Low-Complexity Multi-Symbol Multi-Modulus Weighted Lookup Table Predistortion in UWOC System

Lookup table (LUT) is an efficient digital predistortion technique for mitigating the pattern dependent distortion in the field of underwater wireless optical communication (UWOC) system. However, the complexity of LUT grows geometrically when applied with high-order QAM modulation formats with multi-pattern length sequences. The complexity reduction of LUT is essential for practical applications. In this paper, we study the patterning effects of LUT predistortion and propose to reduce the LUT complexity by pruning its table entries aided with multi-modulus weighted strategy. The size of LUT has been reduced significantly in experiments, which shows that the complexity of the proposed MMW-RLUT only accounts for 17.6%, 9.8%, 4.9% and 14% of full-size LUT for 64QAM, normal 32QAM, square geometrical shaping (SGS) 32QAM and 16QAM modulated UWOC system, without degradation of performance.