Block Space-Time Coding for Underwater Optical Massive MIMO System

The complex underwater environment will cause high attenuation and random fading of the transmitted optical signal. This paper proposes a space-time block coding (STBC) technique for this problem. The massive multiple-input multiple-output (Massive-MIMO) underwater wireless optical communication (UWOC) system is subjected to block coding processing. The STBC coding technology is used in the blocks, respectively, and the spatial multiplexing technology is used between the blocks. Through the use of Massive-MIMO technology to improve the capacity of the communication system, combined with STBC coding technology to further improve the reliability of the communication system, and the communication link of the Massive-MIMO system is fully utilized. The simulation results show that the signal-to-noise ratio (SNR) is improved by about 4dB when the bit error performance (BER) of $\mathbf{4}\times \mathbf{4}$ STBC is 10−6 higher than that of $\mathbf{2}\times \mathbf{2}$ STBC in a weak turbulent environment. In a strong turbulent environment, when the system SNR is 10dB, the BER of the multiplexing system using block STBC coding can reach 10−6.