OFDM系统PAPR和OOB辐射联合抑制算法研究

正交频分复用(OFDM)技术具有频谱效率高和抗多径衰落能力强的优点,但存在高峰值平均功率比(PAPR)和高带外(OOB)辐射的固有缺点。部分PAPR抑制算法会导致OOB辐射升高,因此需要一种联合抑制OFDM系统的PAPR和OOB辐射的算法。本文提出了一种新的结合线性压扩和简化限幅滤波的混合式PAPR和OOB辐射联合抑制算法,该算法采用连续分段线性压扩(CPLC)算法抑制信号PAPR,并对压扩后的信号进行频域滤波;然后采用简化限幅滤波(SCF)算法降低频域滤波导致的峰值再生,保证信号的OOB辐射不再升高。接收端采用迭代接收算法提高系统的误码率性能。仿真结果表明,与CPLC、SCF方案相比,所提算法可以达到更好的PAPR和OOB辐射联合抑制性能,同时通过迭代接收算法获得与原始信号相近的误码率(BER)性能。

PSO-DBNet for Peak-to-Average Power Ratio Reduction Using Deep Belief Network

Data transmission through a wireless network has faced various signal problems in the past decades.The orthogonal frequency division multiplexing(OFDM)technique is widely accepted in multiple data transfer patterns at various frequency bands.A recent wireless communication network uses OFDM in longterm evolution(LTE)and 5G,among others.The main problem faced by 5G wireless OFDM is distortion of transmission signals in the network.This transmission loss is called peak-to-average power ratio(PAPR).This wireless signal distortion can be reduced using various techniques.This study uses machine learning-based algorithm to solve the problem of PAPR in 5G wireless communication.Partial transmit sequence(PTS)helps in the fast transfer of data in wireless LTE.PTS is merged with deep belief neural network(DBNet)for the efficient processing of signals in wireless 5G networks.Result indicates that the proposed system outperforms other existing techniques.Therefore,PAPR reduction in OFDM by DBNet is optimized with the help of an evolutionary algorithm called particle swarm optimization.Hence,the specified design supports in improving the proposed PAPR reduction architecture.

基于OCDM的通信感知一体化信号PAPR抑制方法

5G技术的不断发展和普及,使得无线设备对频谱资源的需求越来越大,频谱资源紧张的问题日益突出。为了提高频谱利用率,有效解决频谱资源紧张的问题,通信感知一体化(Integrated Sensing and Communication,ISAC)技术应运而生。在ISAC系统中,通信模块和感知模块共用同一波形和硬件平台,从而提高了频谱和设备利用率。其中,基于正交线性调频分频复用(Orthogonal Chirp-Division Multiplexing,OCDM)的ISAC系统对多普勒频移的抗干扰性能更好,性能优于传统系统。但是OCDM信号的平均峰值功率比(Peak to Average Power Ratio,PAPR)较高,这是由于其需要利用离散菲涅尔逆变换(Inverse Discrete Fresnel Transform,IDFn T)进行从chirp域到时域的转换造成的,过高的PAPR容易造成非线性失真,从而对ISAC系统的表现造成影响。针对上述问题,提出了一种基于chirp保留方法的OCDM通感一体化信号PAPR抑制方法,通过将OCDM信号的全部chirp分为两部分,一部分用来传输降低总体PAPR的信号,另一部分则正常传输通信数据,分别称为优化子载波和通信子载波。将一体化信号的PAPR与其非周期自相关函数建立联系,并利用Gerchberge-Saxton算法对优化子载波上的所得信号进行优化,以降低信号整体的PAPR,同时所有子载波均用于雷达信号处理以保证感知性能。仿真结果表明,分别利用10%、25%的子载波用于优化信号PAPR,且互补累积分布函数值为10-2时,可以使一体化信号的PAPR分别降低2 dB、3 dB左右。

REDUCING THE PEAK-TO-AVERAGE POWER RATIO OF OFDM SYSTEM WITH LOW COMPLEXITY

This paper proposes a companding scheme, where small signals are enlarged and large signals are reduced, to reduce the Peak-to-Average Power Ratio(PAPR). Computer simulation results show that the proposed technique has two advantages at least when compared with the conventional methods such as partial transmit sequence, selective mapping and the previous companding. First, it gets better PAPR performances with a lower complexity. Second, the scheme achieves greater performances gain with hardly any damnification of OFDM signals in some degree.

