANs

Providing QoS guarantee with appropriate service differentiation in IEEE 802.11 wireless LANs is quite desirable. However, users may be selfish and thus rigorously try to maximize their performance by demanding high services even though the network has already saturated. On the other hand, user misbehaviors such as misuse of priority and over-rate transmission pose further harm to performance of existing flows. These application layer non-cooperation makes successful resource allocation very challenging with existing contention based CSMA/CA channel access. In this paper, we propose a MAC layer coordinated QoS framework of admission control and priority re-allocation for quality of services of real-time applications in wireless LANs. Our focus is on priority based MAC schedulers where each user can set its flow priority in order to receive appropriate level of services. With channel condition information such as available bandwidth and mean delay exchanged among neighboring stations, users can enforce admission control based on the perceived channel status and may re-allocate their priorities to accommodate existing flows as desired. User misbehaviors are identified by estimating the flow transmitting rate and matching priority setting, or even punished by assigning appropriate low priorities. Extensive simulations results show that the proposed framework can effectively coordinate wireless users on keeping reserved transmission rate, using appropriate MAC priority, and allocating sufficient resource. Ming Li received his B.S. and M.S. in Engineering from Shanghai Jiao Tong University, China, in 1995 and 1998, respectively. He is currently a Ph.D. candidate in department of Computer Science, University of Texas at Dallas, where he received M.S. degree in Computer Science in Dec. 2001. His research interest includes QoS schemes for mobile ad-hoc networks and multimedia over wireless networks. B. Prabhakaran is with the faculty of Computer Science Department, University of Texas at Dallas. He has been working in the area of multimedia systems: animation & multimedia databases, authoring & presentation, resource management, and scalable web-based multimedia presentation servers. Dr. Prabhakaran received the prestigious National Science Foundation (NSF) CAREER Award in 2003 for his proposal on Animation Databases. He has published several research papers in various refereed conferences and journals in this area. He has served as guest-editor (special issue on Multimedia Authoring and Presentation) for ACM Multimedia Systems journal. He is also serving on the editorial board of Multimedia Tools and Applications journal, Kluwer Academic Publishers. He has also served as program committee member on several multimedia conferences and workshops. B. Prabhakaran has served as a visiting research faculty with the Department of Computer Science, University of Maryland, College Park. He also served as a faculty in the Department of Computer Science, National University of Singapore as well as in the Indian Institute of Technology, Madras, India.     

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.     

Maximizing Lifetime for Data Aggregation in Wireless Sensor Networks

This paper studies energy efficient routing for data aggregation in wireless sensor networks. Our goal is to maximize the lifetime of the network, given the energy constraint on each sensor node. Using linear programming (LP) formulation, we model this problem as a multicommodity flow problem, where a commodity represents the data generated from a sensor node and delivered to a base station. A fast approximate algorithm is presented, which is able to compute (1−ε)-approximation to the optimal lifetime for any ε > 0. Then along this baseline, we further study several advanced topics. First, we design an algorithm, which utilizes the unique characteristic of data aggregation, and is proved to reduce the running time of the fastest existing algorithm by a factor of K, K being the number of commodities. Second, we extend our algorithm to accommodate the same problem in the setting of multiple base stations, and study its impact on network lifetime improvement. All algorithms are evaluated through both solid theoretical analysis and extensive simulation results. Yuan Xue received her B.S. in Computer Science from Harbin Institute of Technology, China in 1994 and her M.S. and Ph.D. in Computer Science from the University of Illinois at Urbana-Champaign in 2002, and 2005. Currently she is an assistant professor at the Department of Electrical Engineering and Computer Science of Vanderbilt University. Her research interests include wireless and sensor networks, mobile systems, and network security. Yi Cui received his B.S. and M.S. degrees in 1997 and 1999, from Department of Computer Science, Tsinghua University, China, and his Ph.D. degree in 2005 from the Department of Computer Science, University of Illinois at Urbana-Champaign. Since then, he has been with the Department of Electrical Engineering and Computer Science at Vanderbilt University, where he is currently an assistant professor. His research interests include overlay network, peer-to-peer system, multimedia system, and wireless sensor network. Klara Nahrstedt (M ' 94) received her A.B., M.Sc degrees in mathematics from the Humboldt University, Berlin, Germany, and Ph.D in computer science from the University of Pennsylvania. She is an associate professor at the University of Illinois at Urbana-Champaign, Computer Science Department where she does research on Quality of Service(QoS)-aware systems with emphasis on end-to-end resource management, routing and middleware issues for distributed multimedia systems. She is the coauthor of the widely used multimedia book ‘Multimedia:Computing, Communications and Applications’ published by Prentice Hall, and the recipient of the Early NSF Career Award, the Junior Xerox Award and the IEEE Communication Society Leonard Abraham Award for Research Achievements, and the Ralph and Catherine Fisher Professorship Chair. Since June 2001 she serves as the editor-in-chief of the ACM/Springer Multimedia System Journal. An erratum to this article is available at .     

