降低可见光通信OFDM系统峰均比的非线性压扩变换研究

Research on Non-Linear Companding Transform of PAPR Reduction in Visible Light Communication OFDM System

针对指数压扩(EC)方法在可见光通信OFDM系统中误码率(BER)性能较差的问题,提出了一种基于余弦分布的非线性压扩方法。光正交频分复用(O-OFDM)信号的概率密度函数服从高斯分布,基于余弦分布的非线性压扩方法使O-OFDM信号经过压扩变换后服从余弦分布。与EC方法相比,基于余弦分布的非线性压扩方法使系统的峰值平均功率比(PAPR)增大了1.5d B,但是系统的BER性能却提升了5d B。与经典方法 u-law变换相比,在相同PAPR性能的情况下,基于余弦分布的非线性压扩方法使系统的BER性能提升了1d B左右。通过3种方法的仿真对比,采用基于余弦分布的非线性压扩方法后压扩信号频谱的旁瓣功率最小。

In order to solve the problem that the exponential companding（ EC） method has a bad bit error ratio（ BER） performance in the visible light communication orthogonal frequency division multiplexing（ OFDM） system,the nonlinear companding method based on cosine distribution is proposed. The nonlinear companding method based on the cosine distribution can make the O-OFDM signal whose probability density distribution is Gaussian distribution obey cosine distribution. Compared with the EC method,although the new method makes the peak-to-average power ratio（ PAPR） increase by 1. 5d B,the bit error ratio（ BER） increases by 5d B. With the same PAPR performance,the new method has almost 1d B performance increase than the traditional method of u-law transformation. According to the simulation results of the three methods,the companded signal which uses the nonlinear companding method based on the cosine distribution has the smallest sidelobe power.