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Optimized beam selection for efficient long range underwater acoustic communication

Underwater environments are categorized as inhomogeneous habitats which complicates determining long range propagation losses. Basically, transmitted signals tend to refract and change direction in accordance to the encountered sound speed profile (SSP). Therefore, a uniform spreading beam quickly loses its uniformity and complicating the estimation of the signal strength at a beam's wave front. Such complexity degrades a node's ability in determining both the optimum direction and transmitted power to reach neighbors, leading to wasting energy and increases interference. This paper addresses these shortcomings and proposes a propagation loss estimation technique. Our technique introduces a 2D path loss model that leverages both the known SSP and our parabolic ranging method. Then a 3D extension of the model is proposed that utilizes a geographic grid to study the effect of refraction on directional beams. Essentially, the grid is used to identify candidate beams and factor the departure angles and observed SSP to account for medium inhomogeneity. We then utilize the loss models and the wave front shape to determine the best communication angle that minimizes power requirements. We validate our approach through simulation and assess its performance through comparison with contemporary methods.