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

4.8 GEOROUTING IN SENSOR AND ACTUATOR NETWORKS

Geographic routing by an adaptive targeting (RAT) protocol was studied by Shah et al. (2007). RAT provides sensor-to-actuator communication and dynamic coordination of actuators in response to emergencies. It focuses on applications in which time critical data is required to be sent from sensor nodes to actuators. A sensor node is said to be covered by an actuator if the distance between them is not greater than R. Sensors report only to a single actuator. Actuators broadcast subscribe messages to sensors in their covered areas. When they move, such a message is sent with a frequency based on speed and field dimensions. Actuator-actuator coordination is by broadcasting, whose details are not given.

Routing by adaptive targeting consists of two components: delay-constrained geographic-based routing (DC-GEO) and integrated pull/push (IPP) coordination. In IPP, actuator nodes subscribe to specific events of their interest in the field, and sensor nodes disseminate the event readings to subscribed actuators for time periods of subscription life. Sensor nodes push the data as long as there is any actuator interested for the observed event. Delay-constrained geographic-based routing employs greedy forwarding such that the delay constraint can be met as well as energy consumption of forwarding nodes is balanced.

The process of forwarding the data packets toward actuators consists of two steps. The source node sets the time to live (TTL) field ...