Wireless Sensor and Actuator Networks: Algorithms and Protocols for Scalable Coordination and Data Communication

9.1 SENSOR-ACTUATOR COORDINATION

The collaborative operation of sensors enables the distributed sensing of a physical phenomenon. In wireless sensor networks (WSNs), the sink (base station) performs the functions of data collection, processing, and coordination. In wireless sensor actuator networks (WSANs), both sensor-actuator and actuator-actuator coordination are required. After sensors detect an event that has occurred in the environment, the event data is processed (e.g., aggregated with reports from nearby sensors) and transmitted to the actuators, which gather, process, and eventually reconstruct the characteristics of the event. The process of establishing data paths between sensors and actuators is referred to as sensor-actuator coordination (Melodia et al., 2007). Sensor-actuator coordination provides the transmission of event features from sensors to actuators. Sensors and actuators coordinate also for some other tasks, such as sensor placement or improving connectivity.

Akyildiz and Kasimoglu (2004) did the first comprehensive analysis on both sensor-actuator and sensor-sensor coordination. There are few main requirements on the communications in sensor-actuator coordination (Akyildiz and Kasimoglu, 2004). The communications between sensors and actuators in WSANs require energy efficiency to prolong the lifetime of the network. In some real-time applications, for example, detection of fire, the communication traffic is typically delay sensitive. Therefore, sensor-actuator ...