Node Deployment and Mobile Sinks for Wireless Sensor Networks Lifetime Improvement

Abstract

In the last two decades, and owing to advances in MEMS technologies, wireless communications and low-power electronics, the development of low-cost micro sensor nodes was possible. This enabled the deployment of Wireless Sensor Networks (WSN) comprising large numbers of nodes to monitor various physical phenomena in real-time. This can be of prime importance in several industrial, environmental, health, and military applications (Akyildiz et al., 2002; Tavares et al., 2008). A WSN may have up to hundreds or even thousands of sensor nodes densely deployed either inside or close to a monitored area. Nodes process data prior to transmission, to ensure acquisition of accurate and detailed information. Processed information is then passed on to a sink node, which transmits necessary data to some base station. Nodes may also be divided into clusters, with nodes in each cluster sending data to a particular sink node. Sensor nodes typically operate in an unattended environment, and are equipped with small, often irreplaceable batteries with limited power capacity. Thus a major consideration in WSN research is to ensure reliable transmission of data while prolonging network lifetime by making maximum use of the available energy in the nodes (Heinzelman et al., 2002). In this chapter, recent work by the authors in the area of WSN is presented with particular emphasis on maximizing the lifetime of the network. In Section 2, algorithms are described that build upon two well known WSN routing techniques, namely LEACH (Heinzelman et al., 2000) and LEACH-C (Heinzelman et al., 2002) to further optimize network lifetime through carefully planned selection of the sink nodes. Simulation results that illustrate the resulting improvement in network lifetime are presented. The position of sensor nodes need not be predetermined, which allows random deployment in inaccessible terrains. However, in some applications, the deployment of nodes at pre-specified positions is feasible. Taking advantage of this feature is thus considered to achieve further enhancement in network lifetime by considering the effect of various geometrical distributions of nodes and relative sink locations. Further reductions of the transmission energy requirements can be attained by making use of uncontrolled mobile sinks in addition to the distant fixed sinks. It is not possible to 16