无线通信系统信道估计技术研究现状

信道估计技术是未来无线通信系统得以实际应用的关键技术。首先介绍了无线通信系统信道模型的特点以及信道估计方法分类,然后重点阐述了目前无线通信系统中非盲信道估计方法的研究现状,并对各种算法的优缺点和性能进行了分析和比较。     

基于梯度特征与彩色特征相融合的mean shift跟踪方法

针对mean shift跟踪方法中存在的光照变化不稳定问题,提出了基于梯度特征与彩色特征相融合的mean shift跟踪方法。首先分别提取目标的梯度特征和彩色特征,利用多尺度的相似度计算方法进行特征的匹配,然后通过最大化相似度对目标进行跟踪。通过物体和人体等运动目标的跟踪,验证了改进的跟踪算法在光照变化情况下的鲁棒性优于原有的算法,显著降低了跟踪位置误差。     

一种被用于网络管理的性能分析模型和实现

为了提高网络的可靠性以及当今高速通信网络的管理水平,提出了一种用于网络管理的性能及可信度分析模型.该模型能够实时地计算和预测网络的各个性能参数（例如,带宽、吞吐量和延时等）的可靠性（performance-reliability）、可用性（performance-availability）和该网络的平均无故障时间（mean time to failure,简称MTTF）等.由于此模型求真解十分复杂,对于高可靠性网络的管理,给出了该模型的近似模型及其实现.     

Robust H∞ control of uncertain linear impulsive stochastic systems

This paper develops robust stability theorems and robust H_∞ control theory for uncertain impulsive stochastic systems. The parametric uncertainties are assumed to be time varying and norm bounded. Impulsive stochastic systems can be divided into three cases, namely, the systems with stable/stabilizable continuous‐time stochastic dynamics and unstable/unstabilizable discrete‐time dynamics, the systems with unstable/unstabilizable continuous dynamics and stable/stabilizable discrete‐time dynamics, and the systems in which both the continuous‐time stochastic dynamics and the discrete‐time dynamics are stable/stabilizable. Sufficient conditions for robust exponential stability and robust stabilization for uncertain impulsive stochastic systems are derived in terms of an average dwell‐time condition. Then, a linear matrix inequality‐based approach to the design of a robust H_∞ controller for each system is presented. Finally, the numerical examples are provided to demonstrate the effectiveness of the proposed approach. Copyright © 2007 John Wiley & Sons, Ltd.     

Suboptimal filter for continuous‐time linear systems with unknown parameters

The filtering problem for continuous‐time linear systems with unknown parameters is considered. A new suboptimal filter is herein proposed. It is based on the optimal mean‐square linear combination of the local Kalman filters. In contrast to the optimal weights, the suboptimal weights do not depend on current observations; thus, the proposed filter can easily be implemented in real‐time. Examples demonstrate high accuracy and efficiency of the suboptimal filter. Copyright © 2008 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

Geodesic Matching with Free Extremities

In this paper, we describe how to use geodesic energies defined on various sets of objects to solve several distance related problems. We first present the theory of metamorphoses and the geodesic distances it induces on a Riemannian manifold, followed by classical applications in landmark and image matching. We then explain how to use the geodesic distance for new issues, which can be embedded in a general framework of matching with free extremities. This is illustrated by results on image and shape averaging and unlabeled landmark matching. Laurent Garcin is a former student of the Ecole Polytechnique. He obtained his Ph.D. in 2004 at the Ecole Normale de Cachan, working on matching methods for landmarks and images. He is an engineer at the French National Geographic Institute. Laurent Younes is a former student of the Ecole Normale Superieure in Paris. He was awarded the Ph.D. from the University Paris Sud in 1989, and the thesis advisor certification from the same university in 1995. He works on the statistical analysis of images and shapes, and on modeling shape deformations and shape spaces. Laurent Younes entered CNRS, the French National Research Center in October 1991, in which he has been a “Directeur de Recherche" until 2003. He is now a professor at the Department of Applied Mathematics and Statistics Department and the Center for Imaging Science at Johns Hopkins University in July 2003.     

Delay-dependent exponential stability of the backward Euler method for nonlinear stochastic delay differential equations

Recently, several scholars discussed the question of under what conditions numerical solutions can reproduce exponential stability of exact solutions to stochastic delay differential equations, and some delay-independent stability criteria were obtained. This paper is concerned with delay-dependent stability of numerical solutions. Under a delay-dependent condition for the stability of the exact solution, it is proved that the backward Euler method is mean-square exponentially stable for all positive stepsizes. Numerical experiments are given to confirm the theoretical results.     

Robust joint modeling of mean and dispersion through trimming

The Maximum Likelihood Estimator (MLE) and Extended Quasi-Likelihood (EQL) estimator have commonly been used to estimate the unknown parameters within the joint modeling of mean and dispersion framework. However, these estimators can be very sensitive to outliers in the data. In order to overcome this disadvantage, the usage of the maximum Trimmed Likelihood Estimator (TLE) and the maximum Extended Trimmed Quasi-Likelihood (ETQL) estimator is recommended to estimate the unknown parameters in a robust way. The superiority of these approaches in comparison with the MLE and EQL estimator is illustrated by an example and a simulation study. As a prominent measure of robustness, the finite sample Breakdown Point (BDP) of these estimators is characterized in this setting.     

中心差分卡尔曼平滑器

针对一类非线性离散系统的状态平滑问题, 本文设计了一种中心差分卡尔曼平滑器(CDKS). 文中基于最小方差估计准则, 详细推导了非线性系统的状态最优平滑递推公式, 并采用中心差分变换来近似计算状态的后验均值和协方差. 相比于传统中心差分卡尔曼滤波器(CDKF), 所设计的CDKS算法有效提高了非线性状态的估计精度, 拓展了中心差分变换的应用范围. 仿真实例验证了所提出平滑器的可行性和有效性.     

基于线分割的立体匹配算法

给出一种改进的立体匹配算法。根据视差场的极限约束,采用图像线分割的匹配方法得到初始视差,由基于初始视差的交叉检测技术和可信度约束提取高可靠度的GCP点。针对视差图中的不可靠点,加入Bilateral Filter的自适应加权中值滤波,在由均值偏移图像分割算法得到的分割区域内,对像素的视差值进行投票,有效遏制局外点,得到更合理的视差图。在Middlebury test set上进行的测试结果表明,该算法具有较好的视差估计精度。