Code-Domain Resource Mapping for Adaptive Power Allocation in Multiuser Visible Light Communication Systems Using CD-NOMA

Abstract

Visible light communication (VLC) has emerged as a promising solution for high-capacity indoor wireless networks by utilizing the unlicensed optical spectrum and existing LED infrastructure; however, efficiently supporting multiple users under limited bandwidth and power constraints remains a key challenge. This paper proposes a code-domain non-orthogonal multiple access (CD-NOMA) framework that jointly exploits resource mapping and adaptive power allocation for multiuser VLC systems, integrated with DC-biased optical OFDM (DCO-OFDM) and evaluated in a realistic indoor environment with multiple LED transmitters and randomly distributed users under heterogeneous channel conditions. Simulation results show that, at 20 dB SNR, the proposed scheme achieves a bit error rate (BER) of 10−4, representing an order-of-magnitude improvement over OMA-TDMA and OMA-FDMA; in addition, it attains a system sum rate of $\mathbf{2 3 0}-\mathbf{2 4 0} \mathbf{~ M b p s}$ $(\mathbf{2 0}-\mathbf{3 0} \%$ gain) and improves edge-user throughput by more than 40%, while maintaining a fairness index above 0.85. These results demonstrate that the proposed CD-NOMA framework significantly enhances reliabil-ity, spectral efficiency, and fairness, making it a strong candidate for next-generation indoor VLC networks.