APSK调制在基于自适应OFDM的可见光 通信系统中的应用研究 

正交频分复用（OFDM）技术具有频谱利用率高、抗干扰性能好等优点，在基于发光二极管（LED）的可见光通信系统中得到广泛应用。为了减小LED非线性的影响，将幅度-相移联合键控（APSK）与OFDM技术相结合的传输方式引入可见光通信系统中。同时为了提高可见光通信系统的整体性能，实现系统带宽资源的充分利用，将OFDM调制与自适应技术相结合，即根据信道状况的不同，在各个子信道上使用相应阶数的APSK调制方式。文章介绍了3种典型的基于自适应资源分配算法的OFDM技术，并与基于相同阶数APSK调制的OFDM技术进行比较。仿真结果表明，APSK信号的包络要比QAM信号小，自适应OFDM技术的性能要明显优于基于相同阶数APSK调制的OFDM技术。

Application Research of APSK Modulation in Visible Light Communication Systems Based on Adaptive OFDM

Orthogonal frequency division multiplexing （OFDM） technology has advantages of high spectrum efficiency, prominent anti-jamming performance, etc. It is widely used in visible light communication （VLC） systems based on Light Emitting Diode （LED）. In order to decrease the effect of the nonlinear characteristics of LED, a transmission system based on amplitude-phase shift keying （APSK） modulation combined with OFDM technology is introduced in VLC system. This paper also combines OFDM modulation with adaptive technology which uses the corresponding order of APSK modulation in each sub-channel according to the difference in channel condition with the purpose of improving the whole performance of VLC system and making full use of the system bandwidth resource. Three typical OFDM systems with adaptive resource allocation algorithms are introduced, and compared with other OFDM systems based on the same order of APSK modulation. The simulation result shows that the envelope of the APSK signal is smaller than the QAM signal and the per- formance of the adaptive OFDM is obviously better than the OFDM system based on the same order of APSK modulation.