降低FSO-OFDM系统峰值平均功率比研究

Research on reducing the PAPR for FSO-OFDM system

虽然OFDM调制技术在射频领域中已得到了广泛的研究,但在无线光领域中的研究才刚开始。由于FSO-OFDM系统中采用马赫-曾德尔(MZM)调制器进行电光转换,该调制器的转移特性曲线为余弦函数,存在很大的非线性问题,因此,FSO-OFDM系统比射频OFDM系统对PAPR更加敏感。为了降低系统PAPR,重点研究了基于Golay互补序列和Reed-Muller码的编码类降低PAPR的算法,对输入的二进制序列进行编码,产生Golay互补序列作为传输码字,来降低系统PAPR,并通过MonteCarlo方法对其进行了仿真验证,结果表明该算法在QPSK系统中可以将峰值功率控制在3 dB以下,在QAM系统中峰值功率可以降低至4.5 dB。

Although the OFDM modulation technique has been studied extensively （RF） field, it is just beginning in the field of free space optical communication in radio frequency The Mach-Zehnder modulator （MZM）, whose transfer characteristic curve was cosine function, was adopted to achieve electro-optic conversion in the FSO-OFDM system. Due to its big non-linear problem, so FSO-OFDM system was more sensitive to the PAPR than RF system. In order to reduce the PAPR, the algorithm which based on the Golay complementary sequences and Reed-Muller codes was focused on. The input binary sequences were encoded to generate Golay complementary sequence as transmission codes to reduce the PAPR. At last, the algorithm was confirmed by Monte Carlo approach. It is shown that this algorithm can control the peak power below 3 dB in the QPSK system and reduce it to about 4.5 dB in the QAM system.