Inter-node distance estimation from ambient acoustic noise in mobile underwater sensor arrays

As the number of units in underwater sensor arrays grow, low-cost localization becomes increasingly important to maintain network scalability. Methods using ambient ocean noise are promising solutions because they do not require external infrastructure, nor expensive on-board sensors. Here we extend past work in stationary array element localization from correlations of ambient noise to a mobile sensor array [1]. After obtaining inter-node distance estimates using ambient noise correlations, these distances can be used to determine a relative localization of an array of mobile underwater sensor platforms without introducing any external infrastructure or on-board localization sensors. In this work we explore the effects of receiver mobility on inter-node distance estimation via correlations of ambient acoustic noise. Through analysis and simulation, we develop an exact solution along with a more tractable approximation to the peak amplitude of the Time-Domain Green's Function between the two mobile receivers, which provides an estimate of their spatial separation. Here we demonstrate that the mobile noise correlation amplitude at the time delay for a sound wave traveling from one receiver to the other can be modeled with the wideband ambiguity function of a single sound source. We then use this approximation to discuss selection of design parameters and their effects on the noise correlation function.