IEEE TRANSACTIONS ON COMPUTERS, VOL. 46, NO. 3, MARCH 1997 257
Guest Editors’ Introduction—
Mobile Computing:
When Mobility Meets Computation
Imrich Chlamtac,
Fellow
,
IEEE
, and Yi-Bing Lin,
Senior Member
,
IEEE
—————————— ✦ —————————— One of the most challenging and interesting recent trends in
the computer and telecommunications industries is the in-tegration of mobile communications and computing. The resulting distributed network, referred to as a mobile com-puting system, is in more that one way fundamentally dif-ferent from conventional wired computer networks.
Wireless connectivity enhances the functionality of com-puting equipment by freeing communication from the lo-cation constraints of the wireline infrastructure. By chang-ing this basic characteristic, mobile computchang-ing systems op-erate on a set of assumptions made by traditional comput-ing systems, requircomput-ing researchers and users to redefine their model of networked computing.
The successful use of mobile computing faces several challenges, among them:
• The communications link between the mobile host and the base station is unpredictable and varies greatly due to the constantly changing location of the mobile nodes and interference of nonnetwork entities such as buildings.
• The topology of the network changes rapidly due to the movement and resulting connections and discon-nections of the mobile nodes.
• The available bandwidth is limited and variable, de-pending on location. Channel reuse must, therefore, be an integral part of the channel access system in or-der to provide service to as many potential subscrib-ers as possible.
• The power available to mobile nodes is limited and, as a result, the poser required for transmitting and re-ceiving must be minimized.
These constraints are unique to computer networks de-signed for mobile nodes and need to be addressed in order to operate mobile computer networks which can handle large numbers of subscribers, each moving at various speeds across cells while requiring different types of service from the network.
This environment creates new challenges to both the mobile telecommunications and computing fields. Conse-quently, research in the emerging mobile computing field needs to cover a wide area of topics and scenarios.
This special issue consists of eight papers and two brief
correspondences which address various aspects of several of the above mentioned topics.
In Ajay V. Bakre and B.R. Badrinath’s article, the Indirect TCP (I-TCP) approach is proposed and investigated for mobile computing. The approach isolates mobility and wireless related problems from the traditional computing platform by using mobility support routers as intermediar-ies, which also provide backward compatibility with fixed network protocols. Throughput comparison with regular (BSD) TCP shows that I-TCP performs significantly better in a wide range related to wireless losses and host mobility.
Michele Zorzi and Ramesh R. Rao’s article studies error control and energy consumption for mobile communica-tions. The study indicates that classic ARQ strategies lead to a considerable waste of energy. Based on the investiga-tion, a probing scheme is being proposed for energy saving based on slowing down the transmission rate when the radio channel is impaired.
In a mobile computing environment, the performance of a remote file access protocol, such as NSF, may be poor due to low bandwidth and high error rates of the wireless links. Rohit Dube, Cynthia D. Rais, and Satish K. Tripathi’s article proposes two mechanisms to improve NSF performance over wireless links: and aggressive NSF client and link-level retransmissions. Experiments show that compared with the traditional NSF approach, the new scheme improves re-sponse time by up to 62%, which brings the performance to within 5% of that obtained in the optimal case.
The paper by Qi Lu and M. Satyanarayanan deals with the issue of providing traditional support for improved data consistency under the resources constraints of mobile clients. The isolation-only transaction (IOT) mechanism of the Coda File System was used to collect the data on re-source consumption. The data shows that the rere-source con-servation techniques reduce the demands on CPU and I/O usage, disk space, and RVM space. That is, a severely re-source-constrained mobile client can benefit from the im-proved consistency offered by the IOT mechanism.
Kyungshik Lim and Yann-Hang Lee propose an optimal partitioning scheme to minimize the communication cost in a highway mobile computing environment. In this envi-ronment, the radio cells are grouped into clusters. The scheme provides optimal partitioning so that the net cost of the intracluster and the intercluster communications is minimized. The scheme is a dynamic programming algo-rithm that takes into account the physical topology con-straints of the linear arangement of physical cells in high-way cellular systems.
0018-9340/97/$10.00 © 1997 IEEE
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• I. Chlamtac is with the Erik Jonsson School of Engineering and Computer Science, University of Texas at Dallas, P.O. Box 830688, MS EC33, Rich-ardson, TX 83068. E-mail: [email protected].
• Y.-B. Lin is with the Department of Computer Science and Information, National Chiao Tung University.
258 IEEE TRANSACTIONS ON COMPUTERS, VOL. 46, NO. 3, MARCH 1997
Xuefeng Dong and Tan-Hwang Lai propose a mobile call setup and path migration protocol in a cluster of DQDB. The protocol uses a link-state-like routing method for path selection and a source-routing-based scheme for path es-tablishment. In addition, a labeling scheme is used to carry the path information needed by the source routing protocol in a single 53-octet DQDB slot, which results in efficient source routing.
Anthony Joseph, Joshua A. Tauber, and M. Frans Kaashoek describe a software toolkit called “Rover” devel-oped to support the construction of both mobile-transparent and mobile-aware applications. Rover provides a set of programming and communication abstractions that enable the construction of mobile applications with good availability, concurrency, fault tolerance, consistency, and adaptation.
