Wireless Sensor and Actor Networks (WSANs) are composed of a large number of heterogeneous nodes called sensors and actors. The collaborative operation of sensors enables the distributed sensing of a physical phenomenon, while the role of actors is to collect and process sensor data and perform appropriate actions. After sensors detect an event, the event data are transmitted to the actors, which are in charge of estimating the event features. WSANs can be considered a distributed control system that needs to timely react to sensor information with an effective action. For this reason, real-time coordination and communication in WSANs is an important concern so as to provide right actions timely, while the energy efficiency of network communications is also a crucial aspect because of the resource constraints of sensors. In this paper, a coordination framework for WSANs is addressed. A new sensor-actor coordination model is proposed, based on an event-driven clustering algorithm in which cluster formation is triggered by an event so that clusters are created on-the-fly to optimally react to the event itself and provide the required reliability with minimum energy expenditure. The optimal solution is determined by mathematical programming and a distributed solution is also proposed. In addition, a new model for actor-actor coordination is introduced for a class of coordination problems in which the area to be acted upon is optimally split among different actors. An auction-based distributed solution of the problem is also presented. Performance evaluation shows how global network objectives, such as compliance with real-time constraints and minimum energy consumption, can be reached in the proposed framework with simple interactions between sensors and actors that are suitable for large-scale networks of energy-constrained devices.

Keywords

Wireless Sensor and Actor Networks, Mathematical programming/optimization, Real-Time Communications, Energy Efficiency, Task Allocation.