Channel Sharing Scheme for Packet-Switched Cellular Networks

In this paper, we study an approach for sharing channels to improve network utilization in packet-switched cellular networks. Our scheme exploits unused resources in neighboring cells without the need for global coordination. We formulate a minimax approach to optimizing the allocation of channels in this sharing scheme. We develop a measurement-based distributed algorithm to achieve this objective and study its convergence. We illustrate, via simulation results, that the distributed channel sharing scheme performs significantly better than the fixed channel scheme over a wide variety of traffic conditions. This research was supported in part by the National Science Foundation through grants ECS-0098089, ANI-0099137, ANI-0207892, ANI-9805441, ANI-0099137, and ANI-0207728, and by an Indiana 21st century grant. A conference version of this paper appeared in INFOCOM 99. This work was done when all the authors were at Purdue University. Suresh Kalyanasundaram received his Bachelors degree in Electrical and Electronics Engineering and Masters degree in Physics from Birla Institute of Technology and Science, Pilani, India in 1996. He received his Ph.D. from the School of Electrical and Computer Engineering, Purdue University, in May 2000. Since then he has been with Motorola, working in the area of performance analysis of wireless networks. Junyi Li received his B.S. and M.S. degrees from Shanghai Jiao Tong University, and Ph.D. degree from Purdue University. He was with the Department of Digital Communications Research at Bell Labs, Lucent Technologies from 1998 to 2000. In 2000 as a founding member he jointed Flarion Technologies, where he is now Director of Technology. He is a senior member of IEEE. Edwin K.P. Chong received the B.E.(Hons.) degree with First Class Honors from the University of Adelaide, South Australia, in 1987; and the M.A. and Ph.D. degrees in 1989 and 1991, respectively, both from Princeton University, where he held an IBM Fellowship. He joined the School of Electrical and Computer Engineering at Purdue University in 1991, where he was named a University Faculty Scholar in 1999, and was promoted to Professor in 2001. Since August 2001, he has been a Professor of Electrical and Computer Engineering and a Professor of Mathematics at Colorado State University. His current interests are in communication networks and optimization methods. He coauthored the recent book, An Introduction to Optimization, 2nd Edition, Wiley-Interscience, 2001. He was on the editorial board of the IEEE Transactions on Automatic Control, and is currently an editor for Computer Networks. He is an IEEE Control Systems Society Distinguished Lecturer. He received the NSF CAREER Award in 1995 and the ASEE Frederick Emmons Terman Award in 1998. Ness B. Shroff received his Ph.D. degree from Columbia University, NY in 1994. He is currently an Associate Professor in the School of Electrical and Computer Engineering at Purdue University. His research interests span the areas of wireless and wireline communication networks. He is especially interested in fundamental problems in the design, performance, scheduling, capacity, pricing, and control of these networks. His research is funded by various companies such as Intel, Hewlett Packard, Nortel, AT&T, and L. G. Electronics; and government agencies such as the National Science Foundation, Indiana Dept. of Transportation, and the Indiana 21st Century fund. Dr. Shroff is an editor for IEEE/ACM Trans. on Networking and the Computer Networks Journal, and past editor of IEEE Communications Letters. He was the conference chair for the 14th Annual IEEE Computer Communications Workshop (in Estes Park, CO, October 1999) and program co-chair for the symposium on high-speed networks, Globecom 2001 (San Francisco, CA, November 2000). He is also the Technical Program co-chair for IEEE INFOCOM'03 and panel co-chair for ACM Mobicom'02. He received the NSF CAREER award in 1996.     

A Development Environment for OSA-Based Applications over the Interworked WLAN and Cellular Networks

