降低OFDM系统峰均比的改进方法

正交频分复用（OFDM）系统最主要的一个缺点就是峰值平均功率（PAPR）比过高,选择性映射（SLM）虽然能无失真地降低OFDM信号峰均比PAPR,但不能完全避免OFDM系统高峰值的出现。提出一种新的算法,将SLM法与迭代限幅滤波算法结合,通过迭代限幅滤波（RCF）来进一步提高系统的性能。仿真结果表明,该方法可以在不增加系统误码率性能的基础上,在降低OFDM信号峰均比方面,比限幅法、迭代限幅滤波法和SLM法均有很大的提高。     

OFDM系统峰平比问题的研究

OFDM技术最主要的缺点是具有较大的峰值平均功率比（PAPR）。本文就目前降低PAPR对OFDM系统影响的主要方法进行了简单的综述，一类是从OFDM信号着手；包括剪波法（限幅法），编码技术，相位旋转方法；另一类方法是对高频率放大器的实现线性化技术，主要是放大器预失真方法。     

降低OFDM系统高峰均功率比的方法研究

针对OFDM技术具有较高的峰均功率比（peak to average power ration,PAPR）这一主要缺点,提出一种控制OFDM载波信号衍生频谱的迭代算法,在降低系统高峰均功率比的同时,也降低系统的误码率.利用该算法对数据序列长度为64的OFDM信号进行仿真验证,随着迭代次数的增加,衍生频谱系数增大,系统平均功率增加,OFDM信号的峰值功率比得到一定的降低.     

降低OFDM峰均比SLM算法比较

正交频分复用（OFDM）是未来无线通信关键的技术之一,但是高峰值平均功率比（PAPR）一直是将OFDM技术实用化的一大障碍。选择映射（SLM）算法是无失真降低OFDM信号峰平比的有效方法之一。但计算复杂度高和需要发送边带信息是传统SLM算法的主要缺点。通过分析比较了多种改进方法,发现如果能够将传统SLM算法这两方面的缺点综合考虑,就能更好地改善SLM算法的性能,这将是今后研究SLM算法的方向之一。     

OFDM信号峰平比问题的研究

正交频分复用(OFDM)具有抗码间串扰、频谱效率高、可提供高速数据传输等优点,但OFDM信号的峰平比较高,在非线性放大器中会产生信号失真,已成为其实用化的一大障碍。文中分析了多种降低OFDM信号峰平比的方法,重点介绍了利用虚载波降低峰平比的方法,并对各种方法的优缺点做了分析和比较。     

联合法降低OFDM系统的非线性失真

正交频分复用技术(OFDM,Orthogonal Frequency Division Multiplexing)是一种有效的并行多载波传输方案,然而,OFDM技术存在一个主要缺点,即发送信号存在较高的峰值平均功率比(PAPR,Peak-to-Average Power Ratio)。研究表明高带宽效率的限幅类技术着眼于直接降低OFDM信号的峰均比,而幅度和相位预失真方法则是从放大器的角度出发,对放大器进行预失真处理,增大功率放大器的线性范围。这里提出将限幅类技术和预失真处理进行联合实现,从而在系统PAPR减小、失真补偿和误码率之间取得较好的折中。     

PTS-0FDM的一种新的子块分割方法

正交频分复用（OFDM）的一个主要缺点是信号的峰值功率与平均功率比（PAR）很高，部分传输序列（PTS）是一种有效降低OFDM信号PAR的方法。在PTS方法中，采用不同的分割方法可以改善PAR性能。文章提出一种新的子块分割方法——联合分割方法来降低任意子载波数目OFDM系统的PAR。仿真结果表明，联合分割方法既降低了系统的运算复杂度，又降低了系统的PAR。     

正交频分复用信号峰均比抑制技术研究

正交频分复用(OFDM)系统存在峰值平均功率比(PAPR)较高的缺点.通过对PAPR相关特性的深入讨论分析,针对峰值抵消波峰因子降低(PC?CFR)算法引入的非线性失真较大的问题,提出了一种可降低信号非线性失真的峰均比抑制算法,即PC?CFR算法与部分传输序列(PTS)算法联合改进的PAPR抑制方案.仿真结果表明,该方...     

