Filterbank multicarrier for underwater communications

Underwater acoustic (UWA) communication has been the topic of many recent research publications. Because of small ratio of the carrier frequency over the signal band- width, UWA channels may be categorized as super broadband channels. UWA channels are also highly dispersive in both time (because of widely spread multipaths) and frequency (because of fast variation of the gain of each path). In order to combat time dispersion of UWA channels, it has been proposed to deploy orthogonal frequency division multiplexing (OFDM) technique with a sufficiently long cyclic prefix (CP). Moreover, to keep the bandwidth efficiency of the transmission high, long OFDM symbols that are at least four times the length of the CP should be used. This leads to an OFDM system in which channel variation over each OFDM symbol may be unacceptably large, thus, results in a significant level of intercarrier interference (ICI). In this paper, we propose the use of a particular class of filter bank multicarrier (FBMC) systems that are optimized for robust performance in the doubly dispersive UWA channels. The FBMC method which we use is a particular implementation of the filtered multitone (FMT) that we have recently developed. Real data from an at-sea experiment (ACOMM10) are used to demonstrate the superior performance of the proposed FMT system over OFDM.