Underwater Wireless Optical Communication Using Diversity Reception and Pruned-Term-Based Nonlinear DFE

Volterra series-based nonlinear equalization is widely used to ease the nonlinearity in underwater wireless optical communication (UWOC) systems. However, the conventional Volterra series-based model is of high complexity, especially for nonlinearity of higher-order terms or longer memory lengths. In this paper, to reduce the complexity of the conventional Volterra series-based nonlinear equalization, a pruned-term based nonlinear decision-feedback equalization (PT-NDFE) is proposed and experimentally demonstrated. Meanwhile, a pruned-term based absolute operation nonlinear decision-feedback equalization (PT-ANDFE) is also introduced to further balance the performance and complexity. The experimental results show that PT-NDFE exhibits comparable performance as compared to conventional NDFE with a lower complexity. While PT-ANDFE yields suboptimal performance with a slight performance degradation but brings further reduced complexity when considering performance and complexity tradeoff. Moreover, diversity reception is employed to further improve performance. The robustness of the proposed schemes in different turbidity waters is experimentally verified. The proposed scheme is promising for cost-effective UWOC systems.