共查询到20条相似文献,搜索用时 31 毫秒
1.
Khaled Ramadan Khalil F. Ramadan Ahmed S. Fiky Hasna Alam Moawad I. Dessouky Fathi E. Abd El‐Samie 《International Journal of Communication Systems》2020,33(3)
Frequency synchronization has a great importance in preserving the performance of the underwater acoustic (UWA) orthogonal frequency division multiplexing (OFDM) systems. The carrier frequency offset (CFO) estimation can be blind or data‐aided. In this paper, the Zadoff‐Chu (ZC) sequences are used for OFDM synchronization in UWA communications, and they are compared with different data‐aided algorithms. We propose a low‐complexity algorithm for CFO estimation based on ZC sequences. Also, a joint equalization and CFO compensation scheme for UWA‐OFDM communication systems is presented. Simulation results demonstrate that the proposed CFO estimation algorithm allows estimation of the CFO accurately with a simple implementation in comparison with the traditional schemes. Also, the performance of the UWA‐OFDM system can be preserved in the presence of frequency offsets. 相似文献
2.
This paper addresses the problem of carrier frequency offset (CFO) estimation for orthogonal frequency division multiplexing (OFDM) systems with multiple antennas, and links CFO estimation problem in OFDM systems to the compressed sensing trilinear model. Exploiting this link, we derives a compressed sensing trilinear model-based CFO estimation algorithm. The signal model can be expressed as a trilinear model, and there exists three compressed matrices which can compress the trilinear model to be a lower dimensional one. After that, trilinear decomposition is performed for the compressed model to get the estimations of compressed data matrices, and then the CFO can be estimated through solving the sparse recovery problem via \(\ell _0\) -norm constraint. The proposed algorithm has much better CFO estimation performance than ESPRIT method, and performs very close to the trilinear decomposition-based approach which has heavier computational burden and requires much greater storage capacity. Furthermore, our proposed algorithm can even work in condition of no virtual carrier. We derive the Cramer-Rao bound of CFO estimation for multiple antenna OFDM system. Simulation results illustrate performance of our algorithm. 相似文献
3.
Zhang Xiaofei Li Jianfeng Wu Hailang Xu Dazhuan 《Wireless Personal Communications》2012,67(2):139-147
In this letter, we develop a blind carrier frequency offset (CFO) algorithm for orthogonal frequency division multiplexing (OFDM) systems by utilizing a generalized precoding. Generalized precoding is employed to obtain multiple covariance matrices, and then a CFO estimation algorithm for OFDM system using joint diagonalization is proposed. Comparing to estimation of signal parameters via rotational invariance techniques (ESPRIT) method, the algorithm that we presented has improved CFO estimation performance. Furthermore, our algorithm even works well without virtual carrier. Simulation results illustrate performance of this algorithm. 相似文献
4.
电力无线专网在1.8 GHz频段建设4G TD-LTE网络,正交频分复用(OFDM)是其关键技术之一,OFDM系统对信道产生的载波频率偏移(CFO)很敏感,频率偏移会造成系统性能的严重下降。因此,需要对OFDM系统中的频率载波偏移精确估计并补偿,以保证系统的性能。本文提出了一种用于OFDM系统中基于局部搜索的多重信号分类(MUSIC)盲CFO估计的算法,该算法利用频率偏移矩阵列矢量与噪声子空间的正交性和CFO的单峰特性,构造一个改进空间谱函数,然后通过局部谱峰搜索得到频偏估计值。该算法的CFO估计性能优于传统CFO估计算法,且能够克服传统MUSIC算法低信噪比下谱峰缺失的问题。仿真结果证明了该算法的有效性。 相似文献
5.
Yuan Jing Fuliang Yin Zhe Chen 《Communications Letters, IEEE》2008,12(6):453-455
In this paper, an extended Hinfin filter-based carrier frequency offset (CFO) estimator is proposed for orthogonal frequency division multiplexing (OFDM) systems. The design criterion of the proposed estimator is to minimize the effect of worst-case disturbances (noise and model error) on the CFO estimation errors. This data-aided CFO estimator does not require any statistical knowledge of the disturbances. Moreover, its computational complexity is similar to that of the extended Kalman filter (EKF) method. Simulation results show that the proposed method can combat ICI effectively and obtain better bit error rate (BER) performance in the unknown noise for OFDM systems. 相似文献
6.
