共查询到19条相似文献,搜索用时 93 毫秒
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文章对几种常用的基于循环前缀(CP)的最大似然同步算法进行了分析,并对其频偏估计方差进行了比较;同时针对基于CP的同步算法在多径衰落信道下性能较差的情况,提出了一种改进的CP同步算法并进行了仿真,结果表明相比于原ML算法,文中算法在多径信道下可有效提高频偏估计性能. 相似文献
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在多径信道中,循环前缀最大似然估计盲OFDM同步算法的性能较差,循环前缀集相关同步算法增强了对抗多径的能力,获得了较好的同步性能,但同步时延非常大.为了缩短集相关同步算法的同步时延,设计了一种前导符号,基于此前导符号,提出了一种快速集相关运算同步算法.蒙特卡洛仿真结果表明,在多径信道下,该算法比循环前缀集相关同步算法具有更好的同步性能.进一步的分析还证明本文算法的同步时延也大大缩短. 相似文献
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多径传播是无线信道所固有的特性,信道时延的存在将会导致符号间干扰(ISI),严重影响接收端信号的解调.本文重点研究了多径信道下TD-LTE系统中的定时同步模块,并对基于循环前缀(CP)的能量差分算法加以改进,联合主同步信号(PSS)精确估计定时同步位置.仿真结果表明,该算法在多径衰落信道下能获得较好的定时同步性能,即使在信道时延较大的情况下也能够稳定地工作. 相似文献
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一种用于OFDM符号定时跟踪的盲估计算法 总被引:1,自引:0,他引:1
利用具有循环前缀和循环后缀的OFDM帧结构,该文提出了一种新的符号定时跟踪盲估计算法。理论分析及仿真表明,无论在AWGN还是多径衰落信道条件下,该定时算法估计的均方差都小于ML算法。 相似文献
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协作分集技术利用其他用户进行协作传输,可以获得一定的分集增益,但是在频率选择性衰落信道下性能不很乐观。为了对抗频率选择性衰落,采用正交频分复用(ODFM)技术与协作分集技术相结合的方法,研究了基于OFDM技术的协作通信,对在不同调制技术、不同信道估计方法下系统的性能进行了比较,为了进一步提高系统性能,对传统S&C算法进行了改进并应用于该系统中,仿真实验结果表明,改进的定时同步算法性能优于传统的S&C算法。 相似文献
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In this paper we are interested in designing a robust timing synchronization algorithm for OFDM systems that utilize pilot-aided channel estimation. We first characterize the impact of timing errors on the performance of a pilot-aided OFDM system. We derive analytical expressions for average channel estimation error variance in the presence of timing errors in high delay spread fading environments. The derived expressions show that pilot-aided channel estimators are considerably sensitive to timing synchronization errors due to the impact of rotations in different bases. We then show how to utilize this sensitivity to design a robust timing synchronization algorithm, without training overhead. The proposed algorithm is a cross-block design that uses channel estimation information to improve timing synchronization. We confirm our analytical results by simulating the proposed algorithm in high delay spread fading environments. In this paper, i.e. part I, we focus on timing synchronization for low-mobility cases. The analysis and results are then extended to high-mobility applications in part II. 相似文献
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利用多个OFDM符号中相同位置的连续多个抽样点相关求均值的方法,提高了估计精度。根据信噪比的高低和多径时延的大小,动态调整参与相关运算的循环前缀长度,提出了以长度D=Ng作为迭代间隔,降低了算法复杂度。在4径衰落信道模型,子载波数为1024,循环前缀Ng为256,子载波调制方式为QPSK,M取值为6,仿真结果表明,该算法在多径衰落信道下都具有良好的定时和频率偏差估计性能。 相似文献
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Berger C.R. Shengli Zhou Zhi Tian Willett P. 《Communications, IEEE Transactions on》2008,56(10):1606-1611
In this paper we develop a fine synchronization algorithm for multiband OFDM transmission in the presence of frequency selective channels. This algorithm is based on maximum a posteriori (MAP) joint timing and channel estimation that incorporates channel statistical information, leading to considerable performance enhancement relative to existing maximum likelihood (ML) approaches. We carry out a thorough performance analysis of the fine timing algorithm, and link the diversity concept widely used in data communications to the timing performance. We show that the probability of the timing offset equal to or larger than Delta taps has a diversity order of NB min(Delta, L) in Rayleigh fading channels, where NB is the number of subbands and L is the number of channel taps. This result reveals that the timing estimate is very much concentrated around the true timing as the signal to noise ratio (SNR) increases. Our simulations confirm the theoretical analysis, and also demonstrate the robustness of the proposed timing algorithm against model mismatches in a realistic UWB indoor channel. 相似文献
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基于IEEE 802.11a的OFDM系统信道估计算法研究及实现 总被引:1,自引:1,他引:0
无线信道的复杂性和随机性使得信道估计在无线通信系统中的作用尤为重要。针对IEEE 802.11a协议以及无线衰落信道的特点,在MATLAB环境下建立系统仿真模型,采用相应的信道估计算法进行仿真。通过对算法性能以及复杂度的比较选择合适算法并在此基础上对算法进行改进。将改进后的算法在FPGA硬件平台上实现。仿真结果表明,该算法是一种较为理想的信道估计实现方案,具有较好的实用价值。 相似文献
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In this paper we consider the design of a robust timing synchronization algorithm for pilot-aided OFDM systems in high-mobility fading environments. We first analyze the impact of both mobility and timing errors on the performance of a pilot-aided OFDM system for frequency selective fading channels, by deriving an expression for channel estimation error variance. The analysis will show that, even for high levels of mobility, a pilot-aided channel estimator is considerably sensitive to timing errors, due to the impact of rotations in different bases. We then show how this sensitivity can be utilized to design a robust timing synchronization algorithm for mobile OFDM systems, without relying on synchronization training information. Theoretical results are then confirmed by simulating the performance of an OFDM system in high delay and Doppler spread fading environments. Finally, we show how the proposed mathematical framework and algorithm can be used to address timing synchronization in the presence of a frequency offset as well. The analysis of this paper is the extension of the derivations of Part I [8], the accompanying paper on the design of a robust timing synchronizer for low-mobility OFDM systems. 相似文献