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.     

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.     

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.     

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.     

Effective Location Based Services with Dynamic Data Management in Mobile Environments

With the proliferation of mobile computing technologies, location based services have been identified as one of the most promising target application. We classify mobile information service domains based on feature characteristics of the information sources and different patterns of mobile information access. By carefully examining the service requirements, we identify the dynamic data management problem that must be addressed for effective location based services in mobile environments. We then devise a general architecture and cost model for servicing both location independent and location dependent data. Based on the architecture and cost model, we propose a set of dynamic data management strategies that employs judicious caching, proactive server pushing and neighborhood replication to reduce service cost and improve response time under changing user mobility and access patterns. Detail behavior analysis helps us in precisely capturing when and how to apply these strategies. Simulation results suggest that different strategies are effective for different types of data in response to different patterns of movement and information access. Shiow-yang Wu is an associate professor of the Department of Computer Science and Information Engineering at National Dong Hwa University, Hualien, Taiwan, R.O.C. He received the BS and MS degrees in computer engineering from National Chiao Tung University, Hsinchu, Taiwan, ROC, and the PhD degree in computer science from the University of Texas at Austin in 1984, 1986, and 1995, respectively. His research interests include data/knowledge bases, mobile computing, distributed processing, intelligence information systems, and electronic commerce. Kun-Ta Wu was born in Taipei, Taiwan, R.O.C., in 1976. He received the B.S. degree in computer science from Soochow University, Taipei, Taiwan, R.O.C., in 1999 and the M.S. degree in computer science and information engineering from National Dong Hwa University, Hualien, Taiwan, R.O.C., in 2001. Currently, he is an Assistant Researcher in the Domestic Division at Science and Technology Information Center, National Science Council, R.O.C., as a member of Information Gathering and Analysis Group of National Information and Communication Security Taskforce. His research interests include mobile computing, wireless network and information security.     

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.     

Intelligent MBWIMA/UMTS Protocol Using SDMA Scheduling in UTRA TDD Mode

The intelligent medium access control (MAC) protocol based on cascade fuzzy logic control (CFLC) using the first-duplicated space division multiple access (SDMA) scheduling for UTRA TDD mode is presented in this paper. Voice, data and video are integrated for transmission using CFLC-based movable boundary wireless multiple access in the UMTS (MBWIMA/UMTS) protocol. The CFLC-based MBWIMA/UMTS protocol performance with data rate control is optimized using the CFLC to generate the proper maximum number of voice/video slots and a suitable data rate. The first-duplicated SDMA scheduling, which provides the SDMA scheduling management, can increase the wireless mobile system capacity and reduce the voice-video dropping probability. The simulation results demonstrate that the CFLC-based MBWIMA/UMTS protocol using the first-duplicated SDMA scheduling can greatly improve both the voice-video dropping probability and data packet delay, compared with the MBWIMA/UMTS and GPRS/UMTS protocols using the first-duplicated SDMA scheduling at the expense of a small decrease in data packet throughput. Jeich Mar received the M.S. degree in electrical engineering from the National Taiwan University, Taiwan, R.O.C., in 1974 and the Ph.D. degree in electrical engineering from the University of Southern California, Los Angeles, in 1981. From 1981 to 1991, he worked as a Scientist in the Chung-Shang Institute of Science and Technology, Taiwan, where the worked on the development of a signal processor for phased array radar. He is currently a Professor in the Department of Communications Engineering, Yuan-Ze University, Taoyuan, Taiwan. His research interests include mobile communication and ap-plications of signal processing in Radar and Communication. Chih-Yang Kao was born in Hualien, Taiwan, Republic of China, 1974. He received the B.S., M.S. and Ph.D degree in electrical engineering from Yuan-Ze University, Taiwan in 1996, 1998 and 2004, respectively. He is now with Computer & Communications Research Laboratories, Industrial Technology Research Institute (CCL-ITRI). His current research interests include digital video broadcasting and wireless medium access control of next-generation mobile communication 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.     

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.     

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.     

