A design of direct-sequence spread-spectrum acoustic communication system

A direct-sequence spread-spectrum (DSSS) acoustic communication system was proposed. It used a Gold-sequence family to transmit information, which was recovered by a RAKE filter receiver. A Gold-sequence family of large size and of large main-to-side lobe ratio (MSLR) of the quasi-orthogonal function was selected, and the spectral efficiency was improved without communication reliability loss. For the transmitter, message bits were loaded in one symbol by selecting the sequence number in the Gold-sequence family and pulse position modulation (PPM) was used. For the receiver, the transmitted information was recovered using a cyclic correlation method. Field sea experiments were conducted to test this DSSS system. It was robust at low signal-to-noise ratio (SNR) and over complex multipath channels.