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针对60 GHz芯片间无线互连信道中存在的多径衰落问题,将匹配滤波器和最小均方误差算法应用到60 GHz脉冲通信系统,重点分析多径信道下采用最小均方误差合并算法的RAKE接收机的误码性能。在IEEE 802.15.3c信道模型的基础上,对采用不同合并方式、不同干扰用户数目下的RAKE接收机误码性能进行了研究。仿真结果表明,随着干扰芯片数量的增加,引入匹配滤波器和最小均方误差算法的RAKE接收机不仅降低了接收机的采样率,而且有效提高了系统抗多用户干扰的能力,为芯片间无线互连系统的RAKE接收机设计提供了技术参考。 相似文献
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信道估计是光正交频分复用(OOFDM)系统关键技术之一,为了克服光纤色散和模式的传输时延所产生的载波间干扰(ICI),设计了一种基于导频的信道估计器,通过分析最小二乘(LS)和线性最小均方误差(LMMSE)算法估计原理,仿真实验比较两种算法的误比特率和均方误差性能,实验结果表明,LS与LMMSE在OOFDM系统中都有较好的作用,但LMMSE算法性能要优于LS算法。 相似文献
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本文介绍了最小均方误差(LMS)算法和递推最小二乘(RLS)两种自适应滤波理论,并在自适应均衡和信道估计两个应用领域中进行了MATLAB仿真结果. 相似文献
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本文从理论上分析了HF串行数据传输系统抑制CW干扰的性能,求出了系统中自适应均衡器的最佳系数与最小均方误差表达式,并对CW干扰对均衡器收敛性的影响进行分析,指出HF串行数据传输系统中的自适应均衡器既能跟踪信道快速变化,又具有强的抑制CW干扰的能力。 相似文献
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在EDGE( Enhanced Data Rate for GSM Evolution)移动通信系统中,提出了一种基于最小均方误差的自适应8PSK均衡解调算法.利用基于最小均方误差的自适应滤波器,根据突发中已知的训练序列,可快速准确地估计出系统信道参数,然后通过判决反馈均衡消除多径信道对接收信号的干扰,从而保证系统的性... 相似文献
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A comprehensive analytical bit-error-rate (BER) model is presented to analyse the performance of antenna-microdiversity for wideband BPSK modulated signals in the frequency selective fading multipath channel, specified by its complex impulse response. The model includes the disturbance by intersymbol interference (ISI) and co-channel interference (CCI), as well as the channels' impact on the carrier phase- and clock recovery in the receiver. The channel impulse responses at the antenna elements are determined by taking into account the direction of arrival of the individual paths. Computational BER- and SNIR-gain results (SNIR = signal-to-noise+interference-ratio) show that a substantial performance improvement is achieved with antenna combining for wideband signals which suffer ISI and/or CCI. For the indoor multipath channel with exponentially decaying power delay profile, the performance enhancement is compared for several antenna combining schemes. Quasi-coherent equal gain combining (QCEGC) is proposed as an novel EGC scheme based on a less accurate phase estimation technique. For wideband signals, QCEGC shows a slight performance degradation when compared to maximal ratio combining or minimum mean square error combining (MMSEC), but has a much lower implementation complexity. In the channel with CCI, where the best performance is achieved with MMSEC, QCEGC performs very poor. 相似文献
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A channel‐estimate‐based frequency‐domain equalization (CE‐FDE) scheme for wireless broadband single‐carrier communications over time‐varying frequency‐selective fading channels is proposed. Adaptive updating of the FDE coefficients are based on the timely estimate of channel impulse response (CIR) to avoid error propagation that is a major source of performance degradation in adaptive equalizers using least mean square (LMS) or recursive least square (RLS) algorithms. Various time‐domain and frequency‐domain techniques for initial channel estimation and adaptive updating are discussed and evaluated in terms of performance and complexity. Performance of uncoded and coded systems using the proposed CE‐FDE with diversity combining in different time‐varying, multi‐path fading channels is evaluated. Analytical and simulation results show the good performance of the proposed scheme suitable for broadband wireless communications. For channels with high‐Doppler frequency, diversity combining substantially improves the system performance. For channels with sparse multi‐path propagation, a tap‐selection strategy used with the CE‐FDE systems can significantly reduce the complexity without sacrificing the performance. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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This paper proposes a novel multicarrier spread spectrum (SS) watermarking scheme for the application of image error concealment
using multicarrier-code division multiple access (MC-CDMA) with binary phase shift keying (BPSK) transmission in Rayleigh
fading channel. The goal is achieved by embedding important information (image digest) which is extracted from the original
image itself, and is used to introduce sufficient redundancy in the transmitted image. Half-toning technique is applied to
obtain image digest from its low-resolution version. At the decoder side, data demodulation as well as watermark decoding
are done using minimum mean square error combining (MMSEC) strategy. The extracted image digest is used to correct the damaged
regions. The integration of SS watermarking with the existing SS modulation not only simplifies the design but also offers
significant performance improvement for error concealment in fading channel. Authorized users having the knowledge of code
patterns for SS watermarking can only perform the error concealment operation and the method is secured. Experimental results
duly support the effectiveness of the proposed scheme. 相似文献
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In order to accommodate different types of traffic in future wirelesscommunications, it is necessary to consider a system, which can operatesatisfactorily at multiple transmission rates. Due to its capability to copewith the hostile frequency selective fading, that limits transmission rate,and its suitability to handle multi-rate data, multi-carrier CDMA (MC-CDMA)has recently drawn considerable attention as a suitable candidate forsupporting multimedia services in wireless communications. Multi-rate accessschemes where users are able to transmit at different data rates on MC-CDMAsystems are presented in this paper. Four multi-rate access schemes: uncodedfixed spreading length (UFSL), coded fixed spreading length (CFSL), multi-codefixed spreading length (MFSL) and variable spreading length (VSL) schemes areproposed. With these schemes, different traffic such as voice, video and highrate data can be transmitted seamlessly through one MC-CDMA infrastructure.A chip-level minimum mean square error combining (MMSEC) technique is employedfor joint energy combining and interference cancellation purpose. Theperformance of these schemes with MMSEC is compared by both theoreticalderivations and simulation results under frequency selective Rayleigh fadingchannels. 相似文献
