Hierarchical Unequal Clustering Routing Protocol For Wireless Sensor Networks

In wireless sensor networks, because of the limited battery power of senor node,how to maximize the network lifetime is the most critical issue in the design ofrouting protocol for wireless sensor networks. Out of various architecturesproposed for wireless sensor networks, clustering is shown to be a scalable andenergy efficient architecture. Cluster-based routing protocol is an importantresearch subject, which usually contains clustering algorithm and routing algorithm.Because of the limited communication capability, wireless sensor networks usuallyadopt multi-hop model to transmit data. However, multi-hop model usually result inthe “hot spot” problem. Although, the cluster head rotation can balance the energyconsumption among sensor nodes, the “hot spot” problem can not be completeavoided. Besides, frequent re-clustering will cause extra unnecessary overhead.In order to mitigate the problem mentioned above, this thesis proposes alayer-based unequal clustering algorithm. The network is divided into severallayers based on the hop count to the sink of each node. Sink selects the nodeswhose residual energy is higher than the average energy of the layer it belonged asthe cluster head candidate. Furthermore, some nodes with lower residual energy arealso selected as the candidates according to a “explore” approach. The cluster headsis elected among these candidates in each layer by a competition. The nodes in eachlayer are grouped to several non-uniform size clusters. The clusters which arecloser to the sink are smaller. During the data transmission phase, this thesis alsoproposes an asynchronous local re-clustering mechanism, that is, each layerre-selects the cluster at different frequency, which is inversed to the distance to thesink. The simulation results demonstrate that the proposed algorithm is moreeffective in prolonging the network lifetime and balancing the energy consumption.In addition, based on the clusters established, this thesis proposes an inter-clusterrouting protocol. An optimized routing policy is obtained according to a constantlyupdated cost value under a network coverage premise. At last, this thesis alsodiscusses the influence of different values of parameters to the networkperformance.