Distributed systems of sensors and actuators (2009)

The world we live in is becoming smarter. Miniature sensors and actuators integrated with processors are being embedded in our environments to monitor and control the physical processes. These sensor and actuator systems are evolving towards a physically heterogeneous and distributed but functionally coherent environment consisting of both wired and wireless communication components. Battery-powered networked devices are increasingly more common. Mobile ad hoc and wireless sensor and actuator networks are receiving considerable research attention. Applications of intelligent networked sensor and actuator systems are tremendous and have the potential to dwarf the 20th century computing revolution. They include intelligent traffic control and safety, advanced automotive systems, process control, energy conservation, environmental control, advanced medical and health care devices and systems, critical infrastructure control, communications systems, distributed robotics, and security surveillance and protection. For example, transportation systems could benefit considerably from better embedded intelligence in automobiles and in transportation infrastructures, which could improve safety and efficiency. Embedded sensor and actuator systems are not new. Yet most existing systems are special purpose, closed systems with tightly coupled components. Networking and managing a large number of embedded sensors and actuators poses significant technical challenges. For example, in a network environment, the behaviors of sensor and actuator systems are much more unpredictable, and it is impossible to test software under all possible conditions. The technical challenges are not only efficiency, but also robustness, scalability, and predictability. These unique characteristics in the design of distributed systems of sensors and actuators have motivated a growing interest and a considerable amount of research activities in this emerging area. This special issue includes a collection of 13 outstanding research papers which cover diverse topics on the design, analysis, experimental evaluation, and applications of distributed systems of sensors and actuators, particularly the ones connected through wireless networks. This special issue begins with three survey papers on wireless sensor networks (WSN): applications in intelligent transportation systems, radio power management, and mobility-aware MAC protocols. In “Wireless sensor networks in intelligent transportation systems,” Tubaishat et al. reviewed existing sensor network technologies and applications for intelligent transportation systems and proposed new methods for using WSN in traffic modeling and estimation and traffic control that outperform existing methods. In “Mobility handling in MAC for wireless ad hoc networks,” Raja and Su reviewed the current state of the arts in handling mobility in sensor networks, presented simulation results to analyze existing mobility-aware MAC protocols, and discussed open issues in dealing with mobility in sensor networks. In “Towards unified radio power management for wireless sensor networks,” Xing et al. reviewed existing transmission power control and sleep scheduling approaches to reducing radio power consumption in the transmission state and the idle state and proposed a Unified Radio Power Management framework for the design and implementation of holistic radio power management solutions in WSN. The next three papers address architecture, middleware, and data storage issues in WSN. In “Lifetime-maximized cluster association in two-tiered wireless sensor networks,” Song et al. studied the two-tiered WSN architecture and proposed an optimal cluster association algorithm to maximize the overall network lifetime. In “Embedding standard distributed object-oriented middlewares in wireless sensor networks,” Moya et al. analyzed the design space available to middleware developers in the context of WSN and presented a development framework based on standard distributed objects and a set of specific services designed to support highly dynamic and scalable WSN applications. In “Improving data centric storage with diffuse caching in wireless sensor networks,” Ma et al. studied data-centric storage problems in a sensor network and proposed new diffuse caching techniques to alleviate the hot-spot problem and reduce the message overheads. The following three papers present new methods for data aggregation and image delivery in sensor networks. In “Isolines: Efficient spatio-temporal data aggregation in sensor networks,” Solis and Obraczka introduced an energy-efficient data collection technique that takes advantage of spatial and temporal data correlation for monitoring continuously changing conditions. In “Reward oriented packet filtering algorithm for wireless sensor networks,” Shu et al. studied packet filtering for reducing energy consumption in sensor networks and proposed a two-tier buffer model and two packet filtering algorithms for real time and non-real time transmissions, respectively. In “An adaptive approach for image encryption and secure transmission over multirate wireless sensor networks,” Wang et al. proposed a new adaptive secure image delivery approach to achieve effective and efficient image encryption based on an optimal transmission rate in terms of energy efficiency in WSN. The final four papers propose new methods for routing and topology control in wireless networks. In “Energy-efficient geographic multicast routing for error-prone wireless sensor networks,” Sanchez and Ruiz proposed a new protocol, Localized Energy-Efficient Multicast Algorithm, to address the error-prone nature of wireless links when designing routing protocols for WSN. In “Receiver-oriented load-balancing and reliable routing in wireless sensor networks,” Chen et al. proposed a novel receiver-oriented load-balancing and reliable routing protocol that achieves relatively longer network lifetime and higher reliability than other existing schemes. In “QuESt: A QoS-based energy efficient sensor routing protocol,” Saxena et al. used multi-objective genetic algorithm to design a QoS-based energy-efficient sensor routing protocol that determines application-specific, near-optimal sensory-routes demand by optimizing multiple QoS parameters and energy consumption. In “A novel distributed MCDS approximation algorithm for wireless sensor networks,” Xie et al. proposed a novel distributed approximation algorithm to construct the minimal connected dominating set for WSN. This algorithm generates smaller connected dominating sets while requiring less communication overhead compared with the existing distributed approximation algorithms. We thank all the authors who submitted their papers to this special issue. Owing to the limitation of space, we can only include limited number of papers in the special issue. We are grateful to all the reviewers for their time and efforts in carefully reviewing all the papers and providing valuable review comments. We also thank the Editor-in-Chief, Mohsen Guizani, for his continuous support for this special issue, and all the publication staff for their support during the publishing process.