Multiple convergence zone acoustic telemetry feasibility test report

Abstract : This report describes a multiple CZ acoustic telemetry experiment conducted off the coast of California 1/28/90 - 2/2/90. The goal was to design a maximally robust high speed underwater modem suitable for data telemetry for submerged platforms and moorings. Six modulation methods were used to transmit data at rates from 1 to 1000 baud, corresponding to bit rates up to 3kbit/sec. The modulation formates were: (1) Multiple Frequency Shift Keying (MFSK) and Binary Expurgated Modulation (BEX-PERM); (2) Duobinary Frequency Shift Keying; (3) Quadrature Phase - Shift Keying (QPSK); (4) Quadrature Amplitude Modulation (8QAM); (5) Continuous Phase Modulation (CPM) 2DPM4 and 2CPFSK4; and (6) Trellis coded 8PSK. In addition, a large number of channel probe sequences was transmitted in order to estimate channel multipath, fluctuation dynamics and spatial diversity characteristics relevant to acoustic data telemetry. The data was transmitted from a 1 kHz source suspended from the R/V McGaw, and received on a multichannel vertical array tended by the R/V Point Sur The multichannel data was digitally recorded using floating-point digitizers and stored on optical disk for further processing. Approximate transmission ranges were 70, 140, 200 and 250 km. Approximately 8 hrs of transmission were recorded at each data range.