Wireless and Social Networks : Some Challenges and Insights

Abstract

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.