Environmental impact on phase coherent underwater acoustic communications: A physics based approach

Abstract

Phase coherent acoustic communication systems, which employ joint adaptive channel equalization and phase-locking synchronization, have been shown to yield a much higher symbol rate (e.g., 2 kb/s at 3.5 kHz) by successfully tracking and updating time varying phase fluctuations in signals dominated by multipath components. This communication technique holds high promise for many applications. Its performance, however, can strongly influence (and could be limited by) the signal and noise fluctuation characteristics of the propagation channel. A statistical underwater acoustic communication model which incorporates random media propagation physics is needed to predict the performance of phase coherent acoustic communication algorithms. In this paper, the ocean acoustic propagation physics and signal processing issues which must be addressed to develop a physics-based performance prediction model are outlined. Acoustic communication simulation results for a dynamic underwater acoustic channel with time varying internal waves, fine and microfine structures, and surface waves are presented. Initial performance assessments (predictions) are given based on previously measured signal fluctuation statistics as characterized by the signal amplitude fading and phase spectra. [Work supported by the Office of Naval Research.]