Vaining Comparison And Opportunity - 9989 Words

Research efforts on preserving connectivity and coverage As aforementioned, one of the primary objectives of WSNs is to provide full coverage of an FoI as long as possible. Many tasks (i.e., targets tracking or boundary surveillance) require full coverage of FoI at any time. In this case, how to guarantee/preserve the connectivity of a WSN while achieving full coverage is critically important. Many approaches are addressed for this integrated issue. In order to determine the degree of the coverage and connectivity, some researcher tried to derive discriminants for locally determining coverageconnectivity. For example, in [69], by assuming Rc ≠¥ 2Rs, Huang et al. derived a distributed method for the self-testing of coverage-connectivity: In†¦show more content†¦Moreover, many studies have exploited the mobility of sensors to improve the quality of coverage and connectivity. Authors in [74] presented a relative neighborhood graph based connectivity preservation scheme. By assuming that the initial system is connected, the mobile sensor nodes move in the calculated direction and distance (limited by the communication range of the sensor) to approach the required system coverage. During the movement, the connectivity between each pair of connected nodes is preserved. Simultaneously, longer communication links are replaced by the multiple shorter links (by adding intermediate relaying nodes) to balance the transmission energy consumption of the system. As an improvement, the authors in [75] adopted the similar idea to deploy the mobile sensor while avoiding the obstacles in the FoI. In [76], Le et al. designed an environment learning-based phenomenon monitoring system in which the sensor nodes can move to the optimal positions which is selected based on the information that iteratively learned about the environment. Because nodes’ movements consume a large portion of the constrained energy in sensor nodes which will further shorten the lifetime of the WSN. Consequently, the question, â€Å"how to minimize the movements of mobile nodes while achieving desired coverage and connectivity in WSNs†, needs to be solved. In [77], authors