Performance Analysis of OFDM-NOMA Hybrid Scheme in Indoor Visible Light Communication

Abstract

The demand for ultra-high-speed and massive connectivity in indoor wireless environments has positioned visible light communication (VLC) as a promising complementary technology for sixth-generation (6G) networks. However, orthogonal frequency division multiple access (OFDMA) and non-orthogonal multiple access (NOMA) still face a practical trade-off between spectral efficiency and user fairness, particularly under light-emitting diode (LED) dynamic-range constraints and imperfect successive interference cancellation (SIC). This paper proposes a channel state information (CSI)-driven adaptive hybrid framework combining orthogonal frequency division multiplexing (OFDM) and NOMA for indoor multiuser VLC systems. The framework selects the transmission mode before rate evaluation through a channel-gain-ratio-based policy, thereby avoiding oracle-based maximum-rate selection. The system model includes line-of-sight (LOS)-dominant propagation, a first-order non-line-of-sight (NLOS) approximation, direct-current-biased optical OFDM (DCO-OFDM) signaling, and residual interference caused by imperfect SIC. MATLAB-based Monte Carlo simulations show that the proposed scheme achieves a sum-rate of 284.67 megabits per second at a signal-to-noise ratio (SNR) of 30 decibels, representing a 38.9 percent gain over conventional NOMA while remaining close to conventional OFDMA. The scheme also attains a Jain’s Fairness Index of 0.9773 at the same SNR and improves weak-user bit error rate (BER) relative to conventional NOMA. Sensitivity analysis indicates stable performance under variations in residual SIC, NOMA power allocation, and switching threshold. These results demonstrate a practical trade-off between throughput and fairness for next-generation indoor VLC deployments.