MULTI-PEAK MATCH INTENSITY RATIO METHOD OF QUANTI-TATIVE X-RAY DIFFRACTION PHASE ANALYSIS

A new method for quantitative phase analysis is proposed by using X-ray diffraction multi-peak match intensity ratio. This method can obtain the multi-peak match intensity ratio among each phase in the mixture sample by using all diffraction peak data in the mixture sample X-ray diffraction spectrum and combining the relative intensity distribution data of each phase standard peak in JCPDS card to carry on the least square method regression analysis. It is benefit to improve the precision of quantitative phase analysis that the given single line ratio which is usually adopted is taken the place of the multi-peak match intensity ratio and is used in X-ray diffraction quantitative phase analysis of the mixture sample. By analyzing four-group mixture sample, adopting multi-peak match intensity ratio and X-ray diffraction quantitative phase analysis principle of combining the adiabatic and matrix flushing method, it is tested that the experimental results are identical with theory.

Joint Optimization of Peak-to-Average Power Ratio and Spectral Leakage in 5G Multicarrier Waveforms

High peak-to-average-power ratio(PAPR) and spectral leakage are two main drawbacks of multicarrier systems, such as in orthogonal frequency division multiplexing(OFDM), in future 5G wireless communications. For generating optimized wave forms for 5G communications, this paper proposes an iterative scheme combining time-domain N-continuous OFDM(TD-NC-OFDM) and serial peak cancellation(SPC). Based on the theory of projection onto convex sets(POCS), the effectiveness of the proposed scheme is proved, and the optimized time-frequency domain multicarrier waveforms are analyzed in terms of a balanced tradeoff between out-of-band spectral leakage and PAPR. Both theoretical analysis and simulation results show that the proposed scheme can jointly optimize both the PAPR and out-ofband radiation, with moderate computational complexity.

OTFS Modulation and PAPR Reduction for IoT-Railways

The internet of things(IoT)has been widely considered to be integrated with high-speed railways to improve safety and service.It is important to achieve reliable communication in IoT for railways(IoT-R)under high mobility scenarios and strict energy constraints.Orthogonal time frequency space(OTFS)modulation is a two-dimensional modulation technique that has the potential to overcome the challenges in high Doppler environments.In addition,OTFS can have lower peak-to-average power ratio(PAPR)compared to orthogonal frequency division multiplexing,which is especially important for the application of IoT-R.Therefore,OTFS modulation for IoT-R is investigated in this paper.In order to decrease PAPR of OTFS and promote the application of OTFS modulation in IoT-R,the peak windowing technique is used in this paper.This technique can reduce the PAPR of OTFS by reducing the peak power and does not require multiple iterations.The impacts of different window functions,window sizes and clipping levels on PAPR and bit error rate of OTFS are simulated and discussed.The simulation results show that the peak windowing technique can efficiently reduce the PAPR of OTFS for IoT-R.

OFDM系统中基于最优阈值ACE的PAPR抑制

动态星座图扩展(Active constellation extension, ACE)是一种能够有效降低正交频分复用(Orthogonal frequency division multiplexing, OFDM)系统峰均功率比(Peak-to-average power ratio, PAPR)的方法,为解决现有ACE算法因选择固定限幅阈值而限制降低PAPR效果的问题,提出一种最优阈值ACE(Optimal threshold ACE, OTACE)算法,该算法能在每次迭代时根据信号功率求得最合适的限幅阈值,从而增强抑制PAPR的效果.通过数据拟合得到合适的迭代次数,在此基础上对OTACE算法抑制PAPR的效果进行了仿真分析,仿真结果表明,与凸集映射(Projection onto convex sets, POCS)和智能梯度投影(Smart gradient projection, SGP)算法相比,OTACE分别能提高5 dB和3 dB左右的PAPR增益.在广电1、广电6和巴西A三种信道下,分别在多普勒频移为20 Hz和60 Hz时测试OTACE算法对系统误码率(Bit error rate, BER)的影响.实验结果显示,采用OTACE可提高系统的BER性能,并且与POCS相比,OTACE可提高1 dB左右的信噪比(Signal-to-noise ratio,SNR)增益;与SGP相比,OTACE在高SNR时有明显的优势.

