APSK调制在基于OFDM可见光通信系统中的性能分析

在基于正交频分复用(Orthogonal frequency division multiplexing,OFDM)的可见光通信(Visible light communication, VLC)系统中，发光二极管(Light emitting diode,LED)的非线性特性是影响系统性能的一个重要因素。为了减小LED非线性的影响，将幅度-相移联合键控(Amplitude-phase shift keying, APSK)调制与OFDM技术相结合的传输方式引入可见光通信系统中。本文介绍了APSK调制的原理及其在基于OFDM调制的可见光通信系统中的应用，建立了基于APSK-OFDM调制的可见光通信系统模型，并与常用的基于正交幅度调制（Quadrature amplitude modulation, QAM）的OFDM系统性能进行了对比。仿真结果表明，在OFDM系统中，如果信道是理想的，QAM调制的性能要比APSK调制的性能好；但当考虑到LED的非线性特性时，后者的性能要明显优于前者。

Performance Analysis of APSK Modulation in Visible Light Communication System Based on OFDM

The nonlinear characteristics of light emitting diode (LED) is an important factor in visible light communication (VLC) system based on the orthogonal frequency division multiplexing (OFDM). To decrease the effect of LED nonlinear characteristics, a transmission system based on amplitude-phase shift keying (APSK) modulation combined with OFDM technology is introduced in the VLC system. The schemes and the applications of APSK in VLC system based on OFDM are also introduced. The VLC system model based on APSK-OFDM modulation is compared with the system based on quadrature amplitude modulation (QAM). The simulation result shows that in OFDM system, the performance of QAM system is better than that of APSK system in the ideal channel, but the result is reversed when considering the nonlinear characteristics of LED.