A Mobile Ticket System Based on Personal Trusted Device

Advances in wireless network technology and the continuously increasing users of Personal Trusted Device (PTD) make the latter an ideal channel for offering personalized services to mobile users. In this paper, we apply some cryptology (such as public key infrastructure, hashing chain and digital signature) to propose a realistic mobile ticket system such that fairness, non-repudiation, anonymity, no forging, efficient verification, simplicity, practicability and obviate the embezzlement issues can be guaranteed. On the basis of PTD is more portable and personal than personal computer, we gradually perceived that the widely used PTD will present huge commerce profits for mobile ticket service provider and it is convenient to the PTD user. Yu-Yi Chen was born in Kaohsiung, Taiwan, in 1969. He received the B.S., M.S., and Ph.D. in Applied Mathematics from the National Chung Hsing University in 1991, 1993, and 1998, respectively. He is presently an assistant professor of the Department of International Business at Providence University, Taiwan. His research interests include computer cryptography, network security, and e-commerce. Chin-Ling Chen was born in Taiwan in 1961. He received the B.S. degree in Computer Science and Engineering from the Feng Cha University in 1991; the M.S. degree and Ph.D. in Applied Mathematics at National Chung Hsing University, Taichung, Taiwan, in 1999 and 2005 respectively. He is currently an assistant professor of the Department of Computer Science and Information Engineering at Chaoyang University of Technology, Taiwan. He is a member of the Chinese Association for Information Security. From 1979 to 2005, he was a senior engineer at the Chunghwa Telecom Co., Ltd. His research interests include cryptography, network security and electronic commerce. Jinn-Ke Jan was born in Taiwan in 1951. He received the B.S. degree in physics from the Catholic Fu Jen University in 1974 and the M.S. degree in information and computer science from University of Tokyo in 1980. He studied Software Engineering and Human-Computer Interface in the University of Maryland, College Park, MD, during 1984–1986. He is presently a professor in the institute of Computer Science at National Chung Hsing University. He is currently also an editor of Information and Education, an editor of Journal of Computers, and an executive member of the Chinese Association for Information Security. He is a member of IACR and member of IEEE. From 1995 to 1997, he was the Director of the Counseling Office for Overseas Chinese and Foreign Students. From 1997 to 2000, he was the Director of the Computer Center at National Chung Hsing University. His research interests include computer cryptography, human factors of designing software and information systems, ideograms I/O processing, data structures and coding theory.     

Characteristic Investigation of New Pathological Elements

A characteristic investigation of the new pathological elements (i.e voltage mirror and current mirror) has been presented. Many nullor-mirror equivalences are explored. The circuit cascadability is discussed with nullor and mirror concepts. Also, the conventional inverse network transformation has been extended for applying to the circuits with current mirror output. To demonstrate the use of presented properties, practical examples have been given. The derived circuits have been verified with HSPICE simulation and the simulation results confirm with our theoretical prediction.Hung-Yu Wang was born in Kaohsiung, Taiwan, Republic of China, on January 4, 1969. He received the Ph.D. degree in optical sciences from National Central University, Chung-Li, Taiwan in 2002.Since 1993 he has worked on promoting the prototyping IC implementation of academic researches, and propelling the collaboration of the academia and industries in Chip Implementation Center (CIC), National Science Council of the Republic of China. In 2003 he became a researcher and the deputy director in Division of Chip Implementation Service of CIC. He is currently working on South Region Office of National Chip Implementation Center, National Applied Research Laboratories as a researcher and the department manager. His research interests are in current-mode circuits design, analog IC design and analog IP design.Ching-Ting Lee was born in Taoyuan, Taiwan, R.O.C., on November 1, 1949. He received his B.S. and M.S. in Electrical Engineering Department of the National Cheng-Kung University, Taiwan, in 1972 and 1974, respectively. He received Ph.D. degree in Electrical Engineering Department from the Carnegie-Mellon University, Pittsburgh, PA, in 1982.He worked on Chung Shan Institute of Science and Technology, before he joined the Institute of Optical Sciences, National Central University, Chung-Li, Taiwan, as a Professor in 1990. He works on National Cheng-Kung University as the dean of Electrical Engineering and Computer Science and the professor or the Institute of Microelectronics, Department of Electrical Engineering in 2003. His current research interests include theory, design, and application of guided-wave structures and devices for integrated optics and waveguide lasers. His research activities have also involved in the research concerning semiconductor lasers, photodetectors and high-speed electronic devices, and their associated integration for electrooptical integrated circuits. He received the outstanding Research Professor Fellowship from the National Science Council (NSC), R.O.C. in 2000 and 2002. He also received the Optical Engineering Medal from Optical Engineering Society and Distinguish Electrical Engineering professor award from Chinese Institute of Electrical Engineering Society in 2003.Chun-Yueh Huang was born in Taichung, Taiwan, Republic of China, on March 24, 1967. He received the B.S. degree in industrial education from National Chang Hwa Normal University, Chang Hwa, Taiwan in 1991, M.S. and Ph.D. degrees both in electrical engineering from the National Cheng Kung University, Tainan, Taiwan in 1993 and 1997, respectively. Since 1999 he has been with the Kan Shan University of Technology, where he is currently Associate Professor and Chairman of Department of Electronic Engineering. His biography is included in the 7th Edition (2003–2004) of Who’s Who in Science and Engineering.His current researches include current-mode circuits design, VLSI design, analog IC design and analog IP design.     

