On the Nonlinear Companding Transform for Reduction in PAPR of MCM Signals

In this paper, we provide the design criteria of the nonlinear companding transforms for reduction in peak-to-average power ratio (PAPR) of multi-carrier modulation (MCM) signals, which can enable the original MCM signals to be transformed into the desirable distribution. As examples, some novel nonlinear companding transforms have been proposed to transform the amplitude or power of the original MCM signals into uniform distribution, which can effectively reduce the PAPR for different modulation formats and subcarrier sizes without any complexity increase and bandwidth expansion. It has been shown by computer simulations that the proposed schemes can significantly improve the performance of MCM systems including bit-error-rate and PAPR reduction.     

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。     

基于Hadamard矩阵变换降低OFDM系统PAPR的新算法

本文研究了一种基于Hadamard变换降低OFDM系统PAPR的新算法,该算法扩展了传统系统的星座点,减小了频域符号间的相关性,其编解码算法简便,易于实现。文中分析了该算法的基本原理,同时仿真结果表明,采用该算法其PAPR可以比传统方法降低3-4dB;并且可以与其它方法联合使用,从而进一步降低PAPR。     

一种抑制PAPR信号峰均功率比的有效方法

OFDM技术的应用越来越广泛,但是其发送信号功率的峰均功率比（PAPR）比较大是其主要的缺陷之一。本文提出了一个降低OFDM信号PAPR的有效灵活的技术。该方法是通过恰当的选择OFDM调制中各个子载波的时域脉冲波形。仿真结果表明该方法能够大大降低OFDM信号的PAPR值。该技术与现有的其他方法相比实现复杂度也更低。     

Linear Companding Transform for the Reduction of Peak-to-Average Power Ratio of OFDM Signals

A major drawback of orthogonal frequency-division multiplexing (OFDM) signals is their high peak-to-average power ratio (PAPR), which causes serious degradation in performance when a nonlinear power amplifier (PA) is used. Companding transform (CT) is a well-known method to reduce PAPR without restrictions on system parameters such as number of subcarriers, frame format and constellation type. Recently, a linear nonsymmetrical companding transform (LNST) that has better performance than logarithmic-based transforms such as $mu$-law companding was proposed. In this paper, a new linear companding transform (LCT) with more design flexibility than LNST is proposed. Computer simulations show that the proposed transform has a better PAPR reduction and bit error rate (BER) performance than LNST with better power spectral density (PSD).      

一种降低OFDM信号PAPR的新方法

正交频分复用(OFDM)技术的一个缺点是信号的高峰值平均功率比(PAPR)大大降低了系统中线性功放的效率。本文提出一种新的基于Nyquist脉冲成形的PAPR抑制方法。这种方法基于选择适当的Nyquist脉冲波形集合对OFDM的各个子载波进行脉冲成形。分析论证了该方法的PAPR上限值和所用的脉冲成形波形集合。仿真结果表明该方法能有效降低任意子载波数目的OFDM信号的PAPR值,而且与已有方法相比应用更为简单。因此脉冲成形技术不仅能对传输信号进行频谱成形来提高系统的频带利用率,而且还可以减小信号的PAPR值。     

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。     

PAPR Reduction of OFDM Signals Using Partial Transmit Sequences and Reed-Muller Codes

This letter proposes a modified PTS technique using binary Reed-Muller (RM) codes for error correction and PAPR control in BPSK OFDM systems. A RM code is divided into the direct sum of a correcting subcode for encoding information bits and a scrambling subcode for encoding PAPR bits. The transmitted signal of the resulting OFDM sequence is selected with minimum PAPR from a number of candidates which are codewords of a coset of the scrambling subcode. We consider the RM codes in natural and cyclic orderings. Numerical results show that RM codes in cyclic ordering achieve better performance in PAPR reduction than RM codes in natural ordering.     

GA-PTS Using Novel Mapping Scheme for PAPR Reduction of OFDM Signals Without SI

In recent time orthogonal frequency division multiplexing (OFDM) has proved its mettle as a preferred choice for high speed transmission in wireless applications due its efficient mechanism to combat the inter symbol interference. However sudden high peaks in OFDM signal envelope lead to high peak to average power ratio (PAPR). Enhanced values of PAPR result into complex RF amplifier circuit with reduced efficiency. There are various methods available for PAPR reduction, out of them partial transmit sequence (PTS) is most effective proven choice for PAPR reduction. However PTS technique requires cumbersome searching of all possible phase factors to find optimal phase factor which produces lowest PAPR, the information regarding optimal phase set used at the transmitter need to be sent to the receiver as side information (SI) for decoding purpose, however transmitting SI requires additional transmission bandwidth thus reducing overall bandwidth efficiency. To reduce the exhaustive searching genetic algorithm (GA) could be used with PTS leading to GA-PTS system. In this paper a GA-PTS system is proposed which uses novel octagonal geometry for constellation extension purpose. This scheme does not require transmission of any side information for decoding purpose at receiver and at the same time GA-PTS system reduces the required number of searches. Simulations are presented to show that proposed scheme provides similar PAPR performance as conventional PTS but without need of SI transmission at reduced number of searches.     

Boosted PTS Method with Mu-Law Companding Techniques for PAPR Reduction in OFDM Systems

Wireless Personal Communications - This paper proposes an enhanced PAPR reduction technique which combines an enhanced PTS method with Mu-Law companding. The enhanced PTS method improves...     

