次随机分块PTS-Clipping峰均比抑制算法

针对正交频分复用信号存在高峰均比问题,本文提出了一种基于次随机分块的部分传输序列(partial transmit se-quence,PTS)与传统限幅剪切联合处理的峰均比抑制算法.该算法在时域得到随机分块的子块序列,子块序列乘以相位旋转因子得到多个备选序列,从多个备选序列中寻找低峰值OFDM信号,最后利用频域滤波剪切算法限幅.仿真结果表明,所提算法在低复杂度下可以有效降低PAPR.     

降低GFDM峰均功率比的低复杂度算法

为降低广义频分复用(GFDM)系统的峰均功率比(PAPR)、实现复杂度,提出了基于T变换和选择性映射(SLM)的TSLM算法,该算法的设计思想是利用SLM算法增加GFDM时域备选信号的数量以降低其PAPR,利用T变换实现串联的沃尔什-哈达玛变换和离散傅里叶反变换以降低GFDM系统的复杂度。为进一步降低GFDM系统的PAPR,提出了将TSLM算法和转换向量(CV)相结合的TCSLM算法,利用CV向量进一步增加GFDM时域备选信号的数量。结果表明,在子载波数为64、子符号数为3、相位序列数为2时,与SLM算法相比,TSLM算法和TCSLM算法的实现复杂度分别降低约21.9%和60.9%;在互补累计分布函数(CCDF)为10^?3时,TSLM算法和TCSLM算法的PAPR分别降低约0.6 dB和1 dB;在误比特率为10^?3时TSLM算法和TCSLM算法的误码性能均改善约2 dB。     

OFDM系统中峰均比降低的次优化循环移位序列方法

部分传输序列（PTS）方法需遍历所有的可选相位因子,这样的计算量随分割子序列数按指数增长。本文在对循环移位PTS方法 (PTS/CSS) 和次优PTS方法 (sub-OPTS) 进行研究的基础上,提出了一种减少计算复杂度的次优化时域循环移位序列方法（sub-OPTS/CSS）。该方法用快速傅立叶变换（FFT）的时域循环移位特性增加更多备选信号;且仅对变换后的部分备选信号进行相位优化。同时,将其与已有的一些方法的备选信号、冗余比特数、运算量进行了分析和比较。理论分析和仿真结果表明,当使用相同的分割子序列数和相位旋转因子时,sub-OPTS/CSS方法降低PAPR的性能稍次于PTS/CSS方法,但搜索最佳相位时的计算量减少了一半;sub-OPTS/CSS方法降低PAPR的性能要优于sub-OPTS方法。      

一种降低MIMO-OFDM系统PAPR的低复杂度SLM算法

为了降低MIMO-OFDM(多输入多输出正交频分复用)系统中传统SLM(选择性映射)算法的计算复杂度,文章提出将原始频域信号分成实部和虚部后分别进行不同的相位旋转,再通过IFFT(快速傅里叶逆变换)调制模块得到相应的时域序列,最后通过多天线间实部和虚部序列的不同组合来产生更多的具有不同PAPR(峰均功率比)的备选序列。仿真结果表明,所提算法能有效地抑制MIMO-OFDM信号的PAPR。相比传统SLM算法能有效降低计算复杂度。     

降低OFDM系统峰均比的改进算法研究

针对正交频分复用(OFDM)系统的高峰均功率比(PAPR)问题,在对部分传输序列(PTS)算法和限幅法的基本原理进行简要介绍的基础上,提出了一种用哈达玛矩阵初始化翻转迭代PTS初始搜索相位的改进算法,将输出信号通过限幅处理进一步降低OFDM系统的峰均功率比。仿真结果表明,联合算法有效降低了系统的PAPR,证明了有效性。     

OFDM系统中一种联合改进的低复杂度SLM峰均比抑制技术

高的峰值平均功率比(Peak-to-Average Power Ratio,PAPR)是光正交频分复用(Optical Orthogonal Frequency Division Multiplexing,O-OFDM)系统的一个主要缺点,选择性映射(Selective Mapping,SLM)法能有效降低高PAPR出现的概率,但它的计算复杂度较高.一些低复杂度的SLM方案能够有效地降低复杂度,但同时也降低了PAPR的抑制性能.为了平衡这两个因素,将低复杂度SLM方案与次优选择的思想相结合,文章提出了一种联合改进的PAPR抑制方案.在低复杂度方案中,通过将一个复频域信号分为两个实信号,再利用快速傅里叶变换(Fast Fourier Transform,FFT)的平移和反折性质将其重建成新的信号,以得到更多的备选信号,如此便能降低计算复杂度.然后,再结合次优选择的思想,选择PAPR最小的一路以得到最优的PAPR抑制性能.仿真结果验证了该方案的有效性.     

