MULTIPATH PROPAGATION'S IMPACT ON ESTIMATING THE SIZE OF UNDERWATER NETWORKS

Abstract The number of node (cardinality)’ is an important operation parameter in networks, and the parameter can be obtained through conventional protocol-based approaches, yet these methods have several drawbacks for underwater presence, including great propagation delay, high error rate, node motion, capture effect that cannot be negligible and significant path loss. In order to design a good cardinality estimator in this unique area of underwater networking, we have considered a statistical signal processing method namely cross-correlation of Gaussian signals observed by sensor arrays. One of the common challenges for underwater wireless communication is multipath propagation of signals, which result in inter-symbol interference (ISI). Multipath may be built up different direct and indirect paths, such as seabed, sea surface and different reflectors etc. In this paper, seabed and sea surface have been considered as the most common underwater acoustic reflectors. It is shown that, due to high dispersion coefficient of the medium, multipath effect is negligible on estimation and a generalized process of multipath compensation for any dispersion factor is obtained to improve the robustness of this scheme. KEYWORDS: Network size, Multipath effect, CCF, Different reflectors, Underwater environment