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

3.8 OPERATION RANGE ASSIGNMENT IN WSANs

Younis et al. (2008) studied operation range assignment for both sensor nodes and actuator nodes in WSANs. A WSAN is randomly deployed in the field. It assumes that each node, either sensor or actuator, has k different operational ranges, where sensing range of sensors and acting range of actuators are referred to as operational ranges. Each node may not know the location information of its neighbors and itself. Each node is able to compute the relative positions of its neighbors (virtual coordinates) based on distance and two-hop information. The operational range assignment protocol (ORAP) (Younis et al., 2008) is for asynchronous coverage. The goal is to assign operational range for each node, such that the field area is covered with a probability that is larger than a predetermined threshold, and the operational lifetime of each individual node is prolonged as much as possible. It is assumed that coverage probability decreases with distance and increases with selected operational range.

The basic idea of ORAP is to assign longer ranges to nodes that have more residual energy. Furthermore, ORAP is periodically retriggered to reassign the operational ranges, such that the load of nodes is balanced. Operational range assignment protocol works as follows. All nodes are undecided at initialization stage. Each node selects its weight as the ratio of residual and maximal energies. Suppose possible ranges of a node are R₁ < R₂ < ··· < R_k. A node ...