共查询到20条相似文献，搜索用时 734 毫秒
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分别针对无线通信集中式多入多出（MIMO）和分布式MIMO系统,对频偏估计和频偏补偿这两个方面的基本原理和研究现状进行了详细分析,总结出已有研究的不足之处在于对分布式MIMO中的频偏估计以及分布式MIMO-OFDM（正交频分复用）中的频偏补偿的研究尚不完善,指出未来可能的研究方向应主要集中在分布式MIMO中基于一般系统模型的频偏估计方法和分布式MIMO-OFDM中具有实用价值的低复杂度频偏补偿方法两个方面. 相似文献
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基于频域训练序列,深入地分析了MIMO—OFDM系统中基于多项式建模的频偏估计问题．设计训练序列使其结构满足适当的条件,根据相应矩阵的厄尔密特属性和实对称属性,分析出代价函数多项式方程根的成对性,进而提出整数频偏与小数频偏可同时通过直接多项式求根方法估计出来．分析了导数多项式求根方法与直接多项式求根方法,研究出代价函数多项式与其导数多项式具有公共的多项式因子,且代价函数多项式可以表示成该公共多项式因子的二次型,并进一步揭示出二者在估计上的等效性以及后者在实现上的优越性．计算机仿真结果验证了该理论分析结果． 相似文献
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A channel estimation approach for orthogonal frequency division multiplexing with multiple-input and multipleoutput （MIMO-OFDM） in rapid fading channels is proposed. This approach combines the advantages of an optimal training sequence based least-square （OLS） algorithm and an expectation-maximization （EM） algorithm. The channels at the training blocks are estimated using an estimator based on the OLS algorithm. To compensate for the fast Rayleigh fading at the data blocks, a time domain based Gaussian interpolation filter is presented. Furthermore, an EM algorithm is introduced to improve the performance of channel estimation by a few iterations. Simulations show that this channel estimation approach can effectively track rapid channel variation. 相似文献
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The surface acoustic wave (SAW) identification (ID)-tags have great potential for application in radio frequency identification (RFID) due to their characteristics of wireless sensing and passive operation. In the measurements based on the frequency domain sampling (FDS), to expand the range of detection and allow the system work in harsh environments, it is necessary to enhance the identification capability at low SNR. In addition, to identify the tags in real time, it is important to reduce identification time. Therefore, estimation of signal parameters based on the Procrustes rotations via the rotational invariance technique (PRO-ESPRIT) is adopted. Experimental results show that good identification capability is achieved with a relatively faster measurement speed. 相似文献
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赵忠伟 《浙江大学学报(A卷英文版)》2006,7(3):321-325
INTRODUCTION Orthogonal frequency division multiplexing (OFDM) has been treated as the key transmission method in Wireless Local Area Networks (WLANs) based on IEEE802.11a protocol (IEEE Standard 802.11a- 1999). However, the sensitivity of the scheme to the frequency offset limits its development. Moose (1994) proposed maximum likelihood esti-mation for the carrier frequency offset by using two different received symbols, but the limitation of this method is that the acquisition r… 相似文献
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WU Yun LUO Han-wen DING Ming YAN Chong-guang 《浙江大学学报(A卷英文版)》2006,7(12):2104-2109
INTRODUCTION Orthogonal frequency division multiplexing (OFDM) has become a promising technology for future wireless communication systems (Kim et al., 2003; 3GPP TSG-RAN-1.TR, 2004) due to its ability to transform a wideband frequency selective channel to a set of parallel flat-fading narrow-band channels, which substantially simplifies the channel equaliza- tion problem. However, a critical weakness of OFDM is its sensitivity to carrier frequency offset (CFO) since it can only t… 相似文献
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INTRODUCTION Orthogonal frequency division multiplexing(OFDM) is generally known as an effective techniquefor high data rates and has been adopted by standardssuch as Digital Audio and Video Broadcasting (DABand DVB) (ETSI, 1994; 1997). OFDM is robustagainst frequency selectivity of a multipath channeland the single-tap equalization can be used to detectthe transmitted symbols if frequency-selective fadingchannels are known. Although, the use of pilot tonesis the most robust way … 相似文献
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在一般的信道预测方案中,对于信道脉冲响应的预测问题,有些是没有考虑到信道传输函数的相关性,一些预测方案则是实现复杂度较高。针对这些问题,首先实现时域的信道预测方法,再用根据信道传输函数的自相关函数设计出来的滤波器对预测后信道的频率响应进行滤波,可使预测后的信道频域相关性与观测的信道频域相关性一致。这样,时间上的相关性可确保信道预测的可行性,而频域相关性保证了预测前后的空间相关性不变,从而时频联合信道预测方案与其他方案相比具有更可靠的信道预测效果。 相似文献
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Localization of the sensor nodes is a key supporting technology in wireless sensor networks (WSNs). In this paper, a real-time
localization estimator of mobile node in WSNs based on extended Kalman filter (KF) is proposed. Mobile node movement model
is analyzed and online sequential iterative method is used to compute location result. The detailed steps of mobile sensor
node self-localization adopting extended Kalman filter (EKF) is designed. The simulation results show that the accuracy of
the localization estimator scheme designed is better than those of maximum likelihood estimation (MLE) and traditional KF
algorithm. 相似文献
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空时MIMO-OFDM 系统中基于扩展Kalman 滤波的信道估计 总被引：1，自引：1，他引：1
