Bayesian game-theoretic approach based on 802.11p MAC protocol to alleviate beacon collision under urban VANETs

Vehicular Ad-hoc Networks (VANETs) facilitate the broadcasting of status information among vehicles. In the IEEE 802.11p/WAVE vehicle network environment, the strict periodic beacon broadcasting of safety messages requires status advertisement to assist drivers in maintaining safety. The beacon broadcasting is required for real-time communication, and for avoiding the degradation of communication channels in high vehicular density situations. However, a periodic safety beacon in the IEEE 802.11p/WAVE standard can only transmit packets on a single channel using the MAC protocol. In high vehicular density situations, the channel becomes overloaded, thereby increasing the probability of beacon collision, and hence reducing the influx of successfully received beacons, which increases the delay. Many studies have indicated that appropriate congestion control algorithms are essential to provide efficient operation of a network. In this paper, to avoid beacon congestion, we have considered game theoretic models of wireless medium access control (MAC) where each transmitter makes individual decisions regarding their power level or transmission probability. We have evaluated the equilibrium transmission strategies of both the selfish and the cooperative user. In such a game-theoretic study, the central question is whether Bayesian Nash equilibrium (BNE) exists, and if so, whether the network operates efficiently at the equilibrium point. We proved that there exists only one BNE point in our game and validated our result using simulation. The performance of the proposed scheme is illustrated with the help of simulation results.     

车队认知能力增强的通信区块间隙优化方法

为了在单车超越车队的过程中缩短超车车辆与车队间通信范围，减少车队通信压力，锁定影响车辆入队的关键车队区块，同时通过将待进入关键区块的车队进行间隙优化调整，为驾驶人提供定制化换道入队引导服务，提出了基于驾驶人超车风格特征参数的车队内信息传输关键区块锁定算法，通过分析影响驾驶人换道入队位置范围的关键因素，将驾驶人换道入队过程分为本车道速度调整过程与入队速度调整过程，利用非参数贝叶斯算法获取驾驶人超车换道特征数据并提出基于关键区块所在车队位置序列的车辆间隙优化调整策略。研究结果表明：超车车辆加速度、与前车预计碰撞时间、与车队相对速度是影响驾驶人换道入队范围的关键因素；通过非参数贝叶斯算法将超车车辆运行数据分类获取的驾驶人换道入队驾驶操作基元，可准确提供驾驶人行为特征关键参数；通过将驾驶人换道特征分为48个子类型，可锁定驾驶人换道入队范围且车队关键区块范围随着超车车辆与车队速度差值不同在各个特征类型上呈现不同变化趋势；针对驾驶人入队特征对待进入车队关键区块的车辆间隙进行优化调整，不仅可以为驾驶人提供可接受的驾驶辅助信息，同时减少了车队间隙产生过程中车辆加速度范围，提升了车队运行的舒适性。     

车载Telematics系统研究

车载Telematics系统通过位置信息和无线通信网络,整合多种服务应用,为汽车驾乘者提供安防、辅助导航及信息通信、娱乐等综合性服务.本文详细剖析车载Telematics系统服务的主要内容及其产业链上下游的关系,提出可行的Telematics体系架构,另外,采用划分功能模块的方式对车载终端的硬件和软件系统结构进行设计,...     

基于驾驶特性的超车模型研究

超车行驶作为驾驶人行车过程中重要的行为之一,与行驶安全性有着直接的联系。为建立符合驾驶人操作习惯的超车模型,本文通过实车试验采集不同驾驶人在高速公路的超车行驶数据,并以此采用多项式回归拟合建立基于驾驶人操作特性的超车模型,最后利用prescan软件对提出的超车模型进行了仿真分析,结果表明建立的超车模型能够真实地反映驾驶人超车过程中的操作习惯,为超车行为的研究提供了可靠的理论依据。     

