Selected-Mapping Peak-to-Average Power Reduction Method with Orthogonal Pilot Sequences in Underwater Acoustic OFDM System Without Side Information

A novel Selected-mapping (SLM) Peak-to-average power ratio (PAPR) reduction scheme requires no Side information (SI) in Underwater acoustic (UWA) OFDM system is proposed. In the proposed scheme, every distinct phase sequence is represented by a unique Orthogonal comb pilot sequence (OPS), and the orthogonal properties of the OPSs are used to distinguish the index of phase sequences at the receiver. Therefore, the proposed scheme does not need to reserve bits for transmitting SI, so that the data rate can be raised. Simulation results show that the PAPR reduction performance has almost 0.5dB gains comparing to the Conventional SLM (C-SLM) scheme and the Bit error ratio (BER) performance is approximately the same as the SLM scheme with perfect SI. Field experimental results also demonstrate that the proposed scheme can differentiate phase sequences, therefore significantly enhance the quality of the UWA OFDM communication system.     

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.      

A low complexity selected mapping scheme for peak to average power ratio reduction with digital predistortion in OFDM systems

One of the effective methods used for reducing peak‐to‐average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems is selected mapping (SLM). In this paper, a new SLM scheme called DSI‐SLM, which is a combination of dummy sequence insertion (DSI) and conventional selected mapping (C‐SLM) is proposed. Previous techniques have had some drawbacks. In DSI, increasing the number of dummy sequences to have better PAPR degrades transmission efficiency, and in C‐SLM, the complexity rises dramatically when the number of sub‐blocks increases. The proposed DSI‐SLM scheme significantly reduces the complexity because of the reduction in the number of sub‐blocks compared with the C‐SLM technique while its PAPR performance is even better. To enhance the efficiency of the OFDM system and suppress the out‐of‐band distortion from the power amplifier nonlinearity, a digital predistortion technique is applied to the DSI‐SLM scheme. Simulations are carried out with the actual power amplifier model and the OFDM signal based on the worldwide interoperability for microwave access standard and quadrature phase‐shift keying modulation. The simulation results show improvement in PAPR reduction and complexity, whereas the BER performance is slightly worse. Copyright © 2011 John Wiley & Sons, Ltd.     

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.     

改进的SLM算法降低OFDM系统峰均比的研究

正交频分复用(OFDM)技术的一个主要缺点就是传输信号的峰均功率比(PAPR)较高,很容易导致OFDM信号的线性失真和系统性能的下降,这就限制了OFDM技术的广泛应用。因此,如何有效地降低OFDM系统中的PAPR是亟需解决的问题。在对选择性映射(SLM)方法进行深入研究的基础上,提出了基于新的相位序列的SLM技术,与传统SLM方法相比较,它的发送端和接收端不需要辅助信息。在没有数据损失和发送端信号功率稍微增大的情况下,就可以得到与传统的SLM技术相近的性能。并且,在选定合适的系统参数后,系统的SER性能没有得到退化。     

Selective Time-Domain Filtering for Reduced-Complexity PAPR Reduction in OFDM

A new selective time-domain filtering scheme for reducing the peak-to-average power ratio (PAPR) in orthogonal frequency-division multiplexing (OFDM) systems is proposed. The proposed scheme not only relies on conventional pilot symbol channel estimation and demodulation techniques to recover the data in OFDM systems but also uses additional pilot symbols. The proposed scheme has greatly reduced complexity compared with the selective mapping (SLM) scheme and only slightly poorer performance than the SLM scheme. The new scheme achieves significant PAPR reduction at a cost of typically 0.1–0.75 dB in signal-to-noise ratio (SNR) relative to pilot symbol OFDM not having PAPR reduction.      

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.     

Combined Selective Mapping and Binary Cyclic Codes for PAPR Reduction in OFDM Systems

In this paper, we consider reduction of PAPR in OFDM systems with BPSK subcarriers by combining SLM and binary cyclic codes. This combining strategy can be used for both error correction and PAPR reduction. We decompose a binary cyclic code into direct sum of two cyclic subcodes: the correction subcode used for error correction and the scrambling subcode for PAPR reduction. The transmitted OFDM signal is selected that achieves minimum PAPR, from the set of binary cyclic codewords. The received signal can be easily decoded without the need of any side information. Simulations show that the proposed scheme with simplex code as scrambling subcode achieves good PAPR reduction.     