A Novel Peak-to-Average Power Ratio Reduction Scheme via Tone Reservation in OFDM Systems

In this paper, a novel signal-to-clipping noise ratio and least squares approximation tone reservation scheme(SCR-LSA TR) is proposed to reduce the peak-to-average power ratio for orthogonal frequency division multiplexing systems. During the SCR procedure, only the element with the maximal amplitude is picked for processing, which not only decreases the algorithm complexity, but also helps to overcome the BER deterioration. With the LSA method, the amplitude of the peak-cancelling signals can approximate to that of the original clipping noise as much as possible. Through the combination of the optimization factor in the LSA method, the classic SCR method can achieve better PAPR reduction with faster convergence. Simulation results show that the proposed SCR-LSA TR scheme has less in-band distortion and smaller out-of-band spectral radiation. The BER of the proposed scheme shows a better performance especially under the 16-QAM over the additive white Gaussian noise channel.

Analysis of Similarities of Different Species of Boenninghausenia Plants by Common and Variant Peak Ratios Dual Indicator Sequence Method

[Objectives] To analyze the similarities of Boenninghausenia sessilicarpa Levl. and Boenninghausenia albiflora(Hook.) Meiss by the common and variant peak ratio dual indicator sequence method. [Methods] Four different solvents(petroleum ether, chloroform, ethyl acetate and methanol) were used to extract the chemical components of different polar regions of B. sessilicarpa and B. albiflora. UV-visible spectrophotometry(second derivative method) was used to collect the fingerprints of different solvent extracts, and common and variant peak peak ratios were analyzed for the absorption peak data. [Results] The common peak ratio and variant peak ratio data of ground parts of B. albiflora and B. sessilicarpa was S2∶S5(46.2(54.2, 62.5)), compared with the data of other groups, the common peak ratio was the largest, thus the components of ground parts of B. albiflora and B. sessilicarpa were closest and had the largest similarities; the common peak ratio and variant peak ratio data of the components extracted by chloroform from B. albiflora and B. sessilicarpa was Y2∶Y6(54.2(38.5, 46.2)), compared with the data of other groups, the variant peak ratio was the smallest, thus, the chemical components near the chloroform polarity of two kinds of medicinal materials had the largest similarities and smallest differences. [Conclusions] This method is simple and easy to operate, and the ultraviolet fingerprint data of four different polar organic solvent extracts are used for comprehensive analysis, and the results have high specificity and high accuracy. Besides, there are certain similarities and also differences between the chemical components of B. sessilicarpa and B. albiflora. It is expected to provide a new evaluation method for the variety quality of B. sessilicarpa and B. albiflora.

COMPLEMENT BLOCK CODING SCHEME FOR REDUCING PEAK-TO-AVERAGE POWER RATIO OF OFDM SYSTEMS

A new scheme termed as Complement Block Coding (CBC) technique is proposed to reduce the Peak-to-Average Power Ratio (PAPR) of OFDM signals. Utilizing the complement bits which are added to the original information bits,this method can effectively reduce the PAPR of OFDM systems with random frame size N and the coding rate R ≤ (N - k)/N, where kis a positive integer and k ≤ N/2. The performance results obtained with CBC are given and compared with that of some well known schemes, such as Simple Block Coding (SBC), Modified Simple Block Coding (MSBC) and Simple Odd Parity Code (SOPC) for the same purpose. The results show that, at the same coding rate 3/4, the CBC can achieve almost the same performance as SBC, MSBC, but with lower complexity, and that the same performance can be obtained with higher coding rate by using CBC. At the same coding rate (N - 1)/N, the PAPR reduction of CBC is almost the twice as that of SOPC when N ≥ 16. Further more, the PAPR reductions with coding rate (N - 1)/N are almost the same as that with coding rate less than (N - 1)/N,so the proposed scheme CBC is more suitable for the large frame size with high coding rate and can provide error detection.

