Byoung Lee

Graduation Semester and Year




Document Type


Degree Name

Doctor of Philosophy in Computer Science


Computer Science and Engineering

First Advisor

Ramez Elmasri


Wireless sensor networks, which consist of a large number of sensor nodes and a base station, are used for many applications aimed at collecting information. Each sensor node is equipped with a small amount of battery, limited memory, finite radio range and small CPU. It gathers required information and it sends the information to the base station. The large number of sensors can cover a large area by cooperating with each other to build a multi-hop wireless network. However, the small amount of battery is one of the critical concerns because sensor network life time depends on battery longevity. It is hard to replace or recharge the battery in each sensor node. Generally a sensor node consumes its energy during processing, receiving, transmitting and overhearing of messages. Among those, we focus on reducing the data communication and overhearing energy consumption. In order to accomplish these tasks, we propose novel energy efficient routing structures and wakeup schemes in this dissertation.First we propose an energy balanced technique for in-network aggregation with multiple tree structure (MULT). We try to reduce concentrating network traffic on a few special nodes. For building the multiple tree structure, we first create node clusters, and then connect the nodes in each cluster. Finally with cluster head nodes, we construct a multiple tree structure. In the second technique, we propose a sensor network subtree merge algorithm (SNSM), which uses the union of disjoint set forest algorithm to avoid unnecessary energy consumption in ancestor nodes for routing. We reduce the energy consumption for routing in sensor network for spatial range query through the SNSM algorithm. We apply SNSM algorithm to a minimum spanning tree structure. For our third contribution, we make a wakeup scheme to reduce the overhearing energy consumption using different wakeup time scheduling on children nodes. Our wakeup scheme includes two wakeup schedules. One is odd and even wakeup scheduling (OEWS) and another is individual wakeup scheduling (IWS). There is a trade off between reducing overhearing energy consumption and delay time. Therefore we propose double tree structure called DTS to reduce the delay time. Simulation results illustrate that our energy efficient routing structures and wakeup schemes extend the sensor network lifetime and make a small trade-off between energy consumption and delay time.


Computer Sciences | Physical Sciences and Mathematics


Degree granted by The University of Texas at Arlington