用于SFBC MIMO-OFDM系统的改进SLM算法

在空频编码(SFBC)多输入多输出正交频分复用(MIMO-OFDM)系统中传输符号存在较高峰均功率比(PAPR)问题,采用SLM算法能够有效降低系统峰均功率比,但随着发射天线数的增加,较多的快速傅里叶反变换(IFFT)会增加系统的计算复杂度,因此,构造F矩阵并提出了一种基于F矩阵SFBC MIMO-OFDM系统的改进SLM算法。采用F矩阵作为相位序列组对空频编码信号进行独立处理,获得最优相位序列取共轭,将共轭序列中每两个旋转因子为一个单位交换位置,并扰码SFBC后各天线的信号,以此减少了每根发射天线上的IFFT次数。理论和MATLAB仿真分析表明,该算法获得了良好的峰均比性能,同时也降低了系统的计算复杂度。     

基于分数阶Fourier变换减小OFDM系统PAPR的研究

介绍了基于分数阶Fourier变换的OFDM系统,给出了这种系统中经过变换后的信号的表达形式,探讨了该系统在不同的调制方式下（QAM调制和QPSK调制）使用Clipping算法降低系统PAPR的情况,并使用Matlab对不同阶数的CCDF进行了仿真。仿真结果表明,QAM调制下基于分数阶Fourier变换的Clipping算法性能不如基于傅立叶变换的Clipping算法好,而在QPSK调制方式下基于分数阶Fourier变换的OFDM系统PAPR性能比基于傅立叶变换的OFDM系统性能有了显著的提高。     

降低OFDM系统PAPR概率类技术的研究

正交频分复用(OFDM)是第四代移动通信的核心技术.然而OFDM系统中存在较高的峰值平均功率比(PAPR),研究了选择性映射法(SLM)和部分传输序列法(PTS)两种方案降低OFDM系统的PAPR,并且研究了子载波和子信道数目对SLM和PTS算法改善PAPR性能的影响.仿真显示这两种算法都能够减少PAPR出现的概率,从而减小PAPR对OFDM通信系统性能的影响.     

基于载波加权的OFDM信号峰均功率比抑制算法研究

针对OFDM系统中峰均功率比(Peak-to-Average Power Ratio,PAPR)高的问题,提出了一种新的基于载波加权的PAPR抑制算法.对子载波引入幅度和相位的加权值,减小高峰值出现概率,有效抑制OFDM信号的PAPR.同时,推导了寻找最优加权值的迭代算法,证明了其收敛性,推导了收敛值.仿真结果表明采用此算法具有很好的PAPR抑制性能,当分组为16时PAPR的抑制超过4dB.本文的算法能够有效地抑制OFDM信号的PAPR,并且具有寻找最佳的加权值迭代算法,有一定的实用价值.     

Low-complexity PAPR reduction technique for OFDM systems using modified widely linear SLM scheme

In this paper, a modified widely linear selective mapping (MWL-SLM) scheme is proposed to reduce the peak-to-average power ratio (PAPR) of the orthogonal frequency-division multiplexing (OFDM) systems. In the proposed MWL-SLM scheme, through partition one complex signals into two real signals and combining the linear properties of the Fourier Transform, at most 4M² candidate signals can be obtained but only require M inverse fast Fourier transform (IFFT) operations. As a result, the proposed SLM scheme has the ability to generate more candidates when compared with conventional SLM (C-SLM) and widely linear SLM (WL-SLM). Therefore, MWL-SLM outperforms C-SLM and WL-SLM for the same computational cost of IFFT operations. Alternatively, for a given number of candidates, MWL-SLM has slightly inferior PAPR reduction performance to C-SLM and WL-SLM but requires less IFFT operations to be implemented, thus resulting in a lower computational complexity. Simulation results demonstrate the effectiveness of the proposed scheme.     

A hybrid technique for the PAPR reduction of NOMA waveform

Non-orthogonal multiple access (NOMA) is a great contender for future cellular modulation due to its desirable properties like massive connectivity, high data rate transmission, and high spectral efficiency. However, its peak-to-average power ratio (PAPR) is significant, which becomes a significant disadvantage for the efficient operability of the NOMA waveform compared to current techniques. Several PAPR reduction algorithms like selective mapping (SLM), partial transmission sequence (PTS), and companding techniques have been proposed to lower the PAPR of multicarrier waveforms (MCWs). PTS reduces the PAPR but has high complexity. On the other hand, SLM has a less complex framework, but its PAPR performance is not as efficient as PTS. Companding methods reduce the PAPR by compressing the signals at the transmitter, which unfortunately reduces the dynamic range of the signal. In this work, we propose a hybrid algorithm (SLM + PTS) with a companding method for the first time for the NOMA waveform, which efficiently reduces the PAPR with low computational complexity. Furthermore, we compare the performances of a host of candidate algorithms like SLM, PTS, hybrid (SLM + PTS), hybrid + A law (SLM–PTS–A law), and hybrid + Mu law (SLM–PTS–Mu law). The results of the experiments show that the hybrid + Mu law did a better job than the existing PAPR reduction algorithms.     

