一种降低OFDM系统PAPR的联合压扩算法研究

正交频分复用(OFDM)技术的一个主要缺点是其拥有较高的峰值平均功率比(PAPR),当其通过非线性放大器后将产生很严重的性能失真。在众多的降低PAPR的算法中,压扩变换算法因其实现简单得到了广泛的关注。文中提出了一种联合压扩变换算法,实验仿真表明,该算法具有更好的PAPR抑制效果,提高了OFDM系统的性能。     

OFDM系统中基于压缩感知的非线性失真恢复研究

正交频分复用系统(OFDM)的高峰均比(PAPR)问题降低了系统传输效率,增加了解调难度,使高功率放大器(HPA)满负载工作.该文针对削波与HPA引入的非线性失真问题,提出在接收端采取基于泰勒级数的预处理方式对非线性干扰进行处理,最小化信号畸变影响.在发送端通过削波降低信号的PAPR,并利用削波噪声在时域上的稀疏性特性,将传输过程作为整体考虑,最后利用正交匹配追踪算法(OMP)恢复总的非线性失真信号.仿真结果表明,该文所提方法能够有效抑制系统的干扰信号,减少了有用信号受到的非线性影响,验证了该方案的正确性.     

OFDM系统中基于压缩感知的非线性失真恢复研究

正交频分复用系统(OFDM)的高峰均比(PAPR)问题降低了系统传输效率,增加了解调难度,使高功率放大器(HPA)满负载工作。该文针对削波与HPA引入的非线性失真问题,提出在接收端采取基于泰勒级数的预处理方式对非线性干扰进行处理,最小化信号畸变影响。在发送端通过削波降低信号的PAPR,并利用削波噪声在时域上的稀疏性特性,将传输过程作为整体考虑,最后利用正交匹配追踪算法(OMP)恢复总的非线性失真信号。仿真结果表明,该文所提方法能够有效抑制系统的干扰信号,减少了有用信号受到的非线性影响,验证了该方案的正确性。     

DCO-OFDM水下可见光通信系统的峰均比抑制算法

为了解决直流偏置光正交频分复用(DCO-OFDM)水下可见光通信系统中存在的高峰均功率比(PAPR)问题,采用了一种基于范德蒙类矩阵(VLM)预编码与改进的自适应缩放联合PAPR抑制的算法。首先,该算法利用VLM对频域信号进行预编码处理,以此降低其自相关性,再通过比值计算方式改进的自适应缩放因子对时域信号进行缩放,使其更好地减小发光二极管带来的非线性失真,最后实现了抑制系统PAPR的效果。结果表明,在互补累计分布函数为10-3时,相比于原始系统,此联合算法的PAPR下降了3.2dB。由此可知,该研究对抑制DCO-OFDM水下可见光通信系统的PAPR是有帮助的。     

使用μ-law压扩算法降低OFDM系统PAPR的分析

提出使用μ-law压扩算法降低OFDM系统PAPR(峰值平均功率比),对PAPR概率分布进行了理论分析。理论分析和仿真结果表明采用压扩技术可有效地降低OFDM系统的PAPR,同时还对采用预失真放大器AWGN信道中的OFDM系统的性能进行了仿真。     

OFDM系统最大值抵消峰均比抑制算法

正交频分复用(OFDM)系统应用中的一个关键问题是如何降低信号的峰值平均功率比(PAPR).针对这一问题,本文提出一种新的峰均比抑制算法--最大值抵消算法.新算法利用OFDM系统的预留子载波,在子载波上注入冗余数据,形成新的信号,以改变原信号的PAPR值.在处理上,将新信号的PAPR值与原信号PAPR值进行比较,选取PAPR值较小的信号发送,从而降低信号的PAPR.仿真结果表明,由于新的算法不需要发送边带信息,不改变原信号的顺序和相位关系,故而在较好地抑制信号PAPR值的同时,该算法对误码率的影响非常小.这是本方法的主要特点和价值所在.     

多径信道下基于压缩扩张的OFDM系统PAPR抑制算法

OFDM系统中存在较大的峰均比(Peak-to-Average Power Ratio,PAPR),特别在多径信道中接收的信号严重失真,星座图恶化,严重影响了系统传输性能。针对该问题,对多径信道下OFDM系统PAPR抑制进行研究,采用频域均衡技术,提出了一种多径信道下基于压缩扩张的OFDM系统PAPR抑制算法。仿真结果表明,所提算法在抑制PAPR的同时能消除多径效应影响,避免信号失真和星座图恶化。对比传统算法,所提算法星座图EVM最大降低0.19,抑制PAPR能力提升1 dB。     

利用星座扩展降低OFDM PAPR的新方法

通过研究利用星座扩展降低OFDM中峰均功率比(PAPR)的方法,提出了一种寻找次最优映射向量的新方法--联合搜索(JS)算法.该算法联合相邻的若干子载波,通过比较局部的峰值大小搜索次最优映射向量.仿真结果表明,JS算法在降低计算复杂度、提高PAPR抑制增益以及增强应用灵活性等方面都有明显改进.     