Sridhar Alagar and S. Venkatesan propose three causal ordering algorithms for distributed mobile systems. The first algorithm handles the resource constraints of the mo-bile hosts for a small-scale system and does not allow grace-ful host disconnection and connection. The second algo-rithm eliminates this disadvantage at the cost of inhibiting some messages. The third algorithm integrates the two al-gorithms to yield good performance for specific environ-ment conditions.
In one of the two brief correspondence contributions, Kin K. Leung proposes the Primary-Writer Protocol which allows mobile user records in a personal communication network to be efficiently distributed in different databases. While this protocol may result in misrouted calls, the per-formance study indicates that misrouting probability is very small for expected customer behavior while the saving of the signaling traffic is significant.
The brief contribution by B. Gavish and Suresh Sridhar studies priority-oriented control policies for channel as-signment in cellular networks. This investigation indicates that for a given set of conditions, the threshold priority policy can be significantly better than other policies.
We would like to express our sincere thanks to all the authors of the 64 submitted papers and the more than 150 reviewers who provided more than 250 reports for this spe-cial issue. Also, we would like to thank Jane Liu, the Editor-in-Chief, and Satish Tripathi, the Managing Editor, for their assistance in editing this special issue.
The work of Imrich Chlamtac was supported in part by the U.S. Army Research Office under contract DAAH04-95-1-04443. The work of Yi-Bing Lin was supported in part by the Microelectronics and Information Systems Research Center, National Chiao Tung University, and the National Science Council of the Republic of China under contract NSC 86-2213-E-009-072.
Imrich Chlamtac holds a PhD in com-puter science from the University of Minnesota (1979), and BSc and MSc de-grees in mathematics awarded with Highest Distinction. He is a professor and holds the Distinguished Chair in Telecommunications at the University of Texas at Dallas. He is also a member of the Photonics Center at Boston Univer-sity and president of BCN Inc., a company dealing with network design, integration, and technology transfer in wireless data and high speed communications jointly with Boston University.
Dr. Chlamtac’s research interests include research and implementation aspects of mobile networks and wireless communication systems, optical networks, ATM, and mul-timedia communication. He has published close to 200 pa-pers in refereed journals and conferences. He is the author of more than 30 invited papers, multiple book chapters, and encyclopedias. In 1981, he coauthored the first textbook on LANs entitled Local Networks: Motivation, Technology, and
Performance.
Dr. Chamtac serves as the founding Editor-in-chief of the
ACM/URSI/Baltzer Wireless Networks (WINET) and the ACM/Baltzer Journal on Special Topics in Mobile Networks and Applications (MONET). He served on the editorial boards of IEEE Transactions on Communications, Computer Networks and ISDN systems, High Speed Networks Journal, Telecommunica-tion Systems, and the Photonic Network CommunicaTelecommunica-tions Jour-nal. He was a guest editor for the Proceeding of the IEEE, the IEEE Journal on Selected Areas in Communications, IEEE Transactions on Computers, and other journals. He served as
the general chair of leading ACM and IEEE conferences and workshops, including ACM Sigcomm, ACM/IEEE Mobi-com, and IEEE CCW, and acts as the ACM/IEEE Mobicom Steering Committee chair. Dr. Chlamtac is the chairman of ACM SigMobile, the special interest group on Mobile Computing and Networking.
Dr. Chlamtac is a fellow of the IEEE, a fellow of the ACM, winner of the Society of Computer Simulation award, and ACM best paper award. In the past, he has been an IEEE, Northern Telecom, and BNR distinguished lec-turer, and a plenary and keynote speaker at leading confer-ences. He was a Fulbright Scholar and is an honorary member of the Board of Trustees at the Technical Univer-sity of Budapest.
IEEE TRANSACTIONS ON COMPUTERS, VOL. 46, NO. 3, MARCH 1997 259
Yi-Bing Lin (S’80-M-’96-SM’96) received his BSEE degree from National Cheng Kung University in 1983 and his PhD 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, New Jersey. In 1995, he was appointed a full professor in the Department of Computer Science and In-formation Engineering at National Chiao Tung University, Taiwan. In 1996, he was appointed deputy director of the Microelectronics and Information Research Center at Na-tional Chiao Tung University. His current research interests include design and analysis of personal communications services networks, mobile computing, distributed simula-tion, and performance modeling.
Dr. Lin is an associate editor of ACM Transactions on
Modeling and Computer Simulation, a subject area editor of
the Journal of Parallel and Distributed Computing, an associate editor of the International Journal in Computer Simulation,
IEEE Networks, and SIMULATION magazine, an area eidtor
of ACM Mobile Computing and Communication Review, a col-umnist for ACM Simulation Digest, and a member of the editorial boards of International Journal of Communications and Computer Simulation Modeling and Analysis. He was the program chair for the Eighth Workshop on Distributed and Parallel Simulation, the general chair for the Ninth Work-shop on Distributed and Parallel Simulation, program chair for the Second International Mobile Computing Confer-ence, and the publicity chair of ACM Sigmobile. Dr. Lin is guest editor for the ACM/Baltzer WINET special issue on personal communications as well as a guest editor for this special issue of IEEE Transactions on Computers on mobile computing. Dr. Lin is a senior member of the IEEE.
