Design of an OFDM-based Differential Cyclic-Shifted DCSK System for Underwater Acoustic Communications

Given the high transmission loss, severe Doppler spread and large multipath delay in the underwater acoustic (UWA) channel, the channel estimation and tracking in the conventional orthogonal frequency division multiplexing (OFDM) based UWA systems are severely unaffordable. In this paper, we propose a low-complexity and cost-friendly OFDM-based differential cyclic-shifted differential chaos shift keying (OFDM-DCS-DCSK) system which offers a high data rate, superior robustness and enhanced system security for UWA communications without the need for channel state information (CSI). In the system, the information bits are carried by different step lengths of the cyclic shifts. At the receiver, a low-complexity detection method is used to search the position of maximum from the cyclic correlation values and therefore estimate the information bits. Finally, simulation results demonstrate the proposed OFDM-DCS-DCSK system outperforms its competitors both in bit error rate (BER) performance and in system security.