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首先分析混频输入级高频地波雷达中短波通信干扰的特征,借鉴用基于LMS算法的自适应滤波方法抑制短波通信干扰的处理思想,通过构建基于Hopfield神经网络的自适应滤波器来抑制短波通信干扰.通过仿真比较这两种自适应滤波器的处理效果,验证了用基于Hopfield神经网络的自适应滤波来抑制短波通信干扰方案是可行的. 相似文献
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The combination of antenna array beamforming with multiuser detection can effectively improve the detection efficiency of a wireless system under multipath interference, especially in a fast‐fading channel. This paper studies the performance of an adaptive beamformer incorporated with a block‐wise minimum mean square error(B‐MMSE) detector, which works on a unique signal frame characterized by training sequence preamble and data blocks segmented by zero‐bits. Both beam‐former weights updating and B‐MMSE detection are carried out by either least mean square (LMS) or recursive least square (RLS) algorithm. The comparison of the two adaptive algorithms applied to both beamformer and B‐MMSE detector will be made in terms of convergence behaviour and estimation mean square error. Various multipath patterns are considered to test the receiver's responding rapidity to changing multipath interference. The performance of the adaptive B‐MMSE detector is also compared with that of non‐adaptive version (i.e. through direct matrix inversion). The final performance in error probability simulation reveals that the RLS/B‐MMSE scheme outperforms non‐adaptive B‐MMSE by 1–5 dB, depending on the multipath channel delay profiles of concern. The obtained results also suggest that adaptive beamformer should use RLS algorithm for its fast and robust convergence property; while the B‐MMSE filter can choose either LMS or RLS algorithm depending on antenna array size, multipath severity and implementation complexity. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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针对电磁辐射现场测试被测设备信号和干扰未知的情况,提出了一种基于频域块最小均方算法的实时虚拟暗室测试方法。该方法采用双通道接收机,根据测试通道和背景通道中干扰信号的相关性设计自适应滤波器,在频域对背景通道信号滤波以趋近测试通道中的干扰分量,采用瞬时双通道信号迭代更新滤波器系数,滤波器系数收敛后系统输出中只有被测设备信号。仿真与分析表明,该方法在背景通道有无被测设备信号泄露的情况下都能有效抑制干扰,与基于时域最小均方算法的方法相比,在滤波器长度相同的情况下其计算复杂度更低,适用于实时现场测试。 相似文献
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We examine adaptive equalization and diversity combining methods for fast Rayleigh-fading frequency selective channels. We assume a block adaptive receiver in which the receiver coefficients are obtained from feedforward channel estimation. For the feedforward channel estimation, we propose a novel reduced dimension channel estimation procedure, where the number of unknown parameters are reduced using a priori information of the transmit shaping filter's impulse response. Fewer unknown parameters require a shorter training sequence. We obtain least-squares, maximum-likelihood, and maximum a posteriori (MAP) estimators for the reduced dimension channel estimation problem. For symbol detection, we propose the use of a matched filtered diversity combining decision feedback equalizer (DFE) instead of a straightforward diversity combining DFE. The matched filter form has lower computational complexity and provides a well-conditioned matrix inversion. To cope with fast time-varying channels, we introduce a new DFE coefficient computation algorithm which is obtained by incorporating the channel variation during the decision delay into the minimum mean square error (MMSE) criterion. We refer to this as the non-Toeplitz DFE (NT-DFE). We also show the feasibility of a suboptimal receiver which has a lower complexity than a recursive least squares adaptation, with performance close to the optimal NT-DFE 相似文献
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This work presents a novel scheme for identifying the impulse response of a sparse channel. The scheme consists of two adaptive filters operating sequentially. The first adaptive filter adapts using a partial Haar transform of the input and yields an estimate of the location of the peak of the sparse impulse response. The second adaptive filter is then centered about this estimate. Both filters are short in comparison to the delay uncertainty of the unknown channel. The principle advantage of this scheme is that two short adaptive filters can be used instead of one long adaptive filter, resulting in faster overall convergence and reduced computational complexity and storage. The scheme is analyzed in detail for a least mean squares (LMS) LMS-LMS type of structure, although it can be implemented using any combination of adaptive algorithms. Monte Carlo simulations are shown to be in good agreement with the theoretical model for the behavior of the peak estimating filter as well as for the mean square error (MSE) behavior of the second filter. 相似文献
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An adaptive multipath decorrelating multiuser receiver is considered for application in Rayleigh fading multipath channels with significant Doppler spread. Coherent diversity combining is performed using adaptively obtained channel estimates in a manner that minimizes the impact of estimation errors on data detection. The bit-error rate of the receiver is evaluated analytically, showing dependence on the fading rate of the channel and tracking capabilities of adaptive least mean square and recursive least square algorithms, in addition to the order of multipath diversity and the number of active code-division multiple-access users 相似文献