Multicarrier coherent communications for the underwater acoustic channel

We propose a multicarrier transmission scheme for severely spread channels-but not overspread. The underwater acoustic channel is a good representative of this kind of channel. The technique of orthogonal data and pilot symbols allows coherent detection and therefore the use of QAM signal constellations. Some simulated performances of the proposed scheme are presented in both Rayleigh and Rician multipath fading. Acceptable error rate floors are shown to be possible for channel spread factor reaching 0.15.