共查询到19条相似文献,搜索用时 156 毫秒
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数据依赖叠加训练序列(Data-Dependent Superimposed Training,DDST)常用在正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)的信道估计中,由叠加训练序列和数据依赖序列组成,与信息序列并行发送,可以提高带宽利用率。提出了一种基于数据依赖叠加训练序列的OFDM载波频偏估计方法。叠加训练序列的周期性使其DFT能量间隔分布在特定的频点上,利用这个特性可进行频偏估计,只有得到正确的频偏估计时,这些特定频点的能量才得到最大值。仿真表明该方法在不降低传输速率的情况下,有着较好的频偏估计性能。 相似文献
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频率偏移导致用于叠加训练序列系统中的一阶信道估计方法失效.文中提出一种利用叠加训练序列进行OFDM系统的联合频偏和信道估计的方案.在简单介绍所建立的OFDM系统后,文中利用训练序列的周期性推导出频偏特征向量,并根据阵列信号求子空间的原理,利用接收信号矩阵的奇异值分解求出上述向量所在的线性子空间,通过相关匹配求出频率偏移,最后获得时域信道参数.理论分析表明频偏估计范围反比于训练序列周期,因此算法具有估计范围大的优点,且适用于所有叠加周期训练序列系统.仿真分析表明了算法的有效性. 相似文献
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针对正交频分复用(OFDM)系统对同步错误率和频率偏移敏感的问题,提出了一种叠加共轭对称训练序列的OFDM系统时间和频率同步方法。该同步方法将快速傅里叶逆变换(IFFT)调制后的序列构成具有共轭对称特性的训练序列,并叠加到OFDM数据符号上;在接收端,利用叠加训练序列和融合循环前缀信息来获取OFDM系统同步信息。理论分析和仿真表明:在信噪比为5 dB时,该同步算法定时同步正确概率已接近100%;在信噪比为4 dB时,频偏估计精度可以达到10-4;该同步算法不仅具有更好的同步性能,而且节省系统的有效带宽以及降低系统的计算法复杂度。 相似文献
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正交频分多址接入系统作为一种新的多址接入技术受到了极大关注.在OFDMA中,由于子载波分配给不同的用户,用户信号在收端会叠加在一起,那么也给训练序列等信息序列的分配带来一定的困难.文中将分析连续和交织两种不同的训练序列的系统频偏估计性能.并通过仿真得出连续分配的训练序列性能更优. 相似文献
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Ming-Fu Sun Jui-Yuan Yu Terng-Yin Hsu 《IEEE transactions on circuits and systems. I, Regular papers》2008,55(3):943-952
This work presents a novel carrier frequency offset (CFO) estimation algorithm, based on pseudo-CFO (P-CFO), to estimate the CFO value under the conditions of I/Q mismatch for direct conversion structures with 2-dB gain error and 20-deg. phase error in frequency selective fading channels. To circumvent CFO with I/Q mismatch, the proposed P-CFO algorithm rotates three training symbols by adding extra frequency offset into the received sequence to improve CFO estimation. Simulation results indicate that the estimation error of the proposed method is about 0.3 ppm, which is lower than those of two-repeat preamble-based methods. Additionally, the proposed P-CFO algorithm is compatible with the conventional method, and is appropriate for SoC implementation. The proposed scheme is implemented as part of an orthogonal frequency-division multiplexing wireless receiver fabricated in a 0.13-mum CMOS process with 3.3 times 0.4 mm2 core area and 10-mW power consumption at 54-Mbits/s data rate. 相似文献
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We examine the detection problem of signals with narrowband, harmonically related components received by a passive sensor array. We investigate detector structures based on the Fourier method. The harmonic detector estimates the total signal power by combining the DFT coefficients from harmonic frequency bins. This power estimate is normalized by the estimated background noise power and then compared to a threshold. We investigate two harmonic detector structures: one that operates with coherent, correlated signals and the other with uncorrelated harmonic signals. We derive statistical laws governing both detector structures that facilitate setting a power threshold for a given probability of false alarm; and present upper- and lower-bounds for the probability of detection. The results developed and presented demonstrate the inherent advantage of the harmonic detector. At operating conditions characterized by low signal-to-noise power ratio values the harmonic detector exhibits enhanced detection performance by combining the estimated signal power from harmonic frequency bins. We generalize results from single-bin and harmonic detector structures and present them as special cases of a unifying framework 相似文献
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This paper examines the carrier frequency offset (CFO) estimation problem in the tile‐based orthogonal frequency division multiple access (OFDMA) uplink systems, which is very challenging due to the presence of multiple CFOs. The existing solutions to this problem are either too complex to implement or not flexible in subcarrier allocation. To solve these problems, this paper proposes a tile‐structure based iterative multi‐CFO estimation technique. The proposed method is developed based on a special training sequence with repetitive structure. The inherent multi‐user interference (MUI) compression provided by the tile structure allows us to utilize the repetitive property of the training sequence to jointly estimate the CFOs in the frequency domain with low complexity. Combining the CFO estimation with an interference cancellation scheme and performing iteratively, the algorithm achieves high estimation accuracy and fast convergence. The proposed algorithm is suitable for any subcarrier assignment schemes. In addition, as compared with other existing time domain based algorithms, which achieve the Cramer Rao Bound (CRB) at the price of unaffordable complexity, it closely approaches their performance with over 70% computational saving, which is significantly important for practical implementation. