Performance comparison of QAM and APSK-based bit-power-loading discrete multi-tone modulation in underwater visible light communication system

Abstract

In this paper, an underwater visible light communication (UVLC) system is set up to simulate the nonlinear noise channel. Then we adopted Levin-Campello (LC) bit-load algorithm to make the system adaptively modulate input signals according to sub-channel gains and signal noise ratio. The bitrate and bit error rate (BER) are utilized as the main indexes to quantize the performance of amplitude phase shift keying (APSK) and the square geometrical shaping (QAM) modulation format in both linear and nonlinear operating range. Experimental results show that particularly in nonlinear operation range. The result indicates that APSK modulation format can achieve the higher bitrate than that with QAM modulation format, and with LC bit-load algorithm APSK can achieve a 3.18Gbps transmission rate below 3.8 x 10^-3 BER threshold.