A space-time coded multiple-input multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) system is considered as a solution to the future wideband wireless communication system.This paper proposes an extended Kalman filtering-based (EKF-based) channel estimation method for space-time coded MIMO-OFDM systems.The proposed method can exploit pilot symbols and an extended Kalman filter to estimate channel without any prior knowledge of channel statistics.In comparison with the least square (LS) and the least mean square (LMS) methods,the EKF-based approach has a better performance in theory.Computer simulations demonstrate the proposed method outperforms the LS and LMS methods.Therefore it can offer dramatic system performance improvement at a modest cost of computational complexity. 相似文献
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刘顺财 《福建工程学院学报》2014,(6):577-580
系统采用ARM920T作为核心处理器,以低频信号作为信号源,采用DDS技术,从而实现相频,幅度,频率特性的分析仪器,能够简单的实现信号源的时域和具体参数的波形。本系统主要由ARM920T控制处理器,DDS扫频模块,ADC采样模块,DAC输出模块,检波滤波器模块,扫频信号源幅度模块组成。其中处理器采样ARM920T,扫频信号源采样DDS芯片AD9851,检波模块以AD637JQ芯片构成,相位检测模块由AD8302芯片构成,通过DAC芯片TLV5618控制扫频信号的幅度。通过实验本仪器可以检测20Hz到1MH 相似文献
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This paper proposes a new phase feature derived from the formant instantaneous characteristics for speech recognition (SR)
and speaker identification (SI) systems. Using Hilbert transform (HT), the formant characteristics can be represented by instantaneous
frequency (IF) and instantaneous bandwidth, namely formant instantaneous characteristics (FIC). In order to explore the importance
of FIC both in SR and SI, this paper proposes different features from FIC used for SR and SI systems. When combing these new
features with conventional parameters, higher identification rate can be achieved than that of using Mel-frequency cepstral
coefficients (MFCC) parameters only. The experiment results show that the new features are effective characteristic parameters
and can be treated as the compensation of conventional parameters for SR and SI. 相似文献
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LI Mao-hai HONG Bing-rong LUO Rong-hua WEI Zhen-hua 《浙江大学学报(A卷英文版)》2006,7(6):937-944
INTRODUCTION A key prerequisite for a truly autonomous robot is that it can simultaneously localize itself and accu-rately map its surroundings (Kortenkamp et al., 1998), which is known as Simultaneous Localization and Mapping (SLAM), which, when phrased as a state estimation problem, involves a variable number of dimensions. Murphy and Russell (2001) adopted Rao-Blackwellized particle filters (RBPFs) as an effective way for representing alternative hypotheses on robot paths and ass… 相似文献
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研究了在空频块码正交频分复用(SFBC-OFDM)无线通信系统中适用于多径衰落信道下的迭代接收机的设计,导出了一种迭代的联合信道估计与符号检测的算法.在提出的算法中,信道估计器交替地工作于2种模式.在训练阶段,采用基于DFT的估计器估计出信道状态信息,并且采用所提出的算法估计出噪声方差和信道响应的互相关矩阵.在数据传输模式下,迭代地获得发送数据和信道状态信息.为了抑制由于符号检测中误判引起的错误传播,提出了一种简单的错误传播判定准则,并使用了一种自适应的训练机制来抑制误差传播.仿真结果显示,与传统的迭代算法相比,所提出的算法能够提供更好的误码性能,且节约了系统开销. 相似文献
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研究了信道估计的均方误差,利用无限长、非因果的维纳滤波器推导出了它的下界.通过对不同衰落信道多普勒谱的积分,求出了相应的信道估计均方误差下界的闭合表达式,并在此基础上得到了分集系统在独立同分布的衰落信道中采用最大比合并时的误码率下界.数值分析结果表明,非理想信道估计下最大比合并的误码率性能是以理想信道估计的结果为下界,并随着最大多普勒频移的增加或信道估计信噪比的减小而逐渐劣化. 相似文献
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RLS channel estimation with adaptive forgetting factor in space-time coded MIMO-OFDM systems 总被引：1，自引：0，他引：1
LIANG Yong-ming LUO Han-wen HUANG Jian-guo 《浙江大学学报(A卷英文版)》2006,7(4):507-515
INTRODUCTION The very dramatic increase in demand for high-rate data transmission stimulated greater re- search efforts in developing wideband wireless communication systems which could support high- rate transmission over wireless channels. But we have to face the challenges from the multi-path effects because multi-path propagation of wire wave is usu- ally seen as a harmful factor which leads to one of the most troublesome radio channel problems. However, the multi-path effects can beco… 相似文献
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This paper presents a novel low-pass filter （LPF） with sharp rejection, wide stopband and compact size, which are realized by the defected ground structure （DGS） and the defected microstrip structure （DMS）. The equivalent circuit model is proposed and the circuit parameters are extracted by the circuit simulation software. The parameters measured are 3 dB cutoff frequency fc of 5.2 GHz, the insertion loss less than 0.5 dB from DC to 4.0 GHz and S21 less than -20 dB within the wide stopband from 6 GHz to 16 GHz. The results of the circuit optimization agree well with those of the full wave simulation and the measured ones, which validate the effectiveness of the equivalent circuit model. The size of the proposed LPF is decreased compared with normal LPF. This LPF can be applied in rectennas to eliminate high order harmonics. 相似文献
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GUO Rong-hua QIN Zheng 《浙江大学学报(A卷英文版)》2007,8(10):1588-1595
In this study, an unscented particle filtering method based on an interacting multiple model (IMM) frame for a Markovian switching system is presented. The method integrates the multiple model (MM) filter with an unscented particle filter (UPF) by an interaction step at the beginning. The framework (interaction/mixing, filtering, and combination) is similar to that in a standard IMM filter, but an UPF is adopted in each model. Therefore, the filtering performance and degeneracy phenomenon of particles are improved. The filtering method addresses nonlinear and/or non-Gaussian tracking problems. Simulation results show that the method has better tracking performance compared with the standard IMM-type filter and IMM particle filter. 相似文献