THE RESEARCH ON EXTENDING THE LIFETIME OF WIRELESS SENSOR NETWORKS By YOUNGSANG YUN A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY

of dissertation Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy THE RESEARCH ON EXTENDING THE LIFETIME OF WIRELESS SENSOR NETWORKS By YoungSang Yun August 2010 Chair: Ye Xia Major: Computer Engineering We study various problems efficient energy management for wireless sensor networks. First, we research the energy efficient deployment of wireless sensor nodes so that energy consumption rates of all nodes are equal during the lifetime of the wireless sensor network. If the sensors are deployed uniformly across the network, they experience different traffic intensities and energy depletion rates depending on their locations. Usually, the sensors near the sink tend to deplete their energy sooner; when enough of them exhaust their energy, they leave holes in the network, causing the remaining nodes to be disconnected from the sink. One of the solutions to this energy-hole problem is to deploy the sensors non-uniformly. Moreover, we describe a method for deciding the sensor deployment densities so as to equalize the energy consumption rates of all nodes. The method is general and can be applied to other objectives and constraints. Second, we propose a framework to maximize the lifetime of the wireless sensor networks by using a mobile sink when the underlying applications tolerate delayed information delivery to the sink. Within a prescribed delay tolerance level, each node does not need to send the data immediately as it becomes available. Instead, the node can store the data temporarily and transmit it when the mobile sink is at the most favorable location for achieving the longest WSN lifetime. We call the proposed framework as Delay-Tolerant Mobile Sink Wireless Sensor Network. To find the best