Abstract
In this paper, we propose and evaluate a novel light-emitting diode (LED) nonlinearity estimation and compensation scheme using probabilistic Bayesian learning (PBL) for spectral-efficient visible light communication (VLC) systems. The nonlinear power-current curve of the LED transmitter can be accurately estimated by exploiting PBL regression and hence the adverse effect of LED nonlinearity can be efficiently compensated. Simulation results show that, in a 80-Mbit/s orthogonal frequency division multiplexing (OFDM)-based nonlinear VLC system, comparable bit-error rate (BER) performance can be achieved by the conventional time domain averaging (TDA)-based LED nonlinearity mitigation scheme with totally 20 training symbols (TSs) and the proposed PBL-based scheme with only a single TS. Therefore, compared with the conventional TDA scheme, the proposed PBL-based scheme can substantially reduce the required training overhead and hence greatly improve the overall spectral efficiency of bandlimited VLC systems. It is also shown that the PBL-based LED nonlinearity estimation and compensation scheme is computational efficient for the implementation in practical VLC systems.
Highlights
Visible light communication (VLC) relying on white illuminating light-emitting diodes (LEDs) has attracted extensive interest in recent years, due to its inherent advantages such as unregulated spectrum, relatively low implementation cost, enhanced physical-layer security, and electromagnetic interference-free operation [1,2]
After transmitting through the nonlinear VLC system, a corresponding vector r = [r1, r2, · · ·, r N ] T can be detected at the receiver side, which can give the raw estimation of the LED nonlinearity
Based on the analysis above, we evaluate and compare the bit-error rate (BER) performance vs. modulation index (MI) for the orthogonal frequency division multiplexing (OFDM)-based nonlinear VLC system without and with LED nonlinearity compensation, where DC-bias index (DI) = 0.5 and the length of the training symbols (TSs) is fixed at N = 64
Summary
Visible light communication (VLC) relying on white illuminating light-emitting diodes (LEDs) has attracted extensive interest in recent years, due to its inherent advantages such as unregulated spectrum, relatively low implementation cost, enhanced physical-layer security, and electromagnetic interference-free operation [1,2]. Sci. 2019, 9, 2711 multiplexing (OFDM) with high-order quadrature amplitude modulation (QAM) constellations [7] and non-orthogonal multiple access [8,9,10,11], multiple-input multiple-output (MIMO) transmission [12,13], bandwidth extension using various frequency-domain equalization schemes [14,15], and so on Another limitation is that white LEDs suffer from intrinsic nonlinearity which is mainly caused by the thermal effects. For both pre-distortion and post-distortion, time domain averaging (TDA) is usually adopted for accurate estimation of the nonlinear power-current curve of the LED before LED nonlinearity compensation. We for the first time propose a PBL-based LED nonlinearity estimation and compensation scheme for OFDM-based nonlinear VLC systems.
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