Mobile Underwater Acoustic Communication Method Based on VTR-PLFM Spread Spectrum Modulation

Aimed at solving the serious problems of multipath effects and Doppler effect in mobile underwater acoustic communication, this study presents a mobile underwater acoustic communication method based on virtual time reversal -piecewise linear frequency modulation(VTR-PLFM) spread spectrum modulation, to resist both Doppler and multipath interference. Using the piecewise linear frequency modulation(PLFM) signal to perform orthogonal spread spectrum modulation, the PLFM signal can resist broadband Doppler frequency shift, but the PLFM system cannot perform Doppler frequency shift compensation; the virtual time reversal(VTR) technology can be used to gather the energy of multipath signals, weaken the influence of multipath, and improve the performance of the system. In addition, due to the good correlation of PLFM signals, frequency division multiplexing(FDM) can be introduced to improve the utilization rate of the spectrum and the communication rate of the system. The simulation results show that the anti-Doppler frequency shift and VTR technology can effectively improve the performance of the PLFM system. The resulting PLFM system has a lower bit error rate at a lower signal-to-noise ratio and a higher data rate. A field test is conducted to verify the feasibility of the proposed method.