Trellis coded modulation schemes for underwater acoustic communications

Bandwidth efficient phase-coherent modulation techniques such as M-PSK have been made possible over underwater acoustic channels. It is well known that the error probability of the usual linear modulations such as M-PSK over fading channels varies inversely with the signal-to-noise ratio. To increase the slope of the error probability vs. signal-to-noise ratio curve, a diversity technique or an error correcting code may be used. The bandwidth limitations in the underwater channel being severe, we consider trellis-coded modulation for underwater acoustic communications and present simulation results performed to study their performance. Trellis-coded modulation offers a means of introducing diversity without paying in bandwidth.