共查询到20条相似文献,搜索用时 46 毫秒
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本文主要给出了CDMA系统和CDMA多用户检测的一般模型,并列出了目前CDMA多用户检测的几种解决方案及其性能的比较,提出了CDMA多用户检测还有许多需要完善的方面。 相似文献
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文章针对KALMAN算法的盲空时多用户RAKE接收机,提出的检测在性能优于基于RLS算法的检测器,便于实时处理. 相似文献
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近年来,第三代移动通信系统将多用户检测这项关键技术作为CDMA系统中克服多址干扰的一种有效方法,同时解决了远近效应问题,显著提高了系统性能和容量。本文对CDMA系统中基于子空间的盲多用户检测算法进行了详细的阐述。 相似文献
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本文分析了目前数字水印技术所采用算法的特点,提出了一种能够将数字水印嵌入的图像中特定形状的算法,该算法可以有效地保护水印版权.实验证明,算法具有很高的安全性和稳健性,可以有效地抵抗多种信号处理攻击、压缩攻击. 相似文献
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将独立分量分析,即ICA应用于DS-CDMA系统的多用户检测中,提出了基于ICA后处理的最小均方误差MMSE多用户检测方法。该方法用MMSE检测的输出来初始化独立分量分析的迭代.既利用了信源的独立性,又充分利用了已知扩频码的信息,从而提高了多用户检测器的性能。仿真结果表明:此方法在高信噪比的情况下,误码性能得到了较大改善。 相似文献
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提出了一种新的基于DCT-SVD的数字水印算法.该算法将图像分块后,先进行离散余弦变换,再进行奇异值分解,根据数字图像进行奇异值分解后得到的奇异值序列是递减的序列这一特性来嵌入水印.提取水印时不需要原始图像,所以本水印方案是盲的.实验结果表明,该算法不仅对几何失真具有很强的抵抗能力,而且对添加噪声、滤波及JPEG压缩也具有良好的鲁棒性. 相似文献
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Detection of port scan is an important component in a network intrusion detection and prevention system. Traditional statistical methods can be easily evaded by stealthy scans and are prone to DeS attacks. This paper presents a new mechanism termed PSD(port scan detection), which is based on TCP packet anomaly evaluation. By learning the port distribution and flags of TCP packets arriving at the protected hosts, PSD can compute the anomaly score of each packet and effectively detect port scans including slow scans and stealthy scans. Experiments show that PSD has high detection accuracy and low detection latency. 相似文献
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提出了一种DS-CDMA系统盲多用户检测的动量线性约束恒模算法,对算法的收敛性进行了理论上的分析。仿真表明所提算法在动态环境下有较好的收敛性、跟踪性和鲁棒性。 相似文献
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Throughput of mobile ad hoc network (MANET) is limited by collision avoidance. In CDMA-based MANET, this limitation can be overcome by multiuser detection (MUD) because conventional colliding packets can be detached and detected by MUD so that multi-packet reception (MPR) is possible. This paper introduces the principles of MUD algorithm for MANET, and proposes an adaptive blind MUD algorithm. A special medium access control (MAC) protocol is designed to make MANET more efficient. This is achieved by sending more packets to a destination simultaneously. The proposed MUD algorithm and MAC protocol allow CDMA-based MANET to support MPR. Simulations show a remarkable improvement in the throughput performance of MANET. 相似文献
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Based on minimum output energy,an improved blind multiuser detection algorithm is proposed by the use of Hopfield neural network.Compared with traditional algorithms,the proposed algorithm does not need the circuit for constraints.The resources are greatly saved and the complexity is reduced as well.The simulation results show that the performance of the improved algorithm is similar to that of the optimal multiuser detection algorithm which is not suitable for the mobile station.Compared with the traditional gradient blind multiuser detection algorithm,the convergence speed of the improved algorithm is quickened. 相似文献
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针对迭代盲反卷积算法恢复图像在内部灰度对比鲜明的地方、图像边界都出现的"振铃"效应和迭代盲反卷积算法通常去模糊效果好而去噪效果不理想等情况,本研究提出两点改进:首先,迭代盲解卷积算法恢复图像之前对模糊带噪的退化图像进行改进的中值滤波去噪;其次,对恢复出来的图像,通过找到内部灰度变化大的部分和边界并把其像素设置为0,进行去除"振铃"效应.改进后的算法简单,不仅复原了图像的细节,而且很好地去除了噪声.实验结果表明,改进算法取得了比较好的复原效果. 相似文献
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为了达到进一步节省传感器网络中能量的目的,在CABCF(a cluster algorithm based on communication facility)算法的基础上,考虑簇的大小对无线传感器路由算法的影响,对基于便利因子分簇路由算法(CABCF)进行了优化研究,提出了进一步优化的算法(CABCF-DCS:a cluster algorithm based on communication facility with deterministic cluster-size),并通过仿真比较证明了该算法的有效性. 相似文献
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一种基于实数编码的自适应遗传算法 总被引:1,自引:0,他引:1
分析了进化遗传算法的弊端。提出了一种基于实数编码和自适应变异率的改进遗传算法,将变异率定义为自上次进化以来未进化次数的函数,同时采取最优保存策略,有效地避免了采用二进制编码时计算精度与计算量之间的矛盾,克服了基本遗传算法因变异率选择不当引起的“早熟”现象及后期收敛速度慢的问题。计算结果表明,新方法成功地解决了进化遗传算法存在的问题,且计算效率较高。 相似文献
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《Learning and individual differences》1999,11(2):121-136
If test scores are collected from an individual pupil at different points in time and a state-space model is available for describing latent ability development over time, the Kalman filter and smoother turn out to be the optimal procedures for estimating the pupil's latent curves. The Kalman filter is implemented in the Nijmegen Pupil Monitoring System, LISKAL. The essentials of Kalman filtering and smoothing in comparison to traditional cross-sectional factor score estimators are explained, stressing unbiasedness considerations and the initialization problem. The state-space model is represented as an SEM (structural equation model) and estimated by means of an SEM program. The value of the Kalman filter and smoother in pupil monitoring is enhanced by specifying a “structured means” instead of the traditional “zero means” SEM model and by introducing random subject effects. 相似文献
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针对混沌神经网络对噪声敏感的特点.构建了一种基于Aihara混沌神经元的混沌双向联想记忆神经网络(CBAM).在每一层都包含了一个内层联想记忆结构.实验仿真表明,这种改进对提高双向联想记忆神经网络的抗噪能力作用显著. 相似文献