Statistical characterization of very low frequency communication channels at ocean basin-scales

The bit rate for incoherent communication is estimated for low frequency sounds (75 Hz, 0.03 s resolution) transmitted 3115 km between a bottom-mounted source and a towed array. A model for short term fluctuations of sound agrees with measurements without tuning the model to the data. In particular, measured and modeled probability distributions for multipath coherence time and amplitude fluctuations are similar. Temporal evolution of the oceanographic component of the model is governed by the linear dispersion relation for internal gravity waves. The acoustic component of the model is based on the sound-speed insensitive parabolic approximation. This is the third attempt to use the model to predict short-term acoustic fluctuations at basin-scales. All three attempts yielded results similar to measurements. If further comparisons between the model and data are successful, the model could be used to design and implement low frequency communication systems. A simulation yields 4 bits per second for a Benthos modem using an incoherent communication scheme via frequency shift keying