无线网络接入点TCP流时间公平性

对无线网络接入点上下行TCP流存在的时间不公平性现象进行了研究,报告了无线网络接入有线网络存在的拥塞控制问题现状,提出了一种的无线网络TCP流公平调度算法。采用快速的TCP流优先发送方法,既保证了各流吞吐率公平性,又解决了慢速的TCP占用信道时间过多的问题,实现了各流占用信道的时间公平性。通过网络仿真实验证明,新的公平调度算法比传统的算法在性能上有较大的改进,达到了提高网络整体效率的目的。     

A Prediction of Network Traffic Flow Based on Lyapunov Exponent

The prediction of network traffic flow is a problem of great significance in the research work of resource allocation and congestion control. Based on this accurate prediction, the scheme of resource allocation and control can easily adapt to dynamic variations of incoming traffic flow. So the goal of optimal network performance is achieved. There are many sorts of traffic flow of self-similarity characteristics in high-speed network, and some research work has showed this self-similarity keeps in close contact with the attractor of chaos system. A rate prediction of self-similar traffic sources in high-speed network is proposed as well as the maximum of predictable time by applying the technology of phase space reconstruction about chaotic time series. This method has a simple prediction mode, and the result of simulations indicates it also has highly accurate results.     

Survey of Bandwidth Estimation Scheme in TCP

Transmission Control Protocol(TCP) is tuned to perform well in wired networks or environment with low bit errors where packet losses occur mostly because of congestion.However,when TC Pis operated in high BER environment and suffers from significant losses due to bit errors,it does not make the best use of the available bandwidth of links because TC Phavles its current congestion window blindly.As a result,the performance of TC Pwould be deteriorated very much.Recently,the use of enhanced bandwidth estimation procedures within the congestion control scheme of TC Pwas proposed as a way of improving TC Pperformance over links affected by random loss.This paper first analyzes the problems faced by every bandwidth estimation algorithm implemented at the sender side of a TCP connection.Some proposed estimation algorithms,accuracy and performance are estimated.At the same time,the authors discuss the relationshi Pbetweent the bandwidth estimation accuracy and the fairness of protocol.Finally,this paper point out the further work should be done in future.     

An Algorithm to Enhance the Performance of Data Service Over CATV Broadband Networks

Emerging CATV networks are evolution to Hybrid Fiber/Coax plants. It is widely believed that the HFC network will play an important role in providing broadband accessing service to subscribers due to it's large excess bandwidth and high penetration to the home. Asymmetry broadband data service is the main service provided in the HFC broadband access networks now. It's performance will determine whether the subscribers be satisfied or not and affect the growth of HFC broadband access networks. The authors outline the mechanism of transmitting data in the upstream channel of the HFC network, and analyze how it affecting the performance of data service. The performance of data service and TCP protocol in HFC network is examined. An optimal scheme of bandwidth allocating algorithm for the upstream channel is proposed to enhance the performance of the data service over these networks.     

Critical Transport Infrastructure in Urban Areas: Impacts of Traffic Incidents Assessed Using Accessibility‐Based Network Vulnerability Analysis

Incidents (vehicle breakdowns, crashes, roadworks, lane blockages, severe weather, etc.) are believed responsible for about 50 percent of traffic congestion in Australia's major cities, which is a similar situation to that found in cities in many other parts of the developed world. Incident‐based congestion is particularly disruptive because of its random occurrence in space and time, which maximises the operational impacts of the congestion on social and economic activities. This paper discusses a method for assessing critical locations—congestion “hot spots”—in urban road networks, and the development and application of diagnostic tools that will allow urban road system managers to anticipate potential vulnerabilities to incident‐related congestion and take proactive action to avoid congestion rather than react to it. The expected outcomes are then reduced congestion, delays, and pollution; significantly improved performance from the existing urban road system; and reduced pressure to build more roads. The method involves modelling of travel demand, network topology, capacity and road geometry, the identification and assessment of impacts of traffic incidents at specific locations in a road network, and the use of accessibility impact analysis to assess system‐wide effects. Accessibility impact analysis is undertaken using an accessibility framework, which can account for time of day, transport mode and destination choices by individuals, and level of traffic congestion among other factors. A case‐study application to a specific (potential) incident in a real‐world network indicates that the proposed method is feasible and demonstrates its power in identifying not just total impacts but the distribution of those impacts across a region or community. While current approaches to urban road network planning and management tend to be reactive—finding cures for problems as they arise or addressing locations of recurrent congestion or bad incident record—the vulnerability analysis method described in the paper should lend itself to a proactive approach that can anticipate structural weaknesses and vulnerabilities and help to avoid or at least temper potential adverse effects, rather than to react to them afterwards.     

