An efficient traffic control system using dynamic thresholding techniques in wireless mesh networks

Wireless mesh networks (WMNs) depend on a resilient and high‐performance infrastructure to provide users pervasive Internet access. In WMNs, all Internet traffic will be forwarded to the Internet gateways. Hence, these gateways are generally bottleneck nodes. This work proposes a traffic control technique to reduce the bottleneck problem and increase the utilization of network resources. Our approach provides a traffic control strategy that exploits dynamic techniques to adjust the threshold according to the traffic load of each gateway. The base threshold is defined in order to effectively control the traffic. When the current load exceeds the threshold of a gateway, the traffic redirection strategy is implemented by switching border nodes. The service regions can be adjusted for each gateway based on the traffic load. Furthermore, the proposed dynamic thresholding approaches can distribute the workloads of gateways and maintain the thresholds of any two gateways within a level range, making an in‐band balance of load. Thus, our proposed scheme can handle the unnecessary traffic redirection and reduce the traffic control overhead for various distributions of traffic. Experimental results demonstrate that our scheme outperforms other schemes in terms of packet delivery ratio and efficiency, especially in bursty traffic environments. Copyright © 2010 John Wiley & Sons, Ltd.     

基于无线Mesh网络的交通信息系统

本文提出了一种基于无线Mesh网络的交通信息系统,系统由探测汽车采集实时交通信息,依托无线Mesh网络将采集得到的信息发送到信息处理中心.该系统能够提供准确实时的路况信息,无需大量固定基础设施支持,具有建设成本低、周期短、维护费用低的特点,特别适合我国交通事业发展的现状.     

基于无线地磁传感器的交通流检测系统协议设计

提出了一种基于无线地磁传感器的交通流检测系统协议设计,解决了现有智能交通中数据采集的可靠性问题。该系统在Mesh网络拓扑下,采用ZigBee技术作为无线通信方式,设计特有的帧结构,并在调试、常规和配置模式下分别设计出合理的传输协议,达到高可靠性传输的目的。     

智能交通控制系统在城市交通指挥中的应用

针对近年来城市交通的拥挤现象，特别是驾驶员违章严重、交通事故频发、车辆尾气污染超标等问题，介绍丁集计算机、信息、电子及通讯等众多高新科技手段于一体的智能交通指挥中心控制系统。该系统的安装及使用，大大缓解了城市道路堵塞现象、提高了道路的通行能力，减少了驾驶员违章的次数，抑制了交通事故的发生，同时对减轻车辆尾气排放，从而降低环境污染都起到了不可低估的作用。     

VoIP traffic in wireless mesh networks: a MOS‐based routing scheme

Support of Voice over Internet Protocol (VoIP) services in wireless mesh networks requires implementation of efficient policies to support low‐delay data delivery. Multipath routing is typically supported in wireless mesh networks at the network level to provide high fault tolerance and load balancing because links in the proximity of the wireless mesh gateways can be very stressed and overloaded, thus causing scarce performance. As a consequence of using multipath solutions, lower delay and higher throughput can be supported also when a given path is broken because of mobility or bad channel conditions, and alternative routes are available. This can be a relevant improvement especially when assuming that real‐time traffic, such as VoIP, travels into the network. In this paper, we address the problem of Quality of Service (QoS) support in wireless mesh networks and propose a multipath routing strategy that exploits the Mean Opinion Score (MOS) metric to select the most suitable paths for supporting VoIP applications and performing adaptive load balancing among the available paths to equalize network traffic. Performance results assess the effectiveness of the proposed approach when compared with other existing methodologies. Copyright © 2015 John Wiley & Sons, Ltd.     

基于多Agent的交通信息智能预测系统的研究

城市交通控制和诱导系统是智能交通系统(Intelligent Transport System,ITS)的组成部分,而交通流预测特别是短时交通流预测是城市交通控制与交通诱导系统的基础。由于缺乏交通量预测所需历史数据以及判断影响交通量生成与增长因素的准确性不够,致使道路交通量的预测结果与实际值产生了较大差异。论述了灰色模型(Gray Model,GM)以及多Agent理论在交通量智能预测中的方法和应用技术。该方法利用多Agent间的相互通信、协作功能以及灰色模型的累加生成手段和微分方程描述,在一定预测时段内保证了预测数据良好的准确性和实用性。     

城市交通违章罚款智能管理系统

提出了一种用于城市交通违章罚款智能管理系统的设计思路，结合现代无线通讯技术、计算机网络技术和智能IC卡技术在本系统中的具体应用方法作了详细的分析说明。详细阐述了在系统中特殊使用的便携式手持无线罚款仪的软件和硬件的设计方法。     

车载实时路况自动播报系统的研究

为了解决交通拥堵带来的出行不便问题,研究提出一种实时路况语音播报系统,其特点在于不通过现有导航显示仪而仅以语音方式来实时播报交通路况信息,由此可在不影响车辆驾驶情况下,将车辆行驶前方交通路况信息实时告知驾驶员,使驾驶员能够提前预知前方交通路况,并据此规避拥挤路段,免受堵车烦恼,并快捷省时地到达目的地。     

