一种降低OFDM系统峰均功率比的压扩变换方法

为了降低OFDM系统中的峰均功率比,提出利用反正切变换对OFDM信号进行压扩处理.反正切压扩可以在压缩大信号的同时,增强小信号,从而提高了OFDM系统的误码率性能.仿真结果表明,与著名的μ律压扩方法相比,反正切压扩可以获得更好的峰均功率比性能和更低的误码率.该方法应用简单,不受载波数量和调制方式的限制.     

降低LWT-OFDM系统PAPR的联合算法

针对小波提升变换的正交频分复用( LWT-OFDM)系统峰均功率比( PAPR)过高的问 题,采用了部分传输序列( PTS)与指数压扩变换的联合算法?首先由PTS算法选出 系统中峰值最小的一组信号,再通过指数压扩变换来降低峰均功率比?仿真结果表明,相对于其它的限幅类技术,本文所提联合算法在该系统中能更有效的降低峰均功率比,并且误码率相对较低?     

降低OFDM信号峰均功率比的分段线性压扩变换

为了降低OFDM信号的峰均功率比(PAPR),设计了一种分段线性压扩变换.对小幅度通过数乘变换进行线性放大,而对大幅度先利用数乘变换进行线性缩小,再对缩小后的幅度进行等量放大.得到的压扩变换是分段线性且连续的,用低复杂度的线性运算抑制峰均比,同时用分段的方法减小压扩对系统性能的影响.理论分析和仿真表明,通过数乘因子和增...     

降低可见光OFDM系统限幅失真的部分线性压扩变换研究

针对可见光正交频分复用（OFDM）系统发光二极管（LED）限幅失真严重的问题,提出一种部分线性压扩变换方法。输出光功率约束较大或较小时,在发射端对直流光正交频分复用（DCO-OFDM）双极性信号中的正信号或负信号进行线性压缩变换,在接收端对压扩信号进行扩展变换可以有效地减小限幅噪声。输入信号功率一定时,在有效信噪比最大原则下对部分线性压扩变换系数和直流偏置进行优化,系统能够获得最佳性能。仿真实验表明,随着约束光功率增大,系统性能越差,且压缩系数的最优值也越小。随着QAM调制阶数的增加,部分线性压扩变换获得的性能增益越小。      

抑制LOFDM系统PAPR非线性压扩变换算法

针对网格正交频分复用(LOFDM,lattice OFDM)系统具有较传统OFDM系统更高峰均功率比(PAPR,peak-to-average power ratio)的问题,在将传统非线性压扩变换应用于LOFDM系统的同时研究并分析了一种新的基于原信号统计分布特性的连续可导非线性压扩算法。该算法从原信号的渐进高斯分布特性出发并对原信号的幅度分布函数进行截断逼近,在保持平均功率不变的条件下,将压扩后的信号限制在与原信号分布特性一致的特定范围内,使压扩后的信号在保持其原有分布特性的同时,能更大程度改善系统PAPR和误比特(BER,biterror ratio)性能。理论分析和仿真实验表明,所提出的算法性能要显著优于传统非线性压扩算法。     

降低OFDM信号峰均功率比的压扩方法研究

本文通过理论推导和分析,确定了基于误差函数降低正交频分复用(OFDM)系统峰均功率比的非线性压扩方法中两个关键参数的取值,修正了以前的结果,并在此基础上提出了一种新的压扩函数来降低OFDM系统的峰均功率比.理论分析和仿真结果表明,新的压扩方法能够在保持原信号平均功率不变的情况下使峰均功率比降低到7.8dB以下,并且系统具有较好的误比特率性能.     

低复杂度OFDM信号峰均功率比压缩技术

本文提出了一种用于减小OFDM信号峰均功率比(Peak-to-Average Power Ratio,PAPR)的压缩扩张变换技术.该技术能够以相对较低的计算复杂度大大降低OFDM信号的PAPR.作为应用实例,本文分析了线性压缩扩张、非线性对称压缩扩张和非线性准对称压缩扩张的PAPR改善幅度、计算复杂度、及其用于OFDM系统时对系统误比特率(BER)的改善等方面的性能.实验仿真表明,与采用传统的限幅滤波方法相比,本文提出的技术可以获得较明显的性能增益.     

