Energy efficiency and network lifetime are key factors in characterizing wireless sensor networks due to the nodes having a finite and exhaustible source of energy. Due to the nodes limited energy, it is vital to have the node functioning for as long as possible otherwise it will render the technology futile. Transmission is the most energy consuming activity a node undertakes, therefore by decreasing the number of unnecessary transmissions, the energy consumption in the nodes decreases significantly. In order to reduce unnecessary transmissions, energy-efficient data dissemination techniques have been developed to deliver the data using the minimum number of necessary transmissions. The topic of this thesis is to develop a routing protocol that will extend the network lifetime by introducing cognition to routing. Cognitive routing is an approach to make nodes more intelligent by utilizing information from the lower layers and network in order to make more informant decisions. Data from the physical layer can relay important information about the state of the node, its neighbors, and the surrounding environment hence enabling the node to make energy-efficient and aware decisions. The routing protocol formulates an energy profile, a channel profile and a traffic profile in order to make adapted and intelligent decisions. Diversity routing is used to increase the reliability of transmissions in the network to reduce unnecessary transmissions as communication is the primary reason for energy consumption in wireless sensor networks. Combining these two approaches in one protocol allows for cognitive routing to operate based on energy constraints obtained from the lower levels hence optimizing the process yielding a longer network lifetime. / Thesis (Master, Electrical & Computer Engineering) -- Queen's University, 2010-08-25 11:27:09.887

Wireless sensor networks (WSNs) are composed of hundreds of wireless sensors which collaborate to perform a common task. Because of the small size of wireless sensors, they have some serious limitations including very low computation capability and battery reserve. Such resource limitations require that WSN protocols to be extremely efficient. In this thesis, we focus on the Medium Access Control (MAC) layer in WSNs. We propose a MAC scheme, V-MAC, for WSNs that extends that lifetime of the network. We compare V-MAC with other MAC schemes. V-MAC uses a special mechanism to divide sensors in different groups and then all the members of a group go to sleep at the same time. V-MAC protects WSNs against denial of sleep and broadcast attacks. We present the V-MAC scheme in details and evaluate it with simulations. Our simulations show that V-MAC enjoys significantly higher throughput and network lifetime compared to other schemes.

Wireless networks have potential applications in wireless Internet connectivity, battlefields, disaster relief, and cyber-physical systems. While the nodes in these networks communicate with each other over the air, the challenges faced by and the subsequent design criteria of these networks are diverse. In this thesis, we study and discuss a few design requirements of these networks, such as efficient utilization of the network bandwidth in IEEE 802.11 infrastructure networks, evaluating utility of sensor node deployments, and security from eavesdroppers. The presence of infrastructure IEEE 802.11 based Wireless Local Area Networks (WLANs) allows mobile users to seamlessly transfer huge volumes of data. While these networks accommodate mobility, and are a cost-effective alternative to cellular networks, they are well known to display several performance anomalies. We study a few such anomalies, and provide a performance management solution for IEEE 802.11 based WLANs. On the other hand, in sensor networks, the absence of infrastructure mandates the use of adhoc network architectures. In these architectures, nodes are required to route data to gateway nodes over a multi-hop network. These gateway nodes are larger in size, and costlier in comparison with the regular nodes. In this context, we propose a unified framework that can be used to compare different deployment scenarios, and provide a means to design efficient large-scale adhoc networks. In modern times, security has become an additional design criterion in wireless networks. Traditionally, secure transmissions were enabled using cryptographic schemes. However, in recent years, researchers have explored physical layer security as an alternative to these traditional cryptographic schemes. Physical layer security enables secure transmissions at non-zero data rate between two communicating nodes, by exploiting the degraded nature of the eavesdropper channel and the inherent randomness of the wireless medium. Also, in many practical scenarios, several nodes cooperate to improve their individual secrecy rates. Therefore, in this thesis, we also study scenarios, where cooperative schemes can improve secure end-to-end data transmission rates, while adhering to an overall power budget. In spite of the presence of voluminous reservoirs of information such as digital libraries and the Internet, asking around still remains a popular means of seeking information. In scenarios where the person is interested in communal, or location-specific information, such kind of retrieval may yield better results than a global search. Hence, wireless networks should be designed, analyzed and controlled by taking into account the evolution of the underlying social networks. This alliance between social network analysis and adhoc network architectures can greatly advance the design of network protocols, especially in environments with opportunistic communications. Therefore, in addition to the above mentioned problem, in this thesis, we have also presented and studied a model that captures the temporal evolution of information in social networks with memory.