Checkerboard-Like Routing Protocol for Ad Hoc Mobile Wireless Networks

The main purposes of this article are to relieve broadcast problem, to immunize to some prerequisites, and to reduce the number of transmitted control packets. Broadcasting control packets network-wide is the most direct and common method for finding the required destination node in ad hoc mobile wireless networks; however, this causes a lot of waste of wireless bandwidth. To remedy the problem, routing protocols demanding some prerequisites are proposed; nonetheless, hardly can they be used if these prerequisites are missed or become stale. To efficiently reduce the number of transmitted control packets, our routing protocol partitions the network into interlaced gray districts and white districts by the aid of GPS and inhibits an intermediate node residing in a white district from re-transmitting the received control packets. However, a mobile node residing in a gray district is responsible for re-transmitting them till they reach the destination node. Our routing protocol does not demand any prerequisite except the use of GPS. Each mobile node can always obtain its own location information; furthermore, the information may neither be missed nor become stale. Our routing protocol is easy to be implemented, saves precious wireless bandwidth, and reduces almost half a number of control packets as compared with pure flooding routing protocols.Ying-Kwei Ho received the B.S. degree and M.S. degree in applied mathematics and in electrical engineering from the Chung-Cheng Institute of Technology in 1987 and 1993 respectively and the Ph.D. degree in computer engineering and science from the Yuan-Ze University, Taiwan, R.O.C. He joined the Army of Taiwan, R.O.C. in 1987 and worked as a software engineer. From 1993 to 1997, he was an instructor in the War Game Center of Armed Forces University, Taiwan, R.O.C. He is currently an assistant professor of the Department of Computer Science at Chung-Cheng Institute of Technology. His research interests include mobile computing, wireless network performance simulation and evaluation, and modeling and simulation.Ru-Sheng Liu received the B.S. degree in electrical engineering from the National Cheng-Kung University, Taiwan, in 1972 and the M.S. and Ph.D. degrees in computer science from the University of Texas at Dallas, Richardson, Texas, in 1981 and1985, respectively. He is currently an associate professor in the Department of Computer Engineering and Science at Yuan-Ze University, Chungli, Taiwan. His research interests are in the areas of mobile computing, internet technology, and computer algorithms.     

VLSI Architecture for Forward Discrete Wavelet Transform Based on B-spline Factorization

