一个基于IEEE802．11P标准能WAVE模型样机

基于IEEE802．11p标准的车辆通信环境下的无线接入（WAVE）系统为未来的智能交通系统建造了功能性架构,旨在安全性、有效性和方便性方面极大地改善交通环境。文章阐述了WAVE系统的背景、关键技术及其对社会的深刻影响,报告了密歇根大学迪尔拜分校车载通信和网络中心进行的相关研究和进展,包括一个基于现场可编程门阵列（FPGA）的WAVE模型样机和车载网络仿真软件。     

VANET/LTE-Advanced异构网络中基于协议序列-IEEE 802.11p的信道接入机制

摘要：提出了VANET/LTE-Advanced异构网络架构,并重新规划信道使用及接入模式,提高车载设备之间通信的有效性,增强公平性并兼顾自由度。以车辆间通信为研究对象,深入剖析并比较IEEE 802.11p MAC协议,基于协议序列信道接入机制,提出基于协议序列-IEEE 802.11p的信道接入算法,将“基于调度”与“基于竞争”的信道接入结合,完善IEEE 802.11p MAC层协议。仿真结果表明,基于协议序列-IEEE 802.11p的信道接入机制与UI模式及IEEE 802.11p模式相比,实现了用户平均吞吐量和平均数据分组发送时延性能的权衡,具有理论价值和实用价值。     

MCAS:车载网络中带负载均衡的多信道接入机制

近几年车载自组织网络在学术界和工业界都发生了巨大的变化。车载网络运用多信道操作模式来提供开放的安全服务和安全有效的驾驶体验,由此可见多信道接入在车载网络中占据非常重要的角色。吞吐量和时延是两个很重要的指标。基于最新标准,提出了基于信道通信间负载均衡和车辆间信道协作的多信道接入机制MCAS。理论分析和仿真结果都表明,MCAS在吞吐量和服务传输时延上都优于WAVE。     

车联网中基于贝叶斯决策的垂直切换方法研究

车辆需要在车联网的异构无线网络环境下进行垂直切换,针对垂直切换技术普遍不能支持 WAVE, WiMAX和3G cellular间的垂直切换这一问题,提出了一种基于贝叶斯决策的垂直切换算法。首先,根据接入网络的信号强度、传输速率、误码率和网络阻塞率以及车辆终端的速度和运动趋势建立多条件相关的切换概率分布,计算出切换先验概率;然后通过贝叶斯决策算法计算后验概率并进行决策分类,从而选取最优网络接入。仿真实验结果表明,该算法不仅有效地实现WAVE,WiMAX和3G cellular无线接入技术之间的垂直切换,而且避免了乒乓效应,保证了网络及时更新。     

基于IP的WiMAX移动网络的研究

基于IEEE 802.16的WiMAX网络的应用正成为业界的讨论热点,IEEE 802.16m更被选为下一代无线通信标准（IMT-advanced）的候选方案之一。在此深入探讨构建基于IP技术的WiMAX应用网络架构。首先分析IEEE 802.16e规范为支持移动性在物理层和媒质接入层引入的增强技术。随后基于移动IP技术和WiMAX网络参考模型给出基于IP的移动WiMAX网络的可行的应用模型。该应用方案可为基于IEEE 802.16技术的应用提供一个参考。     

基于WAVE的车载通信系统介绍

车载通信网络,由于其在智能交通和车载娱乐方面的广泛应用前景,受到了业界的广泛关注。车载通信具有车辆高速行驶、移动区域受限、网络拓扑变化快、通信过程频繁中断、以及要求私密性等特点。而基于WAVE的应用更容易部署,成本更低,更加符合商业模式,同时WAVE的标准化工作正在顺利进行中,所以关于WAVE的架构及通信过程成为了研究者们首先要关注的问题。     