Modern Network Design

Nowadays the network of high-speed and broadband is required in the application of multimedia technology and information community. Many methods, such as network layering design, address design and routing are introduced to design Enterprise Backbone Network VPN's interrelation protocol is disposed and VPN tunnel is cut to establish virtual private network. Server and run plane design, bowels IP address distribution and network security advisement to design Intelligent Residential Area Network are given. It is pointed out that the method of modern network designs satisfies high-speed, intelligent and broadband for the developments of network technology.     

Dynamic Route Guidance System Based on Genetic Algorithm

The study on Dynamic Route Guidance System (DRGS) is an important research in the field of Intelligent Transportation System(ITS),which guide the behaviors of travelers by providing them with optimal route based on real-time traffic information. As a result the travel time can be saved and the traffic congestion can be avoided. The route guidance algorithm can compute the best route between the begin point and destination. The globe near best property and real-time property must be considered , the Genetic Algorithm have qualifications for globe optimal and parallel algorithm. Genetic algorithm(GA),for solving the shortest route,is proposed in this thesis?The ordered real code rule,crossover,mutation are given. The efficiency of the GA is proved through an example.     

Traffic Engineering and Traffic Matrix in IP Backbone Network Based on MPLS

On current network actuality and development trend, it is necessary to put traffic engineering in practice in IP backbone network on IP/MPLS. The essential demand in actualizing traffic engineering is traffic matrix measurement. After analyzing the defect of current measurement method, traffic engineering model and traffic matrix on LSP in IP backbone network based on MPLS, or relevant routing algorithm are researched. The merit of the traffic matrix's measurement method is that implement of measurement is only located in the edge node; therefore, network resource's cost is lower and it offers a new train of thoughts for resolving the flaw of current main measurement methods, moreover, and condition for actualizing traffic engineering.     

The Algorithm of Pole-Assignment Self Tuning Robust Control

An control algorithm with goed robustness has been developed,based on the combination of poletassignment self- tuning control algorithm with robust estimation and control al-gorithms,while the input signal and process parameters are varied on a large scale. The design of controller based on presented algorithm is simple,with good robustness for parameter changes and a strong ability for overcoming determined disturbance.The simulating research results proved the ef-fectiveness of the pole- assienment self-tuning robust control algorithm.     

考虑预估驾驶行为的跟驰模型及其稳定性分析

在OV模型的基础上,进一步考虑预估驾驶行为对车流的影响,提出一个新的跟驰模型以获得预估驾驶行为与交通拥堵的关系。通过对新模型进行稳定性分析得到了系统的临界稳定条件。数值仿真结果表明：新模型能够模拟诸如时停时走、系统临界相变等实际交通现象,较OV模型更贴近于实际。同时,预估驾驶行为增强了交通流稳定性能,提高了车流陷入交通阻塞状态的阈值。最后以车速的平滑度和波动幅度最小为评价指标得到了新模型中预估参数的最优取值范围。     

智慧设施农业中控制系统的研究进展

随着科学技术的发展，农业的发展越来越趋于信息化、现代化，智慧农业是未来农业发展的必然趋势。温室控制系统是智慧设施农业的核心，是实现设施农业规模化发展、集约化生产的关键。本研究综述了温室控制相关研究进展，以期在今后的研究中起到一定的作用。温室控制系统自20世纪70年代发展至今越来越成熟，本研究对比了温室控制系统的控制算法、主控芯片、各种传感器，通过对近些年来包括控制系统在内的感知层、传输层和应用层等组成部分综述，并介绍了市面上比较主流的传感器、网络传输技术以及主控芯片，旨在为温室控制系统的设计提供一种可选择的方案，并对温室设施农业中存在的问题和未来的发展方向进行了分析和展望。     

模糊控制系统的垂直切换判决算法分析

针对模糊控制系统中切换时延较长和切换次数较多的问题,研究了一种基于模糊控制系统的垂直切换判决算法。在基于信号强度判决时将RSS作为门限值,提高系统判决能力;同时,将网络参数和服务类型作为判决因素,结合层次分析法引入并行的模糊控制系统,缩短了切换判决的时间、选择适合用户的最佳网络,做出垂直切换。仿真结果表明,该算法减少了切换次数,降低了切换时延,增强了系统的性能。与传统的切换算法相比较,该算法对切换的判决因素考虑的更全面,兼顾了用户终端的使用环境及成本问题,有效地保证了网络的服务质量。     

Analysis on the Feasibility of Collecting Traffic Congestion Charges in Beijing

On the basis of analyzing connotation of congestion pricing,through the qualitative analysis of the main content and implementation effect of the congestion policy in cities such as Singapore,London and Stockholm,the basic conditions for urban congestion charges were summarized.Compared with Beijing’s urban development,traffic development status,urban transport infrastructure and social factors,the current policy of traffic congestion charging is still not available from the perspective of the current status of car ownership in Beijing,residents’ travel composition,and population density distribution.     

