面向诱导的交通状态信息提取方法

为实现可变信息板（Variable Message Signs,VMS）的交通状态信息提取,选取速度、饱和度与交叉口平均延误作为交通参数,提出了基于模糊推理的关联路段交通状态信息提取方法。针对驾驶员的VMS信息响应特性,设计了面向拥挤状态的VMS诱导策略,在关联路段均处于拥挤状态时基于Vague集对交通状态进行排序,以判别交通状态相对最优的关联路段进行发布。以实际算例验证了该方法的有效性,所提出的VMS诱导策略能够逐步引导拥挤交通流的分流,并为驾驶员在拥挤状态下进行路径选择提供决策支持。     

城市快速路交通诱导和匝道控制集成仿真模型

为缓解城市快速道路网络交通网络拥挤问题,将网络交通流模型、匝道控制模型、基于可变信息标志（VMS）的路径选择模型等整合为一体,建立了城市快速路交通诱导和匝道控制集成仿真模型。与各种边界条件相结合,测试了匝道控制和路径诱导的控制效果。结果表明城市快速路集成控制方法有助于在空间和时间上均衡交通负荷,提高交通系统整体运行效率。     

基于改进遗传算法的VMS选址研究与分析

随着城市交通的高速发展,交通拥堵和交通事故频繁发生,城市交通诱导作为智能交通系统的重要组成部分,其产生和发展刻不容缓,可变信息板(VMS)是交通诱导系统中实现交通信息传递的重要工具。针对智能交通诱导系统在国内应用的不成熟,采用改进型遗传算法对VMS在路网中的布点位置进行了全局索优,对基本遗传算法中的编码方式,选择方法进行了改进,同时采用动态衰减变异概率进行变异操作,并运用多目标优化算法将多目标函数单一化,针对某一路段上的VMS对该路段下游不同位置的影响程度的不同,引入衰减影响因子;然后以复杂虚拟路网为仿真实例进行了VMS布局仿真检验,结果表明,该方法以VMS效用和经济成本为评价指标,较好地实现了交通路网中VMS选址的最优分布,同时达到了节约资源的目的,具有一定的科学性和实用性。     

Enabling fuzzy technologies in high performance networking via an open FPGA-based development platform

Soft computing techniques and particularly fuzzy inference systems are gaining momentum as tools for network traffic modeling, analysis and control. Efficient hardware implementations of these techniques that can achieve real-time operation in high-speed networking equipment as well as other highly time-constrained application fields is however an open problem. We introduce a development platform for fuzzy inference systems with applications to network traffic analysis and control. The platform addresses the current requirements and constraints of high performance networking equipment. For the development process, we set up a methodology and a CAD tool chain that span the entire design process from initial specification in a high-level language to implementation on FPGA devices. An FPGA development board with PCI/PCIe interface is employed to support an open platform that comprises CAD tools as well as IP cores. PCI compatible fuzzy inference modules are implemented as System-on-Programmable-Chip (SoPC). We present satisfactory experimental results from the implementation of fuzzy systems for a number of applications in analysis and control of Internet traffic. These systems are shown to satisfy operational and architectural requirements of current and future high performance routing equipment. The platform proposed allows for the development of prototypes while avoiding large investments and complicated management procedures which constrain the testing and adoption of soft computing techniques in high performance networking.     

可变交通信息牌的最优分布模型

本文就城市路网中可变交通信息牌（Variable Message Signs, VMS）分布地点的最优选择进行了研究，分析了VMS分布的一般规则，并建立了相应的数学模型. 针对整数规划模型的求解复杂性，采用了遗传算法. 算例表明了模型的有效性．     

VMS行程时间诱导效益分析仿真系统

利用可变情报板(VMS)发布行程时间信息是缓解交通拥挤的有效手段,提出了一种VMS行程时间诱导效益分析仿真系统,并对仿真系统进行设计与开发。运用该仿真系统对两起点两终点的路网进行建模仿真,仿真结果表明,VMS行程时间对于应对交通事件(如需求激增)引起的拥挤作用显著;驾驶员的信息关注率值越大,路网运行效益改善率越明显。研究旨在为相关部门设计、评价控制策略,优化路网运行效益提供辅助决策依据。     