车联网WAVE协议研究

WAVE协议是应用于车与车、车与路边单元之间数据交换的通信协议,主要由802.11p和IEEE 1609两部分组成。该协议充分考虑了车联网高速移动的特点,能支持高速移动的车与车之间的通信,有效缓和了道路拥挤以及车辆的消费和排放。通过车与路边单元之间的通信能够得知交通信号灯、路面状态、天气情况等信息,从而提高交通运输效率。介绍了车载无线通信WAVE(Wireless Access in Vehicular Environment)协议的基本架构和内容,包括其物理层、MAC层、多信道之间的切换机制以及一些尚需完善的问题。     

IEEE 802.16d/e宽带无线接入网络中的切换机制的研究

作为新一代的宽带无线接入技术IEEE 802.16d/e以自身固有的优势正越来越受到关注。相比于固定接入的WiMAX,移动版WiMAX,即IEEE 802.16e具有更好的市场前景,同时也面临更多的挑战。文章在分析和研究了IEEE 802.16e标准中定义的切换模式的基础上,总结了现有的IEEE 802.16e切换机制的研究现状,并建议为IEEE 802.16e的移动宽带接入网络提出一种具有QoS保证的支持无缝移动的移动性管理架构,从而实现了IEEE 802.16e的MS和网络中的通信对端之间实现具有端到端QoS保证的平滑服务。     

车联网网络架构与媒质接入机制研究

车联网旨在实现一体化智能交通体系和无处不在的网络,其关键技术在于全网数据共享和车辆宽带接入。现有车辆网络架构因其不同设计目标而缺少统一的协议栈和数据接口,难以有效进行全网数据共享或协同通信;其多信道机制缺少灵活性,整体网络性能受网络节点密度影响较大。文章提出面向安全应用的车联网无线网络架构及其协同通信协议栈,并对车联网自适应多信道媒质接入协议进行研究。     

EPON和WiMAX融合架构下带宽分配和调度机制的研究

以太网无源光网络(EPON)和IEEE 802.16(WiMAX)的融合网络在固定移动混合接入网中被认为是很有前景的接入方式.文中提出了3种WiMAX无线网络与EPON网络系统融合架构,融合系统同时具有光网络的高带宽和无线网络的灵活性.为了在接入网中支持QoS,本文为融合结构提出了一种动态带宽分配算法(DBA)和调度机...     

基于车辆行为分析的智能车联网关键技术研究

车联网通信系统中通信节点的高移动性、移动行为的复杂性,使得此场景下通信业务呈现数据实时交互性强、空时分布不均、尺度多变、规律复杂的特征,导致传统的车联网网络部署、资源调配难以有效满足用户的差异化服务质量需求。因此,迫切需要设计“车-人-路-云”泛在互联的智能异构车联网网络,通过充分挖掘车辆行为数据的潜在价值,精准预测、刻画车辆行为的空时分布特性,以提升车联网资源利用率、改善车联网服务性能。该文全面梳理了国内外在车辆行为分析、网络部署与接入以及资源优化方面的相关工作,重点阐述了智能车联网关键使能技术,即如何借助先进的人工智能、数据分析技术,探索车联网中车辆行为的空时分布特性,建立车辆行为预测模型,进行智能化网络部署与多网接入、动态资源优化管理,实现高容量、高效率的智能车联网通信。     

Heterogeneous Vehicular Communication Architecture and Key Technologies

Vehicular networks have traditionally been used in specific scenarios, such as Electronic Toll Collection (ETC). New vehicular networks, however, support communication of safety information between vehicles using self-organized ad-hoc technology. Because of limitations in network architecture, current vehicular networks only provide communication for mobile terminals in a vehicle cluster. Vehicles cannot exchange information with an Intelligent Traffic System (ITS) control center nor can they access broadband wireless networks. This paper proposes a novel heterogeneous vehicular wireless architecture based on Wireless Access in Vehicular Environment (WAVE, IEEE 802.11 p) and Worldwide Interoperability for Microwave Access (WiMAX,IEEE 802.16e). A new network infrastructure and system model is introduced, and key technologies are discussed. For WAVE, these technologies include adaptive multichannel coordination mechanism and scheduling algorithm; and for WiMAX, these technologies include group handover scheme and two-level resource allocation algorithm.     

