Adjusting the cluster size based on the distance from the sink

One of the most important issues on the sensor network with resource-limited sensor nodes is prolonging the network lifetime by effectively utilizing the limited node energy. The most representative mechanism to achieve a long-lived sensor network is the clustering mechanism which can be further classified into the single-hop mode and the multihop mode. The single-hop mode requires that all sensor nodes in a cluster communicate directly with the cluster head (CH) via single hop and, in the multi-hop mode, sensor nodes communicate with the CH with the help of other intermediate nodes. One of the most critical factors that impact on the performance of the existing multi-hop clustering mechanism (in which the cluster size is fixed to some value, so we call this the fixed-size mechanism) is the cluster size and, without the assumption on the uniform node distribution, finding out the best cluster size is intractable. Since sensor nodes in a real sensor network are distributed non-uniformly, the fixed-size mechanism may not work best for real sensor networks. Therefore, in this paper, we propose a new dynamic-size multi-hop clustering mechanism in which the cluster size is determined according to the distance from the sink to relieve the traffic passing through the CHs near the sink. We show that our proposed scheme outperforms the existing fixed-size clustering mechanisms by carrying out numerical analysis and simulations.