Guest editorial

International Journal of Pervasive Computing and Communications

ISSN: 1742-7371

Article publication date: 27 June 2008



(2008), "Guest editorial", International Journal of Pervasive Computing and Communications, Vol. 4 No. 2.



Emerald Group Publishing Limited

Copyright © 2008, Emerald Group Publishing Limited

Guest editorial

Article Type: Guest editorial From: International Journal of Pervasive Computing and Communications, Volume 4, Issue 2.

About the Guest Editors

Xiaobo Zhou is based at the Department of Computer Science, University of Colorado at Colorado Springs, Colorado Springs, Colorado, USA.

Bin Xiao is based at the Department of Computing, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, People's Republic of China.

Edwin H.-M. Sha is based at the Department of Computer Science, University of Texas at Dallas, Richardson, Texas, USA.

We are moving towards ubiquitous computing era, in which computing and communications happen all the time, everywhere. Its services will invade every aspect of life to the point that they are disappearing inside all sorts of appliances. The idea of such an environment emerged more than a decade ago and its evolution is due to the natural outcome of research and technological advances in embedded systems, pervasive computing and communications, wireless networks, mobile distributed computing and agent technologies, improved battery technology, and the emerging flexible software architectures. Its explosive impact on academics, industry, government, and daily life can be compared to that of electric motors over the past century but promises to revolutionize life much more profoundly than elevators, electric motors or even personal computer evolution ever did.

This special issue of International Journal of Pervasive Computing and Communications is to report both theoretical and practical solutions to some of problems and technical challenges in ubiquitous computing, and to identify new areas of research. It is in conjunction with the 2006 International Conference on Embedded and Ubiquitous Computing (EUC-06) held in Seoul, Korea, on 1-4 August 2006. There were more than 500 paper submissions from all over the world. Each paper was reviewed by at least three TPC members. It is therefore extremely difficult to select the papers for this special issue because there were so many excellent and interesting submissions. Based on the referee reports, a total of six extended papers from the proceedings of EUC-06 were selected for inclusion in the special issue. They represent recent progresses, including middleware techniques for context-aware computing, energy-efficient clustering algorithms and traffic-adaptive MAC protocols for wireless sensor networks, concurrency control for mobile transactions, and a novel speech and character recognition engine for mobile applications. All of these papers not only provide novel ideas and state-of-the-art techniques in the field, but also stimulate the future research activities in the area of ubiquitous computing.

Context-aware mobile computing requires that mobile applications adapt their behaviors to the changing context. Due to the vagueness nature of contexts and uncertainty in context aggregation for making adaptation decisions, Cheung, Yao, Cao, and Chan introduced an adaptive middleware infrastructure for mobile computing that incorporated a fuzzy-based service adaptation model as the key part of the context-aware inference engine so as to improve the effectiveness of service adaptation. They formalized the service adaptation process by using fuzzy linguistic variables to define the context situations and the rules for adopting the policies for implementing a service. They proposed fitness functions to measure the fitness degree between the current context and the predefined optimal context situation. A campus assistant mobile application is implemented to evaluate the adaptive middleware. It showed that the fuzzy-based solution performs better than conventional threshold-based approaches.

For context-aware computing, there is a requirement of scalable delivery of contexts from the middleware to numerous context-aware applications. Current pure unicast or pure broadcast-based dissemination cannot provide high scalability as well as low average latency. Mehedy et al. proposed a scalable context delivery mechanism for middleware to facilitate the development of large context-aware computing systems. It is based on a hybrid data dissemination technique where the most requested data are delivered through multicast and the rest are delivered through unicast to reduce network traffic. The mechanism dynamically prioritizes and classifies the context data depending on the number of requests and longest waiting time. Moreover, the division of bandwidth for the delivery of different contexts reduces average latency. A prototype implementation was developed based on the Jini framework and Java Reliable Multicast Service library.

Clustering is a popular approach for energy-efficient routing in wireless sensor networks. However, it is expensive that all sensor nodes know their own location information. It is also not desirable that sensor nodes send their own information in each cluster construction phase, causing overhead unnecessarily. Lee et al. proposed a low-cost dynamic clustering algorithm. Instead of using location information of each sensor node, this approach utilizes information on the remaining energy of each sensor node. The changes of cluster head nodes are dependent on the number of sensor nodes alive. The study found that using residual energy of each sensor node and changing cluster head nodes according to the number of sensor nodes alive can be very critical to enhance the sensor lifetime and data transmission rate.

IEEE 802.15.4 is a new standard designed for low rate wireless sensor networks. Chae and Kown proposed a traffic adaptive power control algorithm for beacon relayed distributed wireless sensor networks. A general coordinated sleeping algorithm and a traffic-adaptive algorithm are integrated in a new IEEE 802.15.4 MAC protocol for high-energy efficiency and high communication performance at the same time. In particular, the study focused on the beacon enabled network with respect to throughput, delay and power consumption.

Caching is a popular approach for responsiveness improvement and efficient bandwidth utilization in mobile computing environments. If the data items cached in mobile hosts are updated at the server, a server broadcasts mobile hosts the invalidation report with updated information to ensure the cache consistency. However, the strategy may not guarantee the serialization of mobile transactions. Kim and Hwang proposed FTR-MT method with four types of messages for ensuring the serialization of mobile transactions and the cache consistency of mobile hosts.

There is growing interest in intelligent multi-modal interfaces due to the popularity of mobile information devices. Suk and Chung developed a speech and character combined recognition engine for PDAs and other mobile devices. Feature extraction for speech and for character is carried out separately, but recognition is performed in an integrated engine. The recognition engine employs a continuous hidden Markov model structure that consists of variable parameter topology in order to minimize the number of model parameters and to reduce recognition time.

We are grateful to Dr Laurence Yang, the Editor-in-Chief of the International Journal of Pervasive Computing and Communications for the support and guidance throughout the project. We thank all authors for their valuable contributions and we gratefully acknowledge the efforts of the referees who spent their valuable time to provide reviews. Without their contributions and support, this special issue would not be possible. Congratulations to all authors whose papers have been included in this special issue.

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