An unequal cluster-based routing protocol in wireless sensor networks

Clustering provides an effective way for prolong5 ing the lifetime of a wireless sensor network. Current clus6 tering algorithms usually utilize two techniques, selecting 7 cluster heads with more residual energy and rotating clus8 ter heads periodically, to distribute the energy consumption 9 among nodes in each cluster and extend the network lifetime. 10 However, they rarely consider the hot spot problem in mul11 tihop sensor networks. When cluster heads cooperate with 12 each other to forward their data to the base station, the cluster 13 heads closer to the base station are burdened with heavier re14 lay traffic and tend to die much faster, leaving areas of the net15 work uncovered and causing network partition. To mitigate 16 the hot spot problem, we propose an Unequal Cluster-based 17 Routing (UCR) protocol. It groups the nodes into clusters of 18 unequal sizes. Cluster heads closer to the base station have 19 smaller cluster sizes than those farther from the base station, 20 thus they can preserve some energy for the inter-cluster data 21 forwarding. A greedy geographic and energy-aware rout22 ing protocol is designed for the inter-cluster communica23 tion, which considers the tradeoff between the energy cost 24 of relay paths and the residual energy of relay nodes. Sim25 ulation results show that UCR mitigates the hot spot prob26 lem and achieves an obvious improvement on the network 27