基于移动通信的城市停车诱导信息系统设计

随着汽车保有量不断增加,停车难已成为城市交通普遍问题。从分析城市停车诱导系统功能和提高停车设施利用率的角度出发,结合实际城市交通情况,采用PGIS技术,提出一个整体性、实时动态的停车诱导信息系统。该系统设计通过仿真验证有效．因此将为城市交通管理控制、驾驶员出行提供更准确和有效的诱导决策辅助信息。     

LTE efficiency when used in traffic information systems: A stable interest aware clustering

Long‐term evolution (LTE) technology is critical for the envisioned usage scenarios in the Internet of Vehicles. An important usage scenario is traffic information systems (TIS) for vehicular ad hoc networks (VANETs) that depend on LTE for the delivery of non‐safety information to vehicles. TISs are centralized data warehouses that collect and process traffic information and subsequently allow vehicles to receive such information before and during a road trip. Considering the extensive deployment of VANETs, the LTE demand for TIS is expected to increase. Therefore, we explore and quantify the inefficiency of LTE when used in TIS. By envisioning basic test case scenarios, we establish the trends of data usage while commuting and providing insights into how LTE usage in TIS may lead to the inefficient use of the available wireless spectrum during road trips. To reduce identified inefficiency in LTE usage and cluster instability due to the high speed of the vehicles, we proposed a novel stable interest‐aware clustering (SIAC) mechanism. SIAC consider VANETs mobility constraint, LTE link quality, and exploit interest of the vehicles, in cluster formation phase. Resulting in the reduction in the data demand of the vehicles and frequency of link failures among the vehicles and provides transmission path stability. SIAC performs well as compared with the existing approaches shows more cluster stability and reduces the LTE usage for driving assistance and route planning applications.     

电子信息技术在智能交通信号控制系统中的运用分析

目前,电子信息技术取得了很大的发展成果,被广泛地应用到各智能交通信号控制系统中,极大地提高了系统运行的安全性和稳定性.文章主要探索了电子信息技术在智能交通信号控制系统中的应用情况.     

基于统计网络演算的无线mesh网络流量模型

基于无线mesh网络的基本特征,利用统计网络演算理论,构造了新型的无线mesh网络单节点和多节点的流量模型,该模型充分体现了无线mesh网的随机特性.该流量模型的特征是其求和函数及其输入输出函数的边界函数均受限于一个最小加卷积函数.理论分析证明构造的流量模型能正确描述无线mesh网络的实际情况.     

无线Mesh网中时延约束抖动优化的多路径流量分配算法

针对无线mesh网中多媒体应用的特点,研究多路径传输中路径时延满足约束且路径间抖动最小化的路径流量分配问题。首先,基于网络演算理论分析了数据分组在无线mesh网单路径传输中产生的队列时延,推导出单路径传输的时延上界以及多路径传输中的路径间时延抖动上界,并得到满足时延约束的路径最大容许流入速率;然后,基于时延及其抖动上界,提出满足时延约束抖动优化的路径流量分配算法DCJOTA,该算法根据路径最大容许流入速率按比例分配各路径流量,同时尽可能减小路径间的时延抖动;最后,分析了算法DCJOTA的可行性及其实现方法,并在NS2网络模拟器中验证了该算法的有效性。仿真实验表明,与AOMDV协议相比,集成了DCJOTA算法的多路径路由协议DCJO-AOMDV协议在时延及其抖动方面具有更好的表现:端到端平均时延降低3.9%,端到端平均时延抖动减小24.5%。另外,DCJOTA算法带来协议复杂性略微增加,DCJO-AOMDV协议下的网络吞吐量下降1.7%。     

DCNC: throughput maximization via delay controlled network coding for wireless mesh networks

Network coding (NC) can greatly improve the performance of wireless mesh networks (WMNs) in terms of throughput and reliability, and so on. However, NC generally performs a batch‐based transmission scheme, the main drawback of this scheme is the inevitable increase in average packet delay, that is, a large batch size may achieve higher throughput but also induce larger average packet delay. In this work, we put our focus on the tradeoff between the average throughput and packet delay; in particular, our ultimate goal is to maximize the throughput for real‐time traffic under the premise of diversified and time‐varying delay requirements. To tackle this problem, we propose DCNC, a delay controlled network coding protocol, which can improve the throughput for real‐time traffic by dynamically controlling the delay in WMNs. To define an appropriate control foundation, we first build up a delay prediction model to capture the relationship between the average packet delay and the encoding batch size. Then, we design a novel freedom‐based feedback scheme to efficiently reflect the reception of receivers in a reliable way. Based on the predicted delay and current reception status, DCNC utilizes the continuous encoding batch size adjustment to control delay and further improve the throughput. Extensive simulations show that, when faced with the diversified and time‐varying delay requirements, DCNC can constantly fulfill the delay requirements, for example, achieving over 95% efficient packet delivery ratio (EPDR) in all instances under good channel quality, and also obtains higher throughput than the state‐of‐art protocol. Copyright © 2014 John Wiley & Sons, Ltd.     