Hierarchical Mobility Label Based Network: System model and performance analysis

Hierarchical Mobility Label Based Network (H-MLBN) is a new approach to the network layer mobility management problem that relies on MPLS-aware control plane and MPLS-based forwarding plane to provide IP mobility support for IPv4 and IPv6 mobile hosts and routers while being able to ensure optimal traffic delivery between the communicating devices. The hierarchical system is capable of both macro- and micro-mobility support without the use of Mobile IP and its derivatives thus eliminating the user and network facing performance penalties associated with triangular routing and bi-directional tunneling. This paper presents a system model and provides performance analysis for H-MLBN and compares its performance with the Mobile IP based schemes. The results indicate significant performance improvements in the forwarding plane traffic delivery as well as the control plane network update costs.     

An integrated traffic model for multimedia wireless networks

Multimedia wireless networks are seen today as one of the key factors for the success of the global communication infrastructure in the near future. Such networks will have to handle a range of heterogeneous traffic classes with different QoS requirements. Their design, planning and control must be supported by suitable traffic models capable of dealing with a new set of constraints where QoS management and mobility play an important role.This paper proposes a traffic model for a cellular multimedia wireless network characterized by the integration of mobility and traffic management aspects. User mobility is modeled through a Markov renewal process, which allows for non-exponential cell residence times and may restrict the user mobility to existent paths in the system. A Markov-modulated fluid process is used to describe the changes in the bandwidth requirements of each mobile over the duration of its calls, including the periods where the mobile is inactive (without call).Based on the proposed model, the number of mobiles per class of traffic in a cell and the handoff processes are characterized. System performance results, such as new and handoff call blocking probabilities, for network planning are derived. Also, the distribution of the required capacity in a short time interval for network control is obtained. Simulations were carried out to validate the analytical results. The comparisons have shown that the integrated model may be regarded as a good basis to build useful teletraffic engineering tools for multimedia wireless networks.     

IP协议分析仪的设计与实现

传统的基于SNMP协议流量监测工具有MRTG等,这些工具提供了网络流量的大小和变化的幅度;为了更好地了解互联网流量的本质,目前网络管理的研究集中在“网络流”压技术上。而Cisco的NetFlow服务提供了基于的“网络流”分析的方法。根据中国科技网在实际网络流量管理中的需求,本文介绍了“网络流”模型,分析了Cisco路由器NetFlow技术原理,根据NetFlow数据在流量和安全中的应用,引入了协议分析仪的技术,提出相关的设计和实现方案。     

Enterprise Network Traffic Monitoring, Analysis, and Reporting Using Web Technology

Today's enterprise networks are composed of multiple types of interconnected networks. Furthermore, organizations use a variety of systems and applications on these networks. Operations and management staff must provide an efficient, reliable and secure operating environment to support an organization's daily activities. Enterprise networks must be monitored for performance, configuration, security, accounting and fault management. Current management practices typically involve the use of complex, hard-to-learn and hard-to-use tools. What is needed desperately is a set of simple, uniform, ubiquitous tools for managing networks. Web-based management promises to provide such solutions. This paper focuses on the use of Web technology and the Multi-Router Traffic Grapher (MRTG) for the purposes of enterprise network traffic monitoring and reporting. In this paper, we first examine the requirements for enterprise network traffic monitoring, analysis and reporting, and then present the design and implementation of a Web-based network traffic monitoring and reporting system that satisfies those requirements. We also present guidelines we have formulated and used for analyzing enterprise network traffic. We then discuss our experiences in using such a system for traffic monitoring on two large enterprise networks.     

