Performance Comparison of Differential OFDM Employing Multiple Differential Detection for Underwater Acoustic Communications

Underwater acoustic communications (UWAC) suffer from double selectivity, where doubly-selective channels suffer from severe time and frequency selectivity simultaneously. These channels can be simplified as 2-path static channels with Doppler shifts. This paper compares the performances of differential orthogonal frequency division multiplexing (OFDM) employing multiple differential detection (MDD) with channel prediction on the 2-path static channels, where modulation schemes are differential quadrature phase shift keying (DQPSK) and differential trellis-coded 8 PSK (DTC8PSK). Then, computer simulation results show that differential OFDMs of DTC8PSK employing MDD with channel prediction have excellent performance on the 2-path static channels with the large difference in Doppler shifts between the two paths.