Design and implementation of an all-digital real-time underwater acoustic transceiver using digital signal processors

In this paper, an all-digital transceiver for real-time underwater acoustic (UWA) communications is developed using digital signal processors (DSPs). The design of the transceiver is based on the direct-sequence spread-spectrum (DS/SS) modulation scheme, in which the timing synchronization is efficiently achieved by employing a sliding correlator and a modified noncoherent delay-locked loop for code acquisition and tracking, respectively. In addition, an equal-gain combiner (EGC) and an adaptive decision-feedback equalizer (DFE) are included in the receiver to enhance its interference rejection capability under multipath fading environments. Several real-time UWA transmission tests are conducted in an experimental water tank to evaluate the performance of the transceiver. The test data include plain text and simple image files. The test result shows that reliable real-time UWA communications can be accomplished by the proposed transceiver.