Based on B-spline factorization, a new category of architectures for Discrete Wavelet Transform (DWT) is proposed in this paper. The B-spline factorization mainly consists of the B-spline part and the distributed part. The former is proposed to be constructed by use of the direct implementation or Pascal implementation. And the latter is the part introducing multipliers and can be implemented with the Type-I or Type-II polyphase decomposition. Since the degree of the distributed part is usually designed as small as possible, the proposed architectures could use fewer multipliers than previous arts, but more adders would be required. However, many adders can be implemented with smaller area and lower speed because only few adders are on the critical path. Three case studies, including the JPEG2000 default (9, 7) filter, the (6, 10) filter, and the (10, 18) filter, are given to demonstrate the efficiency of the proposed architectures.Chao-Tsung Huang was born in Kaohsiung, Taiwan, R.O.C., in 1979. He received the B.S. degree from the Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan, R.O.C., in 2001. He currently is working toward the Ph.D. degree at the Graduate Institute of Electronics Engineering, National Taiwan University. His major research interests include VLSI design and implementation for signal processing systems.Po-Chih Tseng was born in Tao-Yuan, Taiwan in 1977. He received the B.S. degree in Electrical and Control Engineering from National Chiao Tung University in 1999 and the M.S. degree in Electrical Engineering from National Taiwan University in 2001. He currently is pursuing the Ph.D. degree at the Graduate Institute of Electronics Engineering, Department of Electrical Engineering, National Taiwan University. His research interests include VLSI design and implementation for signal processing systems, energy-efficient reconfigurable computing for multimedia systems, and power-aware image and video coding systems.Liang-Gee Chen received the B.S., M.S., and Ph.D. degrees in electrical engineering from National Cheng Kung University, Tainan, Taiwan, R.O.C., in 1979, 1981, and 1986, respectively.In 1988, he joined the Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan, R.O.C. During 1993–1994, he was a Visiting Consultant in the DSP Research Department, AT&T Bell Labs, Murray Hill, NJ. In 1997, he was a Visiting Scholar of the Department of Electrical Engineering, University of Washington, Seattle. Currently, he is Professor at National Taiwan University, Taipei, Taiwan, R.O.C. His current research interests are DSP architecture design, video processor design, and video coding systems.Dr. Chen has served as an Associate Editor of IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY since 1996, as Associate Editor of the IEEE TRANSACTIONS ON VLSI SYSTEMS since 1999, and as Associate Editor of IEEE TRANSACTIONS CIRCUITS AND SYSTEMS II since 2000. He has been the Associate Editor of the Journal of Circuits, Systems, and Signal Processing since 1999, and a Guest Editor for the Journal of Video Signal Processing Systems. He is also the Associate Editor of the PROCEEDINGS OF THE IEEE. He was the General Chairman of the 7th VLSI Design/CAD Symposium in 1995 and of the 1999 IEEE Workshop on Signal Processing Systems: Design and Implementation. He is the Past-Chair of Taipei Chapter of IEEE Circuits and Systems (CAS) Society, and is a member of the IEEE CAS Technical Committee of VLSI Systems and Applications, the Technical Committee of Visual Signal Processing and Communications, and the IEEE Signal Processing Technical Committee of Design and Implementation of SP Systems. He is the Chair-Elect of the IEEE CAS Technical Committee on Multimedia Systems and Applications, During 2001-2002, he served as a Distinguished Lecturer of the IEEE CAS Society. He received the Best Paper Award from the R.O.C. Computer Society in 1990 and 1994. Annually from 1991 to 1999, he received Long-Term (Acer) Paper Awards. In 1992, he received the Best Paper Award of the 1992 Asia-Pacific Conference on circuits and systems in the VLSI design track. In 1993, he received the Annual Paper Award of the Chinese Engineer Society. In 1996 and 2000, he received the Outstanding Research Award from the National Science Council, and in 2000, the Dragon Excellence Award from Acer. He is a member of Phi Tan Phi.     

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.     

Location-aware routing protocol with dynamic adaptation of request zone for mobile ad hoc networks