Intelligent QoS management for multimedia services support in wireless mobile ad hoc networks

In this paper, we propose a new intelligent cross-layer QoS support for wireless mobile ad hoc networks. The solution, named FuzzyQoS, exploits fuzzy logic for improving traffic regulation and the control of congestion to support both real-time multimedia (audio/video) services and non-real-time traffic services. FuzzyQoS includes three contributions: (1) a fuzzy logic approach for best-effort traffic regulation (FuzzyQoS-1), (2) a new fuzzy Petri nets technique (FuzzyQoS-2) for modeling and analyzing the QoS decision making for traffic regulation control, and (3) a fuzzy logic approach for threshold buffer management (FuzzyQoS-3). In FuzzyQoS-1, the feedback delay information received from the network is used to perform a fuzzy regulation for best-effort traffic. Using fuzzy logic, FuzzyQoS-3 uses fuzzy thresholds to adapt to the dynamic conditions. The evaluation of FuzzyQoS performances was studied under different mobility, channel, and traffic conditions. The results of simulations confirm that a cross layer design using fuzzy logic at different levels can achieve low and stable end-to-end delay, and high throughput under different network conditions. These results will benefit delay- and jitter-sensitive real-time services.     

Parallel communications for ATM network control and management

This paper describes an end-to-end parallel communications scheme based on a vector routing algorithm (VRA) for ATM network control and management. An information string is partitioned into m parts, which are then coded into k > m parts and sent out on k separate subchannels to the receiver. When m of the k parts are received correctly, the original information can be reconstructed. Two desirable effects are achieved in the context of ATM traffic control: (1) the burstiness of the source traffic can be smoothed out by the partition process; (2) the quality of service in terms of error, loss and delay can be controlled using the number of redundant routes k — m as a control parameter. Our results show that VRA is especially suitable for services with highly bursty traffic. We argue that several network management issues, including reliability, evolution and integration, security, and administration and billing can be addressed in a simple manner using the VRA framework.     

Stochastic modeling and analysis of road–tramway intersections

In the last decades, the socio-demographic evolution of the population has substantially changed mobility demand, posing new challenges in minimizing urban congestion and reducing environmental impact. In this scenario, understanding how different modes of transport can efficiently share (partially or totally) a common infrastructure is crucial for urban development. To this aim, we present a stochastic model-based analysis of critical intersections shared by tram traffic and private traffic, combining a microscopic model of the former with a macroscopic model of the latter. Advanced simulation tools are typically used for such kind of analyses, by playing various traffic scenarios. However, simulation is not an exhaustive approach, and some critical, possibly rare, event may be ignored. For this reason, our aim is instead to adopt suitable analytical solution techniques and tools that can support instead a complete, exhaustive analysis, so being able to take into account rare events as well. Transient analysis of the overall traffic model using the method of stochastic state classes is adopted to support the evaluation of relevant performance measures, namely the probability of traffic congestion over time and the average number of private vehicles in the queue over time. A sensitivity analysis is performed with respect to multiple parameters, notably including the arrival rate of private vehicles, the frequency of tram rides, and the time needed to recover from traffic congestion.

     

SenseVid : A traffic trace based tool for QoE Video transmission assessment dedicated to Wireless Video Sensor Networks

Video applications are being a key component to enhance traditional wireless sensor networks (WSN) applications. As a result, sensor network researchers need adequate and easy to use tools to assess the performances of their proposals. The existing transmission evaluation tools either consider video sequences along with codecs that are unsuitable for WSNs or make use of low cost compression methods for still images without inter-frame coding required for efficient video transmission. In this paper, we present SenseVid, an open source video transmission and evaluation tool that considers WSN specific characteristics. Besides low energy intra-frame compression based on fast pruned discrete cosine transform (DCT), a low complexity inter-frame encoding is provided to allow efficient support of video flows. A configurable fine-grain energy model is provided where both video capture and encoding cost are accounted for on a per frame basis. Video traffic differentiation based on priority levels is also provided. SenseVid adopts the video traffic traces approach, allowing its use in any simulation or real testbed environment. Using SenseVid, the user is able to reconstruct the received video considering lost packets during its transmission as well as estimating the achieved quality of service (QoS) and quality of experience (QoE).     

