Study On Reducing PAPR Based On Visible Light Communication Using MIMO-OFDM

Visible Light Communication using LED (VLC-LED) is an emerging technolog. Compa-ring with WLAN, VLC-LED has a higher rate, more diverse functions and a wider use range. MIMO (multiple input multiple output), OFDM (Orthogonal Frequency Division Multip-lexing) technology are the core technologies of fourth generation mobile communications, MIMO can be effective against flat fading, but poor effect against frequency selective fading; OFDM frequency can be effective against selective fading, but ineffective against flat fading. MIMO-OFDM technology can give full play to MIMO, OFDM technology features, and make up for the shortcomings respect to each other in fading mutual.However, the presence of high OFDM PAPR (peak to average power ratio) disadvantage when OFDM and MIMO together, because MIMO-OFDM is a multi-input multi-output, so this drawback will be more prominent. Experimental results show that a higher peak to average power ratio will easily result in nonlinear distortion, when the signal through the associated power devices, thus seriously affecting the quality of VLC-LED system using MIMO-OFDM. Therefore, reducing the PAPR MIMO-OFDM has become an important way to improve the visible light communication rate.Currently PAPR reduction method can be divided into three categories:pre-distortion of signal, the probability algorithms and coding categories. In this article, we study the former two types of methods to reduce PAPR, and proposed a PTS-Companding joint algorithm superimposed training sequence to reducing PAPR in the visible light communication. Although this method at the expense of a small portion of the data transmission efficiency, but the effect of significantly reducing a PAPR system. By MATLAB simulation and analysis, when the probability threshold is 10-3, the improved algorithm have the same computational complexity and the introducing same errors of PTS-Companding algorithm, but PAPR is around 1dB lower than PTS-Companding joint algorithm; the improved algorithm introduce same errors of Companding algorithm, but PAPR is around 1.5dB lower than Companding algorithm; the improved algorithm have the same computational of PTS algorithm, but PAPR is around 3.5dB lower than PTS algorithm;the PAPR of improved algorithm is about 4.5dB lower than the original signal.