Technologies of Intelligent Vehicle in Intelligent Transportation System (ITS)

Intelligent Transportation System (ITS) is the most effective method to solve the modern traffic problems. Intelligent vehicle plays a very important role on ITS, and it influences the success of ITS directly. Intelligent Transportation System (ITS) is briefly introduced. Then it is given that advanced vehicle control system and electrics stability program (ESP) in the key technology of intelligent transportation system. The control algorithm for vehicle movement is discussed and the test result is given.     

Resolvent and Application of Policy Control for QoS

With the rapid increase of the Internet user and widely application of Web,the current network technology is facing great challenge. More and more multimedia operations occupy plenty of bandwidth,and result in the network congestion. Therefore,people begin to use QoS to utilize the bandwidth effectively,and ensure the transport of the emergent operation data. The paper introduces the protocols and basic components of QoS,then expatiates the conception and the basic principles of policy control QoS, moreover,emphasizes the structure model of policy control QoS and how it runs. At last,it introduces the transport process of data packets under the control of policies in a policy control QoS system,and how to make the policies in the real world.     

The compensation method for the random time-delay of the feedbackchannel and the forward channel in the networked control system

An improved predictive control method is presented to compensate the random time delay in the networked control system. The feedback time delay is compensated by predictive controller based on softened increment input strategy. The forward time delay is unknown for controller, so an extra feedback loop is added to compensate the delay by estimating the error between the actual control signal effected on plant and the output of controller in historical moment. For the controlled system with unknown or slowly varying parameters, the networked feedback correction algorithm is discussed based on a modified recursive least-squares identi cation algorithm. The system stability is analyzed and the simulation results show that the time delay in the networked control system can be accurately compensated. The excellent network performance is ensured with this strategy.     

Research on Cooperative Design Network Security Based on IP-VPN

As the important method and instrument of agile manufacture,the technology of distributed collaborative design and manufacturing has become the hotspot of manufacturing. The basic concept and key technologies of IP_VPN are introduced in this paper,and a collaborative design network model based on IP_VPN is presented. Distributed collaborative design is a multi_user,multitask involved system, which is consisted of lots of collaborative processs,so the network security is the key of distributed collaborative design. We research on the security of collaborative design network based on IP_VPN, hence get a conclusion:we can construct an economical?practical and secure collaborative design network system by the application of data encryption,user authentication and access control based on the role,etc.     

Analysis on the stability of traffic flow with the information of two preceding cars

The stability analysis is one of the important problems in the traffic flow theory, where the congestion phenomena can be regarded as the instability and the phase transition of a dynamical system. An extended optimal velocity model is deduced by considering the effect of the information of two leader cars. The stability condition of the extended model is obtained by using the linear stability theory. The modified Korteweg-de Vries (mKdV) equation is derived to describe the traffic behavior near the critical point by applying the nonlinear analysis. The numerical simulation results demonstrate the analytical results and show that the traffic congests are suppressed more efficiently by considering two vehicles ahead. Therefore, the next-nearest-neighbor car has strong effects on traffic dynamics and plays an important role on stabilizing the traffic flow.     

THE CHARACTERISTICS OF FUZZY AND ADAPTIVE PI COORDINATE DECISION CONTROLLER

On the basis of analysing problems of conventional fuzzy controller in the design of the structure and algorithm, this paper puts forward a kind of control algorithm that is fuzzy and Adaptive PI coordinate decision controller (FACDC) . It adopts the hierarchial control structure imitating intelligent control and combines fuzzy controller and adaptive PI controller. It takes full advantage of two controllers. Since the algorithm of FACDC in model reference fuzzy adaptive algorithm, it avoids the complexity of conventional adaptive algorithm.     

Restoration algorithm with wavelength reservation collision avoidance in ASON

Aiming at the problem of link fault restoration in ASON, an improved equalizing routing algorithm (ERA) is introduced to proportion the load at the routing phase. In order to solve the easy blocking problem for the network without wavelength converter because of the wavelength continuity constraint, the algorithm WRCA is proposed at the wavelength assignment phase. This algorithm is realized by adding collision detection object (CDO) in the path message of the resource reservation protocol with traffic engineering extension (RSVP TE). Depending on the value of the CD flag, different wavelength selection strategies are applied at the destination node, and the blocks resulting from wavelength reservation collision are reduced. The simulation experiments compare four wavelength assignment algorithms with the same routing algorithm ERA. The results show that compared with the traditional first fit algorithm (FF) and random fit algorithm (RD), the FF and RD employing CD scheme can effectively reduce the blocking ratio of the whole network, and enhance the practical applicability of the restoration algorithms.