复杂用户网络在移动通信方面的应用研究

在传统的移动蜂窝系统研究中,所有用户都假设具有相同的行为,即他们以相等的概率打出/接听电话,以及他们以相同的移动性在网络内移动.还有,基础用户网络假设为一个全互联的网络,这暗示着所有的用户都互相认识,且以同一概率进行相互通讯.但在现实的环境中,每个用户有各自的熟人(包括家人、亲戚、朋友和同事)通讯录,其通讯录的大小也视乎个别用户而有所不同.此外,由于用户的移动性取决于各种各样的因素(如工作性质等),不同用户的移动程度也不尽相同.为了估计移动系统更接近实际的性能,我们使用无尺度网络作为潜在的用户网络模型,即一个用户的熟人数目服从幂律分布,并且研究在3种移动性(即零移动性、相同移动性和幂律移动性)下的移动系统.最后,通过计算机仿真来估计系统的性能指标(如承载话务量和阻塞率等).结果表明,用户网络结构以及用户移动性都会对移动系统的性能产生影响.

Anomaly detection for network traffic flow

This paper presents a mechanism for detecting flooding-attacks. The simplicity of the mechanism lies in its statelessness and low computation overhead, which makes the detection mechanism itself immune to flooding-attacks. The SYN-flooding, as an instance of flooding-attack, is used to illustrate the anomaly detection mechanism. The mechanism applies an exponentially weighted moving average (EWMA) method to detect the abrupt net flow and applies a symmetry analysis method to detect the anomaly activity of the network flow. Experiment shows that the mechanism has high detection accuracy and low detection latency.

Network Security Incidents Frequency Prediction Based on Improved Genetic Algorithm and LSSVM

Since the frequency of network security incidents is nonlinear,traditional prediction methods such as ARMA,Gray systems are difficult to deal with the problem.When the size of sample is small,methods based on artificial neural network may not reach a high degree of preciseness.Least Squares Support Vector Machines (LSSVM) is a kind of machine learning methods based on the statistics learning theory,it can be applied to solve small sample and non-linear problems very well.This paper applied LSSVM to predict the occur frequency of network security incidents.To improve the accuracy,it used an improved genetic algorithm to optimize the parameters of LSSVM.Verified by real data sets,the improved genetic algorithm (IGA) converges faster than the simple genetic algorithm (SGA),and has a higher efficiency in the optimization procedure.Specially,the optimized LSSVM model worked very well on the prediction of frequency of network security incidents.

An Efficient Algorithm for Processing Partialmax/min Queries in OLAP

In the process of analyzing the large-scale network security situation,the data we faced are always flooded and messy,and the information is difficult to obtain with respond to the query timely.Online analytical processing which use the Data-cube as a data source directly,calculated all or part of the Data-cube in advance,and it can reduce the query response time significantly.This paper considers a class of queries,called the Partial-MAX/MIN query.We introduce Rank Decision Tree(RD-Tree) and it’s searching algorithm for efficient processing of the partial-max/min queries.Through experiments,we show our approach has an efficient processing capability for partial-max/min queries.

Study on Massive Open Online Course and College English Teaching Reform

English is the universal language. With the development of economic and cultural globalization, the demand for English has gradually increased. Traditional college English teaching cannot meet real requirement, so college English teaching reform is imperative. With the development of online platform, the Internet has brought a great impetus to the curriculum reform. The author thinks that ＂MOOC＂ and College English Teaching Reform have a good point of combining, but there is still a problem remaining to be solved： How to make good use of＂MOOC＂ for College English Teaching Reform service has a lot study space in the future.

Smart Grid Cyber Security： An Overview of Threats and Countermeasures

The smart grid is the next generation of power and distribution systems. The integration of advanced network, communications, and computing techniques allows for the enhancement of efficiency and reliability. The smart grid interconnects the flow of information via the power line, intelligent metering, renewable and distributed energy systems, and a monitoring and controlling infrastructure. For all the advantages that these components come with, they remain at risk to a spectrum of physical and digital attacks. This paper will focus on digital vulnerabilities within the smart grid and how they may be exploited to form full fledged attacks on the system. A number of countermeasures and solutions from the literature will also be reported, to give an overview of the options for dealing with such problems. This paper serves as a triggering point for future research into smart grid cyber security.

A Novel Formal Theory for Security Protocol Analysis of Denial of Service Based on Extended Strand Space Model

Denial of Service Distributed Denial of Service （DOS） attack, especially （DDoS） attack, is one of the greatest threats to Internet. Much research has been done for it by now, however, it is always concentrated in the behaviors of the network and can not deal with the problem exactly. In this paper, we start from the security of the protocol, then we propose a novel theory for security protocol analysis of Denial of Service in order to deal with the DoS attack. We first introduce the conception of weighted graph to extend the strand space model, then we extend the penetrator model and define the goal of anti-DoS attack through the conception of the DoS-stop protocol, finally we propose two kinds of DoS test model and erect the novel formal theory for security protocol analysis of Denial of Service. Our new formal theory is applied in two example protocols. It is proved that the Internet key exchange （IKE） easily suffers from the DoS attacks, and the efficient DoS- resistant secure key exchange protocol （JFK） is resistant against DoS attack for the server, respectively.