Hazard avoidance in wireless sensor and actor networks

A typical wireless sensor network performs only one action: sensing the environment. Our requirement for intelligent interaction with the environment has led to the emergence of Wireless Sensor and Actor Networks (WSANs), where a group of sensors, actors, and a central coordination entity (sink) linked by wireless medium perform distributed sensing and acting tasks.In order to provide tight coupling between sensing and acting, an effective coordination mechanism is required among sensors and actors. In this context, we identify the problem of “hazards”, which is the out-of-order execution of queries and commands due to a lack of coordination between sensors and actors. We identify four types of hazards and show with an example application, the undesirable consequences of these hazards. We also identify and enumerate the associated challenges in addressing hazards. In this context, we discuss the basic design needed to address this problem efficiently. We propose a distributed and fully localized hazard-free approach that addresses the problem and the associated challenges based on the design. Through analytical studies and simulations we study the performance of the proposed solution and two basic strategies, and show that the proposed solution is efficient for a variety of network conditions.