考虑车车与车路通讯并存的路侧单元优化布设方法

路侧单元(Road Side Unit, RSU)作为车路协同系统(Cooperative Vehicle Infrastructure System, CVIS)中路侧感知控制网与网联化车辆自组网的重要节点,其布设方案对车路交互效能、系统建设成本与协同服务水平均产生较大影响。现有RSU优化布设研究主要基于车路(Vehicle to Infrastructure, V2I)通讯,忽视了车车(Vehicle to Vehicle, V2V)通讯的转发和中继作用,也缺乏对RSU设备及线网布设成本的相关考量。针对上述问题,面向V2V和V2I通讯并存环境,考虑信息覆盖正向收益与设备/线网布设负向收益,构建面向综合收益最优的RSU布设方案优化模型。首先结合信息流-交通流耦合模型获取传播时间矩阵,提出权重约束可达性算法,构建布设方案与信息覆盖正向收益之间的关系方程。然后针对动态最优布设方案条件下的最优线网布设问题,提出改进的最小生成树模型,并以此设计综合收益最优的RSU优化布设模型。最后,基于井字形算例路网,进行模型验证和关键系数敏感性分析;并基于Sioux Falls路网,将所提出的模型与现有未...     

典型车联网基本安全消息机制分析

车联网基本安全消息的生成和传播是影响车联网安全应用及智能网联汽车有效性、可靠性的关键因素.在分析车联网基本安全消息基本定义的基础上,对国内外当前LTE-V2X、车载环境下的无线接入(Wireless Access in the Vehicular Environment,WAVE)等多种典型的车联网通信协议体系结构框架...     

基于UDS协议的并线辅助系统动态校准

并线辅助作为汽车智能安全技术的重要组成部分,越来越被重视,它通过车载毫米波雷达检测车辆后方目标的运动情况,提醒驾驶者安全范围内有无障碍物或来车,从而消除视线盲区,提高驾驶员的行车安全。由于车辆自身及雷达支架结构的误差,新安装后的雷达需要进行校准,而UDS诊断协议作为产线设备及售后诊断设备的基础通信协议,将为并线辅助系统动态校准提供网络通信支持。     

超车模型在双车道公路仿真系统中的应用研究

借鉴以往的研究成果，在分析双车道公路超车特性的基础上，将超车过程划分为超车意愿、超车条件、超车行为、超车中止强制回车4个步骤，建立了超车模型。选用超车率、超车次率和区间平均速度作为验证指标来对比仿真结果与实测数据，对比结果符合误差范围，证明了模型的有效性。应用模型进行仿真试验，通过分析得到的超车率一流量关系，发现该关系曲线与实际情况相吻合且呈现出两个阶段，前一阶段随着双车道公路流量的增加，超车率逐渐增大至最大值。后一阶段流量增加而超车率不断下降，当流量达到2900pcu／h以后，超车率几乎为零，以此作为临界点，推荐我国标准2级双车道公路的双向通行能力为2900pcu／h。     

Design and implementation of a UPnP-can gateway for automotive environments

In this paper, we propose a universal plug and play (UPnP) — controller area network (CAN) gateway system using UPnP middleware for interoperability between external smart devices and an in-vehicle network. The proposed gateway consists of a UPnP communication device, a CAN communication device, and a device translator layer. In-vehicle devices are not usually IP-based, so we implemented an in-vehicle device manager in the UPnP communication device which is in the gateway. We developed a vehicle simulator to produce real vehicular data for performance analysis. The CAN communication device transmits and receives real-time vehicle data between the real vehicular simulator and external devices through the UPnP. The device translator layer configures a message frame for enabling seamless data input and output between the CAN and UPnP protocols. After implementation, we generated an internal-external service request and tested the result. Finally, we confirmed the service request and operation between external devices and the internal vehicular device. Additionally, for a variety of external device numbers and communication environments, we demonstrated the gateway performance by measuring the round trip time (RTT) for overall service implementation.     