利用星座扩展来降低OFDM系统中峰均比的新方法

正交频分复用（OFDM）系统有很高的峰均比,这会导致发送端功率放大器的低功率效率和非线性失真.文中提出了一种利用峰值抵消信号来降低OFDM的峰均比的新方法.峰值抵消信号利用未用的或保留的子载波以及星座的可扩展部分通过反馈的方式产生.这种方法可以显著的降低峰均比而不需要边信息.     

基于低密度奇偶校验码的概率整形正交频分复用-光载无线通信系统的传输特性

提出了一种基于低密度奇偶校验码（LDPC）的概率整形（PS）方案，以优化正交频分复用（OFDM）信号在光载无线（RoF）通信系统中的传输性能。首先，理论分析了PS技术和PS-OFDM信号的生成原理，该方案的冗余度为6.7%，相比传统的OFDM信号平均功率降低了约20%。接着，在理论研究的基础上建立了仿真验证系统，与传统OFDM-RoF系统相比，该系统可明显降低OFDM信号的平均发射功率，在相同平均发射功率下改善系统的峰值平均功率比（PAPR）。最后，对该系统在不同光纤传输距离下的误码率分析结果表明，在基带数据速率为2.5 Gbps，射频载波频率为25 GHz的情况下，基于LDPC的PS-OFDM-RoF系统可以有效改善接收机的灵敏度，并增加系统的可靠传输距离。     

一种降低正交频分复用峰均功率比的方法

目前正交频分复用（OFDM）正得到越来越广泛的应用，但其主要缺点是有较高的峰均比（PAPR），虽然有许多降低OFDM信号的峰均比的方案，但是却大大增加了系统的复杂性，本文通过改进一种降低OFDM信号峰均功率的方法，很好地解决了复杂性和峰均比的降低的问题。     

Optimization of Peak to Average Power Reduction in OFDM

Orthogonal frequency division multiplexing (OFDM) a multicarrier system [1, 2] provides base for all advanced wireless communication system. The performance of OFDM is degraded by peak-to-averagepower ratio (PAPR). High PAPR requires high power amplifiers (HPAs). The nonlinearity of the HPA exhibits amplitude and section distortions, that cause loss of orthogonality among the subcarriers, and hence, intercarrier interference (ICI) is introduced inside the transmitted signal. Not only that, high PAPR put together lands up in in-band distortion and out-of-band radiation. Rather than using HPA’s, the only way to improve performance of OFDM system is to reduce PAPR. The PAPR reduction of OFDM system gives fair reduction in PAPR under partial transmits sequence (PTS) and DCT-SLM techniques. Here in this paper we proposed a combination of PTS and DCT-SLM and an algorithm to cut back the PAPR. This hybrid combined technique reduces PAPR effectively and minimizes the complexity of PTS technique.     

Adaptive multiple stage K-best successive interference cancellation algorithm for MIMO detection

In this study, we propose a novel meta-heuristic optimization algorithm for joint peak-to-average power ratio (PAPR) reduction in orthogonal frequency division multiplexing (OFDM) systems. High PAPR not only complicates a distortion of a signal at the nonlinear high-power amplifier of a transmitter the design, but also in significant performance degradation. Tone injection (TI) scheme is a well-known PAPR reduction technique for OFDM systems. The key idea of the proposed method is a distortionless technique that can reduce PAPR significantly without data rate loss and does not require the extra side information. But unfortunately, in optimal TI-based OFDM systems, the PAPR reduction performance mainly requires an exhaustive search over all possible constellations, which is a hard optimization problem and potential problem for practical applications. To address this problem, an efficient scheme based on firefly algorithm is introduced to search over all combinations of possible permutations of the expanded constellation with low complexity and fast convergence. The simulation results reveal that our system can achieve good tradeoff between PAPR reduction performance and low computational complexity.     

