Detecting DDoS Attacks in Cloud Computing Using Extreme Learning Machine and Adaptive Differential Evolution

Wireless Personal Communications - Distributed denial of service (DDoS) attacks disrupt the availability of cloud services. The detection of these attacks is a major challenge in the cloud...     

超复数域小波变换的显著性检测

针对现有频域显著性检测方法得到的显著区域不完整的问题,该文提出一种多尺度分析的频率域显著性检测方法。首先由输入图像特征通道信息构建4元超复数,然后通过小波变换对4元超复数域中幅度谱进行多尺度分解,计算生成多尺度下的视觉显著图,最后由评价函数选出效果较好显著图合成最终视觉显著图。实验结果表明,该文方法能够有效地抑制背景干扰,快速、精确地找到完整的显著目标,具有较高的检测精确度。     

A Fast Computation Method in Frequency Domain for Power Ground Plane Impedance Calculation Using the Mobius Transform

A new method to reduce the computation time in power/ground-plane analysis is proposed. The proposed method is based on an approximation of impedance in the frequency domain using Mobius transform. The power/ground plane impedance is transformed by Mobius transform and is more linear than the raw impedance, which ensures that a simple approximation is possible. After the approximation, an inverse Mobius transform is applied to predict the power/ground plane impedance. This method displays the high speed of computing with good accuracy. In the case of impedance calculation for a 17.78 cm times 10.16 cm printed circuit board (PCB) board, the proposed method has shown to be 12 times faster than conventional methods. This method can be applied to the analysis and design of power/ground-plane where complex computation is needed.     

各类离散W变换的快速Hartley变换算法

本文通过建立各类N阶离散W变换(DWTs)到N阶离散Hartley变换(DHT)的转换,得到了一种利用DHT 统一计算各类DWTs的非常简单的快速算法.该算法结构简单,且每一种转换过程总的运算量均低于5N.     

一个防御DDoS攻击的入侵检测系统

介绍了一种集成了网络流量数据采集与DDoS攻击检测的入侵检测系统,并嵌入攻击报警机制,其算法核心基于网络流量的自相关函数.该系统可根据用户指定攻击的识别概率,漏报概率与误报概率,而后进行有效检测和报警,并实现基于GUI界面的友好风格及C 类的封装.     

DWT变换的另一种快速DHT算法

通过建立各类N阶离散W变换（DWT）到N阶离散Hartley（DHT）的转换,得到了另一种利用DHT统一计算各类DWT的更为简明的快速算法。该算法结构简单,无需事先判断数据长度N的奇偶性,同时可充分利用输入输出数据的对称与反对称性,使运算量进一步减少。     

The Politics of DDoS Attacks

News about distributed-denial-of-service attacks on Estonian government Web sites might have represented more smoke than fire, but it also revealed a new political battlefield. Networking veterans say public officials' accusations can make ad hoc "hacktivism" seem like a state-sponsored attack. When you add porous network defenses and a credulous media, you've got the potential for a real problem.     

使用Radon变换快速检测直线目标的多应用方法

利用Radon变换能够检测直线和反映目标直线结构的能力,根据对目标特征先验知识生成的规则,对图像Radon变换结果进行有效分析。快速检测机场、港口等直线性目标,然后采用基于假设检验策略的方法,经直线拟合得到直线段的精确位置,解决了Radon变换不能精确定位的问题。通过对机场跑道、港口目标图像的实验,显示出简单、快速、多应用、具有良好检测定位效果的特点。     

Efficient Block-Based Frequency Domain Wavelet Transform Implementations

Subband decompositions for image coding have been explored extensively over the last few decades. The condensed wavelet packet (CWP) transform is one such decomposition that was recently shown to have coding performance advantages over conventional decompositions. A special feature of the CWP is that its design and implementation are performed in the cyclic frequency domain. While performance gains have been reported, efficient implementations of the CWP (or more generally, efficient implementations of cyclic filter banks) have not yet been fully explored. In this paper, we present efficient block-based implementations of cyclic filter banks along with an analysis of the arithmetic complexity. Block-based cyclic filter bank implementations of the CWP coder are compared with conventional subband/wavelet image coders whose filter banks are implemented in the time domain. It is shown that block-based cyclic filter bank implementations can result in CWP coding systems that outperform the popular image coding systems both in terms of arithmetic complexity and coding performance.      

LMS算法的领域快速实现

推导了一种替代时域LMS算法的快速频域算法（FLMS），并对其在语音噪声抵消中的应用进行了计算机仿真。计算机仿真的结果证明：它在自适应滤波器权数超过64时，运算量较时域LMS算法有大幅度的下降，但保持了与时域LMS算法相同的收敛速度，同时对算法的局限性和应用范围进行了讨论。     

一种新的三维离散Hartley变换的分裂基快速算法

 离散Hartley变换(Discrete Hartley Transform,DHT)作为实值离散傅立叶变换的一种替代,在信号和图像处理领域已有广泛应用,针对现有三维DHT快速算法均仅能计算长度为2的整数次幂的DHT,本文提出一种适用于更多不同长度三维DHT的分裂基-2/4快速算法,较之将已有最优算法补零计算的方法,该算法有效的降低了计算复杂度.     

