Dynamic Threshold Decision for Real-Time Underwater Wireless Optical Communication Under Turbulence

The dynamic variations in underwater turbulence cause fluctuations of the received optical power for underwater wireless optical communication (UWOC) systems, leading to performance degradation. In this letter, we demonstrate a dynamic decision threshold (DDT) scheme for underwater wireless optical communication (UWOC) systems, based on the slow fading characteristics of underwater turbulent channels. Data is transmitted in frames, with the receiver updating the decision threshold once per frame based on the amplitude of the received preamble. Additionally, we conduct a numerical simulation and demonstrate a real-time UWOC system based on the DDT scheme, achieving a 70.5 Mbps real-time communication data rate. The simulation results show that the DDT scheme provides a 5.5 dB performance improvement at a bit error rate (BER) of $10^{-6}$ in a weak turbulence channel compared to the conventional fixed decision threshold (FDT) scheme. Real-time experimental results further confirm the effectiveness of the DDT scheme, showing a 1.5 dB reduction in the required received optical power at a BER of $10^{-6}$ .