In this paper, we propose an OSA-based development environment for interworking WLAN and 3G cellular networks. The main goal of our work is to establish and create an environment that can serve as a demonstration of a working network for OSA-based application developers while featuring mobile services over the interworked LAN and 3G cellular networks. The proposed simulating environment has (i) a location update scheme that is used to obtain mobile users' locations and status information over the interworked WLAN and cellular networks, (ii) an instant message gateway (IMG) simulator that is developed to send and receive generic messages over the interworked WLAN and cellular networks, and (iii) a mapping of Parlay APIs onto SIP signaling messages for multiparty call applications over the interworked WLAN and cellular networks. An illustrated OSA-based application that utilizes the corresponding system functions and modules is developed and verified using the proposed simulating environment. Chung-Ming Huang received the B.S. degree in Electrical Engineering from National Taiwan University on 1984/6, and the M.S. and Ph.D. degrees in Computer and Information Science from The Ohio State University on 1987/12 and 1991/6 respectively. He is currently a professor in Department of Computer Science and Information Engineering, National Cheng Kung University, Taiwan, R.O.C. He is the director of The Promotion Center for Network Applications and Services, Innovative Communication Education Project, Ministry of Education, Taiwan, R.O.C. His research interests include broadband Internet and applications, wireless and mobile network protocols, ubiquitous computing and communications, and multimedia streaming. Tz-Heng Hsu received the B.S. degree from Department of Computer Science and Information Engineering, Feng Chia University on 1996/6, and the M.S. degree and Ph.D from Department of Computer Science and Information Engineering, National Cheng Kung University on 1998/7 and 2005/7, Taiwan, R.O.C. He is currently a assistant professor in Department of Computer Science and Information Engineering, Southern Taiwan University of Technology. His research interests are wireless and mobile network protocols, applications over interworked WLAN and cellular networks and communications, and multimedia streaming. Chih-Wen Chao received the B.S. degree from Department of Engineering Science, National Cheng Kung University on 2003/6, and the M.S. degree from Department of Computer Science and Information Engineering, National Cheng Kung University on 2005/7, Taiwan, R.O.C. His research interests are OSA-based applications and distributed multimedia systems.     

Mobile multi-layered IPsec

To achieve high throughput in wireless networks, smart forwarding and processing of packets in access routers is critical for overcoming the effects of the wireless links. However, these services cannot be provided if data sessions are protected using end-to-end encryption as with IPsec, because the information needed by these algorithms resides inside the portion of the packet that is encrypted, and can therefore not be used by the access routers. A previously proposed protocol, called Multi-layered IPsec (ML-IPsec) modifies IPsec in a way so that certain portions of the datagram may be exposed to intermediate network elements, enabling these elements to provide performance enhancements. In this paper we extend ML-IPsec to deal with mobility and make it suitable for wireless networks. We define and implement an efficient key distribution protocol to enable fast ML-IPsec session initialization, and two mobility protocols that are compatible with Mobile IP and maintain ML-IPsec sessions. Our measurements show that, depending on the mobility protocol chosen, integrated Mobile IP/ML-IPsec handoffs result in a pause of 53–100 milliseconds, of which only 28–75 milliseconds may be attributed to ML-IPsec. Further, we provide detailed discussion and performance measurements of our MML-IPsec implementation. We find the resulting protocol, when coupled with SNOOP, greatly increases throughput over scenarios using standard TCP over IPsec (165% on average). By profiling the MML-IPsec implementation, we determine the bottleneck to be sending packets over the wireless link. In addition, we propose and implement an extension to MML-IPsec, called dynamic MML-IPsec, in which a flow may switch between plaintext, IPsec and MML-IPsec. Using dynamic MML-IPsec, we can balance the tradeoff between performance and security. Heesook Choi is a Ph.D. candidate in the Department of Computer Science and Engineering at the Pennsylvania State University. She received her B.S. degree in Computer Science and Statistics and M.S. degree in Computer Science from the Chungnam National University, Korea, in 1990 and 1992 respectively. She was a senior research staff in Electronics and Telecommunications Research Institute (ETRI) in Korea before she enrolled in the Ph.D. program at the Pennsylvania State University in August 2002. Her research interests lie in security and privacy in distributed systems and wireless mobile networks, focusing on designing algorithms and conducting system research. Hui Song is a Ph.D. candidate in the Department of Computer Science and Engineering at the Pennsylvania State University, University Park. He received the M.E. degree in Computer Science from Tsinghua University, China in 2000. His research interests are in the areas of network and system security, wireless ad-hoc and sensor networks, and mobile computing. He was a recipient of the research assistant award of the Department of Computer Science and Engineering at the Pennsylvania State University in 2005. Guohong Cao received his BS degree from Xian Jiaotong University, Xian, China. He received the MS degree and Ph.D. degree in computer science from the Ohio State University in 1997 and 1999 respectively. Since then, he has been with the Department of Computer Science and Engineering at the Pennsylvania State University, where he is currently an Associate Professor. His research interests are wireless networks and mobile computing. He has published over one hundred papers in the areas of sensor networks, wireless network security, data dissemination, resource management, and distributed fault-tolerant computing. He is an editor of the IEEE Transactions on Mobile Computing and IEEE Transactions on Wireless Communications, a guest editor of special issue on heterogeneous wireless networks in ACM/Kluwer Mobile Networking and Applications, and has served on the program committee of many conferences. He was a recipient of the NSF CAREER award in 2001. 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 and Security 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 where he led various projects in wireless and mobile networking. He is a Bell Labs Fellow. Dr. La Porta was the founding Editor-in-Chief of the IEEE Transactions on Mobile Computing and served as Editor-in-Chief of IEEE Personal Communications Magazine. He is currently the Director of Magazines for the IEEE Communications Society and is a member of the Communications Society Board of Governors. He has published over 50 technical papers and holds 28 patents. His research interests include mobility management, signaling and control for wireless networks, mobile data systems, and protocol design.     

