滤波器组多载波系统中基于双层优化的峰均比抑制算法

针对部分传输序列(PTS)算法在交错正交幅度调制的滤波器组多载波(FBMC-OQAM)系统中受符号重叠的影响,造成峰值再生,从而导致系统峰值功率比(PAPR)较高、计算复杂度较大等问题,该文提出一种基于双层优化的PTS算法(DO-PTS).该算法对信号数据块进行两层相位因子搜索以获得更好的PAPR抑制性能,第1层充分考虑重叠特性,结合前面重叠数据块进行初步优化,第2层对数据块进行分组,在每组选择对峰值影响最大的数据块进行优化,来减少进行相位因子搜索的数据块数量,并且在第1层优化中缩小相位因子的搜索范围,以降低系统的计算复杂度.通过对计算复杂度和仿真结果的分析表明,同其它主流PTS优化算法相比,所提算法不仅能取得很好的PAPR抑制性能,还具有较低的计算复杂度,同时也保证了系统的传输数据率.     

基于多层循环搜索的部分传输序列算法

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.     

减小OFDM系统PAPR的QEA-PTS联合方法

为了减小正交频分复用(OFDM)系统的高峰值平均功率比(PAPR),提出一种基于量子进化算法(QEA)的低复杂度部分传输系列(PTS)联合方法。该方法通过循环移位对传统的PTS进行改进,利用OFDM系统提供的额外自由度将循环移位与独立旋转相位进行组合优化,并采用QEA来搜索最优相位因子,使得PAPR最小。仿真结果表明,与传统的方法比较,这里提出的QEA-PTS的联合方法更加有效地减小系统的PAPR,同时降低了计算复杂度。     

基于GA-PTS的无厄米特对称光OFDM系统峰均比抑制算法的研究

光正交频分复用（O-OFDM）技术被广泛应用于可见光通信系统（VLC）中以提高数据传输速率，但是O-OFDM系统存在峰值平均功率比（PAPR）高的问题，限制了其系统性能。本文首先针对传统的非对称限幅光正交频分复用（ACOOFDM）系统频谱效率低下以及计算复杂度高的问题，使用无厄米特对称的单极性光正交频分复用（UO-OFDM）系统。其次在UO-OFDM系统上使用传统的部分传输序列（PTS）技术来降低其PAPR，同时针对传统的PTS技术计算复杂度高以及搜索最佳相位旋转因子效率低的问题，提出使用遗传算法（GA）来优化PTS技术。仿真结果表明：GA-PTS相比于传统的PTS技术，在PAPR抑制性能差别不大的情况下极大地减少了搜索最佳相位旋转因子所需的时间；同时与基于GA-PTS算法的ACO-OFDM系统所用的时间相比，基于GA-PTS算法的UO-OFDM系统所用的时间有所减少，且随着最大遗传代数的增加，减少的时间更加明显。     

基于循环迭代的部分传输序列峰均比降低算法

部分传输序列(PTS)算法能够有效的解决正交频分复用(OFDM)系统中的高峰均功率比(PAPR)问题,但是其复杂度非常高.针对该问题,提出了基于一种基于循环迭代的PTS(C-IPTS)算法.所提算法将前一次迭代搜索得到的相位因子作为当前搜索的初始值,经过循环,使其更加接近最优相位因子.同时采用Metropolis准则,避免了相位因子的搜索陷入局部极小值,为最优相位因子的搜索提供了更大的自由度空间,算法的峰均比性能显著提高.仿真结果证明,所提算法不仅能够保持较低的计算复杂度,而且可以获得良好的峰均比降低性能.     

一种OFDM系统峰均比的改良PTS算法

部分传输序列（PTS）方法通过选择合适的相位序列以降低信号峰值出现的概率，该方法不会使信号发生畸变。但是传统的PTS技术计算复杂度非常大，需遍历所有可选的相位因子，其计算量随分割子序列数按指数增长。本文提出了一种正倒二叉树多层相位序列方法，该方法通过对称的树形搜索，搜索出最优的相位序列。仿真结果表明，该方法大大降低系统的复杂度．同时PAPR得到更好地抑制。     

基于PTS抑制OFDM系统PAPR低复杂度算法

为降低基于部分传输序列法(PTS)的峰均功率比(PAPR)抑制技术的复杂度,文中研究了OFDM时域信号最大峰值点的位置与采用部分传输序列法后最大峰值点位置之间的关联性,提出了一种寻找最优相位因子序列的简化算法,该算法用抽样序列代替原始序列进行搜索。由于新算法采用的样点数目少于原始样点数目,因此可以大幅降低PTS处理过程的计算复杂度。仿真结果表明,新算法采用的数据量只有原始数据的50%,而性能仅仅损失0.2~1 dB。     

改进PTS算法降低OFDM峰均功率比的研究

部分传输序列 (PTS) 算法能够有效的降低正交频分复用(OFDM)系统的峰值平均功率比(PAPR).提出了一种改进部分传输序列(IPTS)模型,它是基于优化最佳相位因子加权之前的部分传输序列思想降低OFDM系统平均峰值功率比.利用这种模型,提出了一种基于哈达码矩阵优化的部分传输序列算法(H-IPTS).实验仿真表明,H-IPTS算法以低的计算复杂度可以达到或优于传统PTS算法相当的效果,具有良好的峰值平均功率比性能.     

