AN IMPROVED OPTIMAL CHANNEL SHORTENING ALGORITHM FOR DMT MODULATION SYSTEMS

In Discrete Multi-Tone (DMT) modulation systems, the well-known technique to overcome the Inter-Carrier Interference (ICI)/Inter-Symbol Interference (ISI) caused by the inadequate Cyclic Prefix (CP) length is to use a Time-Domain Equalizer (TDE) at the receiver front-end. An algorithm used to calculate the coefficients of the optimal shortening Time Domain Equalizer (TDE) was given by Melsa. However, this algorithm requires that the length of the TDE must be smaller than or equal to the memory length of the target impulse response. This paper modifies this algorithm and makes it not only fit for calculating the coefficients of the TDE with arbitrary length, but also have a much less computational time.     

广义空间调制MIMO系统的优化检测算法

针对大规模多输入输出（multiple-input multiple-output,MIMO）系统中采用广义空间调制（generalized spatial modulation,GSM）时信号检测复杂度过高的问题,提出一种新型天线分组激活方案.该方案首先需将发送天线分组激活,得到天线索引备选集,然后把天线组合符号按质量因子大小进行排序,最后遵循可信度判断准则进行量化判决检测,以此得到最佳的检测结果.相较于传统算法,所提出的检测算法避免了对信号空间的遍历搜索,在大规模天线系统下的性能更加优异.计算和仿真结果表明,本文提出的算法具有复杂度低、误码率低的特点,在采用广义空间调制的通信系统中具有较高的工程应用价值.     

一种基于循环平稳的MPSK信号调制分类改进算法

给出了一种基于循环平稳的MPSK信号调制分类改进算法.通过对预处理后的MPSK信号进行循环平稳分析,把利用高阶累积量对复基带MPSK信号的调制分类推广到已调信号.这种在高阶循环累积量域构成的分类特征不变量具有良好的抗平稳噪声的能力.通过利用二阶循环累量对码元速率的估计,大大减少了累积量估计的运算量.仿真表明,改进后的算法运算精度与原算法大致相当,运算量大大减少.     

A new likelihood-based modulation classification algorithm using MCMC

In this paper, a new likelihood-based method for classifying phase-amplitude-modulated signals in Additive White Gaussian Noise (AWGN) is proposed. The method introduces a new Markov Chain Monte Carlo (MCMC) algorithm, called the Adaptive Metropolis (AM) algorithm, to directly generate the samples of the target posterior distribution and implement the multidimensional integrals of likelihood function. Modulation classification is achieved along with joint estimation of unknown parameters by running an ergodic Markov Chain. Simulation results show that the proposed method has the advantages of high accuracy and robustness to phase and frequency offset.     

An optimal vector-network-analyzer calibration algorithm

We present an iterative algorithm for calibrating vector network analyzers based on orthogonal distance regression. The algorithm features a robust, yet efficient, search algorithm, an error analysis that includes both random and systematic errors, a full covariance matrix relating calibration and measurement errors, 95% coverage factors, and an easy-to-use user interface that supports a wide variety of calibration standards. We also discuss evidence that the algorithm outperforms the MultiCal software package in the presence of measurement errors and accurately estimates the uncertainty of its results.     

An optimal distributed routing algorithm

A distributed optimal one-level routing algorithm is presented. The algorithm is based on Newton's method. Using the variable reduction method, the Hessian matrix becomes diagonal. An example shows that the algorithm has a much faster convergence rate, more accurate results, and better transient behavior than previous work. The algorithm is shown to be convergent, stable, robust, and loop free     

四边形分类识别算法

四边形的分类识别是图形识别中的重要内容.Hough变换是检测直线的基本工具,利用Hough变换检测出图像中各直线与x轴正方向所形成的夹角,对这些夹角降序排序后再进行比较,从而确定四边形的类型.实验结果表明,算法简单有效,能对复杂图像中的四边形进行分类识别,具有一定的实用价值.     

An optimal algorithm for cycle breaking in directed graphs

This paper describes an exact algorithm for the identification of a minimal feedback vertex set in digital circuits. The proposed algorithm makes use of graph reduction and efficient graph partitioning methods based on local properties of digital circuits. It has been implemented and applied to ISCAS-89 benchmark circuits. Previously, non-optimum solutions were found. In other cases, the optimality of the solution could not be established for all circuits. By using the proposed algorithm we obtained the optimum results for all the circuits in a relatively short CPU time.Supported in part by the Technion fund for the promotion of research.     

WDM光网络中固定路由的优化算法

通过研究WDM光网络中固定路由策略的选取对网络性能的影响，提出了一种新的用于优化固定路由的算法-综合代价法。该算法综合考虑了链路负载和路由跳数这两个因素，以综合代价为策略进行路由优化。计算机仿真结果表明，针对不同的网络负载情况，综合代价法能够有效地降低网络的阻塞率，提高网络的性能。     

An efficient algorithm for constructing nearly optimal prefix codes

A new algorithm is presented for constructing nearly optimal prefix codes in the case of unequal letter costs and unequal probabilities. A bound on the maximal deviation from the optimum is derived and numerical examples are given. The algorithm has running timeO(t cdot n), wheretis the number of letters andnis the number of probabilities.     

