Seasonal dependence of very low frequency basin-scale telemetry observations.

Abstract

Underwater position, navigation, and timing messages are transmitted to moored, single acoustic receivers over basin-scale distances. At a 75 Hz center frequency, the lengthy coherence time allows for successive and long-duration symbol transmissions. Analysis of 2700 M-sequence transmissions from Kauai to receiver H11S2 near Wake Island over a 1.5 yr duration and a nominal 3500 km distance yields a mean channel capacity of 0.028 bits/(s Hz). A low signal-to-noise ratio (SNR) telemetry implementation, based on the same data, achieves a raw bitrate of 0.1 bits/s (without preamble and error correction) corresponding to a gross spectral efficiency of 0.0026 bits/(s Hz). By decoding 10 800 transmitted symbols, the empirical probability of symbol error as a function of SNR is determined for three groups of symbols.