基于多层循环搜索的部分传输序列算法

Partial Transmit Sequences Based on Multi-Loop search method

高峰均功率比是OFDM(Orthogonal Frequency Division Multiplexing)信号的主要缺点之一,峰均比过高会加重OFDM系统的非线性失真。部分传输序列算法(Partial Transmit Sequences,PTS)是有效降低OFDM信号峰均功率比的传统算法。该算法由于采用穷尽式搜索方式搜索最优相位因子组合,因此具有较高的计算复杂度,并且随着子数据块分组数的增加部分传输序列算法计算量呈指数形式上升,很难在实际的通信系统中得到应用。本文提出了一种具有较低计算复杂度的多层循环部分传输序列算法(Multi-Loop PTS),该算法通过对相位因子进行多层循环计算比较,舍去了部分冗余计算,且避免了相位因子搜索陷入局部最优点,在保证算法性能的同时降低了算法复杂度。并且通过仿真分析证明了本文提出的MLPTS算法能够较好的权衡PAPR性能和计算复杂度之间的关系。

High peak-to-average power ratio（PAPR） is the main drawback of the OFDM signal,which increases the ODFM system＇s nonlinear distortion.Partial transmit sequences（PTS） is one of the most attractive schemes to reduce the PAPR in orthogonal frequency division multiplexing systems（OFDM）.However,the optimum PTS scheme requires an exhaustive searching over all combinations of allowed phase factors to obtain the optimal phase factors combination and this result in high computational complexity. What＇s worse,the computational complexity increases exponentially with the number of sub-blocks.Consequently,the PTS scheme is not applicable in practical applications.In this paper,we propose a novel multi-loop comparison scheme with low computational complexity. In the proposed method,the optimum phase factor combination of allowed phase factors is achieved by the method of multi-loop comparison instead of exhaustive searching.The multi-loop comparison scheme can help to skip some redundant computing and avoid being trapped in local optima.The performance analysis shows that multi-loop comparison PTS can reduce the computational complexity dramatically while achieve almost the same PAPR reduction performance compared to optimum PTS.