Routing and quality of service in wireless and disruption tolerant networks

Sammanfattning: Wireless networks have become a common means of communication, and their popularity continues to rise as they enable communication in locations and settings where it was previously unfeasible. While promising many advantages, these networks also pose new challenges. The limited radio coverage, unreliable nature of the wireless channel, and mobility of network nodes can lead to frequent disruption of communication links, dynamic network topology, variable bandwidth availability, and high channel error rates. These challenges seek novel solutions to allow a growing number of wireless, mobile users to run applications and avail network services in ways similar to that in wired networks. This thesis makes contributions to three research areas related to wireless and disruption tolerant networks: (1) routing and forwarding to enable disruption tolerant communication in intermittently connected networks, (2) analysis of properties of human mobility and their effect on network protocols in disruption tolerant networks, and (3) quality of service mechanisms for wireless and mobile networks. In intermittently connected networks, there may rarely or never exist a fully connected path between a source and destination. This invalidates the basic assumption of end-to-end communication prevalent in the Internet and renders traditional routing protocols impractical. We propose PRoPHET, a novel routing protocol for intermittently connected networks. PRoPHET takes advantage of the mobility of nodes, and the predictability of that mobility for routing. The protocol and various forwarding strategies and queueing policies are studied in detail. The benefits of PRoPHET are evident on comparing its performance with contemporary work. Communication in intermittently connected and disruption tolerant networks is often highly dependent on the mobility of the nodes in the network. Thus, it is important to have good understanding of basic properties of user mobility in order to design network protocols that can operate under those conditions. Using real-life traces, we characterize human mobility patterns and their impact on forwarding algorithms in mobile networks with and without infrastructure. Finally, the thesis presents our work on two different aspects of quality of service in wireless and mobile networks. We evaluate four mechanisms for providing service differentiation in a wireless LAN, and give recommendations on their use in different scenarios. We propose a novel admission control scheme for mobile ad hoc networks, which is able to better cope with high mobility in the network compared to previous solutions.