| Wireless sensor network (WSN) is a novel network that is proposed to collect, transmit and communicate to Base Station (BS). Because the nodes of WSN always work outdoor and are battery-powered, the energy of WSN is strictly constrained. AS a result, how to prolong the lifetime of WSN is of great importance to WSNs. As far as how to prolong the lifetime of WSN is concerned, the leading solution is clustering which aims to solve two essential challenges, the scale of clusters and the distribution of cluster heads. Most of the clustering schemes existed choose the cluster heads randomly, so it is hard to guarantee that all the nodes' energy of WSN consumed equally.Based on the background mentioned above, the characteristics, applications, foregrounds of WSNs and the challenges of routing protocol design are introduced. Then several typical routing protocols of WSNs are discussed and mainly discussed cluster-based routing protocol Low Energy Adaptive Clustering Hierarchy (LEACH). After particularly analyzing LEACH protocol, the limitations of LEACH are pointed out and proved by simulation. Both analysis and simulation indicate that LEACH and other protocols that based on LEACH can not guarantee that the scale of clusters and the distribution of cluster heads are reasonable. Meanwhile, they did not point how the nodes of large scale wireless sensor network communicate with BS through multi-hop forwarding. Based on the analysis results, an unequal clustering method is pointed in this paper. Then the new clustering method is used in WSN the node communicate with BS directly and through multi-hop communication.The improved method is simulated in this paper. Compared with LEACH, improved method did not only save energy of the network but also balance all nodes' energy consumption. So, the improve method prolong the nodes' lifetime and improve WSNs' performances.At last, the main work of the thesis is concluded and the problems that need to study in future is pointed out. |
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