Research On The Technology Of Node Deployment In Wireless Sensor Networks

Wireless sensor network has become a hotspot in the research of the domestic and foreign scholars because of the wide using and practicability. Wireless sensor networks are generally deployed on a large scale which is the no man’s land or the relatively harsh environment area. The nodes are randomly thrown to the target area by planes, and rely on battery power. Human can’t update the batteries, so the energy of the node is limited. Therefore, how to improve nodes’energy efficiency to prolong the service life of the network also is a top priority of research in wireless sensor network. The nodes deployment is the foundation of wireless sensor networks, is the premise of the follow-up monitoring task. This paper focuses on the nodes deployment strategy. In the first part, we consider the static wireless sensor network, and study on the minimum cover set of deployment strategy. Then, joining mobile nodes of a certain proportion at the initial deployment, the strategy of self-healing holes is been studied by us.In the initial deployment, a lot of the nodes are thrown in the target area. If all of the nodes are joined to the network, it will lead to a complex communication. The monitoring data exist lots of redundancy; data fusion more difficult; and increase energy consumption of the nodes. All of these are unnecessary. It not only is useless to monitor the target, but also increases the difficulty of network and energy consumption, is not desirable. Therefore, a coverage strategy of static wireless sensor networks is proposed based on minimal cover set, called MCS-GAA (Minimal Cover Set-Greedy Approximation Algorithm). This algorithm use Mr. Lu’s GA algorithm for reference, and take the residual energy of nodes and simultaneous covering two intersections into account. The nodes are added into the cover set one by one, and each time the node which is selected to join the cover set is the optimal node of current situation. So it is an approximate greedy algorithm. In order to evaluate the performance of MCS-GAA algorithm, it is compared with the CVT algorithm and GA algorithm by simulation on the MATLAB platform. The simulation results show that the GAA algorithm are better than the other two algorithms in the coverage set size and network coverage redundancy.After a period of operation, due to the node energy depletion or environmental damage and other reasons, there will be some nodes death constantly. Cover holes will appear in the network. In this paper, for healing the holes, a strategy is proposed by using mobile nodes based on fuzzy logic, called FEHRA (fuzzy logic energy efficient hole repair algorithm) algorithm. The strategy contains two steps:1) use the sleeping static nodes to repair the hole. If the static node can heal the area is greater than or equal to the node’s sensing range, then wake up the static node to repair the hole. Judge the static nodes which in the hole range one by one, and update the hole area.2) After all of the static nodes in the hole region are judged over, the rest range of the hole will be repair by mobile nodes. When considering using which mobile nodes to healing the rest hole, a strategy was proposed by us based on fuzzy logic. Considering the remaining energy of mobile nodes, the distance from mobile nodes to hole, the density of mobile nodes, the membership function and the rule table were defined to select the most optimal mobile node to repair the hole. In order to evaluate the performance of the FEHRA algorithm, this paper compares it with the DCM algorithm and FSHC algorithm. The simulation results show that the FEHRA algorithm is more energy-efficient in healing hole, and the network is more balance.