Xihua Dong Xiaochen Li Dapeng Wu 《Wireless Communications and Mobile Computing》2013,13(11):1014-1026
A recursive maximum likelihood carrier frequency offset (CFO) estimator is proposed in this work, where redundancy information contained in the cyclic prefix of multiple consecutive orthogonal frequency‐division multiplexing (OFDM) symbols is exploited in an efficient recursive fashion. Because the estimator is based on multiple OFDM symbols, the time‐varying CFO must be considered. We investigate the effect of time‐varying CFO on the performance of the estimator and the trade‐off between fast tracking ability and low estimation variance. We show that, without channel noise, the mean squared error (MSE) of estimation due to CFO estimation variation increases approximately quadratically with n, where n is the number of OFDM symbols used for CFO estimation (estimation window size), whereas the MSE due to channel noise decreases proportionally to 1/n (approximately) if the CFO is constant. A closed‐form expression of the optimal estimation window size (approximately) is derived by minimizing the MSE caused by both time‐varying CFO and channel noise. For wireless systems with time‐varying rate of change for CFO, the proposed estimator can be implemented adaptively. In addition, typical optimal estimation window sizes for WiMAX, DVB‐SH and MediaFLO systems are evaluated as an example. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
7.
In this paper, we address the problem of carrier frequency offset (CFO) estimation for orthogonal frequency division multiplexing
(OFDM) systems with multi-antenna receiver. The received signal can be reconstructed to form data model with multi-invariance
property, and then a multi-invariance MUSIC algorithm for CFO estimation is proposed. This algorithm has better performance
of CFO estimation than ESPRIT method, multi-invariance ESPRIT method and trilinear decomposition algorithm, and also qualifies
the estimation for both integer CFO and fractional CFO. Simulation results illustrate validity of this algorithm. 相似文献
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9.
Li Jun Liao Guisheng Wu Yuntao 《电子科学学刊(英文版)》2006,23(1):121-123
Most of the blind Orthogonal Frequency Division Multiplexing (OFDM) Carrier Frequency Offset (CFO) estimators necessitate large number of samples to ensure the estimation accuracy. However, the number of samples can not be selected too large because of the carrier offset drift. In this letter, a new closed form algorithm for blind OFDM CFO estimation in frequency-selective channel is proposed. This method utilizes the propagator obtained from data matrix and the diagonal loading technique, thus it has better performance even only using one or two OFDM blocks. Furthermore, the range of the CFO estimation which can be handled is overall transmission spectral. Simulation results confirm its effectiveness. 相似文献
10.
Carrier frequency offset (CFO) in orthogonal frequency-division multiplexing(OFDM) systems, which can induce the loss of orthogonality among subcarriersand result in significant performance degradation, is critical to be estimatedand compensated for. In this paper, a suboptimal scheme is proposed to estimatethe CFO using subcarriers. In the proposed scheme, the CFO is dividedinto the fractional part and the integer part, with the fractional CFO estimatedfollowed by the integer CFO estimation. Compared with previous work using subcarriers and exhaustive search, the implementation complexity of theproposed scheme is significantly lower due to the fact that the main componentrequired is a simple correlator. Furthermore, with only one trainingOFDM symbol and proper subcarrier allocation, the estimation range ofthe proposed scheme can be the inverse of the sampling duration. In contrast,conventional schemes with the same estimation range and complexity require two OFDM symbols. To achieve good performance,it will be shown that the subcarrier allocation should be based uponsome specific binary sequences such as the proposed extended m-sequences. It willalso be shown by simulations that the same subcarrier allocation criterionshould be employed for optimal maximum-likelihood CFO estimation. 相似文献
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The symbiotic FM radio data system(SRDS)is a radio data system that a specially designed OFDM signal co-lives with FM signal,which enables a significantly higher data rate than existing radio data systems.The cyclic prefix of the OFDM symbol has the same length as the OFDM body,which enables the analytic separation of the co-channel OFDM and FM signal at receiver side,utilizing the fact that the OFDM body and prefix is equal.In this work,we show that the OFDM body and prefix cannot be viewed as equal when there is sufficient carrier frequency offset(CFO).Thus,we propose a two-step CFO estimation algorithm for FM and SRDS hybrid signal.The first step estimates the coarse CFO by exploring the characteristics of the FM signal.Once the coarse CFO is removed,the residual CFO is small enough for FM and OFDM separation.The second step fine estimates CFO from the OFDM-only signal using its repeated PN structure after the separation.Detailed mathematical equations are formulated and simulation results are given.The results show that the proposed algorithm works fine with the simulation setup and has a final residual CFO less than 3.9Hz. 相似文献
13.
