Experimental demonstration of 16QAM/QPSK OFDM-NOMA VLC with LDPC codes and analog pre-equalization

Non-orthogonal multiple access (NOMA) via power domain multiplexing is widely deployed in bandwidth-limited light-emitting-diode-based visible-light-communication (VLC) systems due to its excellent spectral efficiency. However, quadrature phase-shift keying (QPSK) or even lower-order modulation formats are dominant; therefore, the spectral efficiency can be further improved with the higher-order quadrature amplitude modulation (QAM) modulation. Besides, error propagation (EP) deteriorates the system performance of lower power users during demodulation with imperfect successive interference cancellation. In this paper, we experimentally demonstrate a low-density parity-check (LDPC) codes-enabled 16QAM/QPSK modulation scheme for the orthogonal frequency-division multiplexing-based NOMA-VLC transmission system. Moreover, the analog pre-equalization technique is employed to enhance the modulation bandwidth. The experimental results exhibit that the EP can be significantly mitigated, and the bit error rate performance of lower power users can be improved by up to about 2 orders of magnitude by using LDPC codes and an analog pre-equalization technique. (C) 2022 Optica Publishing Group