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Academic Editor:Chih-Yung Chang
Northeastern University, Shenyang 110819, China
Received 21 November 2013; Revised 27 March 2014; Accepted 1 April 2014; 6 May 2014
This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
1. Introduction
Wireless sensor network (WSN) consists of a large number of autonomous sensors to monitor physical conditions of an area-of-interest. Sensor nodes typically use batteries as the power supply, and replacing the batteries may be very inconvenient in practise. Therefore, energy efficiency is one of the most crucial problems in the design and implementation of WSN [1]. Tremendous research work has been done to reduce the energy consumption of WSN to extend their lifetime (see Section 2 for a brief review of related work).
In many WSN systems, sensor nodes send the collected data to the sink nodes by multihop transmission [2, 3]. In such systems, the energy of sensor nodes closer to the sink node is exhausted faster than others because of traffic imbalance among sensor nodes. This is known as the energy hole problem. Xu et al. [4] reported that when the energy of sensor nodes that are one hop away from the sink node is completely exhausted, nodes farther away still have up to 93% of their initial energy. Therefore, it is a big challenge to balance the sensor node energy depletion and increase the lifetime of large-scale WSN systems.
In this paper, we study the lifetime maximization problem of a larger-scale three-dimensional WSN with uniform sensor node distribution. Comparing with one- and two-dimensional WSN, three-dimensional WSN has received little attention in literatures. However, three-dimensional WSN is useful in many environmental monitoring applications. Examples include the GreenOrbs project [5], Wagyromag, and sea monitoring [6]. A three-dimensional monitoring system would help people to get more intuitive and accurate sensor data. The WSN in this study is based on the corona structure, where the whole three-dimensional monitoring area is a globe, and the globe is divided into layers by concentric spheres. The nodes in the same layer are configured with the same transmission distance (which decides the transmission energy consumption of the node)....