语义物联网：物联网内在矛盾之对策*

为应对物联网自身固有的物的信息的表示形式的多样化和物的信息的使用主体的理解能力不足的内在矛盾,提出了将其改进为语义物联网的思路,具体措施为：a）物的信息的表示,要基于本体进行语义标注;b）物的信息的使用,要基于本体实现机器理解。借助于语义分析和科学定义方法,建立了语义物联网的集合表示模型和图示模型。该模型的意义在于指明了语义物联网的实现需要有效推进四项主要任务,即本体的构建、RFID系统的建设、物的信息的预处理（即编码为UID或EPC,添加语义标注,嵌入RFID电子标签）和物的信息上载管理与下载管理。     

面向大型社会活动的快速路网控制策略仿真评价方法*

为了缓解大型社会活动期间短时需求激增对快速路运营的压力,提出了基于宏观交通仿真的快速路网控制策略评价方法,旨在为交通控制与管理提供辅助决策依据。该方法运用网络交通流仿真模型对候选控制方案进行仿真和评价,得到较优方案。采用GANFreSP仿真程序对一实例路网的交通流演化进行仿真,刻画拥挤发生、传播和消散的过程,并模拟基于分流诱导的拥堵应对策略,给出交通状态时变轨迹图、路网全局交通状态快照图等可视化结果,以及不控制和分流诱导情况下的路网总体性能指标。仿真案例表明,网络交通流演化是复杂动态过程,局部节点拥挤易演     

城市交通噪声环境承载力分析模型及算法

以城市噪声环境容量为约束条件计算城市区域路网最大交通承载力。分析模型是一个双层优化问题,其中上层是噪声环境容量约束下的最大路网交通流量模型;下层是道路网上的用户均衡分配模型。应用遗传算法进行求解,仿真示例表明该模型和算法是可行的、有效的,可以为城市交通可持续发展的规划和需求管理提供依据。     

大规模高速网络流量测量研究

随着互联网的发展,理解网络行为对于网络管理、规划和发展都有重要意义,网络流量测量是研究网络行为的基础。根据网络测量流量的不同,测量方法分为主动测量和被动测量,每种测量方法有其应用背景和优缺点。为了从不同角度研究网络行为需要定义不同的测度,IETF的IPPM工作组现已经定义了一整套用于流量行为测量的测度。根据测量的环境和应用背景的区别,国外不同的研究机构建立了不同的测量体系结构和测量工具。同时,由于网络带宽越来越大,全流量测量和分析研究越来越困难,为了解决这一问题,近几年,流量抽样测量研究现已成为高速网络流量测量的研究重点。     

Hierarchical control of traffic signals using Q-learning with tile coding

Multi-agent systems are rapidly growing as powerful tools for Intelligent Transportation Systems (ITS). It is desirable that traffic signals control, as a part of ITS, is performed in a distributed model. Therefore agent-based technologies can be efficiently used for traffic signals control. For traffic networks which are composed of multiple intersections, distributed control achieves better results in comparison to centralized methods. Hierarchical structures are useful to decompose the network into multiple sub-networks and provide a mechanism for distributed control of the traffic signals. In this paper, a two-level hierarchical control of traffic signals based on Q-learning is presented. Traffic signal controllers, located at intersections, can be seen as autonomous agents in the first level (at the bottom of the hierarchy) which use Q-learning to learn a control policy. The network is divided into some regions where an agent is assigned to control each region at the second level (top of the hierarchy). Due to the combinational explosion in the number of states and actions, i.e. features, the use of Q-learning is impractical. Therefore, in the top level, tile coding is used as a linear function approximation method. A network composed of 9 intersections arranged in a 3×3 grid is used for the simulation. Experimental results show that the proposed hierarchical control improves the Q-learning efficiency of the bottom level agents. The impact of the parameters used in tile coding is also analyzed.