A Low Complexity Selected Mapping Scheme by Use of Time Domain Sequence Superposition Technique for PAPR Reduction in OFDM System

By using the time domain sequence superposition (TDSS) technique, in this paper, we propose a low complexity selected mapping (LC-SLM) scheme for the peak-to-average power ratio (PAPR) reduction of the orthogonal frequency division multiplexing (OFDM) system. Unlike the conventional selected mapping (SLM) scheme which needs several inverse fast Fourier transform (IFFT) operations for an OFDM signal, the proposed scheme requires to implement two IFFT operations only. Thus, it can remarkably reduce the computational complexity. Simulation results show that the proposed scheme can achieve similar PAPR performance as the conventional SLM scheme.      

光OFDM系统中一种改进的SLM峰均比抑制方案

针对光正交频分复用(O-OFDM)系统中峰值平均功 率比(PAPR)较高的缺点,对PAPR抑制技术的选择性 映射法(SLM) 进行了深入研究。基于低复杂度SLM方案的深入研究,提出了一种改进的次PAP R选择的思 想与低复杂度SLM相结合的PAPR抑制方案。改 进的SLM方案能够成倍降低传统SLM方案的计算复杂 度。仿真分析表明,改进的SLM方案在载波数为256的O-OFDM系统中,计算复杂度能降低50%以上,并 且随着子载波数的增加,其复杂度降低程度更为高效;同时,该改进的SLM方案又能使其PAPR抑制性能优于传统的SLM方案,从而进一步提升了低复杂度SLM 方案的实用价值。     

SLM‐based PAPR reduction method using partial data circulation and side information insertion in OFDM systems

In this paper, two selected mapping (SLM)‐based schemes are proposed to reduce the peak‐to‐average power ratio (PAPR) in the orthogonal frequency division multiplexing (OFDM) systems. One is SLM‐based partial data circulation (PDC) scheme. The other is SLM‐based PDC with hamming coded side information (SI) scheme. In the PDC scheme, the partial samples within the data sequence are scrambled by circularly shifting to obtain a set of candidate sequences and, then, each sequence is combined with the corresponding SI to form the candidate OFDM symbol. With the selection of the candidate OFDM symbols with the lowest PAPR, the PAPR of the transmitted signal could be greatly reduced. In the other scheme, hamming code is used to protect the SI to improve the system performance. Simulation results show that the proposed method could reduce PAPR and it has a better bandwidth efficiency and less modules of inverse fast Fourier transform than that with the SLM‐based dummy sequence insertion scheme. Copyright © 2008 John Wiley & Sons, Ltd.     

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...     

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.     

Novel Conversion Matrices for Simplifying the IFFT Computation of an SLM-Based PAPR Reduction Scheme for OFDM Systems

There have been a set of conversion matrices proposed recently by Wang and Ouyang to simplify the inverse fast Fourier transform (IFFT) computation involved in the selected mapping (SLM) scheme for reduction of the peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems. As compared to the conventional SLM scheme, the modified approach achieves close PAPR reduction with much lower complexity but degraded bit error rate (BER) performance. In this paper, we propose a new set of conversion matrices for the SLM scheme such that the complexity can be reduced without sacrificing the BER performance. It is shown that the improved SLM method has better BER performance and lower complexity than the previous work by Wang and Ouyang, at the cost of a slight PAPR reduction loss.     

Low-complexity selected mapping schemes for peak-to-average power ratio reduction in OFDM systems

Orthogonal frequency-division multiplexing (OFDM) is an attractive transmission technique for high-bit-rate communication systems. One major drawback of OFDM is the high peak-to-average power ratio (PAPR) of the transmitter's output signal. The selected mapping (SLM) approach provides good performance for PAPR reduction, but it requires a bank of inverse fast Fourier transforms (IFFTs) to generate a set of candidate transmission signals, and this requirement usually results in high computational complexity. In this paper, we propose a kind of low-complexity conversions to replace the IFFT blocks in the conventional SLM method. Based on the proposed conversions, we develop two novel SLM schemes with much lower complexity than the conventional one; the first method uses only one IFFT block to generate the set of candidate signals, while the second one uses two IFFT blocks. Computer simulation results show that, as compared to the conventional SLM scheme, the first proposed approach has slightly worse PAPR reduction performance and the second proposed one reaches almost the same PAPR reduction performance.     