OFDM系统中降低峰均功率比算法的研究

正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)系统中,峰均功率比(Peak to AveragePower Ratio,PAPR)过高会导致收发器的非线性失真,严重影响系统的性能。传统的部分传输序列(Partial TransmitSequence,PTS)算法能够有效地降低PAPR,然而其计算复杂度随着分块数目增长呈指数增加。在研究PTS的基础上提出了双重迭代PTS算法,该算法利用增加迭代次数,并且每次迭代时选择不同的相位旋转因子集合来优化OFDM系统的峰均比性能。该算法在峰均比性能上优于常规OFDM系统以及普通迭代PTS算法,在降低峰均比性能和计算复杂度之间取得了较好的折衷。     

FrFT-OFDM系统的低复杂度峰均功率比抑制技术研究

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。     

A Phase Adjustment Based Partial Transmit Sequence Scheme for PAPR Reduction

The peak-to-average power ratio (PAPR) of an orthogonal frequency division multiplexing signal is normally very large and is crucial for the analog amplifier in the transmitter. It is therefore necessary to reduce the PAPR before the signal is transmitted. In this paper, a PAPR reduction scheme is presented based on the partial transmit sequence (PTS) method. By allowing each subblock of data to be rotated by an arbitrary angle, a simple yet efficient phase search algorithm is proposed. With a prespecified number of iterations, the proposed method gives the best phase vector for a combination of data blocks to achieve the smallest PAPR value. Our simulation results show that the proposed scheme provides significant computational savings while yielding a performance similar to that of the conventional PTS method.     

一种降低OFDM信号峰均比的低复杂度双层搜索算法

在OFDM峰均比抑制技术中,采用传统的PTS算法得到的相位旋转因子随着长度的增加,存在搜索代价过高的问题,从而影响了系统的性能。为有效降低系统的峰均比,同时避免过多的搜索代价,设计了一种新的峰均比抑制算法。与传统算法相比较,该算法将汉明距离的概念应用到传统双层搜索算法中,针对不同的相位旋转因子长度,在每一层进行不同策略的搜索,得到不同的改进方案。仿真结果表明,在搜索次数相近的情况下,该算法相较传统算法能将峰均比在原有基础上再降低0.1 dB左右,而且随着相位旋转因子长度的增加,效果更加明显。同时,该算法在系统性能与搜索次数上的平衡相对传统算法也更为灵活。     

OFDM系统中基于迭代和门限理论降低PAPR的改进PTS方法

传统的部分传输序列法（PTS）中,如果要得到最佳的相位旋转因子,需要遍历所有的可选相位,这样的计算量随分割的子序列数按指数增长。本文提出两种减少计算复杂度的改进PTS方法（经迭代的IPTS和经门限的IPTS）。这两种方法都利用快速傅立叶变换（FFT）的时域循环移位特性增加备选信号,改善PAPR降低的性能。首先提出了一种利用反复迭代移位的IPTS方法(经迭代的IPTS),该方法的计算量随子序列数按线性增长。接着提出了一种利用预先设定的门限值以降低计算复杂度的IPTS方法(经门限的IPTS)。最后理论分析、比较了PTS、PTS/CSS方法与本文方法的计算复杂度。Matlab软件仿真显示,当使用相同的分割子序列数和相位旋转因子时,两种IPTS方法能够以较小的运算量达到了PTS/CSS方法性能;两种IPTS方法降低PAPR的性能要优于PTS方法,但计算复杂度并没有增加。      

A novel search method to reduce PAPR of an OFDM signal using partial transmit sequences

One of the main drawbacks of orthogonal frequency division multiplexing (OFDM) is the high peak‐to‐average power ratio (PAPR) of the transmitted OFDM signal. Partial transmit sequence (PTS) technique can improve the PAPR statistics of an OFDM signal. As ordinary PTS technique requires an exhaustive search over all combinations of allowed phase factors, the search complexity increases exponentially with the number of sub‐blocks. In this paper, we propose a novel PTS technique with reduced complexity that each level inverts twice of phase factor bits from previous level. Then we also use initial random phase sequence to find the better search way of PAPR reduction. Numerical results show that the proposed method can achieve significant reduction in search complexity with little performance degradation. Copyright © 2006 John Wiley & Sons, Ltd.     