一种适用于图像传感器接收机的最佳接收算法

根据图像传感器的工作模型和及其器件噪声特性,分析了图像传感器作为可见光信号接收机时的工作特性,并根据可见光通信(VLC)系统误码率(BER)随图像传感器感光时间和判决门限的变化特性,提出一种适用于图像传感器接收机的最佳接收算法。仿真实验结果表明,本文算法可以根据可见光信号的出射角、传输距离、入射角和码速率等参数,设置图像接收机的最佳感光时间和系统判决门限,有效提高了VLC系统的抗干扰能力,使VLC系统的BER达到最佳。     

An improved LBP algorithm for texture and face classification

Local Binary Pattern (LBP) has achieved great success in texture classification due to its accuracy and efficiency. Traditional LBP method encodes local features by binarying the difference in local neighborhood and then represents a given image using the histogram of the binary patterns. However, it ignores the directional statistical information. In this paper, some directional statistical features—including the mean and standard deviation of the local absolute difference—are integrated into the feature extraction to improve the classification ability of the extracted features. In order to reduce estimation errors of the local absolute difference, we further utilize the least square estimate technique to optimize the weight and minimize the local absolute difference, which leads to more stable directional features. In addition, a novel rotation invariant texture classification approach is presented. Experimental results on several texture and face datasets show that the proposed approach significantly improves the classification accuracy of the traditional LBP.     

一种改进的BPSK/QPSK信号调制识别算法

提出了一种基于顺序统计量特征的二进制相移键控/正交相移键控(BPSK/QPSK)信号调制识别算法.对观测信号进行平方并做离散傅里叶变换运算,将变换结果取模后去除最大值得到修正频谱,并取修正频谱的最大值作为识别特征量,利用恒虚警准则确定判决门限,将识别特征量与门限比较来完成对BPSK和QPSK两种调制信号的识别.计算机仿真表明,当信噪比适度时,所提算法可对BPSK及QPSK两类信号进行有效识别.当信噪比大于1 dB时,算法的平均识别正确率达到90%以上.     

An exact algorithm for optimal MAE stack filter design.

We propose a new algorithm for optimal MAE stack filter design. It is based on three main ingredients. First, we show that the dual of the integer programming formulation of the filter design problem is a minimum cost network flow problem. Next, we present a decomposition principle that can be used to break this dual problem into smaller subproblems. Finally, we propose a specialization of the network Simplex algorithm based on column generation to solve these smaller subproblems. Using our method, we were able to efficiently solve instances of the filter problem with window size up to 25 pixels. To the best of our knowledge, this is the largest dimension for which this problem was ever solved exactly.     

一种CPFSK信号调制指数估计方法

随着通信技术与通信方式的快速发展,通信信号调制方式与通信系统越来越复杂。复杂通信信号连续相位频移键控(CPFSK)由于其频谱利用率高,大量用于卫星通信等领域。针对复杂信号CPFSK的参数估计问题,提出一种基于李雅普诺夫指数的CPFSK信号调制指数估计方法。通过CPFSK信号李雅普诺夫指数与调制指数的数学关系模型,提取李雅普诺夫指数估计信号调制指数。仿真验证了算法性能,得到CPFSK调制指数估计均方根误差随信噪比的变化曲线。此方法计算复杂度低且实现简单,适用于CPFSK信号与常规频移键控(FSK)信号的调制指数估计。     

连续相位调制信号的信噪比估计

针对连续相位调制（CPM）信号信噪比估计子空间分解算法运算量较大和最大似然估计（MLE）算法信噪比小于0dB时精确度差的问题,提出了一种精确度较高的快速算法。该算法是对常用的最大似然算法的改进,利用接收信号的统计和互相关特性,无需获得信号的初始相位,便可快速准确地估计出信号的信噪比。信噪比在-20dB～20dB之间时,估计误差小于1dB。MATLAB和FPGA仿真验证了该算法的有效性。     

OOFDM系统恒定吞吐量自适应调制算法

在光通信系统中,光纤对系统性能影响较大.为了减小多模光纤的色散对光正交频分复用(00FDM)系统性能的影响,阐述了一种新的基于恒定吞吐量的自适应调制算法,改进的算法与原始的恒定吞吐量的自适应调制算法相比,在系统误码率变化不大的情况下,算法的复杂度降低了,仿真结果证明改进算法是正确可行的.     

An optimal scheduling algorithm for testing interconnect using boundary scan

Systems will soon be built with ICs that conform with the IEEE 1149.1 boundary scan architecture. Due to the hierarchical nature of such systems, they may contain many boundary scan chains. These chains can be used to test the system, subsystem, and board interconnect. To reduce test time, the application of test vectors to these scan chains must be carefully scheduled. This article deals with problems related to finding an optimal schedule for testing interconnect. This problem is modeled using a directed graph. The following results are obtained: (1) upper and lower bounds on interconnect test time; (2) necessary and sufficient conditions for obtaining an optimal schedule when the graph is acyclic; (3) sufficient condition for obtaining an optimal schedule when the graph is cyclic; and (4) an algorithm for constructing an optimal schedule for any graph.This work was supported by Defense Advanced Research Projects Agency and monitored by the Office of Naval Research under contract No. N00014-87-K-0861. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the Defense Advanced Research Projects Agency or the U.S. Government.     

An exact algorithm for wirelength optimal placements in VLSI design

We present a new algorithm designed to solve floorplanning problems optimally. More precisely, the algorithm finds solutions to rectangle packing problems which globally minimize wirelength and avoid given sets of blocked regions. We present the first optimal floorplans for 3 of the 5 intensely studied MCNC block packing instances and a significantly larger industrial instance with 27 rectangles and thousands of nets. Moreover, we show how to use the algorithm to place larger instances that cannot be solved optimally in reasonable runtime.     

一种面向多业务恢复的路由优化算法

讨论了在WDM光传送网中完成多业务恢复时所出现的恢复路由资源竞争问题，并提出了一种基于遗传算法的面向多业务恢复的路由优化算法。该算法可以有效地解决恢复路由资源竞争问题，得到全局最优恢复路由。通过对实际网络的计算，验证了该算法在解决多业务恢复路由优化问题上所具备的优势。