A coherent COFDM modulation system for a time-varying frequency-selective underwater acoustic channel

This paper considers the benefits of using orthogonal frequency division multiplexing (OFDM) and coded OFDM for underwater acoustic communications where the channel characteristics are extremely dispersive due to severe multipath propagation and Doppler spread and the channel statistics are non-stationary. The fundamental concepts and characteristics of the COFDM underwater acoustic communication system are first described. Computer simulations of a coherent COFDM system for a low frequency medium range shallow underwater acoustic (UWA) communications channel using QPSK modulation are then presented. The robustness of the technique (quantified in terms of the system constellation diagram and the bit error rate) is then demonstrated.