Measured channel sounding characteristics and their relationship with the performance of a parametric communication system

This paper presents the results of experiments carried out in the Mediterranean Sea using parametric transduction to effect acoustic communication. Short duration, pulsed carrier signals were used to estimate the impulse response of the channel and these observations were related to the performance of a parametric communication system operating under the same conditions. The statistical characteristics and spectra of the amplitude and phase fluctuations were used to analyse the pulsed response over short observation periods. Typically, the amplitude fluctuations experienced by the main path were Ricean in nature with a spectral content in the sub-Hertz range whilst the phase fluctuations tended towards more Gaussian-like behaviour with a comparable frequency spectra. Under these conditions a high data rate differential phase shift keyed (DPSK) telemetry link was established over a 1.7 km path. The ensuing performance of the communication system, characterised by the bit error rate for various symbol rates, is presented and demonstrates the viability of a parametric telemetry system.