Improving multi-channel wave-based V2X communication to support advanced driver assistance system (ADAS)

The advent of vehicle-to-everything (V2X) communication has opened the opportunity to design advanced driver assistance systems (ADAS) that collect information from sensors in neighboring vehicles and roadside infrastructure. IEEE and ETSI have designed network protocol standards for V2X communications. Despite the differences between the vehicular wireless communication architecture defined by ETSI and the IEEE protocol stack, the two standards have multichannel operations as a main commonality, with some channels dedicated to safety-critical applications and others to nonsafety services. Some recent studies have demonstrated that these standards might not provide sufficient channel utilization for reliable exchange of information in mid- and heavily congested scenarios. In this paper, we propose and evaluate the performance of a driver-assistance system to reduce the connectivity gaps between vehicles and roadside units (RSUs). This cooperative system of multi-service channel allocation will improve radio channel utilization. We also show that the required latency for this inter-vehicle communication can be obtained using the IEEE-WAVE standards and dedicated short-range communication (DSRC) proposed for vehicular environments. Simulation results show that the proposed scheme can improve the average throughput by up to 15 % in various traffic density conditions compared with the dynamic channel allocation method.     

基于事故特征耦合影响的城市道路交通事故影响分析

城市道路交通事故发生后,由于事故车辆占用车道,使得车辆通行的车道数目减少,道路的通行能力降低,造成排队和交通拥堵,对交通运行产生一定的影响。以双向6车道的城市道路为例,运用Vissim仿真软件模拟交通事故下的交通运行,分析车流量、占道类型、事故持续时间以及借道超车4种因素下的交通影响。结果表明,流量越大、事故持续时间越长、占道数目越多,事故对交通的影响越大。当流量达到3 400 veh/h（D级服务水平）,占1个车道的车辆延误显著增加,直至流量达到4 000 veh/h时才逐渐趋于平稳,且占据车道2比占据车道1和占据车道3的延误要大;当流量达到1 900 veh/h（B级服务水平）,占2条车道的车辆延误显著增加直至流量达到2 700 veh/h时才逐渐趋于平稳,占据车道1和3的车辆延误要小于占据车道1和2以及占据车道2和3的延误;在相同占道情况下,不同事故持续时间下的车辆延误随流量变化的趋势大体是一致的;当事故道路服务水平为D/E/F级,对向道路服务水平在A/B/C/D级时（事故占用内侧1个车道）,以及当对向道路服务水平在A/B/C级时（事故占据内侧2个车道）,进行借道超车均能有效减少事故路段车辆延误。      

双车道公路超车两难区域研究

基于超车行为分析,提出了双车道公路超车行为的两难区域概念,在该区域内超车车辆既无法完成超车动作又不能在避免与对向车辆相撞前安全避让。应用运动学理论建立了下游车队规模、车速、设计车速与两难区域范围以及安全超车视距之间的关系,发现与超越单车的视距要求相比,超越车队所需的安全视距较大,且随着设计车速、下游车队规模以及车速的增大而增大。并发现当流量或车速较大时,两难区域出现的概率较大,且因驾驶者错误估计引发交通事故的机会增多。最后给出了不同下游车队规模条件下安全超车的速度限制及视距要求,为制定安全行车策略以及道路安全管理提供了理论依据。     

物理分割的非机动车道超车事件延误动机模型

表征骑车者舒适程度的指标＂超车事件数＂较为合理地体现了非机动车道路服务水平。基于超车物理机理的Hummer非机动车超车事件数预测模型已得到广泛应用,但中国道路及自行车有着鲜明的自身特点,因此其在中国地区运用尚存不足。据此,修正模型引入影响较大的延误事件和自行车骑行者的超车动机2个参数,对物理分割的非机动车超车事件数进行了研究。比较南京实地勘测的事件数据和各类预测数,相关性相对Hummer模型增大,拟合结果验证了修正模型的准确性。     

