共查询到20条相似文献,搜索用时 15 毫秒
1.
针对成形偏移四相相移键控-TG(Shaped Offset Quadrature Phase Shift Keying-Telemetry Group version, SOQPSK-TG)信号在训练序列长度受限时频偏估计精度较低的问题,利用双二进制分解(Doubinary Decomposition, DBD)原理提出基于期望最大化(Expectation Maximization, EM)的SOQPSK半盲载波频偏(Carrier Frequency Offset, CFO)估计算法。为了确保EM算法收敛到预期性能范围,使用基于非线性四次方码元定时估计算法的非数据辅助频偏估计方法优化了EM算法初始点选择。仿真实验结果表明,该算法相比于使用训练序列进行数据辅助估计的方法,在不增加辅助数据数量的前提下能够进一步提升CFO估计的精度,并在较高信噪比下拥有接近序列总长度所对应的克拉美罗界(Cramér-Rao Bound, CRB)的优秀性能。 相似文献
2.
This article proposes a new algorithm of joint channel and carrier frequency-offset OCCFO) estimation for multi-user multi-input and multi-output orthogonal frequency division multiplexing (MIMO-OFDM) systems. A least square (LS) channel estimation and a carrier frequency offset (CFO) correlation estimation are combined in this contribution. CFOs are generally estimated using training sequences in a special synchronization timeslot. In this contribution, CFO estimation is further improved by taking advantages of channel estimation based on pilot symbols in traffic timeslots. The CFOs can be first obtained from the primary channel estimation. And then, with the knowledge of the CFOs estimated, channel estimation can be enhanced greatly. Computer simulation results indicate that the proposed JCCFO scheme is of good performance. Besides, the computational complexity is low. 相似文献
3.
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
4.
Moosvi S.M.A. McLernon D.C. Orozco-Lugo A.G. Lara M.M. Ghogho M. 《Communications Letters, IEEE》2008,12(3):179-181
In this letter we propose, for the first time, a solution to the problem of carrier frequency offset (CFO) estimation within the data dependent superimposed training (DDST) framework for channel estimation. While time division multiplexed (TDM) trained systems can use the TDM sequence to determine the CFO, the original attraction of DDST for channel estimation was that it avoided any TDM training. So in this letter we show how CFO estimation can still be very effectively performed with the DDST algorithm, while continuing to preclude the need for any additional bandwidth-consuming TDM training. Finally, simulations are presented that verify the theoretical results. 相似文献
5.
提出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,为了减小信息序列对叠加训练序列的影响,引入数据依赖序列使信息序列DFT在这些特定频点上为零,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,这些旋转后的信息序列在这些特定频点的能量才得到最小值。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
6.
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
7.
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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9.
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
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11.
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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13.
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
14.
《Broadcasting, IEEE Transactions on》2009,55(1):84-94
15.
In this paper, we investigate the problem of carrier frequency-offset (CFO) synchronization and channel estimation in multiple-input multiple-output orthogonal frequency-division multiplexing systems operating over unknown frequency-selective fading channels. We first propose a novel joint CFO and channel estimator, assuming time-domain training blocks are available. The proposed joint estimator consists of two recursive least-square (RLS) algorithms which iterate their estimated CFO and CIR values. We then derive a more precise pilot-aided RLS algorithm to estimate the residual frequency synchronization errors or track small CFO changes. With this, the accuracy of channel estimation is also enhanced. The analysis and simulation results show that, the proposed estimation and tracking scheme which is fully compatible with the existing standards is able to attain fast convergence, high stability, and ideal performances as compared with relevant Cramer–Rao bounds in all ranges of signal-to-noise ratio. Moreover, it can work well for wide tracking range up to ±0.5 of the subcarrier spacing. 相似文献
16.
正交频分复用(OFDM)技术是多进制、多载频、并行传输的,其能够提高频带利用率、抗多径传输能力,并且以更高的速率传输数据。面对其多普勒频移会导致系统存在载波频率偏差(CFO)的问题,本文介绍了基于训练序列的Moose和Classen频域CFO估计技术,然后发现两者结合后系统的频偏估计更稳定。通过MATLAB仿真发现:在[-0.370.37]之间,两者结合后的频率估计技术载波频率偏差较好,并通过均方误差(MSE)显示出其系统的稳定性也较好。 相似文献
17.
In this paper a novel technique for timing and carrier frequency offset (CFO) estimation for orthogonal frequency division multiplexing (OFDM) systems is presented. This technique is a modification of extended cyclic prefix for correlation sequence (ECPCS) based technique, called as selective extended cyclic prefix for correlation sequence (SECPCS) based technique. In cyclic prefix (CP) based technique, magnitude of timing metric near the exact starting point of CP is quite similar which causes problem in timing estimation. SECPCS is utilized in order to increase the difference between magnitudes of timing metric at the exact starting point of time of CP and its adjacent timing instants. In SECPCS technique, first of all correlation length of CP is extended using available CP samples and then those sequences which enlarge the difference in the magnitude of timing metric is selected. In the proposed technique the difference between magnitude of timing metric at exact starting point and its adjacent timing instants is significantly large compared to the previous techniques. The performance of different techniques is evaluated in terms of mean square error (MSE) in estimation of timing and CFO estimate. Further signal-to-interference-plus-noise ratio (SINR) loss of different techniques in different channel conditions is also estimated. From the simulation results it is observed that under different channel conditions, performance of the proposed SECPCS based technique is significantly better than previous techniques. 相似文献
18.
Qingfeng Jing Weizhi Zhong Yuping Lu Xiaoju Yan 《Radioelectronics and Communications Systems》2013,56(1):29-35
Carrier frequency offset (CFO) due to Doppler frequency shift or frequency mismatch between the transmitter’s and receiver’s oscillators can introduce severe inter-symbol and inter-carrier interference into OFDM systems. A simplified OFDM system model is considered to analyze effects of CFO in theory and simulation. The article briefly reviews some traditional CFO estimation algorithms. Relying on relatively good correlation characteristic of pseudo-noise (PN) sequence, the PN preamble based algorithm of CFO estimation is developed. Performance characteristics of traditional and the new improved algorithms are simulated under different conditions. Results indicate that the PN preamble based algorithm of CFO estimation is more accurate, resource-saving and robust even under poor communications channel condition, such as low SNR and big normalized CFO. 相似文献
19.
Xiaoli Ma Mi-Kyung Oh Giannakis G.B. Dong-Jo Park 《Communications, IEEE Transactions on》2005,53(1):162-172
We design pilot-symbol-assisted modulation for carrier frequency offset (CFO) and channel estimation in orthogonal frequency-division multiplexing transmissions over multi-input multi-output frequency-selective fading channels. The CFO and channel-estimation tasks rely on -subcarrier and nonzero pilot symbols that we insert and hop from block to block. Because we separate CFO and channel estimation from symbol detection, the novel training patterns lead to further decoupled CFO and channel estimators. The performance of our algorithms is investigated analytically, and then compared with an existing approach by simulations. 相似文献