An efficient k‐Means authentication scheme for digital certificates revocation validation in vehicular ad hoc networks

Vehicular ad hoc networks are emerging as a promising approach to improve traffic safety and provide a wide range of wireless applications to drivers and passengers on the road. In order to perform reliable and trusted vehicular communications, one requirement is to ensure peer vehicle credibility by means of validating digital certificate attached to messages that are transmitted by other vehicles. However, in vehicular communication systems, certificate validation is more time consuming than in traditional networks because each vehicle receives a large number of messages in a short period. Another concern is the unsuccessful delivery of information between vehicles and other entities on the road due to their high mobility rate. For these reasons, we seek new solutions that will aid in speeding up the process of certificate validation. In this article, we propose a certificate revocation status validation scheme using the concept of clustering from data mining that can meet the aforementioned requirements. We employ the technique of k‐Means clustering to boost the efficiency of certificate validation, thereby enhancing the security of a vehicular ad hoc network. Additionally, a comprehensive security analysis for this scheme is presented; the analysis shows that this scheme can effectively improve the validation of certificates and thus increase the communication security in vehicular ad hoc networks. Copyright © 2012 John Wiley & Sons, Ltd.     

Communication patterns in VANETs

Vehicular networks are a very promising technology to increase traffic safety and efficiency, and to enable numerous other applications in the domain of vehicular communication. Proposed applications for VANETs have very diverse properties and often require nonstandard communication protocols. Moreover, the dynamics of the network due to vehicle movement further complicates the design of an appropriate comprehensive communication system. In this article we collect and categorize envisioned applications from various sources and classify the unique network characteristics of vehicular networks. Based on this analysis, we propose five distinct communication patterns that form the basis of almost all VANET applications. Both the analysis and the communication patterns shall deepen the understanding of VANETs and simplify further development of VANET communication systems.     

基于反向散射通信的车辆精准定位技术

高精度车辆定位是自动驾驶、车联网中的关键技术环节,其中一个研究热点和难点是如何在高密度城市、隧道、地下车库等无法获取GPS或蜂窝网基站定位信号的区域实现低成本、高可靠的车辆精准定位。对此,创新性地提出了一种基于反向散射通信的车辆精准定位技术(即"BackCom车辆定位技术"),其仅须在车辆顶端安装一个包含2根天线的定位阅读器以及在道路边部署至少一个定位标签,便可实现高精度车辆定位。经仿真验证,BackCom车辆定位技术可以取得极高的定位精度。同时,BackCom车辆定位技术极易扩展,通过增加其定位阅读器中的天线数量,可进一步提升其定位精度。BackCom车辆定位技术具备低成本、低功耗、高精度、高可靠、部署方便等优点,适用于各种行车环境,具备极高的理论研究价值和商用价值。     

Security in service-oriented vehicular networks - [Service-oriented broadband wireless network architecture]

Service-oriented vehicular networks support diverse infrastructure-based commercial services including Internet access, real-time traffic concerns, video streaming, and content distribution. The success of service delivery in vehicular networks depends on the underlying communication system to enable the user devices to connect to a large number of communicating peers and even to the Internet. This poses many new research challenges, especially in the aspects of security, user privacy, and billing. In this article we first identify the key requirements of authentication, privacy preservation, and billing for service delivery in vehicular networks. We then review the existing industrial and academic efforts on service- oriented vehicular networks. We also point out two security challenges, minimizing vehicleto- infrastructure authentication latency and distributed public key revocation, which are considered among the most challenging design objectives in service-oriented vehicular networks. A novel fast vehicle-to-infrastructure authentication based on a vehicle mobility prediction scheme and an infrastructure-based short-time certificate management scheme are then proposed to address these two challenges.     