OFDM无线通信中高峰均比及其抑制算法研究

凭借很强的抗符号间干扰(ISI)和抗衰落能力,采用正交频分信道的OFDM技术的无线通信越来越受到人们的重视。但是作为一种多载波调制方式,OFDM技术同样存在着高峰均比(PAPR)的问题,高的PAPR会导致信号畸变,造成子信道间的相互干扰,从而影响OFDM的性能。针对此,重点介绍了OFDM系统中的PAPR比问题的概念,并对降低PAPR的主要算法进行了论述。     

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.     

PAPR Reduction in OFDM Signals: An Adaptive-Network-Based Fuzzy Inference Approach

In this paper, an adaptive-network-based fuzzy inference system (ANFIS) based scheme is analyzed and proposed for reducing the peak-to-average power ratio (PAPR) in multicarrier signals under additive white Gaussian noise and multipath fading (Raleigh) channel environment. This scheme involves training of ANFIS structure in time domain using Orthogonal Frequency Division Multiplexing signals with low PAPR, such as those obtained by approximate gradient project–null subcarrier switching (AGP–NCS) method. Once the ANFIS module is trained, the proposed scheme approximately offers similar reduction in PAPR as compared to AGP–NCS method, with significantly less convergence time and computational complexity. he results show that proposed approach is not only less complex but also maintains the data rate and bit error rate performance compared with other conventional schemes.     

Bit-Based SLM Schemes for PAPR Reduction in QAM Modulated OFDM Signals

In this paper, we propose two bit-based selected mapping (SLM) schemes for reducing peak to average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signals with quadrature amplitude modulation (QAM), called bitwise SLM (BSLM) and partial bit inverted SLM (PBISLM). Contrary to the conventional SLM which rotates the phases of QAM symbols in the frequency domain, the proposed schemes change the magnitudes as well as the phases of QAM symbols by applying binary phase sequences to the binary data sequence before mapped to QAM symbols. Simulation results show that the proposed schemes have better PAPR reduction performance with shaping gain than the conventional SLM scheme for the QAM modulated OFDM signals, especially for the small number of subcarriers.      

An Adaptive Clipping and Filtering Technique for PAPR Reduction of OFDM Signals

In recent years, many peak-to-average power ratio (PAPR) reduction techniques have been proposed for orthogonal frequency division multiplexing (OFDM) signals. Among various techniques, the iterative clipping and filtering (ICAF) technique has been considered as a practical scheme, and widely used owing to its non-expansion of bandwidth, low computational complexity, and simplicity in implementation without receiver-side cooperation. However, the performance of conventional ICAF technique is degraded, because the same signals are iteratively clipped with a fixed clipping threshold (CT) in every clipping operation. In this paper, we analyze the performance of conventional ICAF technique, and then propose an adaptive ICAF scheme, which clips the signal with an adaptively modified CT in every clipping operation to achieve enhanced PAPR reduction of OFDM signals. Simulation results show that the proposed scheme significantly outperforms the conventional scheme, in PAPR reduction of OFDM signals at the same number of iterations.     

Optimizing the Reduction of PAPR of OFDM System Using Hybrid Methods

Wireless Personal Communications - Orthogonal Frequency Division Multiplexing (OFDM) is a multi-carrier modulation, which transfers multimedia data in both wired/wireless communications. It suffers...     

OFDM系统中基于非均匀量化的PAPR抑制方法

对利用非均匀量化技术来降低OFDM系统的PAPR值的方法进行了理论分析,并且将这一方法与实际的无线局域网IEEE802.11a系统进行了仿真。提出了在保证系统性能指标的前提下通过确定非均匀量化最优参数来最大程度降低PAPR值的方法。     

降低正交频分复用系统峰均功率比的部分压扩算法

针对现有压扩变换法系统性能差的缺点,提出了一种降低系统峰均功率比的部分压扩算法。该方法根据正交频分复用(OFDM)系统信号幅度服从瑞利分布的统计特性,仅压缩大幅度信号保持了系统信号幅度的分布特征,弥补了现有压扩变换的不足,且具有带外功率小的优点。在M阶调制方式下的系统仿真结果表明,部分压扩方法与选择性映射和部分传输序列等方法相比,可获得相近的峰均功率比压缩效果并且在同样的系统误码率条件下比指数压扩法获得约log2(M)dB信噪比增益。     

A Low-Complexity PTS-based PAPR Reduction Technique for OFDM Signals without Transmission of Side Information

Increased peak-to-average power ratio (PAPR) imposes a design challenge for orthogonal frequency division multiplexing-based signals. An efficient technique to address the increased PAPR problem is the partial transmit sequences (PTS) approach. A significant drawback of PTS is the fact that it multiplies the transmitted symbol with weighting factors selected by the transmitter. Since the weighting factors are required for decoding, they are explicitly transmitted, in most cases. This paper proposes a new low-complexity technique for retrieving the weighting factors in the receiver. The proposed decoder uses the predefined values of pilot tones and explores all the permissible combinations of weighting factors in order to identify the factor combination employed by the transmitter. The proposed decoder requires no additional pilot tones or explicit transmission of side information, therefore no data rate loss is implied. Furthermore this paper presents a digital very large scale integration implementation of the proposed PTS decoder and demonstrates its low-power properties.     

降低OFDM峰均比的无边信息传输低复杂度PTS算法

部分传输序列(PTS)技术是正交频分复用(OFDM)系统中一种非常有效的降低峰均功率比方法.其缺点是在发送端需要选择权重因子与发送符号相乘来进行发送,而权重因子通常会作为边信息被额外地传输.本文首先讨论了一种基于导频音来恢复权重因子的PTS算法,它在接收端通过收到的导频音进行判决恢复.采用这种算法,能有效抑制系统的PA...