Adaptive PAPR Reduction Scheme for OFDM Using SLM with the Fusion of Proposed Clipping and Filtering Technique in Order to Diminish PAPR and Signal Distortion

One of the main disadvantages of multicarrier transmission is the high peak-to-average power ratio (PAPR) of the transmitted signal. If the highest transmitted power is confined by the application restrictions or regulatory, the result is to decrease the average power permitted under multicarrier transmission. Selected mapping (SLM) is a standard PAPR reduction scheme that is appropriate for orthogonal frequency division multiplexing (OFDM) scheme as it realizes the performance of PAPR reduction without signal distortion. This paper proposes a method in order to handle the difficulties of high PAPR in OFDM scheme. The offered system is an arrangement of two distinguished methods, such as clipping and SLM. Compared to other hybrid methods, where the individual methods are implemented sequentially, this paper integrates the clipping method in the SLM procedure. This produces a supplementary PAPR reduction associated to the serial arrangement. Simulation results specify that the offered scheme acquires the performance of appropriate PAPR reduction with low computational complexity. The PAPR reduction at different number of subcarriers is analyzed and compared with the existing research work. The performance of relative energy efficiency has also been focused on this paper.

     

Modified selected mapping technique for PAPR reduction of coded OFDM signal

High peak-to-average power ratio (PAPR) of the transmitted signal is a major drawback of orthogonal frequency division multiplexing (OFDM). In this paper, we propose a modified selective mapping (SLM) technique for PAPR reduction of coded OFDM signal. In this technique, we embed the phase sequence, which is used to lower the PAPR of the data block, in the check symbols of the coded OFDM data block. It is shown that we can achieve both PAPR reduction from the SLM technique as well as error performance improvement from the channel coding with no loss in data rate from the transmission of side information. In addition, approximate expression for the complementary cumulative distribution function (CCDF) of the PAPR of the modified SLM technique is derived and compared with the simulation results.     

SFBC MIMO-OFDM peak-to-average power ratio reduction by polyphase interleaving and inversion

Many PAPR reduction schemes have been proposed for OFDM systems. Among these, the signal scrambling methods such as the partial transmit sequences (PTS) (S. H. Muller, et al., 1997) and selective mapping (SLM) (R. W. Bauml, et al., 1996) are attractive as they obtain better PAPR property by modifying OFDM signals without distortion. These schemes can also be applied to a SFBC MIMO-OFDM system, which is advantageous for dispersive channels, in a straightforward way by performing signal scrambling on data sequence before it is distributed to the transmit antennas according to employed encoding scheme. Note however that in the case of PTS PAPR reduction in the time domain is not possible, which leads to prohibitively large complexity of such scheme. In this letter, we introduce more effective approach, the polyphase interleaving and inversion (PII) PAPR scheme and its reduced complexity version (RC-PII), which is designed to suppress peaks in SFBC-OFDM, transmit diversity.     

RBF Neural Network Based SLM Peak‐to‐Average Power Ratio Reduction in OFDM Systems

One of the major disadvantages of the orthogonal frequency division multiplexing system is high peak‐to‐average power ratio (PAPR). Selected mapping (SLM) is an efficient distortionless PAPR reduction scheme which selects the minimum PAPR sequence from a group of independent phase rotated sequences. However, the SLM requires explicit side information and a large number of IFFT operations. In this letter we investigate a novel PAPR reduction method based on the radial basis function network and SLM.     

SLM based PAPR reduction of OFDM signal using new phase sequence

One of the main issues of orthogonal frequency division multiplexing (OFDM) is the high peak-to-average power ratio (PAPR) of the transmitted signal which adversely affects the complexity of power amplifiers. The selected mapping (SLM) technique is one of the promising PAPR reduction techniques for OFDM. In this reported work, rows of normalised Riemann matrices are selected as phase sequence vectors for the SLM technique. MATLAB simulations show PAPR reduction of around 2.3 dB using the proposed method compared with methods reported in the literature.