MIMO-OFDM系统峰均比抑制技术的研究

针对MIMO-OFDM系统的高峰均功率比(PAPR)问题,提出了一种改进的PTS与限幅的联合算法。该联合算法先将MIMO-OFDM信号经过改进的PTS优化算法进行处理从而选出PAPR值最小的那一路信号,然后再将其经过限幅处理进一步降低系统的PAPR。仿真结果显示,该联合算法不仅可以有效地降低系统的PAPR,还可以减小信号经过限幅后引起的非线性失真,从而显著提高系统的整体性能。     

降低光正交频分复用系统PAPR的算法研究

本文针对光正交频分复用(O-OFDM)系统的高峰均比(PAPR)问题,提出了联合降低PAPR算法,利用选择映射法随机改变OFDM码元的初始相位分布,降低码元峰值出现的概率,采纳限幅加窗方法降低码元峰值,从而达到降低系统的PAPR。仿真结果表明,联合降低PAPR算法有效降低了O-OFDM系统的PAPR。     

光OFDM系统中一种联合改进的低复杂度PTS峰均比抑制技术

光正交频分复用系统(O-OFDM)的缺点之一是存在高的峰值平均功率比(PAPR),部分传输序列(PTS)技术能够有效降低高PAPR出现的概率,但其计算复杂度较高。针对该问题,提出一种可降低计算复杂度的二阶PTS和削波(Clipping)联合改进的PAPR抑制方案。该方案首先将初始的输入信号进行d级逆快速傅里叶变换(IFFT)运算,再进行子块划分,然后进行剩下的n-d级IFFT运算。仿真结果表明,该方案大大降低了计算复杂度,并且在峰均比抑制效果和系统误码率(BER)方面都得到了较好的改善,具有较高的实际应用价值。     

A computationally efficient selected mapping technique for reducing PAPR of OFDM

In orthogonal frequency division multiplexing (OFDM) system, high value of peak-to-average power ratio (PAPR) is an operational problem that may cause non-linear distortion resulting in high bit error rate. Selected mapping (SLM) is a well known technique that shows good PAPR reduction capability but inflicts added computational overhead. In this paper, using Riemann sequence based SLM method, we applied reverse searching technique to find out low PAPR yielding phase sequences with significant reduction in computational complexity. Additionally, we explored side-information free transmission that achieves higher throughput but sacrifices PAPR reduction. Finally, to overcome this loss in PAPR reduction, we proposed application of Square-rooting companding technique over the output OFDM transmitted signal. Simulation results show that the proposed method is able to compensate the sacrifice in PAPR and achieved PAPR reduction of 8.9 dB with very low computational overhead.     

一种非线性信道MIMO-OFDM系统性能改进算法

多输入多输出正交频分复用(MIMO-OFDM)可以提高系统在频率选择性衰落信道的传输性能.与OFDM系统一样,MIMO-OFDM系统也存在高峰值平均功率比(PAPR)的问题.为此,提出了一种降低空时分组编码MIMO-OFDM系统PAPR的正交部分传输序列算法,运用这种算法,利用傅里叶变换的性质,通过调整空时编码与基带正交调制的顺序,对两天线发射端,可以降低算法近一半的复杂度,且可以减少一半的边信息.利用高功率放大器的非线性模型,得到了瑞利衰落信道下PAPR降低后系统的误码率性能.仿真结果证明了该方法的有效性.     

基于功放效率的OFDM信号幅度的最佳分布——峰均比抑制

星座图扩展（ACE）技术可以无损地降低OFDM信号的峰均比,本文的论述指出仅追求低峰均比对应的功放效率和效能并不是最好.笔者提出了OFDM信号的最佳互补累积分布函数（OCCDF）峰均比抑制方法,即考虑OFDM信号的幅度分布及出现概率,整体地评估其对放大器失真的影响,以OFDM信号放大器的效率为评估峰均比优劣的标准,在算法上以限定MER条件下得到尽可能低的功放输入功率回退（IBO）为迭代收敛目标,预见了应该存在最高功放效率意义匹配的所谓OFDM信号的最佳幅度分布.实验证实：相比原始OFDM系统,在放大基于OCCDF准则优化后的OFDM信号时,放大器获得了3.15dB的IBO性能改善,对比同等条件下单载波系统仅差0.05dB.     

