Geographical Routing And Holes Handling Algorithms For Wireless Sensor Networks

Wireless sensor network (WSN) is a network system, it consists of lots of sensor nodes distributed over a specific region and connected with the wireless medium. And it is used to gather data and accomplish some tasks together, sent the results to terminal user at last. Because of its own characteristics make it be widely used in many fields, such as medical, military, industrial, agriculture, etc. It involves hardware, software technology, wireless communication technology, sensor technology, etc. It intersperses in different subjects, and attracts many researchers or research institutions. There are a lot of research branches of WSN. Such as node coverage, time synchronization technology, multimedia technology, routing protocols, congestion control, etc. This paper mainly research on the routing protocols of WSN which based on geographic locations.Since the sensor nodes are generally random spread and uneven distribution. It is easily affected by their own and environmental factors which may lead to routing hole. The geographical routing protocols are affected greatly by the factors above. They use greedy algorithm for data transmission mostly. It is possible to get a better path while the density of network nodes is larger or the distribution of nodes is relatively uniform. It will not execute and data transmission will break when it meets the hole. If it wants to deliver data, needs to bypass the hole. The strategies of bypassing the hole are needed at this time. So if there is no reasonable way of the next hop selecting strategy or bypass the hole, it causes data transmission failure or create new hole easily. Not only waste of network resources, but also destroy the network connectivity and effective coverage of the target area. The holes problem has been a problem that should be solved immediately in WSN Geographic routing algorithms.Firstly, this paper introduces the concept of WSN and focuses on some geographical routing algorithms. And it describes and concludes the characteristics and problems of geographical routing protocols and the solutions are introduced. Reading a vast amount of literatures to gain a deeper understanding the algorithms. It puts forward the improved algorithms for the strategies of next hop selection and the methods of bypassing the hole. The experiment and simulation results show the feasibility of improved algorithm. It improves in routing hop, rate of packet success, energy consumption of node etc. Conclusion of this paper is as follows:(1) In this paper, the second chapter introduces the GPSR routing protocol and its advantages and disadvantages. The third chapter puts forward the improved algorithm EN-GPSR. It optimizes the greedy selection strategy of GPSR algorithm. It thinks about the idea of partition, and selects subarea according to the average residual energy of neighbor nodes in left and right area. Then after determine the forwarding partition, selecting the maximum transmission probability of nodes for the next hop. It takes the residual energy of node, the number of neighbor nodes, the quality of communication into consideration. It modifies the original greedy selection strategy. Through the experiment and simulation and compare with GPSR algorithm and other algorithm, the results show that the improved algorithm optimizes the routing hop, energy consumption of nodes etc.(2) Since most geographic routing algorithms change the path of transmission when them come across the hole. So the selection of the path is passive, and the number of routing hops will increase. The fourth chapter puts forward a heuristic algorithm bypassing the hole. At first it identifies the nodes of the boundary of the hole through the boundary detecting algorithm. Then it establishes a virtual coordinate system by the nodes’ coordinate. It chooses the forward zone based on this coordinate system. It chooses the intermediate nodes by the position of the source node. At last it transmits data according to the intermediate nodes. It can reduce the number of hops, save energy. At the same time, it resolves the problems some nodes can’t forward in Virtual Circle algorithm and the triangle routing and bypassing the hole blindly problems in GPSR algorithm.