BER performance of the polar-coded underwater wireless optical communication

Aiming at the phenomenon of signal fading and system performance degradation due to the light intensity fluctuation and beam off-axis drift in the line-of-sight (LOS) transmission of laser-based cross-medium communication systems, which are affected by absorption, scattering, and turbulence, a joint coding scheme based on polar codes and pulse position modulation (PPM) is proposed to study the encoding and decoding as well as the method to improve system performance for laser-based signal transmission from atmosphere to underwater. The laser wireless transmission characteristics and the principle of channel merging and splitting of polar codes are analyzed. Furthermore, in terms of bit error ratio (BER) comparisons are made by simulations between the PPM systems with and without polar codes over weak turbulent channels, and meanwhile the effects of code length and rate on BER are discussed. The simulation results show that, compared to the traditional PPM systems without polar codes at the same BER, a system using the joint coding of the Polar Codes and PPM can obtain a code gain from 1 to 2, namely its BER performance and anti-interference ability could be improved. And thus this research can provide a new technical means for practical applications.