A moving cluster architecture and an intelligent resource reuse protocol for vehicular networks

Real-time data transmission, especially video delivery over high-speed networks have very stringent constraints in terms of network connectivity and offered data rate. However, in high-speed vehicular networks, direct communication between vehicles and road side units (RSU) often breaks down, resulting in loss of information. On the other hand, a peer-to-peer based multihop network topology is not sufficient for efficient data communication due to large packet loss and delay. In this paper, a novel ‘moving cluster multiple forward’ (MCMF) architecture is proposed and investigated for efficient real-time data communication in high speed vehicular networks. MCMF involves novel aspects in relation to the formation of clusters and managing the communication between groups of vehicles and introduction of a hierarchical multiple forwarding mechanism which enables communication between any vehicle and RSU via other vehicles. Additionally, a novel protocol called ‘alternate cluster resource reuse’ (ACRR) is proposed and its detailed communication mechanism is presented. Simulation tests show how the use of MCMF and the ACRR protocol results in superior bit-rate performance—around three times that obtained in peer-to-peer multihop communications and twice that of MCMF with no ACRR protocol. Further, the average delay in MCMF-based transmissions from vehicle to RSU is around 50 % that of a peer-to-peer multihop communication mechanism. MCMF/ACRR has the potential to support multimedia traffic according to the IEEE 802.11p standard, even with a sparse investment in the infrastructure.     

AMOEBA: Robust Location Privacy Scheme for VANET

Communication messages in vehicular ad hoc networks (VANET) can be used to locate and track vehicles. While tracking can be beneficial for vehicle navigation, it can also lead to threats on location privacy of vehicle user. In this paper, we address the problem of mitigating unauthorized tracking of vehicles based on their broadcast communications, to enhance the user location privacy in VANET. Compared to other mobile networks, VANET exhibits unique characteristics in terms of vehicular mobility constraints, application requirements such as a safety message broadcast period, and vehicular network connectivity. Based on the observed characteristics, we propose a scheme called AMOEBA, that provides location privacy by utilizing the group navigation of vehicles. By simulating vehicular mobility in freeways and streets, the performance of the proposed scheme is evaluated under VANET application constraints and two passive adversary models. We make use of vehicular groups for anonymous access to location based service applications in VANET, for user privacy protection. The robustness of the user privacy provided is considered under various attacks.     

Location-Aware Services over Vehicular Ad-Hoc Networks using Car-to-Car Communication

Recent advances in wireless inter-vehicle communication systems enable the establishment of vehicular ad-hoc networks (VANET) and create significant opportunities for the deployment of a wide variety of applications and services to vehicles. In this work, we investigate the problem of developing services that can provide car drivers with time-sensitive information about traffic conditions and roadside facilities. We introduce the vehicular information transfer protocol (VITP), a location- aware, application-layer, communication protocol designed to support a distributed service infrastructure over vehicular ad- hoc networks. We describe the key design concepts of the VITP protocol and infrastructure. We provide an extensive simulation study of VITP performance on large-scale vehicular networks under realistic highway and city traffic conditions. Our results demonstrate the viability and effectiveness of VITP in providing location-aware services over VANETs.     

Decision-making models for group vertical handover in vehicular communications

In vehicular communications across composite radio environments, the one prominent feature is network heterogeneity, which means that diverse radio access networks co-exist with each other. And another particular feature is group mobility, because multiple mobile equipments in the vehicle are moving at the same time. Therefore, with movement of vehicle, many mobile terminals (MTs) in a train or bus may operate vertical handover actions almost at the same time, which is regarded as the group vertical handover (GVHO). However, the current literatures on vertical handover (VHO) mainly focus on when to trigger handover and how to select the best target network for single user, if these VHO schemes were applied in vehicular communication scenario, it may lead to system performance degradation or network congestion, because the MTs with these VHO decision-making methods selfishly select the best networks regardless of the influences from other concurrent VHO users. Therefore, in order to provide reliable QoS guarantee and keep service connectivity for group mobility in vehicular communications across heterogeneous networks, three models are proposed in this paper to deal with the decision-making problems of incomplete and inaccurate information in GVHO scenario. Two of them adopt MT controlled VHO, while another adopts network assisted VHO. The performances of these schemes are studied with regard to the average transmission delay and average packet losses rate.