One possibility direction to assist routing in Mobile Ad Hoc Network (MANET) is to use geographical location information provided by positioning devices such as global positioning systems (GPS). Instead of searching the route in the entire network blindly, position-based routing protocol uses the location information of mobile nodes to confine the route searching space into a smaller estimated range. The smaller route searching space to be searched, the less routing overhead and broadcast storm problem will occur. In this paper, we proposed a location-based routing protocol called LARDAR. There are three important characteristics be used in our protocol to improve the performance. Firstly, we use the location information of destination node to predict a smaller triangle or rectangle request zone that covers the position of destination in the past. The smaller route discovery space reduces the traffic of route request and the probability of collision. Secondly, in order to adapt the precision of the estimated request zone, and reduce the searching range, we applied a dynamic adaptation of request zone technique to trigger intermediate nodes using the location information of destination node to redefine a more precise request zone. Finally, an increasing-exclusive search approach is used to redo route discovery by a progressive increasing search angle basis when route discovery failed. This progressive increased request zone and exclusive search method is helpful to reduce routing overhead. It guarantees that the areas of route rediscovery will never exceed twice the entire network. Simulation results show that LARDAR has lower routing cost and collision than other protocols. Tzay-Farn Shih was with Department of Electrical Engineering, National Taiwan University. Tzay-Farn Shih received the B.S. degree in Information Management from Chinese Culture University, Taiwan, in 1992, the M.S. degree in Computer Science Engineering from Tatung University, Taiwan, in 1996, and the Ph.D. degree in Electrical Engineering from National Taiwan University, Taiwan, in 2006. He is presently an assistant professor of Computer Science and Information Engineering at Chaoyang University of Technology, where he initially joined in August 2006. He is currently an overseas member of the Institute of Electronics, Information and Communication Engineers (IEICE). His current research interests include computer simulation, computer networks routing protocol, wireless networks, Mobile Ad Hoc networks and sensor networks. Hsu-Chun Yen was born in Taiwan, Republic of China, on May 29, 1958. He received the B.S. degree in electrical engineering from National Taiwan University, Taiwan, in 1980, the M.S. degree in computer engineering from National Chiao-Tung University, Taiwan, in 1982, and the Ph.D. degree in computer science from the University of Texas at Austin, U.S.A., in 1986. He is presently a Professor of Electrical Engineering at National Taiwan University, where he initially joined in August 1990. From August 1986 to July 1990, he was an Assistant Professor of Computer Science at Iowa State University, Ames, Iowa, U.S.A. His current research interests include Petri net theory, formal methods, design and analysis of algorithms, and complexity theory. Dr. Yen is an editor of International Journal of Foundations of Computer Science (IJFCS, World Scientific Publisher).     

An Efficient Adaptive Grouping for Single Code Assignment in WCDMA Mobile Networks

For achieving high utilization and efficient code management of the OVSF code tree in 3G WCDMA networks, several researches have extensively studied. Based on combining both the code assignment and the reassignment mechanisms, it increases obviously high utilization and reduces completely the code blocking. Nevertheless, the required rate of traffic should be powers of two of the basic rate, i.e. 1R, 2R, 4R, …, etc., which is impractical and results in wasting the system bandwidth while the required rate is not powers of two of the basic rate. Several multi-code assignment mechanisms have proposed to reduce the waste rate. Nevertheless, these methods bring two inevitable drawbacks including, high complexity of handling multiple codes, and increasing the cost of using more rake combiners at both the base stations and mobile nodes. Therefore, we propose an adaptive grouping code assignment herein to provide a single channelization code for any possible rate of traffic, even though the required rate is not powers of two of the basic rate. Based on the dynamic programming algorithm, the adaptive grouping approach forms several calls into a group. Then it allocates a subtree to the group and adaptively shares the subtree codes for these calls in the concept of time-sharing of slots during a group cycle time. Therefore, the waste rate and code blocking are thus reduced obviously while using a single rake combiner. Since the delay problem may be occurred in such a time-sharing approach, we propose two schemes of cycle interleaving methods to reduce delay. Numerical results indicate that the proposed adaptive grouping approach reduces significantly the waste rate and thus increases the system utilization. Moreover, the proposed cycle interleaving scheme reduces data delay significantly. Ren-Hung Hwang received his M.S. and Ph.D. degrees in computer science from University of Massachusetts, Amherst, Massachusetts, USA, in 1989 and 1993, respectively. He joined the Department of Computer Science and Information Engineering, National Chung Cheng University, Chia-Yi, Taiwan, in 1993, where he is now a full Professor and the Chair of the Department of Communication Engineering. His research interests include Internet QoS, peer-to-peer infrastructure design, and 3G QoS. Ben-Jye Chang received his M.S. degree in computer engineering from University of Massachusetts, Lowell, in 1991 and the Ph.D. degree in computer science and information engineering from National Chung-Cheng University, Taiwan, in 2001. He joined the Department of Computer Science and Information Engineering faculty at Chaoyang University of Technology, Taiwan, in 2002, where he is currently an Associate Professor. His research interests include QoS-based networks, QoS wirless networking, resource management for wireless networks and mobile cellular networks, and performance evaluation of networks. Min-Xiou Chen received the BS degree in computer science and information engineering from Tung Hai University, Tai-Chung, Taiwan, in 1996, and the MS and PhD degrees in computer science and information engineering from National Chung Cheng University, Chia-Yi, Taiwan, in 1998 and 2005, respectively. He is now an assistant professor at the Department of Computer Science and Information Engineering, Chung Hua University, Hsin-Chu, Taiwan. His research interests include wireless communication, SIP, sensor network and resource management in WCDMA systems. He is a member of the IEEE. Kun-Chan Tsai received the BS degree in information engineering and computer science from Feng Chia University, Taichung, Taiwan, in 2001, and the MS degree in computer science and information engineering from National Chung Cheng University, Chia-Yi, Taiwan, in 2003. His research interests include wireless communications and resource management in WCDMA systems.     

