An underwater acoustic OFDM communication system based on cyclic shift keying and chirp spread spectrum

Because of the limited bandwidth in underwater acoustic communication, the OFDM technology has been widely studied in recent years in order to achieve high bandwidth efficiency. However, the conventional OFDM system has the PAPR problem and is susceptible to frequency selective fading in underwater acoustic channel. In this paper, the authors proposed a novel OFDM system based on cyclic shift keying (CSK) and chirp spread spectrum (CSS) modulation. On the one hand, the CSK modulation can effectively solve the high PAPR problem, on the other hand, the CSS modulation can suppress the frequency selective fading because the multi-path signals will be expanded from each other in the frequency domain after dispreading at the receiver. In CSK-CSS-OFDM system, the upper limit of PAPR is no more than 6dB. The different simulation results and pool experimental results both show that CSK-CSS-OFDM system can improve the BER performance greatly compared with other related systems.