共查询到19条相似文献,搜索用时 140 毫秒
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针对传统的OFDM信号参数估计方法在短循环前缀条件下存在估计准确率不高、所需OFDM符号数过多等问题,提出了一种基于符号峰态的OFDM信号参数盲估计方法。首先利用OFDM信号相关参数样本区间内的预估值对接收信号进行解调,然后根据解调出的OFDM基带符号构造符号峰态特征函数,最后从理论上证明了可通过检测符号峰态的最小值实现OFDM信号循环前缀长度和有效符号长度的联合估计。实验仿真结果表明,该算法克服了传统方法难以估计短循环前缀OFDM信号参数的缺陷,仅用较少的OFDM符号数就可以实现短循环前缀OFDM信号的参数估计,并且其估计性能优于传统方法。 相似文献
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给出了一种适用于MPSK、MQAM和MPAM解调的非数据辅助(NDA)载波频偏估计算法,利用自相关函数提取载波频偏信息,该方法具有速度快、频偏估计范围大的优点。计算机仿真结果表明了估计范围可以达到±80%的符号速率。 相似文献
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为解决采用单一特征量预测轴承剩余寿命误差较大、有限数据样本条件下轴承剩余寿命难以估算的问题,提出了一种基于主元特征融合和支持向量机(SVM)的轴承剩余寿命预测方法。该方法采集振动加速度信号构建数据样本,提取有效值、峰值、小波熵等表征轴承退化趋势的特征指标;采用主元分析融合多个特征指标,消除特征间的冗余和相关性,构造出相对多特征的退化特征量;将退化特征量输入SVM模型中进行轴承剩余寿命预测。现场工程应用结果表明,基于主元特征融合和SVM的轴承剩余寿命预测方法可在小样本条件下筛选出包含信号绝大部分信息的主元,从而在保证预测精度的同时,减少了计算量。 相似文献
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提出一种多径平坦衰落信道下的盲信噪比估计方法.该算法首先利用数字通信信号的循环平稳统计特性构造接收信号的循环自相关矩阵,然后对该矩阵进行奇异值分解,由分解出的特征值信号子空间和噪声子空间,最后通过利用AIC信息准则分别估计信号子空间和噪声子空间的维数并最终估计出信道的平均信噪比.以MPSK信号为例进行了计算机仿真,结果表明了算法的有效性. 相似文献
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Orthogonal frequency division multiplexing (OFDM), a very promising technique that is leading the evolution in wireless mobile communication to sideline the bandwidth scarcity issue in spectrum allocation, is severely affected by the undesirable effects of the frequency offset error, which generates inter carrier interference (ICI) due to the Doppler shift and local oscillator frequency synchronization errors. There are many ICI cancellation techniques available in the literature, such as self-cancellation (SC), maximum likelihood estimation (MLE), and windowing, but they present a tradeoff between bandwidth redundancy and system complexity. In this study, a new energy-efficient, bandwidth-effective technique is proposed to mitigate ICI through cyclic prefix (CP) reuse at the receiver end. Unlike SC and MLE where the whole OFDM symbol data is transmitted in duplicate to create redundancy at the transmitter end, the proposed technique uses the CP data (which is only 20% of the total symbol bandwidth) to estimate the channel, and it produces similar results with a huge bandwidth saving. The simulation results show that the proposed technique has a significant improvement in error performance, and a comparative analysis demonstrates the substantial improvement in energy efficiency with high bandwidth gain. Therefore, it outperforms the legacy ICI cancellation schemes under consideration. 相似文献
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针对现有相移键控(PSK)信号码速率估计方法在脉冲噪声下性能退化甚至失效的问题,提出一种循环平稳理论框架下基于相关熵的码速率估计新方法.构造信号的循环相关熵函数,并理论推导给出在二相相移键控(BPSK)信号下的循环相关熵函数.该方法可通过检测PSK信号循环相关熵函数的离散谱线实现码速率估计,不需要噪声的先验信息,且能够直接利用FFT计算信号的循环相关熵函数的延迟切片,实现简单.仿真结果表明,所提出方法能有效抑制脉冲噪声,尤其在强脉冲噪声环境下,具有良好的PSK信号码速率估计性能. 相似文献
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Cheng-Ying Yang Gwo-Ruey Lee Wen-Hui Kuan Jyh-Horng WenAuthor vitae 《Digital Signal Processing》2011,21(6):710-717
