FrFT-OFDM系统的低复杂度峰均功率比抑制技术研究

Peak to Average Power Ratio Reduction with Low Computational Complexity in FrFT-OFDM System

针对基于分数阶Fourier变换的OFDM系统(简称FrFT-OFDM系统)的高峰均功率比(PAPR)问题,该文提出一种低复杂度的峰均比抑制算法。通过对随机相位序列采用周期延拓至FrFT-OFDM符号长度,相位因子加权后与子载波调制前的数据相乘的方式,实现对高峰均比的有效抑制。该算法只需要一次逆离散分数阶Fourier变换(IDFrFT),所有备选信号直接通过时域chirp圆周移位的加权和得到。仿真结果表明,当备选信号个数相同时,该算法与选择映射(SeLecting Mapping,SLM)算法的PAPR抑制性能相当,比部分传输序列(Partial Transmit Sequence,PTS)算法具有更好的PAPR抑制性能,同时,该算法较SLM和PTS算法的运算量降低。

This paper proposes a low-complexity Peak to Average Power Ratio （PAPR） reduction method in Orthogonal Frequency Division Multiplexing （OFDM） system based on the Fractional Fourier Transform （FrFT）. The method reduces PAPR effectively through periodic extension of random phase sequence to the length of FrFT-OFDM symbol, weighting it with phase factors and multiplying transmitted data vector. Only one Inverse Discrete Fractional Fourier Transform （IDFrFT） operation is performed in the proposed method, and the signal candidates can be calculated in time domain via weighted summation of the chirp circularly shifted FrFT-OFDM symbols. The simulation results show that, in the case that all the methods have 32 candidates, the proposed method has almost the same performance, when compared with the SeLecting Mapping （SLM） and performs even better than the Partial Transmit Sequence （PTS）. More importantly, the proposed method has lower computational complexity compared with SLM and PTS.