A PHASE SCRAMBLING SCHEME FOR SUPPRESSION OF PEAK TO AVERAGE POWER RATIO FOR OFDM

The complex-valued modulating vectors for the subcarriers consist of two kinds of components: One is the information-bearing components superposed with pseudo-randomized phases and the other is the suppression components with specified scrambling phases. The pseudo randomized phases are generated according to the predefined polynomial and mapping function whereas the scrambling phases are from a gradient algorithm. The simulation results verify the rationality and validity of the phase scrambling.

A correlation OPTS algorithm for reducing peak to average power ratio of FBMC-OQAM systems

A correlation overlapping partial transmit sequence(C-OPTS) algorithm is proposed to solve the issue of high complexity of overlapping partial transmit sequence(OPTS) algorithm in suppressing the peak to average power ratio(PAPR) of filter bank multicarrier-offset quadrature amplitude modulation(FBMC-OQAM) signals.The V subblocks in partial transmit sequence(PTS) are regrouped into U combinations according to the correlation coefficient p,and overlapping subblocks are allowed between adjacent groups.The search starts from the first group and sets the phase factors of the subsequent groups to 1.When the phase factors of the non-overlapping subblocks in the first group are determined,the subsequent groups are searched in turn to determine their respective phase factors.Starting from the second data block,the data overlapped with it should be taken into account when determining its optimal phase factor vector.Theoretical analysis and simulation results indicate that compared with the OPTS algorithm,the proposed algorithm can significantly reduce the computational complexity at the cost of slight deterioration of PAPR performance.Meanwhile,compared with the even-odd iterative double-layers OPTS(ID-OPTS) algorithm,it can further reduce the complexity and obtain a better PAPR suppression effect.

A new strategy for ionospheric remote sensing using the 130.4/135.6 nm airglow intensity ratios

We demonstrate here that global-scale determination of a key ionospheric parameter,the peak height of the F_(2)region(h_(m)F_(2)),can be obtained by making a simple ratio measurement of the atomic oxygen 130.4 and 135.6 nm emissions in the far-ultraviolet nightglow with a nadir-viewing system such as a pair of photometers suitable for flight on a CubeSat.We further demonstrate that measurements from an altitude that is within the typical range of nighttime h_(m)F_(2)250−450 km can provide the ratios that are needed for retrieval of the h_(m)F_(2).Our study is conducted mostly through numerical simulations by using radiative transfer models of the two emissions coupled with empirical models of the atmosphere and ionosphere.Modeling results show that the relationship between the h_(m)F_(2)and the intensity ratio is sensitive to the altitude from which the emissions are observed,primarily because of the distinctly different degrees of resonant scattering of the two emissions in the atmosphere.A roughly quadratic relationship can be established for observations from an orbit of~400 km,which enables h_(m)F_(2)retrieval.Parametric analysis indicates that the relationship can be affected by the ambient atmospheric conditions through resonant scattering and O2 absorption.For typical nighttime conditions with h_(m)F_(2)250−450 km,retrieval of the h_(m)F_(2)from synthetic observations shows that the typical errors are only a few kilometers(up to~20 km),depending on the accuracy of the ambient conditions predicted by the empirical models.Our findings pave the way for use of the 130.4/135.6 nm intensity ratios for global-scale monitoring of the nighttime ionosphere at mid to low latitudes.

Peak-to-average power ratio reduction using selective mapping with unequal power distribution

A new approach for peak-to-average power ratio (PAPR) reduction in orthogonal frequency division multiplexing (OFDM) systems was proposed.This approach is based on assigning powers to the different subcarriers of OFDM using an unequal power distribution strategy.In addition,a reduced complexity selective mapping (RC-SLM) scheme was proposed.The proposed scheme is based on partitioning the frequency domain symbol sequence into several sub-blocks,and then each sub-block is multiplied by different phase sequences whose length is shorter than that used in the conventional SLM scheme.Then,a kind of low complexity conversions is used to replace the IFFT blocks.The performance of the proposed RC-SLM scheme along with the new approach was studied with computer simulation.The obtained results show that the proposed RC-SLM scheme is able to achieve the lowest computational complexity when compared with other low complexity schemes proposed in the literature while at the same time improves the PAPR reduction performance by about 0.3 dB.