联合迭代滤波与压扩参数优化的OFDM信号峰平比抑制

针对现有基于压扩变换处理的信号峰平比抑制方法性能单一且参数固定等缺陷,提出一种联合迭代滤波与自适应压扩参数优化的OFDM信号峰平比抑制方案。该方案能够同时对信号的峰平比PAPR和接收端误码率BER性能进行联合优化,并在迭代过程中有效消除因信号幅度畸变所引起的带外频谱再生;所提信号压扩及解压扩函数形式简单,计算复杂度较小;推导并给出了该方案可获得的PAPR抑制增益和BER理论性能界。仿真结果表明,该方案可同时获得较好的信号PAPR抑制、误码率以及带外功率谱性能,并在迭代过程中对压扩参数进行自适应调整,能够有效提高算法的适用灵活性。     

降低OFDM系统峰均比的压扩算法对系统误码率的影响

讨论了降低OFDM系统峰均比所采用的基于数值变换的压缩扩张算法,给出了几种压扩函数,推导出了使用压扩变换后OFDM系统的误码率公式,由此分析了压扩算法对OFDM系统性能的影响。可以看出,该算法不仅能有效降低OFDM系统的峰均比,而且能降低系统的误码率。仿真结果表明,本文给出的公式较好地反映了使用该算法后OFDM系统的误码性能。     

基于载波干涉和压扩技术的OFDM系统PAPR降低算法

提出一种新的基于联合使用载波干涉技术和μ-law压缩扩张技术的正交频分复用(OFDM)系统峰均比(PAPR)降低算法.该方案通过载波干涉扩展在一定程度上降低了系统的峰均比,并获得了较大的频率分集增益.此外,更为显著的峰均比降低在压缩扩张单元获得.仿真结果表明,通过合理选取压扩参数,该方案以较低的计算复杂度有效地降低了OFDM系统的峰均比,同时获得可靠的系统误码率性能.     

Reduction of peak-to-average power ratio of OFDM system using acompanding technique

A companding technique is proposed to reduce the peak-to-average-power ratio of the orthogonal frequency division multiplexing (OFDM) signal in this paper. The probability density function of the amplitude of the OFDM signal is determined. Because of the Gaussian distribution of the OFDM signal, the companding technique can be quite effective, since a large OFDM signal only occurs infrequently. The peak-to-average power ratio of an OFDM system and the optimal companding coefficient are determined in this paper. The symbol error rate of the systems after the companding is derived. The performances of the system with and without the companding are also compared     

Hybrid Zadoff‐Chu and multilateral piecewise exponential companding transform–based PAPR reduction technique in OFDM systems

The orthogonal frequency‐division multiplexing (OFDM) is a multicarrier modulation system that is used to transmit the large volume of data to the receiver. Reducing the peak‐to‐average power ratio (PAPR) in OFDM system is one of the demanding and crucial task in recent days. For this reason, various precoding and companding mechanisms are developed in the traditional works, but it remains with the limitations of increased complexity, reduced performance, and nonlinear distortion. The reduction of PAPR is achieved by minimizing the companding distortion with the enhancement of the bit error rate (BER) performance significantly. Then, in order to avoid clipping in OFDM, a multilateral piecewise exponential companding transform (MPECT) method has been utilized rather than using piecewise exponential companding transform (PEC) where PAPR is getting reduced. The OFDM is very sensitive to synchronizing error. To overcome this sensitivity, employ the Zadoff‐Chu sequence to carrier frequency offsets. Zadoff‐Chu matrix transform (ZCMT) has numerous merits among the other ODFM systems such as the improvement in the performance of the channels that are fading away and provides an ideal periodic autocorrelation and a constant magnitude periodic cross correlation. Both of these techniques provide improvement in the ODFM systems. To get more efficiency, this paper aims to develop a hybrid technique by integrating the ZCMT and MPECT techniques for reducing the PAPR in OFDM systems. Further, convolutional encoding is applied for better BER and PAPR. The simulation results of the proposed ZCMT‐MPECT technique are evaluated and compared with the conventional OFDM and other precoding methods.     

