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基于遗传算法的最小误码率线性多用户检测 总被引:1,自引:1,他引:0
本文提出了一种多用户检测算法,算法基于最小误码率准则,应用内核密度估计方法来估计误码率函数,并采用基于实数编码的遗传算法来搜索误码率函数全局最小点。该算法解决了由于误码率函数存在局部最小点而难以用普通的梯度算法来求解全局最优点的问题。算法对初值的选取无特殊要求,可随机选取。仿真结果表明,梯度算法求解最小误码率检测器由于可能收敛到次优的局部极小点,故检测器不能达到最小误码率性能;而本文基于遗传算法的多用户检测由于能很好的避免收敛到次优的局部极小点,因而得到的检测器性能逼近最小误码率。 相似文献
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设计余弦调制QMF组的一种新方法 总被引:5,自引:0,他引:5
通过适当矩阵变换,本文首先将精确重建余弦调制正交镜像滤波器组的设计转化为一种带约束的非线性优化问题,它是一种带二次型约束的最小二乘(QCLS)优化问题,然后,我们提出了一种变参量的罚函数方法来有效求解该类QCLS优化问题,通过直接采用原型滤波器系数为优化变量,我们构造了一个特殊的凸函数作优化代价函数,故可获得该问题的全局最小点,最后,采用本文提出的设计方法进行了一个具体实例设计,结果表明我们的方法 相似文献
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本文介绍了一种将正交频分复用(OFDM)技术和码分多址(CDMA)技术相结合的多载波CDMA (MC-CDMA)系统,分析了MC-CDMA系统的发射端和接收端的结构,建立了MC-CDMA系统的信号模型,详细分析了MC-CDMA中的多址干扰形式,以及针对MC-CDMA系统的多用户检测原理,提出了一种基于最小误码率准则的多用户检测算法。理想的基于最小误码率准则的多用户检测算法在实际中难于实现,本文采用估计概率密度函数的方法,推导出了一种自适应实现的最小误码率多用户检测算法。仿真结果表明,该算法能够有效抑制多址干扰,降低误码率,同时,该算法还具有比基于最小均方误差准则的多用户检测器更低的误码率的优点。 相似文献
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考虑二维线性相位矩形对称FIR滤波器的约束最小二乘设计问题,即在通带和阻带逼近误差不超过给定值的约束下使逼近误差平方和最小.提出一个投影最小二乘算法,它是一个交替地更新有效约束集及将二次误差无约束极小点(最小二乘解)逐次投影到有效约束边界的迭代过程.通过二维FIR低通圆形滤波器和方形滤波器的设计例子,对算法的性能进行了仿真,并与基于内点算法和有效集方法的设计程序进行了比较,结果表明本文算法具有很高的效率. 相似文献
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多用户检测技术在OFDM-CDMA系统中的应用 总被引:1,自引:0,他引:1
OFDM-CDMA是继第三代移动通信之后移动通信技术中的新热点,这里分别对单用户检测器,解相关检测器,线性最小均方(MMSE)检测器和采用最陡下降常模算法(SDCMA)的盲多用户检测器在OFDM-CDMA系统中的误码率性能进行了比较和分析。 相似文献
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将二进制二次规划问题连续化为一个带等式约束的二次规划问题,借助于求解等式约束的Lagrangian乘子法,推导出Lagrangian乘子与用户信息码及信道噪声之间的关系.同时,根据多用户检测问题的特殊性,还给出了估计Lagrangian乘子的方法,进而得到了一种新的多用户检测器.仿真结果表明,新算法的误码率与最佳多用户检测器大致相同,低于一般的次最优多用户检测器. 相似文献
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Constrained minimum-BER multiuser detection 总被引:3,自引:0,他引:3
A new linear multiuser detector that directly minimizes the bit-error rate (BER) subject to a set of reasonable constraints is proposed. It is shown that the constrained BER cost function has a unique global minimum. This allows us to develop an efficient Newton barrier method for finding the coefficients of the proposed detector using information about timing, amplitudes, channels, and the signature signals of all users. Although the new detector cannot be shown to be optimal among linear multiuser detectors without the constraints imposed, extensive simulations demonstrate that it achieves the lowest BER. Furthermore, in some cases, the BER of the proposed detector can be significantly lower than that of the decorrelating and MMSE detectors 相似文献
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本文提出一种离散余弦变换(DCT)域加嵌入隐藏信息的鲁棒检测方法.该方法使用具有代数拖尾的α稳定分布模型来描述交流DCT系数统计分布的尖峰脉冲和强拖尾特性,并利用隐藏信息的不可感知特性,在弱信号条件下依概率模型进行统计推断,从而实现广义Neyman-Pearson准则下隐藏信息的鲁棒检测.实验结果表明:(1)新检测器的性能比目前广泛采用的匹配滤波器的性能优越;(2)新方法与基于广义高斯分布模型的检测方法相比性能相当,却不需要"点消除"过程,从而简化了检测器的实现. 相似文献
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彩色图像特征点检测算子 总被引:3,自引:0,他引:3
图像特征点的定位检测是计算机视觉中的一个关键问题,特征点检测算子的性能会直接影响到相机参数标定和视觉测量结果。本文在传统的Harris灰度图像的特征点检测算子基础上,利用彩色图像RGB三分量数据融合,提出了彩色图像特征点检测算子;提出了2个空间位置约束条件,使检测到的特征点均匀分布在图像各个区域;还提出了采用Bilateral滤波器取代Gaussian滤波器,得到一种既能保持边缘信息又能有效平滑噪声的图像滤波方法。通过对加噪彩色图像的特征点检测实验证明所提方法特征点定位准确,分布合理,抗噪声干扰性能好。 相似文献
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A family of detectors that exploit signal constraints is developed for maximum-likelihood detection for multiple-input-multiple-output (MIMO) systems. Real constrained detectors and decision-feedback detectors are proposed for real constellations by forcing the relaxed solution to be real. A generalized minimum mean square error (GMMSE) and constrained least squares MIMO detectors are also developed for unitary and nonunitary signal constellations. Using these constrained detectors, we propose a new ordering scheme to achieve a tradeoff between interference suppression and noise enhancement. Moreover, to mitigate the inherent error propagation, the decision-feedback MIMO detectors are integrated with signal constraints. The simulation results show that our combined detector achieves a significant performance gain over vertical Bell Laboratories layered space-time (V-BLAST) detection. 相似文献
