Abstract
The limited modulation bandwidth of the light emitting diodes (LEDs) presents
a challenge in the development of practical high-data-rate visible light
communication (VLC) systems. In this paper, a novel adaptive coded
probabilistic shaping (PS)-based nonorthogonal multiple access (NOMA) scheme is
proposed to improve spectral efficiency (SE) of VLC systems in multiuser uplink
communication scenarios. The proposed scheme adapts its rate to the optical
signal-to-noise ratio (OSNR) by utilizing non-uniformly distributed discrete
constellation symbols and low complexity channel encoder. Furthermore, an
alternate optimization algorithm is proposed to determine the optimal channel
coding rate, constellation spacing, and probability mass function (PMF) of each
user. The extensive numerical results show that the proposed PS-based NOMA
scheme closely approaches the capacity of NOMA with fine granularity. Presented
results demonstrate the effectiveness of our scheme in improving the SE of VLC
systems in multiuser scenarios. For instance, our scheme exhibits substantial
SE gains over existing schemes, namely, the pairwise coded modulation (PCM),
geometric shaping (GS), and uniform-distribution schemes. These findings
highlight the potential of our approach to significantly enhance VLC systems.