一种降低正交频分复用调制信号峰平比的融合方法

提出了一种降低峰平比(PAPR)的融合算法,该算法在发射端对正交频分复用(OFDM)调制信号进行两次降低峰值处理,因而降低PAPR的能力远远优于常规的选择性映射法和压扩法,而该新方法传输信号的性能与压扩法相当。     

基于联合法降低OFDM水声通信峰均比的研究

高峰均功率比限制了正交频分复用（OFDM）技术的广泛应用,如何选择合适有效的方法来降低高峰均比是这一领域的研究重点。利用压扩方法和限幅方法在性能上的互补性,提出一种联合方法。仿真结果表明,该方法有效地降低了OFDM系统的峰均比,而且简单易于实现。     

新的低复杂度降低OFDM信号峰均功率比的压缩扩张技术

本文提出了一种新的降低OFDM信号峰均功率比的压缩扩张技术.文中通过与传统压缩扩张技术的对比,详细介绍了新压缩扩张技术的方法和计算复杂度、并从统计角度分析了对峰均功率比及其用于OFDM系统时对系统误比特率的改善等方面的性能.数值仿真说明,与传统压缩扩张技术相比较,新压缩扩张技术不仅具有更低的计算复杂度,而且可以获得更为高效的性能增益.     

降低OFDM峰均比的压扩变换方法研究

基于压扩变换的OFDM信号PAPR抑制方法具有实现简单、抑制效果明显的优点。对现有压扩变换PAPR抑制方法进行了分析和研究,并在此基础上,提出了一种基于均匀分布的压扩变换方法。该方法能够将任何分布的调制信号均变为均匀分布。仿真结果表明,与现有方法相比,该方法抑制PAPR的效果较为明显,且易于实现,具有较好的实用性。     

Exponential companding technique for PAPR reduction in OFDM systems

In this paper, a new nonlinear companding technique, called "exponential companding", is proposed to reduce the high Peak-to-Average Power Ratio (PAPR) of Orthogonal Frequency Division Multiplexing (OFDM) signals. Unlike the /spl mu/-law companding scheme, which enlarges only small signals so that increases the average power, the schemes based on exponential companding technique adjust both large and small signals and can keep the average power at the same level. By transforming the original OFDM signals into uniformly distributed signals (with a specific degree), the exponential companding schemes can effectively reduce PAPR for different modulation formats and sub-carrier sizes. Moreover, many PAPR reduction schemes, such as /spl mu/-law companding scheme, cause spectrum side-lobes generation, but the exponential companding schemes cause less spectrum side-lobes. Computer simulations, which consider a baseband OFDM system with Additive White Gaussian Noise (AWGN) channels and a Solid State Power Amplifier (SSPA), show that the proposed exponential companding schemes can offer better PAPR reduction, Bit Error Rate (BER), and phase error performance than the /spl mu/-law companding scheme.     

一种降低OFDM系统PAPR的改进压扩方法

正交频分复用（OFDM）技术是一种多载波调制方式。作为第四代移动通信系统的核心技术,OFDM己成为当今高速无线通信领域的研究热点。正交频分复用（OFDM）系统存在高峰值平均功率比（PAPR）问题,这一问题会导致系统性能降低,为其实用化设置了障碍。文中研究了一种改进的降低PAPR的非线性压缩与扩展算法,可以得到更好的PAPR性能。该方法的特点在于采用一种计算复杂度较低的非线性压扩函数,同时融合了叠加训练序列方法的改进非线性压扩算法,从而有效地降低系统PAPR。理论研究和仿真结果表明,与传统方法相比,所提出的改进压缩与扩展方法可以在降低系统复杂度的同时得到更好的PAPR性能。     

Transforming the Statistical Distribution of Wireless OFDM Signal for PAPR Reduction

To reduce the high peak-to-average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signal, a novel nonlinear companding transform (CT) scheme is proposed in this paper. This scheme can reallocate both the amplitude/power as well as statistical distribution of the companded signal more reasonably and flexibly than existing CT methods with low computational complexity. By choosing an appropriate companding parameter, it can provide more effective PAPR reduction but at the price of a minimal amount of bit-error-rate (BER) performance degradation caused by the companding distortion. The closed-form expressions including the achievable PAPR gain, signal attenuation factor, and corresponding selection criteria for the companding parameter were derived. Computer simulations demonstrate that the scheme significantly improves the overall performances of OFDM system in terms of PAPR, BER and bandwidth efficiency under the multipath fading channel or with the high power amplifier.