基于改进人工势场的自动驾驶汽车弯道超车动态路径规划

动态路径规划是自动驾驶汽车避障控制的关键技术。针对自动驾驶汽车弯道超车工况，建立基于改进人工势场(Artificial Potential Field, APF)的动态路径规划方法。为使基于APF的动态路径规划方法能运用于包含弯曲道路的复杂交通环境，将已在直道环境验证过的道路APF函数通过极坐标系与笛卡尔坐标系的相互转换，建立考虑道路曲率的弯曲道路APF函数。针对根据车辆质心位置判断车辆碰撞风险方法存在的缺陷，提出考虑车辆体积的碰撞风险预判方法，建立综合考虑车辆位置、速度和体积的障碍车辆APF函数。基于弯曲道路APF和改进障碍车辆APF，建立道路环境综合APF，引导车辆实现弯道超车。为避免目标函数中子目标相互干涉，提高弯道超车安全性，提出根据本车与障碍车辆相对位置关系自适应调整权重矩阵的方法。基于Carsim/Simulink联合仿真平台，分别在静态障碍车辆和动态障碍车辆2种工况下，验证自动驾驶汽车弯道超车动态路径规划的有效性。研究结果表明：所建立的弯曲道路APF能引导车辆转弯行驶，避免冲出车道；目标函数权重自适应调整方法能根据超车过程动态调整子目标的权重，规划出符合道路交通安全法规的路径，避免车辆超车时提前折返原车道，提高了超车安全性；考虑车辆体积的障碍车辆APF提高了车辆碰撞风险的预判精度，有效避免碰撞事故发生。     

全球车载通信DSRC标准发展及应用

研究了新一代车车、车路之间通信标准协议,即专用短程通信(Dedicated Short Range Communications,DSRC)和车载环境下的无线接入协议。调研了欧洲、日本、美国和中国车载通信标准的最新发展情况,阐述了DSRC系统架构、技术原理以及通信标准,重点分析了DSRC物理层和MAC层关键技术,比较了IEEE 802.11和IEEE 802.11p异同点,最后展望了DSRC技术在汽车工业、汽车通信上的发展前景。本文全面深入讲述DSRC技术特点,为下一步我国制定车载通信发展战略提供参考依据。     

基于GIS的高速公路安全管理系统数据库框架设计

为了提高高速公路的安全服务水平，有必要建立一个先进的高速公路安全管理系统。文中研究了系统的核心部分——基于GIS的数据库。通过对系统的应用状况进行全面、仔细的调查，在系统需求分析的基础上，提出了以高速公路基础信息库、空间要素数据库、决策模型参数库、安全管理对策库为主体的数据库整体框架，并介绍了各专题数据库的内容与结构，以及高速公路交通网络空间数据模型的设计。     

车车通信环境下考虑交通拥堵状态的碰撞时间混合分布建模研究

碰撞时间（TTC）是评价车车碰撞风险的有效指标，然而该指标分布规律受到交通状态影响。为研究车车（V2V）通信环境下不同交通状态的TTC分布规律，通过构建基于LTE-V技术的车车通信环境，开展实车实验获取4种典型城市道路中的驾驶数据。考虑加速度和航向角建立动态冲突辨识模型，计算车辆以任意角度接近时的TTC值；针对TTC值的结果出现多峰值现象，将交通流分为“拥堵、缓行、畅通”这3种状态，构建了考虑交通流状态的高斯混合模型以描述不同交通状态下的TTC分布规律，并采用最大期望（EM）算法进行参数求解。将所建高斯混合模型与负指数分布、对数正态分布、负指数/对数正态混合分布这3种传统的TTC分布模型进行对比，采用校正决定系数R2评价模型的拟合优度，并通过K-S检验验证模型的有效性。在此基础上，将所建高斯混合模型应用于非车车通信条件下不同交通状态的TTC分布拟合描述，进一步验证模型的适用性。结果表明:车车通信环境下“拥堵、缓行、畅通”这3种交通状态下的高斯分布均值逐渐增大，所处交通场景的碰撞风险依次降低；考虑交通状态的TTC高斯混合模型拟合优度为0.950 5，相较于其他TTC混合分布模型，拟合优度提升了0.057 5。      

