LED dimming and nonlinearity effects on link selection in hybrid VLC/RF networks

Abstract

Abstract The codeployment of visible light communication (VLC) and radio frequency (RF) technologies has attracted research interest for indoor capacity enhancement. Many existing hybrid VLC/RF link selection schemes assume that the LED behaves as a perfectly linear device, an assumption that fails under practical dimming and nonlinearity conditions. The Bussgang decomposition is applied to the Rapp model to derive an effective SNR at the VLC receiver, accounting for signal attenuation and nonlinear distortion. An LED-condition-aware link selection criterion is then formulated using this corrected SNR. The VLC subsystem employs asymmetrically clipped optical OFDM (ACO-OFDM) with 16-QAM modulation, while the RF link is characterized using the WINNER II A1 indoor path loss model. The system is evaluated with 15 mobile users, 4 VLC access points, and 1 RF access point over 20 Monte Carlo realizations. Results show that the conventional scheme incurs a BER degradation exceeding two decades relative to the proposed scheme at γ = 0.3, alongside an effective SNR deficit of 15 dB. A critical nonlinearity threshold near p* ≈ 0.25–0.3 is identified, below which VLC link quality collapses regardless of user position. Handover probability peaks near this threshold, demonstrating a coupling between LED operating conditions and network switching behavior.