Research On Cluster-head Selection And Node Fault Recovering Technique In Hierarchical Wireless Sensor Networks

Wireless sensor networks (WSNs) consisit of low-cost, low-power tiny sensor nodes which can communicate with each other to perform sensing and data processing cooperatively. Cluster-head selection algorithm of hierarchical wireless sensor networks and energy consumption are two primary problems in wireless sensor networks. Cluster-head selection determines the performance of hierarchical sensor networks. The lifetime of hierarchical sensor networks depends on energy consumption. This thesis focuses on energy-efficient cluster-head selection and node fault-tolerance technique in wireless sensor networks.Firstly, this thesis introduces basis conceptions and research issues of wireless sensor networks. The classical LEACH protocol of hierarchical sensor networks is analyzed and discussed in detail. Cluster formation algorithm is the main content of LEACH protocol. Cluster-head selection is the key technique of cluster formation algorithm. Simulation programm of LEACH protocol on NS2 is researched and analyzed at length.Secondly, this thesis presents a mixed cluster-head selection algorithm (LEACH-M). In hierarchical sensor networks there is an optimum cluster-head number which makes energy consumption of a network to be least. The author of LEACH protocol said the expected number of cluster heads per round is k. Through mathematical analysis it is not k. On the contrary it is a function. According to the deficiency of cluster-head selection algorithm, this thesis proposes a mixed cluster-head selection algorithm, LEACH-M. The base station broadcasts the number of nodes which have been cluster heads. So all nodes will know the actual candidate cluster heads number. The expected number of cluster heads per round is just k.Thirdly, this thesis studies the node fault-tolerance technique of wireless sensor networks. A sub-minimum hop fault-tolerant routing algorithm is proposed to recover sensor networks from failure nodes. The failure of any node in the path is detected and recovered using the same level hop nodes. In clustered sensor networks cluster-heads fault will make cluster members unaccessible. This thesis presents a cluster-heads fault recovering algorithm. An efficient way to recover cluster is to pick out a cluster-head neighbor node as candidate cluster-head.Finally, the LEACH-M and fault-tolerance routing protocols are simulated on NS2. These simulations demonstrate that LEACH-M outperforms LEACH in terms of both the lifetime of the network and the number of packages which are received at the base station. The simulation results of fault tolerance routing protocols show this node fault recovery method is efficient.