A new model for network traffic forecast based on user's mobility in cellular networks with highway stretches

Wireless communications have always faced the scarceness of bandwidth and until today the cellular division has solved this problem by making radio cells always smaller. However, as cell size is reduced, more users will probably require handoffs, and signaling can overload the system. Further, the decrease in cell dimension cannot ensure the best utilization of system resources, because user density in the cell is not constant over the time. Dynamic allocation might be the solution, but it is a complex task, basically due to complexity of the models for the mobility prediction, especially in those environments where users move very fast (e.g. highways). This last one is a typical environment where high mobility of vehicles does not allow small cell sizes and thus system capacity is intrinsically bounded. In this paper, we deploy an analytical model for a cellular network operating in a high mobility environment. Such a model is capable of representing and forecasting wireless system evolution in terms of channel occupancy, starting from the current state of the mobile network and road traffic. This model has been defined by integrating a vehicular traffic model with a wireless cellular communication one. With such approach the dynamic behaviour of the most critical mobile terminals, those associated with vehicles, are described in a very precise and specific way with respect to mobility. Many results obtained with specific simulation tools and herein reported show the good behaviour of our proposal. Copyright © 2004 John Wiley & Sons, Ltd.     

温湿度实时采集与无线传输系统的研究

设计了一套远程温湿度实时监控系统。该系统包括温湿度检测与显示模块,无线发射模块以及无线接收和处理模块。对搭建后的系统测试结果表明：系统使用灵活、成本低廉,能够同时实现多点温湿度的测量与传输。该系统可方便地嵌入到无线监测系统中。     

Code pruning in opportunistic routing through bidirectional coding traffic comparison

Opportunistic routing (OR) significantly improves transmission reliability and network throughput in wireless mesh networks by utilizing the broadcast nature of the wireless medium. Through the integration of network coding (NC), the complicated coordination to select the best forwarding node (FN) in OR can be bypassed. However, the introduction of NC exacerbates the redundant‐packet‐transmission problem. To mitigate this issue, existing coded OR protocols either adopt the loss‐rate‐based approach, employ orthogonal vectors as coded feedback, or pursue the stream‐based coded OR model. However, these three solutions suffer inaccuracy and obsolescence of the loss‐rate measurement, false‐positive/false‐negative problem, and unavailability of hop‐by‐hop stream‐based OR, respectively. To address the previous problems, we propose a simple but practical coded feedback scheme, cumulative coding coefficient acknowledgement (C³ACK), based on the relevance between forward (coded packets received from upstream nodes) and backward coding traffic (coded packets overheard from downstream nodes), and apply C³ACK to both batch‐based and stream‐based coded OR models in order to prune redundant forward and backward coding traffic. Both testbed evaluation and simulation study show that our code‐pruning schemes can outperform existing approaches in terms of expected throughput and transmission count. Copyright © 2014 John Wiley & Sons, Ltd.     

基于单片机的区域交通信号控制系统

介绍了一种基于单片机的区域交通信号控制系统设计方案,阐述了系统的工作原理及各主要模块的软硬件实现方法。系统能够根据车流量信号动态地改变交通信号灯各状态配时,并通过无线通信技术,有效地解决了特定区域内各路口信号机之间数据的传输,实现了区域交通信号的智能控制。该系统抗干扰能力强,可靠性高,使用非常方便。     

集成成像3D信息获取技术

集成成像作为一种新型裸眼三维(3D)显示技术,能够完整获取3D信息并还原再现,是目前最具发展前景的裸眼3D显示技术之一。其中,对3D信息的完整获取通过记录场景不同角度的视差信息,并以微图像阵列形式进行呈现,不仅能够为集成成像显示提供3D内容,更作为一种多维度信息获取手段,在被遮挡场景的探测成像、目标识别、2D/3D信息加密和显微3D成像等多个领域得到应用。文中对集成成像3D信息获取的基本原理、不同类型的集成成像3D信息获取技术以及集成成像3D信息实时获取技术进行综述,并讨论现存的一些问题以及未来发展趋势。     

Characteristics analysis and modeling of frame traffic in 802.11 wireless networks

In this paper, we analyze the impacts of different frame types on the self‐similarity and burstiness characteristics of the aggregated frame traffic in a real 802.11 wireless local area network (WLAN). We find that the impacts of different frame types are related to the mean frame sizes and the proportions of specified frame types in the aggregated frame traffic. Furthermore, we propose an analytical model to capture the relationship of self‐similarity characteristics between the aggregated frame traffic and different frame types. These new results provide an insight of frame traffic characteristics and some practical guidelines for developing new efficient algorithms to improve the common medium utilization and system throughput performance. Copyright © 2009 John Wiley & Sons, Ltd.