OFDM系统中一种联合改进的低复杂度SLM峰均比抑制技术

高的峰值平均功率比(Peak-to-Average Power Ratio,PAPR)是光正交频分复用(Optical Orthogonal Frequency Division Multiplexing,O-OFDM)系统的一个主要缺点,选择性映射(Selective Mapping,SLM)法能有效降低高PAPR出现的概率,但它的计算复杂度较高.一些低复杂度的SLM方案能够有效地降低复杂度,但同时也降低了PAPR的抑制性能.为了平衡这两个因素,将低复杂度SLM方案与次优选择的思想相结合,文章提出了一种联合改进的PAPR抑制方案.在低复杂度方案中,通过将一个复频域信号分为两个实信号,再利用快速傅里叶变换(Fast Fourier Transform,FFT)的平移和反折性质将其重建成新的信号,以得到更多的备选信号,如此便能降低计算复杂度.然后,再结合次优选择的思想,选择PAPR最小的一路以得到最优的PAPR抑制性能.仿真结果验证了该方案的有效性.     

一种降低OFDM系统PAPR的低复杂度盲SLM方法

针对传统选择映射方法复杂度过高和需要传输边信息的问题,提出了低复杂度的盲选择映射方法。该方法巧妙地设计了一组相位旋转矢量,并将一个或几个正交频分复用符号看作一个符号块,使得每个符号块中都有一个符号具有导频符号,利用设计的相位旋转矢量对应的转换矩阵与原信号块的时域相乘运算代替反傅里叶变换运算产生的备选信号块。在接收端通过导频符号估计出包含相位旋转矢量信息的等效信道,从而实现了不需要边信息的盲数据检测。分析与仿真结果表明,与常规选择映射方法相比,提出的方法复杂度大大降低,在不需要传输边信息的情况下可以达到相近的降峰均比性能。     

PAPR Reduction in OFDM Systems Using Modified SLM with Different Phase Sequences

Wireless Personal Communications - High Peak-to-average power ratio (PAPR) is one of the main issues in multicarrier modulation systems. PAPR is mainly caused due to the summation of various...     

VLM Precoded SLM Technique for PAPR Reduction in OFDM Systems

Orthogonal frequency division multiplexing (OFDM) is perhaps the most spectrally efficient, robust transmission technique discovered so far for communication systems, and it also mitigates the problem of multipath environment. High peak-to-average power ratio (PAPR) has always been a major drawback of the OFDM systems. In this article, a new precoding technique has been proposed based on Vandermonde-like matrix (VLM) and selective mapping (SLM) to reduce PAPR in OFDM systems. VLM precoding reduces the autocorrelation of the input sequences while SLM takes an advantage of the fact that the PAPR is very sensitive to phase shifts of the signal. The main advantage of this proposed scheme is to achieve a significant reduction in PAPR without increasing the system complexity. Computer simulations show that, the proposed method outperforms the existing precoding techniques without degrading the error performance of the system.     

Partial Shift Mapping for PAPR Reduction with Low Complexity in OFDM Systems

The high peak‐to‐average power is one of the main drawbacks in OFDM systems. This letter proposes a partial shift mapping (PSM) method for peak power reduction in OFDM systems. By utilizing the properties of the discrete Fourier transform, the proposed method generates a set of candidate signals without additional complex multiplication and selects the one with minimum peak power for transmission. Analyses and simulations confirm that the PSM method achieves satisfactory peak power reduction performance and low complexity compared with other kindred methods, for example, selected mapping and partial transmit sequences.     

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。     

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.     

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。     

一种OFDM系统中PAPR的抑制算法

为降低正交频分复用(OFDM)系统中发射信号的峰值功率,提出了在一个OFDM符号内使用两种信号星座图对二进制数据进行编码,通过在各个子载波处选用合理的信号星座图来实现对峰值均值功率比(PAPR)的抑制。由于算法不改变现有OFDM系统的实现结构,在不影响OFDM中其它信号处理性能的条件下,仿真表明算法能有效地降低系统的峰值均值功率比。     

A New PAPR Reduction Scheme for OFDM Systems Based on Gamma Correction

Orthogonal frequency division multiplexing (OFDM) is perhaps the most spectrally efficient method discovered so far for communication systems and yet have an excellent immunity against multipath fading and inter-symbol interference. One of the major drawbacks of OFDM systems is their high peak-to-average power ratio (PAPR), which degrades system performance when nonlinear high power amplifiers (HPA) are employed. In this article, a new companding technique based on gamma correction (GC) function is proposed and analyzed. Through extensive computer simulations, it is shown that the proposed technique outperforms the previously suggested A-law and μ-law companding methods for PAPR reduction. A thorough investigation of GCC companding is presented in terms of computational complexity (CC), complementary cumulative distribution function (CCDF), power spectral density (PSD), and bit-error-rate (BER). It is also shown that the proposed method is independent of modulation schemes and can be applied to any number of subcarriers.     

基于SLM的减小OFDM系统PAPR的改进技术

OFDM系统的峰均功率比过大是一个严重的问题.降低OFDM系统的峰均功率比中的选择性映射法(SLM)方法需传送边带信息,但边带信息传送需要严格的信道编码,增加了系统复杂性,占用了频带宽度.文中将传统的OFDM峰均功率比降低技术SLM方法加以改进并与限幅技术结合起来,所生成的新算法有效地弥补了传统SLM技术限制峰均功率比不足的问题,并且不用传输边带信息.仿真表明,该方法有良好的性能.     