一种基于SLM的抑制PAPR的改进算法研究

正交频分复用(OFDM)作为一种特殊的多载波传输(MCM)方案,具有较高的频带利用率和良好的抗多径干扰能力。但较高的峰均功率比(PAPR)是限制其应用的一个主要缺点。选择性映射(SLM)算法是无失真降低OFDM系统PAPR的有效方法,但其复杂度较高。因此提出了一种基于SLM的抑制PAPR的改进算法。仿真结果表明,该方法即有效地降低了SLM实现的复杂度,又大幅降低了PAPR,提高了OFDM系统性能。     

A Low Complexity Partition Dummy Sequence Insertion PAPR Reduction Method for the OFDM System

Orthogonal Frequency Division Multiplexing (OFDM) technique has been widely adopted in many wireless communication systems because it can divide a wideband channel into several narrowband ones to avoid the frequency selective fading. However, one major drawback of the OFDM signal is the high peak-to-average power ratio (PAPR) problem. The high PAPR results in the in-band distortion and out-of-band radiation when the OFDM signal is fed into a nonlinear power amplifier. In this paper, we propose a Low Complexity Partition Dummy Sequence Insertion method to reduce the PAPR and computational complexity of the Partition Dummy Sequence method. Simulation results of the PAPR, Bit Error Rate and complexity reduction for the proposed method are evaluated to demonstrate its capabilities.     

OFDM系统中基于限幅和压缩感知的非线性失真补偿算法

正交频分复用（Orthogonal Frequency Division Multiplexing,OFDM）信号具有较高的峰均功率比（Peak to Average Power Ratio,PAPR）,不仅影响功率放大器（High Power Amplifier,HPA）的工作效率,而且HPA使得OFDM信号产生严重的非线性失真,导致系统的误比特率（Bite Error Rate,BER）增大.本文基于限幅和压缩感知（Compressive Sensing,CS）提出了改进的补偿算法,发送端采用限幅降低信号的PAPR,接收端首先采用改进的逆模型方式减小HPA引入的非线性失真,再采用CS抵消由限幅引入的信号失真.仿真表明,所提方法不仅明显降低了OFDM信号的PAPR,而且有效提高了系统的BER性能.     

一种降低OFDM系统峰均比的改进算法

选择映射（SLM）技术是一种无失真降低正交频分复用（OFDM）系统信号峰均比的方法,为更好地降低正交频分复用系统的峰均比,文中提出了一种基于SLM级联抵消技术降低PAPR的优化算法。该算法首先利用改进的SLM算法,对系统PAPR特性进行优化,然后利用抽样信号作为参考函数,实现对系统峰均比的有效降低。通过分析SLM级联峰...     

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.

     

A New PAPR Reduction Technique in OFDM Systems Using Linear Predictive Coding

High peak-to-average power ratio (PAPR) has always been as a major problem in orthogonal frequency division multiplexing (OFDM) that leads to a severe nonlinear distortion in practical hardware implementations of high power amplifier. In this article, a new PAPR reduction method is proposed based on linear predictive coding (LPC). This method proposes the use of signal whitening property of LPC as a preprocessing step in OFDM systems. Error filtering of the proposed method removes the predictable content of stationary stochastic processes which can reduce the autocorrelation of input data sequences and is shown to be very effective solution for PAPR problem in OFDM transmissions. It is shown that the proposed method can achieve a significant reduction in PAPR without degrading the power spectral level, error performance or computational complexity of the systems. It is also shown that the proposed method is independent of modulation schemes and can be applied to any number of subcarriers under both additive white gaussian noise and wireless Rayleigh fading channel.     

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.