Contents List of Figures vii List of Tables ix

Robust Loop-free On-demand Routing in Ad hoc Networks by Hari Rangarajan In this thesis, we explore new techniques for robust, efficient, loop-free on-demand routing in Mobile Ad hoc Networks (MANETs) using the same information (i.e., topology information, sequence numbers, etc.,) used in prior on-demand routing protocol proposals. We provide new insights into the robustness of protocols based on destination-sequence numbers when operating with node failures and loss of routing information, and present a new destination-sequence number framework that works correctly even with failure conditions. We also show how destination-sequence numbers can be manipulated as routing labels for improving performance, rather than being strictly treated as time-stamps. We present two different routing approaches that exploit the topology information that can be collected on-demand during the route request flood search. The first approach translates topology information into labels that are then stored at nodes in strict ”lexicographic” ordering along any successor path to a destination. Loop-freedom is maintained by allowing nodes to only pick ”smaller” labels. The second approach maintains a list of topology information that should not be trusted in-addition to the known path to a destination. Using the notion of trusted topology, nodes can always make routing decisions only with the correct topology information, which ensures loop-freedom. We conclude our research with a new on-demand routing technique that exploits the route request flood search process, which is an integral part of any on-demand routing protocol. Without requiring any additional mechanisms or information, we use the uniqueness of route requests to realize a on-demand routing framework. We, then, present extensions to the basic framework to improve performance using more information that can be collected during the flood search process. Through extensive simulations, we show that all our new proposed approaches perform better than the current state-of-the-art MANET protocols prescribed by the IETF working group.