一种降低FBMC-OQAM系统PAPR的ASSABC-PTS算法

针对滤波器组多载波-偏移正交幅度调制技术(Filter Bank Multicarrier-Offset Quadrature Amplitude Modulation,FBMC-OQAM)存在峰均功率比(Peak-to-Average Power Ratio,PAPR)过高的问题,以及传统部分传输序列(Partial Transfer Sequence,PTS)算法对PAPR抑制效果不明显,提出了一种新的基于自适应搜索策略的人工蜂群部分传输序列算法(Adaptive Search Strategy Based Artifical Bee Colony PTS,ASSABC-PTS)。首先,根据FBMC-OQAM系统特性,利用传统PTS算法对系统进行初步优化,以降低FBMC-OQAM系统的PAPR;然后,针对PTS算法中存在的计算复杂度问题,引入人工蜂群(Artificial Bee Colony,ABC)算法进行优化;最后,在ABC算法中引入自适应搜索策略提升算法的局部寻优能力,加快ABC算法的收敛速度和搜索精度。仿真实验表明,ASSABC-PTS在有效降低系统算法复杂度的同时,也极大降低了FBMC-OQAM系统的峰均功率比。     

PAPR reduction of an OFDM signal by use of PTS with low computational complexity

One of the major drawbacks of orthogonal frequency division multiplexing (OFDM) is the high peak-to-average power ratio (PAPR) of the transmitted OFDM signal. Partial transmit sequence (PTS) technique can improve the PAPR statistics of an OFDM signal. However optimum PTS (OPTS) technique requires an exhaustive search over all combinations of allowed phase factors, the search complexity increases exponentially with the number of sub-blocks. By combining sub-optimal PTS with a preset threshold, a novel reduced complexity PTS (RC-PTS) technique is presented to decrease the computational complexity. Numerical results show that the proposed approach can achieve better performance with lower computational complexity when compared to that of other PTS approaches.     

Novel Low-Complexity Partial Transmit Sequences Scheme for PAPR Reduction in OFDM Systems Using Adaptive Differential Evolution Algorithm

A low-complexity partial transmit sequence (PTS) technique for reducing the peak-to-average power ratio (PAPR) of an orthogonal frequency division multiplexing signal is presented. However, the conventional PTS scheme requires an exhaustive searching over all combinations of allowed phase factors. Consequently, the computational complexity increases exponentially with the number of the subblocks. This paper presents a novel approach to the PAPR problem to reduce computational complexity based on the relationship between phase weighing factors and transmitted bit vectors. In this paper, we aim to obtain the desirable PAPR reduction with the low computational complexity. Since the process of searching the optimal phase factors can be categorized as combinatorial optimization with some variables and constraints, we propose a novel scheme, which is based on a stochastic optimization technique called modified differential evolution, to search the optimal combination of phase factors with low complexity. To validate the analytical results, extensive simulations have been conducted, showing that the proposed schemes can achieve significant reduction in computational complexity while keeping good PAPR reduction.     

PAPR Reduction of OFDM Signals Using Partial Transmit Sequences With Low Computational Complexity

Partial transmit sequences (PTS) is one of the attractive techniques to reduce the peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) system. As conventional PTS technique requires an exhaustive searching over all the combinations of the given phase factors, which results in the computational complexity increases exponentially with the number of the sub-blocks. In this paper, we aim to obtain the desirable PAPR reduction with the low computational complexity. Since the process of searching the optimal phase factors can be categorized as combinatorial optimization with some variables and constraints, we propose a novel scheme, which is based on a nonlinear optimization approach named as simulated annealing (SA), to search the optimal combination of phase factors with low complexity. To validate the analytical results, extensive simulations have been conducted, showing that the proposed schemes can achieve significant reduction in computational complexity while keeping good PAPR reduction.     

Partial Transmit Sequence Optimization Using Improved Harmony Search Algorithm for PAPR Reduction in OFDM

This paper considers the use of the Partial Transmit Sequence (PTS) technique to reduce the Peak‐to‐Average Power Ratio (PAPR) of an Orthogonal Frequency Division Multiplexing signal in wireless communication systems. Search complexity is very high in the traditional PTS scheme because it involves an extensive random search over all combinations of allowed phase vectors, and it increases exponentially with the number of phase vectors. In this paper, a suboptimal metaheuristic algorithm for phase optimization based on an improved harmony search (IHS) is applied to explore the optimal combination of phase vectors that provides improved performance compared with existing evolutionary algorithms such as the harmony search algorithm and firefly algorithm. IHS enhances the accuracy and convergence rate of the conventional algorithms with very few parameters to adjust. Simulation results show that an improved harmony search‐based PTS algorithm can achieve a significant reduction in PAPR using a simple network structure compared with conventional algorithms.     

Sub-optimum PTS for PAPR reduction of OFDM signals

As an attractive technique for peak-to-average power ratio (PAPR) reduction, partial transmit sequences (PTS) provides good PAPR reduction performance for orthogonal frequency division multiplexing (OFDM) signals. However, optimum PTS (OPTS) requires an exhaustive search over all combinations of allowed phase factors, resulting in the high complexity. Proposed is a sub-optimum partial transmit sequences (sub-OPTS) for PAPR reduction of OFDM signals. In sub-OPTS, both the alternate optimisation and the linear property of inverse discrete Fourier transform are employed. Simulation results show that sub-OPTS can reduce the computational complexity dramatically and achieve almost the same PAPR reduction performance compared to OPTS.