Research On Energy Efficiency And Fault Tolerance Of Wireless Sensor Network

With the combination of sensor, embedded computing, network and wireless communication, the wireless sensor network has emerged as a brand-new information access and procession technology, which surely will be broadly applied in the future.In most circumstances, a wireless sensor network is deployed under a distant and severe environment. Once it is done, it is difficult to maintain the network, and to change the nodes, battery as well. Consequently, the network's energy efficiency has become one of the most important issues when the researchers attempt to design a wireless sensor network.The operation on wireless sensor network's MAC layer consumes a lot of energy. Based on the researchers' work, a node would use from 50％up to 100％of its whole energy to keep listening the channel, so we firstly present a protocol of MAC layer, which is named CBPCEEP(Cluster Based Power Control Energy Efficient Protocol). Our protocol divided the network nodes into clusters, and we also use the power control to reduce the collision between nodes. Our ultimate goal is to improve the energy efficiency of the wireless sensor network. Among traditional cluster protocols, the network's performance would deteriorate very fast during the second half of its whole lifecycle, and it is mainly caused by the inappropriate proportion between the cluster head nodes and non-cluster head ones. Consequently, we divide the wireless sensor network's working period into two parts, and they are named normal working period and deteriorating period separately. During the normal working period, the nodes are classified into cluster head nodes and non-cluster head ones. The former ones are in charge of sampling data from the supervising area, and transfer them to the sink node. While the total network's energy reduced to the 40％of its initial energy level, it then begins its deteriorating period. During this period, the nodes' communication slots are no longer decided by the cluster head node, instead, they are arranged based on the fork distribution algorithm. The collision problem is also highly influential to the energy efficiency of the network, and we solved the problem through power control. The method to compute the communication radius is also presented.Since the wireless sensor network is energy constrained, nodes could be run out of their energy or destroyed by the environmental attacks, the CBPCEEP should fulfill the fault tolerance demand on the network layer as well. This problem is also solved by the power control, and a detailed demonstration is also proposed.In the last chapter, we discuss how to realize our CBPCEEP on the NS2 simulation platform, and the simulation result proves that the protocol satisfied our original demand.Although the CBPCEEP had reached our initial demand, there are still a lot of aspects need to be improved, such as during the deteriorating period, some new nodes would be deployed. How to recognize these new nodes and how to regulate the network to fulfill the new application demand, these issues are also relevant to the scalability of the network. Further research upon the above problems is also necessary. In a word, the wireless sensor network is still a brand-new research area, and there are still a lot of problems need to be explored.