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.     

VE-mobicast: a variant-egg-based mobicast routing protocol for sensornets

In this paper, we present a new “spatiotemporal multicast”, called a “mobicast”, protocol for supporting applications which require spatiotemporal coordination in sensornets. The spatiotemporal character of a mobicast is to forward a mobicast message to all sensor nodes that will be present at time t in some geographic zone (called the forwarding zone) Z, where both the location and shape of the forwarding zone are a function of time over some interval (t _start ,t _end ). The mobicast is constructed of a series of forwarding zones over different intervals (t _start ,t _end ), and only sensor nodes located in the forwarding zone in the time interval (t _start ,t _end ) should be awake in order to save power and extend the network lifetime. Existing protocols for a spatiotemporal variant of a multicast system were designed to support a forwarding zone that moves at a constant velocity, , in sensornets. To consider the path of a mobile entity which includes turns, this work mainly develops a new mobicast routing protocol, called the variant-egg-based mobicast (VE-mobicast) routing protocol, by utilizing the adaptive variant-egg shape of the forwarding zone to achieve high predictive accuracy. To illustrate the performance achievement, a mathematical analysis is conducted and simulation results are examined. Yuh-Shyan Chen received 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 Jan. 1996, respectively. He joined the faculty of Department of CSIE, Chung-Hua University, Taiwan, in 1996. He joined the Department of Statistic, National Taipei University in Aug. 2000, and joined the Department of CSIE, National Chung Cheng University in Aug. 2002. Dr. Chen is an associate Professor from Aug. 2003. Since 2006, he has been a Professor at the Department of CSIE, National Taipei University, Taiwan. Dr. Chen served as Co-Editors-in-Chief of International Journal of Ad Hoc and Ubiquitous Computing (IJAHUC); Editorial Board Member of Telecommunication System; Guest Editor of Telecommunication Systems, special issue on “Wireless Sensor Networks” (2004). He was a Vice Co-Chair, Wireless IP Symposium of WirelressCOM, USA (2005); Workshop Co-Chair, IEEE AHUC06, Taiwan (2006); Program Co-Chairs, IFIP NCUS06, Korea (2006). Dr. Chen also served as Program Committee Member of ICPP’03, ICDCS’04, ICCCN’01–06, MSN’05, CCN’02–06, CSA’04 06, NCS’06, MSEAT’03–06, WASN06, USN06, MHNET06, PESYS06, ML06, IWWN06, UIC06, ICWMC06, and HWN-RMQ06; IASTED Technical Committee on Telecommunications (2002–2005); WSEAS International Scientific Committee Member (from 2004). 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, and 4G system. Dr. Chen is a member of the IEEE Computer Society and Phi Tau Phi Society. Shin-Yi Ann received the B.S. degree in computer science and engineering from the National Taiwan Ocean University, Taiwan, Republic of China, in June 2002 and the M.S. degree in computer science and information engineering from National Chung Cheng University, Taiwan, Republic of China, in July 2004. His research interest includes wireless sensor network. Yun-Wei Lin received the B.S. degree in computer and information science from the Aletheia University, Taiwan, Republic of China, in June 2003 and the M.S. degree in computer science and information engineering from National Chung Cheng University, Taiwan, Republic of China, in July 2005. His research interests include mobile ad hoc network and wireless sensor network.