光OFDM系统中基于PTS算法对峰均比抑制技术的分析

针对光正交频分复用(OFDM)系统中峰值平均功率比(PAPR)较高的缺点,重点研究了基于部分序列传输法(PTS)的峰均比抑制技术,提出一种改进的加强迭代PTS搜索技术(EIA-PTS),该技术能够降低原PTS的计算复杂度.仿真表明:原PTS方法随着相应参数的增加,迭代次数呈指数型增长,而EIA-PTS技术的迭代次数基本保持平稳且低于原PTS方法.在此基础上,又将EIA-PTS与削波(Clipping)技术相结合,提出了峰均比EIA-PTS-Clipping联合抑制技术.与EIA-PTS技术相比,该技术进一步提升了系统PAPR的抑制性能,能在系统误码率(BER)性能与PAPR抑制效果之间取得更好的折衷,具有较高的利用价值.     

降低可见光DCO-OFDM系统峰均比的DCT-GCS方法

为了克服现有降低OFDM峰值平均功率比的方法在可见光通信中效果不好的问题,通过分析发现DCO-OFDM系统输入序列的共轭对称形式增强了序列的相关性,使传统方法的PAPR抑制性能有明显下降,所以提出了离散余弦变换(DCT)与分组循环移位(GCS)结合的降低系统PAPR的方法。该方法中的分组循环移位能够在DCT的基础上降低输入序列的相关性,使系统输出信号具有更低的PAPR。仿真结果表明:提出的方法比仅采用DCT或者GCS能够更好地抑制系统的PAPR。在CCDF=10-4时,DCT-GCS方法使系统的PAPR下降了5.4dB。DCT-GCS具有较低的PAPR,且计算复杂度要远远低于PTS和SLM方法。      

降低峰均值比的时域交织分割PTS算法及分析

本文根据交织分割部分传输序列(IPTS)的特点,利用具有周期结构的序列DFT的性质,提出基于时域的IPTS算法;同时,将其和常规PTS算法、选择映射算法(SLM)及基于时域循环卷积的PAPR降低算法(TCM)的计算量、性能等进行比较和分析.仿真实验和分析说明本文方法能降低常规IPTS算法的运算量,同时以较小的运算量达到常规相邻分割PTS(APTS)算法的性能.     

光OFDM系统中一种改进的SLM峰均比抑制方案

针对光正交频分复用(O-OFDM)系统中峰值平均功 率比(PAPR)较高的缺点,对PAPR抑制技术的选择性 映射法(SLM) 进行了深入研究。基于低复杂度SLM方案的深入研究,提出了一种改进的次PAP R选择的思 想与低复杂度SLM相结合的PAPR抑制方案。改 进的SLM方案能够成倍降低传统SLM方案的计算复杂 度。仿真分析表明,改进的SLM方案在载波数为256的O-OFDM系统中,计算复杂度能降低50%以上,并 且随着子载波数的增加,其复杂度降低程度更为高效;同时,该改进的SLM方案又能使其PAPR抑制性能优于传统的SLM方案,从而进一步提升了低复杂度SLM 方案的实用价值。     

Peak-to-average power ratio of selective mapping technology involving a phase generation mechanism based on polar codes for orthogonal frequency division multiplexing with index modulation systems

In this paper, a novel selective mapping (SLM) method is proposed for reducing the peak-to-average power ratio (PAPR) of orthogonal frequency division multiplexing with index modulation (OFDM-IM) systems. In the proposed method, polar codes are used to construct the SLM phase generation mechanism. This systematic structural design is superior to conventional methods in which phases are randomly generated. Moreover, polar codes and Reed–Muller codes are selected to protect the input data of the OFDM-IM system. The weight distribution of the Reed–Muller codes is then used to determine the location data of the active subcarriers in the OFDM-IM system, and these data are used to determine the error correction capacity. Simulation results indicated that the PAPR improvement achieved using the proposed method is similar to that achieved with conventional SLM methods. Moreover, linear block codes are used to construct the active subcarrier selection and SLM phase generation mechanisms to ensure that both mechanisms have systematic structural designs.     

A partial transmit sequence technique with error correction capability and low computation

Orthogonal frequency division multiplexing (OFDM) is a popular transmission technique in wireless communication. Although already widely addressed in many studies, OFDM still has flaws, one of which is the occurrence of high peak‐to‐average power ratio (PAPR) in the transmission signal. The partial transmit sequence (PTS) technique is one method adopted to reduce high PAPR in OFDM systems. However, as PTS utilizes phase factors to generate multiple candidate signals, large amounts of calculation and time are required to search the candidate signal with the minimal PAPR, which will then be adopted as the final transmission signal. This paper proposes a novel PAPR reduction method, which can be applied in OFDM systems with M‐ary phase‐shift keying modulation. It not only requires less computation but also possesses error correction capabilities. More precisely, the proposed method is to divide a block‐coded modulation code into the direct sum of a correcting subcode for encoding information bits and a scrambling subcode for generating phase factors. Our proposed method is a suboptimal technique with low computation, because it uses a genetic algorithm with a partheno‐crossover operator as the transmitted signal selection mechanism. Simulation results show our proposed method has better PAPR performance than the GA‐PTS scheme. Based on the simulation results in Figures 5 and 6, it is evident that our proposed method can be employed in any OFDM system by using M‐PSK modulation.Copyright © 2013 John Wiley & Sons, Ltd.