On Striping Traffic over Multiple IEEE 802.11(b) Wireless Channels

Due to interference, path loss, multipath fading, background noise, and many other factors, wireless communication normally cannot provide a wireless link with both a high data rate and a long transmission range. To address this problem, striping network traffic in parallel over multiple lower-data-rate but longer-transmission-range wireless channels may be used. In this paper, we propose a new striping method and evaluate its performances over multiple IEEE 802.11(b) channels under various conditions. Our extensive simulation results show that this method is quite effective for such an application. S.Y. Wang is an Associate Professor of the Department of Computer Science and Information Engineering at National Chiao Tung University, Taiwan. He received his Master and Ph.D. degree in computer science from Harvard University in 1997 and 1999, respectively. His research interests include wireless networks, Internet technologies, network simulations, and operating systems. He is the author of the NCTUns 2.0 network simulator and emulator, which is being widely used by network and communication researchers. More information about the tool is available at http://NSL.csie.nctu.edu.tw/nctuns.html. C.H. Hwang received his master degree in computer science from NCTU in 2002 and currently is working for a network company. C.L. Chou currently is a third-year Ph.D. student at the Department of Computer Science and Information Engineering, National Chiao TungUniversity (NCTU), Taiwan. He received his master degree in computer science from NCTU in 2002.     

Multi-radio diversity in wireless networks

This paper describes the Multi-Radio Diversity (MRD) wireless system, which uses path diversity to improve loss resilience in wireless local area networks (WLANs). MRD coordinates wireless receptions among multiple radios to improve loss resilience in the face of path-dependent frame corruption over the radio. MRD incorporates two techniques to recover from bit errors and lower the loss rates observed by higher layers, without consuming much extra bandwidth. The first technique is frame combining, in which multiple, possibly erroneous, copies of a given frame are combined together in an attempt to recover the frame without retransmission. The second technique is a low-overhead retransmission scheme called request-for-acknowledgment (RFA), which operates above the link layer and below the network layer to attempt to recover from frame combining failures. We present an analysis that determines how the parameters for these algorithms should be chosen. We have designed and implemented MRD as a fully functional WLAN infrastructure based on 802.11a. We evaluate the MRD system under several different physical configurations, using both UDP and TCP, and measured throughput gains up to 3× over single radio communication schemes employing 802.11’s autorate adaptation scheme. Computer and Communication Sciences, EPFL, Switzerland. Allen Miu received his Ph.D. degree at the Massachusetts Institute of Technology in 2006 and is currently a wireless systems architect at Ruckus Wireless, Inc. He received his S.M. in Computer Science from MIT and a B.Sc. with highest honors in Electrical Engineering and Computer Science from the University of California at Berkeley. He previously worked on the Cricket Indoor Location System and was a research intern at Microsoft Research, Redmond in 2000 and Hewlett-Packard Laboratories, Palo Alto in 2002. His research interests include wireless networks, location systems, mobile computing, and embedded systems. Hari Balakrishnan is an Associate Professor in the EECS Department and a member of the Computer Science and Artificial Intelligence Laboratory (CSAIL) at MIT. His research interests is in the area of networked computer systems. In addition to many widely cited papers, several systems developed as part of his research are available in the public domain. He received a Ph.D. in Computer Science from the University of California at Berkeley in 1998 and a B.Tech. from the Indian Institute of Technology (Madras) in 1993. His honors include an Alfred P. Sloan Research Fellowship (2002), an NSF CAREER Award (2000), the ACM doctoral dissertation award for his work on reliable data transport over wireless networks (1998), and seven award-winning papers at various top conferences and journals, including the IEEE Communication Society’s William R. Bennett Prize (2004). He has also received awards for excellence in teaching and research at MIT (Spira, Junior Bose, and Harold Edgerton faculty achievement awards). C. Emre Koksal received his B.S. degree in Electrical Engineering from the Middle East Technical University, Ankara in 1996. He received his S.M. and Ph.D. degrees from MIT in Electrical Engineering and Computer Science in 1998 and 2002 respectively. He was a postdoctoral fellow in the Networks and Mobile Systems Group in the Computer Science and Artificial Intelligence Laboratory at MIT until 2003. Since then he has been a senior researcher jointly in the Laboratory for Computer Communications and the Laboratory for Information Theory at EPFL, Switzerland. His general areas of interest are wireless communications, computer networks, information theory, stochastic processes and financial economics. He also has a certificate on Financial Technology from the Sloan School of Management at MIT.