共查询到19条相似文献,搜索用时 78 毫秒
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讨论了基于OFDM传输系统中频率偏移的估计技术,它利用了OFDM符号中重复的信号结构,用来扩大偏移估算范围和增加其估算的精度。另外,提出了适合于突发数据的平均直接判决信道估计(ADDCE)技术。 相似文献
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无线信道中OFDM系统的频偏估计 总被引:3,自引:0,他引:3
OFDM技术作为一种适用于高速无线传输的调制技术近年来越来越受到关注。但 OFDM系统的显著问题是对频率偏移十分敏感。针对OFDM信道传输系统,提出了一种频率 偏移估计算法。该估计器采用内插技术,通过频域来实现,与传统的最大似然估计器相比,该 算法具有良好的性能和较简单的结构。 相似文献
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介绍了802.11a系统的信道估计技术,包括LS(最小平方)信道估计技术,维纳滤波器方法,以及它们的基本原理和主要算法.在802.11a系统的仿真平台上用LS和维纳滤波器方法分别对信道进行估计.仿真结果表明,对瑞利衰落信道,在相同的传输速率下,Wiener-Filter的信道估计比LS信道估计都有一定的性能提高。 相似文献
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分别介绍了基于梳状导频和块状导频的OFDM信道估计的原理,重点研究了上述两种导频在不同的信道环境中的信道估计性能.仿真分析展示了两种导频模式对传输信道的不同参数的敏感程度,由此给出了在不同的传输信道条件下导频模式的选择依据. 相似文献
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LIU Xiao-ming LIU Yuan-an Wireless Communication Center Beijing University of Posts Telecommunications Beijing P.R. China 《中国邮电高校学报(英文版)》2004,11(Z1)
1 Introduction OrthogonalFrequencyDivisionMultiplexing(OFDM )isaneffectivetransmissionschemetocombatmultipathfading[1 ] .Byinsertingaguardin tervalbetweensymbolblockscalledcyclicprefix ,theInterSymbolInterference (ISI)canbemitigat ed.OFDMwasadoptedasthemodulationschemeforaDigitalAudioBroadcasting(DAB)system[2 ]andADSL (AsymmetryDigitalSubscriberLoop) [3]andwasalsoproposedastheterrestrialHDTVtransportinEurope[4] . OFDMsystemsareverysensitivetocarrierfre quencyoffset,andcarrie… 相似文献
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This article puts forward a novel channel estimation and inter-carrier interference (ICI) suppression method for time-varying orthogonal frequency division multiplexing (OFDM) systems. The proposed adaptive finite impulse response (FIR) filter utilizes the time domain correlation of the subcarriers. Based on the one order auto-regressive (AR) model, a modified Kalman filter is exploited to track the channel variance. By solving the Yule-Walker equation, the coefficient of the AR process can be obtained from zero order Bessel function. However, when the channel is assumed not perfectly known, the above criterion will lead to an impractical application. To deal with it, the coefficient of the AR process is taken as a constant. Subsequently a new state space model is deduced and found. Simulation results show that the proposed method can work effectively at the speed of 144 km/h with a phase noise of -85 dBc/Hz at 100 kHz offset. The proposed method yields an improvement bit error rate (BER) compared with three of the existing algorithms with much lower complexity. 相似文献
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无线OFDM系统中基于导频的信道估值器的比较分析 总被引:2,自引:0,他引:2
本文对无线OFDM系统中基于导频的信道估值器进行了比较分析,对比了四种估值器在均方误差(MSE)上的性能。本文针对时频两维的信道估值,分别分析了时频分离和时频不分离两种处理方法。文中还讨论了信道估值的低阶近似算法,并进行了给定复杂度下的不同估值器的性能对比。结果表明,在相同的复杂度下,使用时频分离的估值器比时频不分离的估值器性能要好,分离估值器经过低阶近似,性能得到了进一步的提高。 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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介绍MIMO-OFDM系统中几种基于导频的信道估计方法。首先研究了单天线OFDM系统的信道估计算法。一方面重点关注三种估计准则的原理,仿真表明LMMSE准则具有最佳的性能;另一方面介绍了几种插值的方法用来恢复非导频处的信道信息。 相似文献
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Carrier frequency offset (CFO) in OFDM systems results in loss of channel orthogonality and hence degrades the system's performance. In this paper, we propose a new method for joint CFO/channel estimation for OFDM systems with two receive antennas. Our method avoids the complexity of full search methods in one or two dimensions. Using one training OFDM symbol and utilizing the knowledge of the structure of the inter‐channel interference that results from CFO, we develop a two‐stage estimation procedure. The first stage derives an initial CFO/channel estimate based on a one shot minimization step. The second stage refines this joint estimate by conducting a small CFO search in the vicinity of the initial estimate. This procedure provides CFO estimates over a full range of −N /2–N /2, (N : number of subcarriers), as well as the channel estimates. Computer simulations show an excellent performance that is very close to the Cramer–Rao lower bound and superior to some existing methods. The effect of antenna correlation on performance is also investigated through computer simulations, showing small performance degradation even at medium correlation coefficients (0.3–0.6). Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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主要研究了正交频分复用(OFDM)系统中基于导频辅助的低秩信道估计方法,提出了一种秩的取值及自适应秩跟踪方法。低秩估计方法利用信道的频域(和/或时域)相关性以及奇异值分解技术。其中关键的秩估计也就是信号子空间的维数判定必须在计算复杂度和估计误差两方面折中考虑。仿真表明给出的秩估计方法能够比较准确地反映出信号子空间的大小,大大降低运算复杂度。在此基础上的低秩方法与线性最小均方误差(LMMSE)估计的性能几乎一样并且对子载波总数的大小和信道环境变化的敏感性相当小,通过分块估计还可以进一步降低运算量。 相似文献