Ad Hoc Network Congestion Management Based on Entropy and Third-Party Nodes

Abstract

This thesis investigates the use of an entropy estimator as a metric to determine congestion in ad hoc networks. It also aims to design a network routing protocol to resolve congestion in such networks. The protocol proposed here, RAODV, builds on the AODV (Ad hoc On-demand Distance Vector) routing protocol, a reactive routing protocol intended for ad hoc networks. This thesis introduces RAODV and the algorithms it uses to mitigate congestion, and evaluates its performance in a number of settings. Unlike previous ad-hoc routing protocols, RAODV does not use the congested nodes themselves to manage congestion. Instead, RAODV detects congestion via a third party: from a monitoring neighbour node, which may also replace the congested node to repair the aected route locally. Moreover, the source node of an aected route may find a bypass route by sending a new RREQ to a monitoring neighbour node to relieve congestion. Another novel aspect of RAODV is that it proposes an entropy threshold algorithm to adapt different scenarios that may occur: Connections in ad hoc networks can be aected by serious self-interference with high entropy as the hop count increases. RAODV thus classies the nodes in the network into different categories, and the role a node can play in the network depends on its classication. A series of simulation experiments in this thesis show that RAODV can indeed improve goodput compared to AODV in certain circumstances. That is, RAODV provides benefits under congestion when the monitoring neighbour node has the ability to provide assistance to relieve congestion for the connection involved. Hence, this thesis designs experimental scenarios for its RAODV validation experiments from two aspects: Firstly, it studies scenarios that induce congestion either through interference or through contention for the same network capacity. Secondly, it investigates scenarios where a suitable alternative node/route exists in the designed network topology. The thesis concludes that the algorithms used by RAODV may also be useful in other routing protocols in other types of networks.