《Signal Processing, IEEE Transactions on》2006,54(8):3125-3135
In this paper, we address the problem of blind carrier frequency offset (CFO) estimation in orthogonal frequency-division multiplexing (OFDM) systems in the case of frequency-selective channels. CFO destroys the orthogonality between the carriers leading to nondiagonal signal covariance matrices in frequency domain. The proposed blind method enforces a diagonal structure by minimizing the power of nondiagonal elements. Hence, the orthogonality property inherent to OFDM transmission with cyclic prefix is restored. The method is blind since it does not require a priori knowledge of the transmitted data or the channel, and does not need any virtual subcarriers. A closed-form solution is derived, which leads to accurate and computationally efficient CFO estimation in multipath fading environments. Consistency of the estimator is proved and the convergence rate as a function of the sample size is analyzed as well. To assess the large sample performance, we derive the CramÉr–Rao bound (CRB) for the blind CFO estimation problem. The CRB is derived assuming a general Gaussian model for the OFDM signal, which may be applied to both circular and noncircular modulations. Finally, simulation results on CFO estimation are reported using a realistic channel model. 相似文献
14.
最近兴起的基于差分空时调制的正交频分复用系统可以采用非相干接收,从而避免了对时变多径信道状态信息的复杂估计,但存在的载波频率偏差会导致系统性能的下降。本文充分利用差分空时调制和循环前缀的特点,提出了的一种高效率高精度的频率偏差估计算法。该算法不需要任何辅助信号和信道估计,经过捕获和一次跟踪,解决了频率偏差的估计问题。理论分析表明,本文提出的算法能有效估计系统中存在的小数频率偏差。此外,仿真结果显示新算法在较低Eb/N0时,较常规算法有一个数量级以上的精度提高,而在高Eb/N0时可以有超过3个数量级的精度改善。 相似文献
15.
《Vehicular Technology, IEEE Transactions on》2006,55(5):1677-1690
An accurate estimation of carrier frequency offset (CFO) is a crucial task for orthogonal frequency-division multiplexing (OFDM) systems but should be performed with affordable computational complexity for practicality. In this paper, the authors derive two new estimation algorithms (one for the integer part and the other for the fractional part of CFO), each of which utilizes only one OFDM block with null subcarriers but offers improved accuracy and reduced complexity. The proposed estimator for fractional CFOs operates iteratively and is insensitive to the initial CFO. The other proposed estimator for integer CFOs employs a pseudonoise binary random sequence to assist in subcarrier arrangement and accurate estimation of the integer CFO. To demonstrate the efficiency of the proposed methods, numerical results are provided from computer simulation and analysis, and comparisons are made with other existing methods in the literature. 相似文献
16.
Non-data-aided carrier-frequency offset estimation for pulse-shaping OFDM/OQAM systems 总被引:2,自引:0,他引:2
In this paper we consider the problem of blind carrier-frequency offset (CFO) estimation for pulse-shaping orthogonal frequency-division multiplexing (OFDM) systems based on offset quadrature amplitude modulation (OQAM). In particular, under the assumption of low signal-to-noise ratio, three maximum-likelihood (ML) CFO estimators for non-dispersive channels are derived. Due to their significant computational complexity a more feasible closed-form CFO synchronization algorithm is considered. The performance of the derived blind estimators is assessed via computer simulations and compared with that of a blind CFO estimator previously proposed in the literature, exploiting the second-order cyclostationarity property of the OFDM/OQAM signal. 相似文献
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18.
We propose a novel subcarrier allocation (SCA) based approach for compensating carrier frequency offset (CFO) and I/Q imbalances in direct-conversion OFDM receivers. From the matrix representation of OFDM signals with CFO and I/Q imbalances, maximum likelihood CFO estimation and the associated SCA are given. Then, an SCA-based algorithm is proposed for the I/Q imbalances compensation. Moreover, the proposed approach is extended to a blind compensation scheme for OFDM signals with asymmetric SCA. 相似文献
19.
In this paper, we address the problem of carrier frequency offset (CFO) estimation for Orthogonal Frequency Division Multiplexing
(OFDM) communications systems with multiple antennas. We reconstruct the received signal to form data model with multi-invariance
property, and subsequently derive a multiple-invariance ESPRIT algorithm for CFO estimation. This algorithm has improved CFO
estimation compared to ESPRIT method and maximum likelihood method. Simulation results illustrate performance of this algorithm. 相似文献