Applications of the MFSK Acoustic Communications System

Requirements for control and data acquisition from remote subsea wellheads are expected to grow during the 1980s. In this paper, the implementation of an underwater acoustic approach is developed, together with the companion problems-achieving hardware reliability and low power consumption. A companion paper, "MFSK-The Basis for Robust Acoustical Communications," outlines a technique for achieving reliable acoustical communications. The goals that were set included long-range communications, up to 10 kiloyards; dependable communications, 99-percent correct messages under worst-case noise and multipath; secure communications, probability of an undetected error of less than 1 by
10^{-8}
; high reliability, 95-percent probability of successful operation for 5 years; and operation from a practical-sized battery pack. Using acoustical communications hardware together with a microprocessor, a theme of total subsea control capability is developed. Practical examples include sequential hydraulic control with acoustical data acquisition and backup control, as well as electro-hydraulic multiplex BOP control with acoustic backup.