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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In this paper, we study carrier frequency offset (CFO) and symbol timing offset (STO) estimation in the uplink of multiuser offset QAM filter bank multicarrier (FBMC) communication systems. A low-complexity frequency-domain CFO estimator using periodical training sequence is proposed. Also a good estimate of STO is obtained by maximizing the energy of subcarriers subject to training sequence at the output of analysis filter bank. Furthermore we derive the theoretical MSE for the proposed CFO estimator. Computer simulations show that the derived MSE matches the simulated MSE closely. Compared with state-of-the-art time domain estimator, the proposed estimator achieves better performance with a lower computational complexity. 相似文献
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Welch's (1967) method for spectral estimation of averaging modified periodograms has been widely used for decades. Because such an estimate relies on random data, the estimate is also a random variable with some probability density function. Here, the PDF of a power estimate is derived for an estimate based on an arbitrary number of frequency bins, overlapping data segments, amount of overlap, and type of data window, given a correlated Gaussian input sequence. The PDFs of several cases are plotted and found to be distinctly non-Gaussian (the asymptotic result of averaging frequency bins and/or data segments), using the Kullback-Leibler distance as a measure. For limited numbers of frequency bins or data segments, the precise PDF is considerably skewed and will be important in applications such as maximum likelihood tests 相似文献
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该文提出了一种用于重叠码调制-正交频分复用(SCM-OFDM)系统中基于信号检测的频偏估计方法。这种估计方法首先利用SCM迭代检测器输出的判决符号重构接收信号,再利用最小均方误差准则对频偏进行估计。该方法不需要额外的训练序列或导频符号,是一种高效的盲频偏估计方法。此外,该文还提出了一种改进的频偏估计方法。在改进的方法中,接收机将频偏估计与信号检测进行联合迭代;这样在每一次迭代过程中,信号检测和频偏估计都需要执行一次,并且接收机在信号检测时可以利用上一次得到的频偏估计值进行频偏补偿。仿真结果表明,该文提出的基于信号检测的频偏估计方法能够高效并准确地估计出SCM-OFDM系统的频偏。 相似文献
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Ann-Chen Chang 《Wireless Personal Communications》2013,73(3):779-790
This letter presents an iterative carrier frequency offset (CFO) estimator based on the minimum variance distortionless response criterion for interleaved orthogonal frequency division multiple access uplink systems, without using specific training sequences. The proposed estimator iteratively searches for the correct CFO vector by minimizing the objective function using a first-order Taylor series approximation of the CFO vector with the one initially given. However, the proposed estimator is not only can estimate CFO, but also has less computational load. Several computer simulation results are provided for illustrating the effectiveness of the blind estimate approach. 相似文献
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Yanxiang Jiang Hlaing Minn Xiqi Gao Xiaohu You Yinghui Li 《Wireless Communications, IEEE Transactions on》2008,7(4):1244-1254
This paper addresses carrier frequency offset (CFO) estimation and training sequence design for multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems over frequency selective fading channels. By exploiting the orthogonality of the training sequences in the frequency domain, integer. CFO (ICFO) is estimated. With the uniformly spaced non-zero pilots in the training sequences and the corresponding geometric mapping, fractional CFO (FCFO) is estimated through the roots of a real polynomial. Furthermore, the condition for the training sequences to guarantee estimation identifiability is developed. Through the analysis of the correlation property of the training sequences, two types of sub-optimal training sequences generated from the Chu sequence are constructed. Simulation results verify the good performance of the CFO estimator assisted by the proposed training sequences. 相似文献