Path Planing Algorithms For Mobile Sink In Hiding Problem

Wireless Sensor Networks (WSNs), one of the most important technologies in 21st century, have emerged as promising platforms for many applications, such as environment monitoring, battlefield surveillance, and health care. A sensor network may consist of a large number of small sensor nodes with sensing, processing and communicating components. Also, it may contain some sink node to collect data. In the battlefield, the sensor networks are always deployed in a hostile environment and working under monitoring and detection of malicious nodes deployed by enemies. And these malicious nodes would try to monitor, detect and even destroy the nodes in sensor networks. Thus in order to bring the sensor networks into practice in the battlefield, trying to hide the sensor nodes against the detection and monitoring of malicious nodes is one of the most important steps. In this dissertation, we perform some researches on the hiding problem in this paper. And we mainly consider the following problems.Firstly, we introduce the concept of hiding problem and mobile sensor networks. According to the different hiding target and the model of sensing, we classify, generalize, and conclude the hiding problems. Sensor networks composed by mobile sink or mobile base station are also hot and novel fields in recent years. We classify these works on mobile sensor networks according to the types of mobile behavior. And we realized that these works are all about energy saving problems, coverage problems and so on. Few of them studied the hiding problems. Due to the different research targets, resolutions in previous works of energy-saving problems and coverage problems are not suitable in hiding problems.Secondly, we study the path planning problems for mobile sink in hiding problems. The aim of our research is to study how to solve the hiding problems using mobile sink under certain conditions. We first analyze and define the hiding problems, including defining the detection model of malicious nodes and the traveling limitation of mobile sink. Based on these two definitions, we convert the hiding problem into the problems that reduce the number of message transmission happened in the sensor networks. Our solution is to design a traveling path for the mobile sink to follow the path to traverse forward through the field and decrease the probability of being detected by malicious nodes while collecting data. Our solution, called TFT moving strategy, is a partial greedy algorithm. In this moving strategy, the mobile sink enters the field from one point of one edge, traverses forward through the field following the moving limitation and leaves the field from one point of the opposite edge. We also design a shortest-path routing protocol for the static nodes to transmit the data to the sink in a multi-hop way.Finally, we implement a simulation to verify the TFT moving strategy. In the simulation, we deploy the static nodes using both uniform pattern and asymmetric pattern. Also, we implement three comparative moving strategies to compare with TFT algorithm including random walk, peripheral moving, and diagonal moving. The simulation results prove that TFT moving strategy is more feasible and effective. Moreover, when the static nodes are deployed asymmetrically, TFT moving strategy, as an adaptive moving strategy, could recognize the deployment pattern of the static nodes, and find the field with high density to traverse through which generates less number of transmission in the network.