Error Characterization of Differential Detection and Non-Differential Detection for MIMO UWOC Systems in Seawater Turbulent Channels

Abstract

Ocean turbulence is an important factor affecting the development of underwater wireless optical communication (UWOC). To improve the error characteristics of the underwater optical communication system, we propose a differential detection-based multi-receiver-multi-transmitter (MIMO) underwater laser communication transmission method. Additionally, we derive the expressions for calculating the average BER of the MIMO underwater wireless optical communication system with differential detection and non-differential detection in the case that the two transmitted beams are completely uncorrelated. The error characteristics of the MIMO system are simulated and analyzed from the perspective of ocean turbulence intensity and link distance. The simulation results show that the differential detection method has a lower average BER compared to the non-differential detection method in the case of moderate-to-strong ocean turbulence. In addition, the differential detection methods do not have the error floor effect, and non-differential detection methods have the error floor effect. The more the turbulence intensity affects the average BER of the MIMO UWOC system with the increase of the communication link distance, the more obvious is the effect of the turbulence intensity on the average BER of the MIMO UWOC system. Accordingly, the simulation analysis shows that the differential detection method is more suitable for the construction of communication links under long-distance and medium-strong turbulence.

Performance Evaluation of Maximum Ratio Combining Diversity Technology and Traditional System Based on Comprehensive Noise Analysis in Underwater Wireless Optical Communication

“…However, the UWOC system is subject to great challenges since the optical beam is attenuated significantly by the scattering and absorption effects of water's molecular and suspending particles, such as chlorophyll, water-soluble salts, and minerals. In addition, the UWOC system also suffers from serious underwater optical turbulence, which is physically the refractive index fluctuation of water with random variations in temperature and pressure [10,11]. These adverse effects will increase the path loss, expand the impulse response, and cause multipath fading.…”