Basin-scale ocean acoustic telemetry: Digital waveforms for transmitting oceanographic corrections

Basin-scale acoustic positioning, navigation, and timing are affected by ocean variability, which introduces uncertainty in acoustic travel time and position. Here, a cyclic code-shift keying (CCSK) direct-sequence spread-spectrum waveform is demonstrated for transmitting compact digital information over a 3500 km acoustic path. Information is encoded in cyclic shifts of a maximum-length sequence while retaining matched-filter compression and processing gain. Analysis of 42 transmissions at a 75-Hz center frequency shows symbol error rates of 4.8% or less for the first six symbols, with later-symbol performance degrading, consistent with finite channel coherence. A conceptual method for quantizing effective travel-time corrections and mapping them to the CCSK symbol alphabet is presented, providing a pathway toward integrated basin-scale navigation and ocean observation.