Reliable Communications over Heterogeneous Wireless Networks

The recent years have seen an enormous advance in wireless communication technology and co-existence of various types of wireless networks, which requires effective inter-networking among the heterogeneous wireless networks in order to support user roaming over the networks while maintaining the connectivity. One of main challenges to achieve the connectivity over heterogeneous wireless networks is potential intermittent connections caused by user roaming. The issue is how to maintain the connection as the user roams and how to ensure service quality in the presence of a long disconnection period. In this dissertation, we apply the delay tolerant network (DTN) framework to heterogeneous terrestrial wireless networks, and propose a system architecture to achieve the connectivity in the presence of excessive long delays and intermittent paths. We study several possible approaches, discuss the applicability of each of the approaches and propose the super node architecture. To demonstrate the effectiveness of the proposed super node architecture, we give a simulation study that compares the system performance under the super node architecture and under the epidemic based architecture. Within the proposed architecture that employs the idea of super nodes, we further study how to effectively route a message over access networks. We present a new routing technique for mobile ad-hoc networks (MANETs) based on the DTN system architecture. We introduce the concept of virtual network topology and redefine the dominating-set based routing for the challenged network environment under consideration. In addition, we propose a time based methodology to predict the probability of future contacts between node pairs to construct the virtual network topology. We present a simulation study that demonstrates the effectiveness of the proposed routing approach as compared