一种降低OFDM系统PAPR的低复杂度算法

选择映射(SLM)是一种无失真降低OFDM信号峰平比(PAPR)的有效方法,但该方法通过串并转换将一路信号变为U路信号,再对U路信号进行IFFT处理,计算量大,同时也降低了信号传输速率。文中提出了一种改进的随机筛选法方案,该方法在IFFT模块之前就对序列进行选择,根据判决门限选择其中随机性最好的一路信号进行传输。其与SLM法相比,只进行一路信号的IFFT计算,复杂度大幅降低,且提高了信号传输效率,并在较大程度上降低了OFDM信号的峰平比。     

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.     

降低MC-CDMA系统峰均功率比的SLM改进方法

多载波码分多址（MC-CDMA）被广泛认为是未来4G通信的核心技术,但MC-CDMA信号的高峰均功率比（PAPR）会引起非线性失真并导致误码率性能恶化。针对MC-CDMA系统的高峰均功率比的问题,对传统的选择性映射（SLM）算法进行改进。提出一种自适应选择复用帧数的选择性映射系统,在误码率满足一定条件的基础上,通过自适应选择复用帧数的算法选择出最适合系统的复用帧数的个数,使系统在复杂度较低的基础上仍能有效的降低信号的峰均功率比。仿真结果验证其有效性。     

利用虚拟子载波抑制OFDM系统PAPR及其低复杂度算法

研究了利用虚拟子载波抑制OFDM系统PAPR及其算法简化的问题.通过对虚拟子载波技术迭代过程进行简化,得到了运算量只是系统子载波数量级的低复杂度迭代算法,减小了算法实现的复杂度.计算机仿真表明,通过增大虚拟子载波数量或迭代次数,可使系统PAPR性能在一定范围内得到明显改善.由于不用传输边带信息,系统具有较强的可靠性和抗干扰能力.     

Metric-Based and Angle-Rotated Tone Reservation Scheme for PAPR Reduction in OFDM Systems

High Peak-to-average power ratio （PAPR） has been a crucial problem in Orthogonal frequency divi- sion multiplexing （OFDM） systems. In all PAPR reduc- tion schemes, Tone reservation （TR） technology is consid- ered as one of the most promising methods because of no additional distortions no side information, and low imple- mentation cost. For conventional TR approaches, the as- signed value to reserved subcarriers just considers one peak value and this brings peak value up again easily. In this paper, a novel scheme named Metric-based angle-rotated （MBAR） for TR is presented. The scheme employs a met- ric to measure how much each subcarrier contributes to the output signal samples of large magnitude and then subcarriers with the largest positive metrics are selected to reduce PAPR. The simulation results show that when the reserved subcarriers number is 1.46 percent, the PAPR gain of the proposed method can achieve 0.4？dB at least at the probability of 10-3.     

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.      

基于准循环LDPC码和SLM法降低PAPR的新方法

由于具有频谱利用率高、抗多径衰落能力强等优点,正交频分复用(OFDM)技术已成为通信领域的研究热点之一。但是OFDM技术中存在的高峰均功率比(PAPR),为其实用化设置了障碍。本文提出利用不规则准循环低密度奇偶校验(QC-LDPC)码作为信道编码技术,联合选择映射(SLM)算法抑制高峰均功率比。其中,不规则QC-LDPC码的生成矩阵由校验矩阵中的子矩阵直接构造得到。相对于传统的选择映射算法,该方法能发挥LDPC码和SLM法的联合优势,同时由于采用基于置信传播(BP)的迭代译码算法,计算复杂度低、译码速度快。仿真结果表明,该联合方法既能有效地改善OFDM信号的PAPR特性,又能保证系统获得可靠的误码率性能,且实现简单。      

一种基于OPTS的降低OFDM峰均比的低复杂度算法

正交频分技术最主要缺点之一就是传输信号的高峰均值功率比,部分传输序列法是解决高峰均值功率比的最有效方法之一。虽然最优部分传输序列方法性能很好,但其计算复杂度非常大,搜索复杂度随着子块数指数增加,这样降低搜索复杂度显得尤为重要。本文改进TOPTS搜索过程中计算时域矢量的计算方法,使其计算复杂度大大降低,但系统性能不受影响。     

Reduction of the PAPR in OFDM Systems by Intelligently Applying Both PTS and SLM Algorithms

The orthogonal frequency division multiplex (OFDM) technique, which is used in the 4G communications, has a shortcoming of having a high peak to average power ratio (PAPR), and thus a lot of research has been conducted to reduce the PAPR in OFDM systems. The typical algorithms in this research area are the multi-time clipping algorithm, the \(\mu \)-law compression algorithm, SLM algorithm, PTS algorithm, and Golay complement sequence algorithm. It is found in this paper that the SLM and PTS algorithms have good performance in reducing the PAPR while having less information overhead than the Golay complement sequence algorithm, less distortion than the \({\mu }\)-law compression algorithm, and less BER than the clipping algorithm. Thus, a new PAPR reduction algorithm is proposed, which tries to intelligently apply both PTS and SLM algorithm, while utilizing their complementary advantages and avoiding their disadvantages. According to simulation results, the performance of the proposed algorithm has much better performance in reducing the PAPR than the SLM and PTS algorithms, with comparable computational complexity, BER performance, and information overhead.