A phase coherent all-digital transmitter and receiver for underwater acoustic communication systems

This paper proposes a phase coherent all-digital transmitter and receiver system for underwater communication, which allows the system to reduce complexity and increase robustness in time variant underwater environments. It is designed in the digital domain except for amplifiers and implemented by using a multiple digital signal processors (DSPs) system. For phase coherent reception, conventional systems employed phase-locked loop (PLL) and delay-locked loop (DLL) for synchronization, but this paper suggests a new frame synchronization scheme based on the quadrature receiver structure without using them. We show experimental results in the underwater anechoic basin at KRISO. The results indicate that the frame synchronization is performed without PLL. Also, we show that the adaptive equalizer can compensate frame synchronization error and the correction capability is dependent on the length of equalizer.