Date of Award


Degree Type


Degree Name



Computer Science

First Advisor

Bandyopadhyay, Subir (School of Computer Science)


Computer Science.




A sensor network is an interconnection of sensor nodes, each equipped with sensor(s), a micro-processor, some memory, and a wireless transceiver. Data from sensor nodes are usually collected at a central entity known as the base station or sink. Sensor nodes are powered by lightweight batteries, and it is often not feasible to replace or recharge these batteries. Therefore, the lifetime of a sensor network is considered to be over as soon as the batteries of critical nodes are depleted. For scalability and efficient data gathering, a hierarchical two-tier architecture has been proposed in the literature, where the sensor nodes constitute the lower-tier. The network is organized as a number of clusters, and, in each cluster, one node is assigned the role of the cluster head. The cluster heads constitute the upper-tier of the network. Each cluster head receives data from the sensor nodes in the corresponding cluster and communicates the data to the base station. The cluster heads may communicate with the base station either directly, using single-hop communication, or by forming a network among themselves using multi-hop communication. In recent years, a special node, provisioned with higher initial energy and communication capabilities, called the relay node, has been proposed in the literature to act as a cluster head in hierarchical sensor networks. The three major sub-problems when designing this type of network are i) to find a suitable placement of the relay nodes within the network, using the minimal number of relay nodes, so that each sensor node can communicate effectively with its cluster head, and the upper-tier network can tolerate fault(s), ii) to assign sensor nodes to clusters in an energy efficient manner, and iii) to compute a routing scheme for the relay nodes, such that the network lifetime is maximized. In this dissertation, we present two strategies for the placement of relay nodes, and five energy-aware strategies for the clustering and routing in a hierarchical, heterogeneous, two-tiered sensor network using relay nodes as cluster heads.