基于分数阶Fourier变换的反辐射导弹检测技术

针对反辐射导弹的检测问题,主要是消除载机信号的干扰.本文研究了单频信号和线性调频信号的分数阶Fourier变换模函数的时移特性.研究表明,单频信号和线性调频信号的FRFT模函数具有不同的时移特性.分数阶Fourier变换是线性变换,不存在交叉项,采用分数阶Fourier变换搜索匹配动目标信号,使其能量汇聚.根据以上特点本文提出了一种基于观测信号以及其时延信号的分数阶Fourier变换模之差的反辐射导弹检测方法.此方法可以有效的消除载机信号的干扰,并且对背景噪声幅度有一定的抑制作用.仿真结果表明,在低信噪比下能有效的检测出反辐射导弹.     

分数阶Fourier变换域的反辐射导弹检测技术

通过推导单频信号和线性调频（LFM）信号旋转角正负对称的分数阶Fourier变换（FRFT）模函数,得到一个有用的结论：单频信号正负对称旋转角的FRFT模值相等,模函数关于中心点对称,而对于LFM信号,其模幅度差别很大。根据此结论提出了一种基于观测信号正负对称旋转角的FRFT模之差的反辐射导弹（ARM）检测方法。此方法可以有效地消除载机信号的干扰。仿真结果表明,此方法在低信噪比下能有效地检测出ARM。     

A Statistical Model for Early Detection of DDoS Attacks on Random Targets in SDN

Wireless Personal Communications - Software Defined Networks (SDNs) have accelerated and simplified the management, configuration and error detection in today’s networking systems. However,...     

Real-Time Method for DDoS Attacks Detection Based on Self-Similarity and Wavelet Analysis

Traditional wavelet methods are not efficient to detect the real-time traffic anomaly. To address this drawback, on the basis of self-similarity and wavelet analysis, this paper proposes one real-time method for DDoS attacks detection. Firstly, to effectively analyze new network state, we extracted data packets from network monitor in backward time direction. Secondly, for reducing admissible computing time, we applied time scale selfadjust according to last packets arrival speed. Finally, we adopted three parallel computing strategies to improve real-time performance. Experimental results show that proposed method can quickly and accurately detect DDoS attacks.     

A Time Domain Reflectometer Using a Semiautomatic Network Analyzer and the Fast Fourier Transform

A time domain reflectometer system is simulated by measuring the reflection coefficient in the frequency domain and then computing the time domain signal by the Fourier transform. The program has been written for the Hewlett-Packard 8409A Semiautomatic Network Analyzer. The computation time has been minimized by using the fast Fourier transform. The problems imposed by the difficulty of switching the HP 8409A between low- and high-frequency ranges are also discussed.     

Blind Multiuser Detection in Frequency Domain for MC-CDMA Systems Using Particle Swarm Optimization

In digital communication systems, the constant modulus algorithm (CMA) for blind multiuser detector has some disadvantage such as slow convergence speed and weight phase rotation. In this paper, we put forward a novel receiver, which combines CMA blind adaptive multiuser detection and particle swarm optimization (PSO) technique in frequency domain for multi-carrier direct sequence code division multiple access (MC DS-CDMA) systems. By this approach we present an adaptive multistage structure based on PSO technique. In this structure, the weights are obtained by PSO technique between the received signal and its estimate through a CMA. The resulting weights contain reliability information for the hard decisions made in the previous stage. The simulation results show that BER performance of the PSO-based CMA blind multiuser detector is superior to that of steepest decreasing constant modulus algorithm (SDCMA), linearly constrained constant modulus algorithm (LCCMA), CMA based multiuser detection and is worthy due to its significant detection performance to achieve desirable improvement in convergence speed and tractability.     

Hybrid Algorithm to Detect DDoS Attacks in VANETs

Wireless Personal Communications - Security and safety are fundamental issues in any wireless network. The problem becomes serious when the specified network is Vehicular Adhoc Network (VANET)....     

一种快速的频域盲语音分离系统

对真实环境中的混迭语音信号进行盲分离是一个非常困难的任务。许多在仿真信号环境下工作很有效的算法常常不能成功地分离真实环境中录取的混迭语音信号。本文通过对一系列预处理(如解相关),独立分量分析和后处理(解排列和尺度不定性)算法进行优化和有机结合,提出了一种快速的频域盲语音分离系统,有效地实现了对卷积混迭的语音信号的盲分离。特别,文中引入一种改进的数据白化算法,它可以节省运算量并提高独立分量分析算法的收敛速度。基于真实录音信号的仿真实验显示该系统能够快速和稳健地分离卷积混迭的语音信号。     

小波变换用于快速跳频信号的测频

小波变换具有局部显微特性,对瞬时信号有较强的捕获能力。该文从连续小波变换与离散小波变换的定义出发,分析了小波变换的带通滤波特性与分析尺度的关系,并通过比较不同尺度下小波变换结果,得到了一个小波变换测频方法,理论与仿真结果表明,与傅立叶交换相比,该方法可以大大改善快速跳频信号的测频精度与抗噪声性能。