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

3.6 MULTICOVERAGE BY SENSORS

Fault tolerance of some applications may require that any point in the sensing area is covered multiple times. Even if single coverage suffices, it may be energy-efficient to partition and schedule the sensors to work in round-robin manner, such that the sensing area could be covered multiple times.

Gallais and Carle (2007) proposed an adaptive localized algorithm for multiple sensor area coverage. The algorithm follows the assumptions and algorithms, including options, outlined in Gallais et al. (2008) and in Section 3.5.1. The only difference is in the evaluation criterion applied to reach a decision. To address the k-coverage problem, the basic idea is to divide the sensing area into grids, and it is required that every grid point be covered by at least k neighbors. Alternatively, the k-cover criteria from Theorem 3.5 could be utilized.

In the k-layer coverage problem, active neighbors add their layer number to their positive acknowledgments. A node determines that its sensing area is fully k-layer covered if and only if there are at least k active layers and each of them fully covers sensing area of the node. The problem was studied in Simplot-Ryl et al. (2005). The algorithm (Simplot-Ryl et al., 2005) adjusts k dynamically to reflect the sensor density. Each sensor node selects a time-out. Suppose that node A received a message from a neighbor that informed about i, the cover layer number selected by that neighbor, and its geographic coordinates. ...