Previously, Beek?s scheme for timing and frequency offset estimation in the OFDM system employs cyclic prefix (CP) has been proposed under the assumption of independent identified distributed (i.i.d.) OFDM symbols. Actually, the real data in the OFDM modulated symbol, transferred by the inverse fast Fourier transform (IFFT), has the characters of complex symmetry. With these characters, more information in the whole OFDM symbol could be used for the timing and frequency offset estimation. In this paper, two conjugate symmetry characters of the OFDM BPSK-modulated symbol are used to achieve blind timing estimation algorithm in the OFDM systems. One is symbol-based symmetry and the other is CP-based symmetry. With these two conjugate characters applied to the proposed algorithm, the timing of the OFDM BPSK-modulated symbol could be derived. Under an AWGN channel, based on the performance of lose symbol timing rate and estimator mean square error, the proposed algorithm is with a tremendous improvement compared with Beek?s estimation method. Under a multipath fading channel, the results show that performance including lose symbol timing rate and estimator MSE with the proposed algorithm is better than those algorithms with Beek?s estimation method. In practical OFDM applied system, the OFDM BPSK-modulated symbol could be used to replace the preamble or training sequences in the standard to obtain an accurate timing and frequency offset estimation and to avoid the data rate decreasing with the proposed algorithm. 相似文献
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针对低信噪比下MPSK (M-ary phase shift keying)信号的码元速率估计问题, 提出一种优化算法.该算法无需先验知识, 通过Hilbert变换提取瞬时相位基带序列, 经多尺度小波变换, 对每个尺度下的小波系数的模值的平方进行叠加, 对叠加后的结果再进行功率谱计算, 在码元速率整数倍处有离散谱线, 估计正确率在信噪比大于1 dB时大于90 %. 相似文献
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对于多径频率选择性衰落信道以及低信噪比环境下线性调制信号的同步参数盲估计问题,提出基于循环累积量的载波频偏、初始相偏和符号定时误差前向联合盲估计算法。通过理论推导得出多径频率选择性衰落信道下信号的循环累积量与初始相偏和符号定时误差的数学关系。在此基础上先以较大频率间隔进行粗估计确定频偏范围,再以较高精度遍历检测信号特定循环频率,提高载波频偏估计精度,进而由累积量值估计出初始相偏和符号定时误差,不依赖于信道衰落和加性噪声的分布特性,尤其适用于频偏、相偏、定时误差和信道衰落同时存在的复杂情况。仿真结果表明,该算法
能有效实现低信噪比和多径频率选择性衰落信道下对线性调制信号同步参数的联合盲估计。 相似文献
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An algorithm, based on frequency domain accumulation for the cyclic autocorrelation of MC-CDMA signals, is proposed to estimate the signal parameters: useful data duration, symbol duration, and chip duration in multipath fading channel. Firstly the cycle autocorrelation of received MC-CDMA signals is computed, then frequency domain accumulation is used to reduce the influence of noise. At last, through interval measurement between the peak pulses in different slices, parameters mentioned above can be estimated. Meanwhile, for the estimation of symbol duration, a novel accumulative average method is developed: by averaging amplitudes of the spectral lines in each column parallel to the time-delay axis in the three-dimensional diagram, the symbol duration can be obtained. The cyclic autocorrelation expression of MC-CDMA signal has been derived, and simulation results show that the proposed algorithm is effective and works well under the condition of low signal-to-noise ratio (SNR). 相似文献