3.5 SYNCHRONOUS SENSOR AREA COVERAGE
3.5.1 Coverage with Low Communication Overhead
Tian and Georganas (2002) proposed a localized coverage-preserving node scheduling algorithm for synchronous sensor networks. The algorithm guarantees full coverage of the sensing area. A node decides to go to sleep mode if and only if the sensing area of the node is fully covered by the union of sensing areas of its active neighbors. A random back-off scheme was proposed to determine the time nodes make decisions. Decisions to turn off are announced to neighbors. Upon receiving such an announcement, adjacent nodes with longer back-off time periods will delete the sender's information from active neighbor lists. Therefore, sleeping neighbors (at decision time) will not be considered for sensing coverage. The algorithm was extended by Jiang and Dou (2004) by adding a round of location information exchange, and applying the perimeter coverage criterion.
Gallais et al. (2008) proposed several localized and synchronous sensor area coverage protocols for heterogeneous sensor networks. Each sensor may have its own SR and transmission radius (Gallais et al., 2008). The covering criterion presented in Theorem 3.1 was used to efficiently decide whether or not a sensing area is fully covered by neighboring sensors. Neighbor discovery is not needed. Nodes wait for a random time-out duration while receiving activity decision messages from neighbors. The maximum time-out duration can be tailored to prefer sensors ...