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OFDM同步跟踪阶段的频偏估计算法 总被引:1,自引:0,他引:1
OFDM对栽频偏差是很敏感的,因此不仅在同步的捕获阶段,而且在同步的跟踪阶段,精确的频偏估计是很重要的。文献[3]提出了一种简化的相干判决反馈的迭代算法来估计同步跟踪阶段的载频偏差,对于128个子载波、QPSK调制的OFDM系统,在多径衰落信道下,当频偏小于子载波间隔的15%时,频偏估计的标准方差小于1%,但是这个结果是在假设信道频率响应、定时偏差、载波相位等参数已知的条件下取得的,而当这些参数的估计存在误差时,由仿真结果可看出,频偏估计性能恶化了,因此,提出了采用差分判决反馈的频偏估计算法,虽然只能估计小于子载波间隔 8%的频偏,但差分判决反馈算法不需要知道信道的参数,由于在同步跟踪阶段,频偏一般都较小,因此采用差分判决反馈算法可以很好地估计出同步跟踪阶段的频率偏差。 相似文献
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对OFDM系统中一种基于接收时域信号重构的载波频率盲估计算法进行了进一步的研究,分析了在这种方法中影响估计精度的4个方面的因素。为了减少载波频率估计的剩余误差,通过在频率补偿时增加反馈因子,提出了一种基于判决反馈的载波频率同步环路结构。通过调整同步环路的环路增益,可以获得更好的频率跟踪性能。如果信噪比达到9dB,即使存在较大的频率漂移,剩余频偏也被限制在子载波间隔的1%以内。 相似文献
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正交频分复用(OFDM)因其在抗频率选择性衰落和窄带干扰方面具有良好的性能而被广泛应用,但是OFDM系统比单载波系统对定时和频偏更加敏感。提出了一种简单有效的帧同步与频率跟踪算法,与传统的最大似然估计算法相比,实现更加容易,而且能保证精确的帧和频率同步。 相似文献
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提出了一种正交频分复用(OFDM)系统的频率同步方案。该方案包含一个细同步算法和一个粗同步算法。细同步算法是对MOOSE算法的改进,使其频率捕获范围扩大一倍;粗同步算法通过对特殊的长训练序列进行频域相关运算,来估计大范围的频率偏移,它与改进的细同步算法相结合,能够纠正达到半个系统带宽的频偏。仿真表明这是一种准确而可靠的频率同步方案。 相似文献
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本文提出了一种正交频分复用(OFDM)系统的频率同步方案。该方案包含一个细同步算法和一个粗同步算法。细同步算法是对MOOSE算法的改进,使其频率捕获范围扩大一倍;粗同步算法通过对特殊的长训练序列进行频域相关运算,来估计大范围的频率偏移,它与改进的细同步算法合,能够纠正达到半个系统带宽的频偏。仿真表明这是一种准确而可靠的频率同步方案。 相似文献
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《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
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Orthogonal frequency division multiplexing (OFDM) systems are highly sensitive to carrier frequency errors. In this paper, a new method utilizing pilots to do frequency synchronization in frequency domain is proposed with large estimation range. It needs no such prerequisite assumption that a perfect symbol timing synchronization [IEEE Transactions on Communications 42 (1994) 2908; 45 (1997) 1613] has been done before performing integer carrier frequency synchronization. Also, a new adjusting model for fine carrier frequency is proposed. Simulation and performance analysis show that our overall frequency estimator has high accuracy. The corresponding FPGA circuit through test in high definition TV (HDTV) prototype in Team of Expert Engineering Group (TEEG) in China proves its availability and feasibility.Bo Ai (M2001) was born in Shannxi Province in China on February 7, 1974. He received a B.Sc. degree from Engineering Institute of Armed Police Force and a Master degree, a Ph.D degree from Xidian University in 1997, 2002 and 2004 in China respectively. He has once participated in the key research project on HDTV in TEEG (Team of Engineering Expert Group) of China, and has published over forty papers in his research area till now. He is senior member of Chinese Electronics Institute (CIE), an editorial commitee member of journal of Computer Simulations. His current interests are the research and applications of OFDM technique with emphasis on synchronization.Jian-hua Ge was born in September, 1961 in JiangSu Province in China. He received the B.Sc., Master and Ph.D. degree from Xidian University in 1982, 1985 and 1989 respectively. He is now the professor in both Xidian University in Xian and Shanghai Jiaotong University in Shanghai. He is the senior member of Chinese Electronics Institute. He has won lots of scientific and technical prizes in China and published many papers. His interests are transmission communications and web security.Yong Wang (M2003) was born in Shannxi Province in China in 1976. He received a B.Sc. and Master degree from Xidian University in China in 1997 and 2002 respectively, and is now working towards the Ph.D. degree on communications in the Key Laboratory of ISN in Xidian University. He has once participated in the key research project on HDTV in TEEG of China and his interests are broadband multimedia communications.Dian-fu Zhang was born in Shannxi Province in China in 1954. He received a B.Sc. degree from Xidian University in China in 1977. He is now working as a professor and the chairman of the telecommunication department in Engineering College of Armed Police Force. His interests are mobile communications.Jun Liu was born in Beijing in China in 1963. He received his B.Sc. degree from Nanjing University Of Aeronautics and Astronautics in China in 1984. He is now a professor in Engineering College Of Armed Police Force. His research interests include integrated circuit design and artificial intelligence. 相似文献
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MIMO OFDM短波无线通信的频率同步技术研究 总被引:1,自引:0,他引:1
多输入多输出(MIMO)技术是最近几年发展起来的无线通信技术。目前利用MIMO技术提高短波通信的传输速率和可靠性的研究已经开展。论文着重研究了MIMO OFDM短波无线通信的频率同步技术,利用频域正交的训练序列完成了系统各个发射/接收天线对之间频偏不同时的载波频偏估计。 相似文献
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文中给出一种应用于正交频分复用系统中帧同步和载波同步的最大似然估计算法,它是基于循环前缀和脉冲成形推出的。本文详细阐述了算法推导过程,并给出了计算机仿真结果分析了其性能,最后由此算法提出一种估计器的设计方案。 相似文献
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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... 相似文献
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Orthogonal frequency division multiplexing (OFDM) systems are highly sensitive to carrier frequency offset (CFO), especially in doubly-selective fading environment. Cyclostationarity-based blind synchronization methods are appealing in high-data-rate applications and low signal-to-noise regions. However, the cyclostationarity has not been exploited for frequency synchronization of OFDM systems under doubly-selective fading channels. In this paper, we derive the close-form second order cyclic statistics of the received OFDM signal in presence of CFO, by modeling the doubly-selective fading channel with basis expansion model. Both transmitter-induced cyclostationarity and doubly-selective channel information are contained in the derived cyclic moments, and they are efficiently utilized for CFO estimation. Simulation results demonstrate that the proposed estimator provides significant improvements on frequency synchronization performance. 相似文献