Estimation by cross-correlation of the number of nodes in underwater networks

Knowledge of the number of nodes in a network is very useful in practical network operations. To date techniques employed to estimate the number of nodes in a network have been based on some aspect of the communications protocol(s) in use. Unfortunately, underwater networks have properties such as long propagation delay, high absorption, and dispersion that limit protocol-based techniques for estimating the number of nodes in a network. This paper investigates the estimation of the number of signal sources (N) in a region of interest through the cross-correlation of the acoustic signals received at two nodes. It is shown that the N can be expressed as a function of the mean and the standard deviation of the cross-correlation function. On the assumption that the signal sources are nodes in an underwater network, this method can be used to estimate the number of network nodes.