Abstract

Mobile ad hoc networks (MANET) consist of mobile nodes that autonomously establish connectivity with each other via multihop wireless communications. Swarm intelligence (SI) refers to complex behaviors that emerge from simple individual behaviors and interactions, and is often observed among social insects such as ants and honeybees.

This dissertation addresses three different problems in mobile ad hoc networks by applying the metaphor of swarm intelligence. Specifically, we address the problem of unicast routing, multicast packet delivery, and P2P systems in MANET. Applying SI techniques allows us to converge to good solutions quickly and adapt to the dynamic nature of MANETs without needing global information or centralized control.

Our unicast routing protocol, ANSI, is a hybrid protocol which works over networks with both pure MANET nodes and infrastructure nodes (hybrid networks). We show, using simulation studies, that ANSI exhibits better or comparable performance when compared to AODV under a variety of conditions in a number of scenarios, both for UDP and TCP traffic. ANSI also responds faster to link breakages and shows better utilization of the MAC layer by expending lesser network overheads per packet delivered. The performance and characteristics of ANSI also motivates the use of TCP as a legitimate evaluation tool for studying the behavior of MANET unicast routing protocols. Simulation studies show that TCP reveals properties of routing protocols which are not understood when using UDP traffic, and points to the different behavior of MANET routing protocols under different scenarios.

Our approach to packet recovery for multicast protocols, PIDIS, allows multicast routing protocols to recover lost packets without membership information and is persistent with packet recovery, while striking a balance between the variability of packet delivery and the aggressiveness of packet recovery. PIDIS maintains information about the next hops which help recover lost packets rather than maintain information about members which help recover lost packets, making the process less sensitive to topological fluctuation. Using simulation studies, we show that PIDIS shows better performance than a competing protocol by taking a different approach to gossip-based packet recovery.

Our approach to peer-to-peer (P2P) systems over MANET, BTM, adapts the BitTorrent framework to MANET by introducing features of decentralized behavior, redundant services, and cross-layer interactions. In our simulations, BTM performs better in the MANET context as compared to a straightforward implementation of BitTorrent in MANET. We attribute the favorable observations of BTM to its decentralized, resource-redundant characteristics, which, when interacting with a congestion-aware routing protocol such as ANSI, improves TCP performance, and is able to provide an appropriate medium for content distribution in MANET.