PAPR Reduction in OFDM Systems Based on Autoregressive Filtering

Orthogonal frequency division multiplexing (OFDM) has a very high peak-to-average power ratio (PAPR) that causes a severe nonlinear distortion in practical hardware implementation of high power amplifiers (HPA). In this article, a new PAPR reduction method is proposed based on autoregressive (AR) error filtering. This method proposes the use of signal whitening property of error filtering as a preprocessing step to remove the predictable content of stationary stochastic processes which can reduce the autocorrelation of input data sequences and is shown to be a very effective solution for the PAPR problem in OFDM systems. It is shown that the proposed method can achieve a significant reduction in PAPR without degrading the error performance or power spectral levels. It is also shown that the proposed method is applicable to any modulation scheme and can work for any number of subcarriers under both additive white Gaussian noise and wireless Rayleigh fading channel.     

Peak to Average Power Ratio Reduction in ECMA-368 Ultra wideband Communication Systems Using Active Constellation Extension

Multiband Orthogonal Frequency Division Multiplexing (MB-OFDM) is an efficient approach for The ECMA-368 Ultra Wideband (UWB) wireless communication Standard. However, the high Peak to Average Power Ratio (PAPR) of MB-OFDM UWB signals, limits the power efficiency of the High Power Amplifier (HPA) due to nonlinear distortion. Hence the need to reduce the PAPR of MB-OFDM UWB signals. In this paper, the efficiency of some recently proposed methods including the Active Constellation Extension Approximate Gradient-Project technique (ACE-AGP) is evaluated in real ECMA-368 communication system, with the use of typical HPA models and the UWB channel models defined in IEEE 802.15.3a standard. The PAPR measure and the bit error rate (BER) are used as performance measures in this evaluation.The results indicate that the ACE-AGP algorithm introduces a significant reduction of PAPR about 6.7 dB and reduces the BER degradation in all UWB channel models with different data rates.     

基于梯度投影的OFDM峰值功率控制算法研究

OFDM系统中的高峰值功率会引起系统误码率性能恶化和非线性失真.文中研究了一种基于星座扩展的梯度投影算法,能有效地对OFDM系统中的高峰值功率进行控制.该算法采用一个在数据上呈现多零的预限幅向量,大大减小系统进行傅里叶变换时的计算量.仿真结果证明,梯度投影算法在保持峰值功率控制性能的同时,有效地加快了收敛速度,显著地降低算法的计算复杂度.     

The New Peak-to-Average Power Reduction Algorithm in the OFDM System

In this paper, we proposed a new peak-to-average power reduction (PAPR) algorithm of orthogonal frequency division multiplexing (OFDM) system using block coding scheme and discrete cosine transform (DCT). We are using DCT to concentrate the energy of the original signal into a few coefficients. After the DCT data were fed into the IDFT, the output of signal of OFDM appeared to have uniform distribution. With the newly proposed schemes, that we founded those three important properties, the first property is the PAPR used be reduced by 9.4419 dB for BPSK mapper. The second property is the OFDM signals have capability of noise immunity and of error correction. And the third property is the effect of PAPR reduced can be implement by cascaded different method.     

A Computationally Efficient Tree-PTS Technique for PAPR Reduction of OFDM Signals

The high peak-to-average power ratio (PAPR) of time domain signals has been a major problem in orthogonal frequency division multiplexing (OFDM) systems, and thus various PAPR reduction algorithms have been introduced. Partial transmit sequence (PTS) is one of the most attractive solutions because of its good performance without distortion. However, it is considered as an impractical solution for the realization of high-speed data transmission systems due to its high computational complexity. In this paper, a novel PAPR reduction algorithm based on a tree-structured searching technique is proposed to reduce the PAPR with low complexity. In the proposed scheme, the computational complexity of searching process is decreased by adjusting the size of tree with two parameters, width and depth, while preserving good performance. The simulation results show that proposed scheme provides similar performance with optimum case with remarkably reduced computational complexity.     

An erasure-based scheme for reduction of PAPR in spatial multiplexing MIMO-OFDM using Reed-Solomon codes over GF(216 + 1)

In this paper, a novel erasure-based scheme which uses long Reed-Solomon (RS) codes over GF(65537) is proposed for the reduction of the peak-to-average power ratio (PAPR) in coded orthogonal frequency division multiplexing (OFDM). The motivation for using the field GF(65537) is to generate long code words (up to 65536 symbols in just one code word). Using long codes results in greater flexibility to search for low PAPR OFDM frames within the subsets of symbols of a code word because RS codes are maximum distance separable and any subset of a high enough number of symbols is sufficient for the recovery of data. Over this field, the lengths of code words are exponents of 2. Hence, low-complexity radix-2 fast Fourier transform can be exploited. RS codes are deployed for both PAPR reduction and error correction. Simulation results show that in similar PAPR reduction performances, the proposed scheme outperforms the previously reported work with RS codes in both error correction and computation complexity. The proposed scheme can be applied to both single-input single-output and multi-input multi-output systems.