共查询到19条相似文献,搜索用时 265 毫秒
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介绍了正交频分复用(OFI)M)的基本原理,围绕OFDM同步过程中的符号定时和载波频率偏差问题进行描述,对一种基于保护间隔/循环前缀(PL/CP)的联合实现符号定时和载波同步最大似然估计(MLE)算法进行叙述并仿真。 相似文献
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在分析无线信道环境对OFDM系统影响的基础上,对目前该学术领域提出的多种同步算法进行了分析比较,探讨了数据辅助性估计的OFDM系统的同步过程,该过程包括符号同步、载波同步和采样率同步。该算法在时域上引入了一种更有效的导频方案,在此前提下,利用该PN序列的共轭对称性完成符号定时,然后通过一种基于PN的重复数据最大似然估计理论算法完成频偏估计。仿真结果证明,这种同步体制具有较好的同步精度。 相似文献
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刘淼 《信息技术与信息化》2011,(3):39-41
虽然OFDM技术有很多优势,但相对于单载波系统或者一般的频率复用通信系统来说,它对同步要求更高。假设终端与基站无法实现同步,终端甚至无法接入,同步技术是OFDM系统以及MIMO-OFDM系统的关键技术,是保证系统高稳定和高性能重要技术。最大似然估计算法在OFDM符号定时同步和载波频率同步中得到了广泛的应用,通过基于循环前缀的最大似然估计方法,避免了基于导频符号同步估计带来功率和数据资源浪费。通过仿真可以看到,该算法能够很好地实现OFDM系统的符号同步和载波同步。 相似文献
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首先介绍了OFDM系统同步问题的研究背景,然后分别说明了传统的OFDM和MIMO-OFDM的系统模型,接着重点介绍了这两个系统近年来具有代表性的同步算法,并对算法的优缺点进行了分析,最后总结并对以后工作进行展望。 相似文献
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介绍了LTE—FDD系统主同步序列的产生,给出了一种基于主同步信道的时频同步算法,包括符号定时同步算法和频偏估计算法。定时同步算法引入了多径能量窗,并且根据LTE系统同步信道的特点,对多个同步信道上的相关值进行非相干合并,有效地提高了同步性能。对所给出的算法进行仿真,并采用DSP实现同步算法。仿真和实验结果表明,所给出的算法具有良好的性能,能够满足LTE系统对同步性能的要求。 相似文献
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MIMO OFDM同步技术研究 总被引:1,自引:0,他引:1
MIMO OFDM作为一种多天线、多载波传输技术,具有频谱利用率高、抗干扰能力强、传输速度快、传输容量大等特点,目前已经成为4G技术的热门标准之一。但是由于MIMO OFDM系统对频偏和定时比较敏感,因此同步问题的研究显得尤为重要,文中针对目前主流的同步方法做了全面的分析和总结。 相似文献
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OFDM系统中定时偏移的估计技术 总被引:1,自引:0,他引:1
在T.M.Schmidl和D.C.Cox提出的解决正交频分多路复用(OFDM)系统定时同步的基础上,给出了两种改进算法。在加性高斯白噪声信道(AWGN)和存在符号间干扰(ISI)的两种信道中,分别对估值进行比较,这两种改进算法得到估值的方差要小得多。 相似文献
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In this paper the problem of data-aided symbol timing and frequency offset estimation in OFDM systems is considered. A synchronization
scheme based on a pilot symbol containing two identical parts obtained by transmitting BPSK data symbols on the even subcarriers
and setting zero on the remaining subcarriers is proposed. In this case, if the number of subcarriers is sufficiently large,
the pilot symbol can be modeled as a noncircular (NC) complex Gaussian random vector (CGRV). By exploiting the joint probability
density function of NC-CGRVs, the joint maximum likelihood estimator for the parameters of interest is derived. Since its
implementation complexity is high, a simpler synchronization scheme is obtained. Moreover, refined symbol timing and frequency
offset estimators, that assure relevant performance in multipath channels, are proposed.
T. Fusco was born in Naples, Italy, on March 22, 1977. She received the Dr. Eng. degree (summa cum laude) in electronic engineering
from the Second University of Napoli in 2002. Since November 2002 she has been a Ph.D. student at the Department of Electronic
and Telecommunication Engineering of the University of Napoli Federico II. Her current research and study interests lie in
the area of statistical signal processing, with emphasis on parameter estimation problems in the context of OFDM communications.
M. Tanda was born in Aversa, Italy, on July 15, 1963. He received the Dr. Eng. degree (summa cum laude) in electronic engineering
in 1987 and the Ph.D. degree in electronic and computer engineering in 1992, both from the University of Napoli Federico II.
Since 1995, he has been an Appointed Professor of Signal Theory an the University of Napoli Fe-de-ri-co II. Moreover, he has
been an Appointed Professor of Electrical Communications (from 1996 until 1997) and Telecommunication Systems (from 1997)
at the Second University of Napoli. He is currently Associate Professor of Signal Theory at the University of Napoli Federico
II. His research activity is in the area of signal detection and estimation, multicarrier, and multiple access communication
systems. 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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为了提高船舶自动识别系统(AIS)的容量,提出了基于正交频分复用技术(OFDM)的新型AIS系统设计方案.新系统设计主要包括系统参数设计、系统帧结构设计.新系统链路容量和信道传输速率均较传统AIS系统提高了6倍,实现了频域资源的有效利用.该系统对符号定时偏差和载波频率偏差特别敏感,因此对接收信号的同步处理必不可少,在设计的新系统基础之上提出了一种新的盲估计算法,利用包含在循环前缀内的冗余信息,在多径信道信息未知的情况下,直接通过对接收信号做相关构造一个归一化的相关特性函数,通过此函数可得到符号时延位置和多径信道长度,进而得到载波频率偏差.仿真结果表明在多径信道下该算法也具有较好的性能. 相似文献
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JIANG Feng SONG Mei GUO Da SONG Jun-de CAD PCN Center Electronic Engineering Institute Beijing University of Posts Telecommunications Beijing China 《中国邮电高校学报(英文版)》2007,14(1):96-99
The article presents a novel orthogonal frequency division multiplexing (OFDM) frame synchronization method. The method uses the preamble that contains two identical halves, and the energy difference of the two similar parts of the received preamble in receiver is used to obtain the frame's correct starting point. Furthermore, an improvement of the proposed method is presented, which uses the preamble that can be divided into four similar portions, and the energy difference of the four similar parts of the received preamble in receiver is used to obtain the frame's correct starting point. The performances of the frame synchronization methods in multipath channel are compared in terms of mean square error (MSE) obtained by simulations. It can be seen from the simulation results that the proposed methods have better performances than Schmidl's, Minn's, and Park's method in multipath channel. 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