Assessing the Potential Impacts of Connected Vehicles: Mobility,Environmental, and Safety Perspectives

The connected vehicle is a rapidly emerging paradigm aimed at deploying and developing a fully connected transportation system that enables data exchange among vehicles, infrastructure, and mobile devices to improve mobility, enhance safety, and reduce the adverse environmental impacts of the transportation systems. This study focuses on micromodeling and quantitatively assessing the potential impacts of the connected vehicle (CV) on mobility, safety, and the environment. To assess the benefits of CVs, a modeling framework is developed based on traffic microsimulation for a real network located in the city of Toronto, Canada, to mimic communication between enabled vehicles. In this study, we examine the effects of providing real-time routing guidance and advisory warning messages to CVs. In addition, to take into account the rerouting in nonconnected vehicles (non-CVs) in response to varying sources of information such as apps, global positioning systems (GPS), variable message signs (VMS), or simply seeing the traffic back up, the impact of fraction of non-CV vehicles was also considered and evaluated. Therefore, vehicles in this model are divided into; uninformed/unfamiliar not connected (non-CV), informed/familiar but not connected (non-CV) that get updates infrequently every 5 minutes or so (non-CV), and connected vehicles that receive information more frequently (CV). The results demonstrate the potential of connected vehicles to improve mobility, enhance safety, and reduce greenhouse gas emissions (GHGs) at the network-wide level. The results also show quantitatively how the market penetration of connected vehicles proportionally affects the performance of the traffic network. While the presented results are pertinent to the specifics of the road network modeled and cannot be generalized, the quantitative figures provide researchers and practitioners with ideas of what to expect from vehicle connectivity concerning mobility, safety, and environmental improvements.     

高速移动环境下的信道模型

对高速移动环境下的信道建模与测量活动进行了分类与总结,指出目前V2V信道建模与测量活动所存在的不足。首先对V2V信道建模的现状进行简单的介绍,给出信道冲击响应的一般表达式,论证信道建模的重要性;然后对目前国内外一些重要的信道建模与测量活动,特别是关于VTD对信道统计特性影响的测量活动进行了分类,将其按建模环境(几何的与非几何的)与环境中物体的分布(随机的与确定的)分为3个主要类型。最后,为了建立完善的信道模型,提出了未来信道建模所面临的挑战,为今后的信道建模与测量活动指引了方向。     

Understanding the socioeconomic characteristics of paratransit drivers and their perceptions toward electric three-wheeled rickshaws in Delhi,India

In India, electric rickshaws (ERs) prove to be a sustainable and affordable paratransit mode for the public. The ER service is also creating employment and income opportunities for the unskilled labor force. Many Indian state governments are proposing ER services to cater to first and last-mile trips. Therefore, planners must identify the significant factors that can affect ER services' adoption and expansion. Because of this, the present study investigates the perceptions of drivers of three prominent paratransit modes toward ERs. The research also provides a better understanding of the socio-economic conditions of these paratransit drivers. The study utilizes data of 620 paratransit drivers obtained from a face-to-face survey conducted in Delhi, India. Grey relation analysis is applied to assess the three paratransit driver groups' perceptions about ERs. The data reveals that paratransit drivers belong mostly to low financial and educational backgrounds. Male drivers constitute many paratransit drivers in the city. The lack of facilities such as designated parking and fixed charging stations and fare regulation is perceived as critical ER services barriers. Similarly, the absence of separate lanes and unsafe overtaking attempts by fast-moving vehicles are the major causes of accidents involving ERs. Further, the light body of ERs and careless driving and traffic rule violations of drivers in mixed traffic conditions are the primary safety issues. The study also highlights potential policy recommendations to design an efficient electric version of the paratransit service for achieving sustainable development goals.