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MIMO系统中16-QAM信号的软值输出半正定松弛检测 总被引:1,自引:0,他引:1
使用最优化理论与方法研究了MIMO系统中16-QAM信号的软值输出半正定松弛检测问题,推导了16-QAM信号的软值输出半正定松弛检测器软值计算所需附加的约束条件,并提出了一种降维近似处理方法,通过降维近似处理大大降低了软输出检测器的复杂度。仿真结果表明:通过附加约束条件和降维近似处理,软值输出半正定松弛检测器获得了较好的检测性能,降维近似处理降低了软输出SDR检测器的运算复杂度,但会产生0.2~0.4dB的性能损失。 相似文献
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该文提出MC-CDMA系统下一种基于递归最小二乘(Recursive Least-Squares, RLS)的最小输出能量(Minimum Output Energy, MOE)噪声抑制线性共轭多用户检测算法.该算法定义了一种新的基于MOE准则的代价函数,同时将噪声子空间作为MOE代价函数的约束条件,设计了一种噪声抑制的线性共轭检测器,并采用RLS算法自适应得到权向量.所提算法将权向量和噪声子空间正交,消除了权向量中的噪声分量,并且利用了伪自相关矩阵的信息,从而提高了系统的性能.仿真结果证明了本文算法的有效性和优越性. 相似文献
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Shadow-aware object-based video processing 总被引:1,自引:0,他引:1
Cavallaro A. Salvador E. Ebrahimi T. 《Vision, Image and Signal Processing, IEE Proceedings -》2005,152(4):398-406
Local illumination changes due to shadows often reduce the quality of object-based video composition and mislead object recognition. This problem makes shadow detection a desirable tool for a wide range of applications, such as video production and visual surveillance. In this paper, an algorithm for the isolation of video objects from the local illumination changes they generate in real world sequences when camera, illumination and the scene characteristics are not known is presented. The algorithm combines a change detector and a shadow detector with a spatio-temporal verification stage. Colour information and spatio-temporal constraints are embedded to define the overall algorithm. Colour information is exploited in a selective way. First, relevant areas to analyse are identified in each image. Then, the colour components that carry most of the needed information are selected. Finally, spatial and temporal constraints are used to verify the results of the colour analysis. The proposed algorithm is demonstrated on both indoor and outdoor video sequences. Moreover, performance comparisons show that the proposed algorithm outperforms state-of-the-art methods. 相似文献
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Xiaofu Wu Cong Ling Songgeng Sun 《Electronics letters》1999,35(15):1222-1223
A new data-aided phase tracking detector for frequency-shifted DPSK signals is proposed in which the baseband frequency shift compensation technique of Choi and Lee (1997) is incorporated into the structure of data-aided phase tracking detection. Simulations show that the new detector outperforms the differential detector with perfect frequency-shift compensation for a wide range of frequency shifts, and even approaches the coherent detector in terms of its performance 相似文献
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Blind multiuser detection for asynchronous MC-CDMA systems without channel estimation 总被引:2,自引:0,他引:2
Gaonan Zhang Guoan Bi Liren Zhang 《Vehicular Technology, IEEE Transactions on》2004,53(4):1001-1013
This paper presents a blind adaptive decorrelating detector for asynchronous multicarrier code-division multiple-access (MC-CDMA) systems with Rayleigh-fading channels. This detector is derived by making use of the cross-correlation matrix between the consecutively received signals. The main attraction of the detection algorithm is its simplicity, since the detector can be implemented blindly without channel estimation, except for the synchronization of the desired user. To implement the proposed detector, a new adaptive subspace-tracking algorithm for any Hamiltonian matrices is developed, while the previously reported subspace-tracking methods can only estimate the subspace of a positive Hamiltonian matrix. Since a common drawback of the multiuser detector based on the subspace method is the existence of a phase factor that usually deteriorates the performance of the detector, a new method is developed to compensate for the phase of the proposed detector, based on the property of the complex white Gaussian noise. Results of extensive computer simulations show the performance improvement of the proposed detector. 相似文献