Reducing Peak-to-Average Power Ratio of a Turbo Coded OFDM

Peak to Average Power Ratio (PAPR) is defined as the instantaneous power (maximum value) to the average power ratio. PAPR is considered to be a major problem in OFDM systems. This problem can cause radical unexpected behavior of the signal fluctuation. This fluctuation is constituted by a large number of power states. The enormous number of these states leads to an additional complexity of ADCs and DACs. This research addresses the previous problem in OFDM systems utilizing Turbo Codes. μLaCP technique is employed for the purpose of decreasing PAPR. Moreover, our OFDM system was simulated in the presence of an AWGN channel with four types of codes (without the presence of ADCs and DACs). These were constituted of PCCC (typical and new), SCCC, and Convolutional Codes. Our Turbo Coded OFDM exhibited unchanged BER performance before and after the use of μLaCP technique. This was accomplished by modifying our previous PAPR reduction technique without sacrificing greatly its attributes.

OTFS系统中抑制PAPR的三段线性压扩算法研究

针对正交时频空间系统中传统线性压扩算法导致的系统误码率性能恶化问题,提出了一种三段式线性压扩算法。算法根据正交时频空间调制信号统计特性,在压缩大幅度信号的同时增强小幅度信号,从而保证信号平均功率恒定;对分布最为集中、出现频率最高的中幅度信号不进行压扩处理,以此来降低压扩失真的影响,提升算法的误码率性能。此外,算法可动态调节压扩程度,从而在保证误码率的条件下,以较低的复杂度显著降低正交时频空间系统的峰均比。仿真结果表明:在参数选择合理的情况下,所提算法可以在拥有与传统线性压扩算法相近的峰均比抑制性能的同时,较大程度地提升误码率性能。

一种低复杂度的降低FBMC系统PAPR的PTS方法

滤波器组多载波技术(Filter Bank Multicarrier, FBMC)具有高峰均功率比(Peak-to-Average Power Ratio, PAPR)的问题,部分传输序列(Partial Transfer Sequence, PTS)是一种常用降低方法。提出一种基于多种群文化遗传算法(Multi-population Cultural Genetic Algorithm, MCGA)的改进分段PTS(Improved Segmental PTS,ISPTS)方法来降低PAPR。在传统分段PTS的方法基础上利用惩罚因子减少需要优化的段避免无效优化。利用MCGA进行相位因子搜索,减少了算法复杂度。仿真结果验证了该算法的优越性。

Simulation on Peak-to-Average Power Ratio for Orthogonal Frequency Division Multiplexing

Clipping is a simple and convenient PAPR （peak-to-average power ratio） reduction method for high speed OFDM （orthogonal frequency division multiplexing） communication system. In this paper, we propose a new PAPR reduction method for Wireless-MAN（metropolitan area network）-OFDM system based on IEEE 802.16, which is over-sampling clipping arithmetic. Simulation and performance of the over-samples clipping＇s PAPR reduction capability, BER effect is given. The simulation indicates that the PAPR of at least 99.9% OFDM symbol is below 6dB after 2 Nyquist rate clipping, and the performance of BER has 1dB SNR（signal noise ratio） loss. The results prove that this method has better capacity to reducing PAPR. So it can be well used in WMAN-OFDM system.

Proton acceleration from picosecond-laser interaction with a hydrocarbon target

As an intense picosecond laser pulse irradiates a hydrocarbon target,the protons therein can be accelerated by the radiation pressure as well as the sheath field behind the target.We investigate the effect of the laser and hydrocarbon target parameters on proton acceleration with two/threedimensional particle-in-cell simulations.It is found that the resulting two-ion species plasma can generate a multiple peaked charge-separation field that accelerates the protons.In particular,a smaller carbon-to-hydrogen ratio,as well as the thinner and/or lower density of the target,leads to a larger sheath field and thus proton beams with a larger cutoff energy and smoother energy spectrum.These results may be useful in achieving high-flux quasi-monoenergetic proton beams by properly designing the hydrocarbon target.