Doppler-Resistant Orthogonal Chirp Division Multiplexing With Multiplex Resampling for Mobile Underwater Acoustic Communication

Mobile underwater acoustic communication technology has been widely employed in marine measurement and offshore engineering. The irregular relative motion between the transmitter and receiver causes time-varying Doppler shifts, which can cause severe inter-carrier interference (ICI) and thus affect the performance of orthogonal chirp division multiplexing (OCDM) communication. Conventional techniques such as resampling and residual carrier frequency offset can only handle constant Doppler frequency shift. In this paper, we propose a new method for handling time-varying Doppler shifts by adding multiplex resampling to OCDM communications. This method extends the resampling range based on the measured Doppler standard deviation and thus reduces the bit error rate (BER) in mobile underwater acoustic communications. The application of the variable number of branches in multiplex resampling reduces the computational complexity and saves the computational cost by approximately 30% compared with the fixed number of branches. We detail the implementation and parameter selection of the Doppler-resistant OCDM in mobile underwater acoustic communication, and compare the performance of multiplex resampling and single resampling by simulation and actual measurement in Qiandao Lake. The BER and frame error ratio (FER) results verify the feasibility of the proposed method and the superiority of its anti-time-varying Doppler shifts performance.