How best to utilize bandwidth in underwater acoustic communication?

In a recent shallow water experiment, acoustic communication transmissions were carried out over the 10-32 kHz band in ~100 m deep water over a 3 km range. A natural question is how best to utilize that bandwidth. In one multiband approach discussed previously, the band was divided into four smaller subbands that were processed independently using time reversal decision-feedback equalizers (TR-DFEs). This paper presents a complementary wideband approach using data from the same experiment achieving a data rate of up to 60 kbits/s with 32-QAM (quadrature amplitude modulation). These results suggest that a wideband approach can be beneficial in terms of spectral efficiency with modest computational complexity using a TR-DFE.