Connected fixed node degree based topologies in ad hoc networks

Abstract

Topology control in an ad hoc network can provide better spatial reuse of the wireless channel and assist in conserving the power usage. A number of distributed topology control algorithms have been proposed to remove the need of a centralised controller. Distributed algorithms such as location information no topology (LINT), location information link state topology (LILT), MobileGrid (MG) and K-Neigh, aim to achieve overall network connectivity and low transmission range by maintaining a fixed node degree value. In the case of a non-uniform node distribution, maintaining a fixed node degree can unnecessarily partition a network. In this paper, we identify cases where a fixed node degree approach may result in a disconnected network and lead to isolated nodes and disjointed clusters. We propose two distributed algorithms that utilise one hop neighbours and their location information to improve the connectivity of the fixed node degree approaches, by incorporating unidirectional link information in topology control decisions and maintaining a number of critical links. A distributed mechanism to construct and maintain a network topology is proposed, which can be integrated with a neighbour discovery protocol. Furthermore, we identify and investigate the convergence issue related to LINT, MG and LILT as a result of independent direct power control decisions. We compare the performance of such algorithms with the graph based approaches. A worked example and a simulation based analysis of the proposed algorithms are provided for a number of node degree values. Simulations and analysis indicate that that the proposed algorithms are able to achieve higher connectivity for different node distributions and provide a more fault tolerant topology.