Implementation trade-offs for a short-headway vehicle-follower automated transit system

An important aspect in the design of automated guideway transit (AGT) systems is the communication requirements for the longitudinal control of vehicles, that is, the requirements to measure vehicle states, transmit this information between vehicles, and subsequently control the individual vehicles. This paper examines the trade-offs in the data rates, word lengths, and allowable transmission time lags needed to maintain an acceptable level of vehicle performance, and how these requirements relate to the allocation of control computation between vehicle- and wayside-based computers. A nonlinear control law designed for short-headway vehicle-follower systems provides a baseline to examine these trade-offs. The specification of the parmeters entering the problem is approached through analytically derived results, using simplified linear models with verification and expansion of these results through a detailed simulation.     

A state-constrained vehicle-follower approach to the station-egress problem

Vehicle following represents one approach to the longitudinal control of vehicles in an automated guideway transit (AGT) system. Requirements for the use of such control for the merging of a vehicle from an off-line station into a mainline vehicle stream are discussed. Recently, a technique has been developed that incorporates state-variable constraints into the control law of a vehicle-follower controller. A successful application of this technique to the station-egress problem has been formulated which safely merges the egressing vehicle between two vehicles initially operating at minimum headway on the mainline. It is demonstrated that for short headway operations of approximately three seconds or less, the finite length of station ramps introduces to the developed control laws an additional constraint, which must be implemented to assure safe operations. Finally, design trade-offs are shown to exist between the egress ramp lengths and the relative disturbances to mainline traffic as a result of station-egress maneuvers.     

区块链赋能的6G零信任车联网可信接入方案

6G网络将带来全场景按需服务泛在智能新范式,其中可信可靠网络服务是泛在智能的关键技术指标。该文面向6G零信任网络的通信需求,以区块链为“信任桥梁”,研究6G车联网边缘计算中的可信可靠接入管理方法。首先,采用基于2次剩余的零知识身份验证算法,在不暴露车辆隐私的前提下完成基站和车辆之间的相互验证与授权。然后,为提高验证效率并节省基站能耗,建立了基于契约理论的路侧冗余算力激励模型,将基站的一部分验证任务分配给边缘服务器或停泊车辆,再给予相应的报酬。最后,建立了基于双层区块链的6G零信任车联网架构,利用基站群维护的主链与边缘算力维护的辅链记录车联网身份验证的重要参数,实现零信任网络环境的可信接入。通过与现有方法比较,该文所述方法在不泄露车辆隐私的前提下显著提升了车辆验证效率,降低了基站能耗,具有更高的安全性。     

QoS-aware Two-level Dynamic Uplink Bandwidth Allocation Algorithms in IEEE 802.16j Based Vehicular Networks

Wireless communications play an important role in improving transportation environment safety and providing Internet access for vehicles. This paper proposes a QoS-aware two-level uplink dynamic bandwidth allocation (DBA) algorithm for IEEE 802.16j-based vehicular networks. IEEE 802.16j is an extension of standard IEEE 802.16 to support relay mode operation where traffics from/to subscriber stations (SS) are relayed to/from a base station (BS) via a relay station (RS). In such a vehicular network, the IEEE 802.16j BSs are installed along a highway, RSs are installed in large vehicles such as coaches, and the 802.16j interface is equipped on SSs such as individual passengers’ mobile devices within a moving coach. In the proposed DBA algorithm, a utility function, which considers characteristics of different types of services, is designed. The objective of the proposed two-level DBA algorithm is to allocate bandwidth to different types of services from BS to RSs and then from a RS to SSs with given quality of service (QoS) requirements. It aims at maximizing the utility of the overall network and minimizing the average queuing delay of the overall network. The simulation results show the effectiveness and efficiency of the proposed DBA algorithm.     

An optimized small-cell planning procedure for Heterogeneous Network to improve network energy efficiency

Cell planning in conventional networks has gained more attention as it directly affects the network performance and deployment cost. Existing cell planning methodologies are framed either with identical base stations or constructing a network without any infrastructure. But heterogeneous networks (HetNets) allow the service provider to deploy small cells over the region to enhance the network performance and signal coverage probability. Thus, a small-cell planning procedure is presented in this research work considering the low-powered base station and deployment cost to enhance the energy efficiency of the HetNet. An adaptive fuzzy expert system is used for cell dimensioning, and a nature-inspired ant colony optimization model is employed for automatic base station placement. Simulation analysis demonstrates that the proposed small-cell planning procedure attains better energy efficiency and user satisfaction ratio compared to conventional planning strategies. In the two cases of simulation analysis, the proposed model attains an average of 85% user satisfaction ratio for case 1 and 87% for case 2, which is better than existing strategies like density-based spatial clustering of applications with noise (DBSCAN), k-means, and number-based spatial clustering (NBSC) algorithms.     

Analysis and Design of Warning Delivery Service in Intervehicular Networks

This paper focuses on inter-vehicular networks providing warning delivery service. As soon as a danger is detected, the propagation of a warning message is triggered, with the aim of guaranteeing a safety area around the point in which the danger is located. Multiple broadcast cycles can be generated so that a given lifetime of the safety area is guaranteed. The service is based on multi-hop ad hoc inter-vehicular communications with a probabilistic choice of the relay nodes. The scenario we consider consists of high speed streets, such as highways, in which vehicles exhibit one-dimensional movements along the direction of the road. We propose an analytical model for the study of this service and derive performance indices such as the probability that a vehicle is informed, the average number of duplicate messages received by a vehicle and the average delay. Moreover, we use the model to discuss system design issues, which include the proper setting of the forwarding probability at each vehicle, so that a given probability to receive the warning can be guaranteed to all vehicles in the safety area. The model is validated against simulation results. Since it is very accurate, the model can be instrumental to the performance evaluation and design of broadcasting techniques in inter-vehicular networks.     

基于ARM Linux的3G无线车载视频监控系统

为了加强客运服务中心对长途车辆在客运过程的监管,提出了基于ARMLinux的3G无线车载视频监控系统。该系统基于ARMLinux嵌入式系统与ARM处理器,通过USB摄像头采集车内视频数据,由GPS定位模块获取车辆的位置数据,然后将采集的数据经过H．264压缩成适合网络传输的形式。最终通过3G无线发射模块经过具有宽带传输能力的3G移动通信网络传输给监控服务中心,监控服务中心可以看到车内清晰流畅的视频画面以及车辆所在位置。     

A buffer‐aware fleet‐based cooperative H.264/SVC streaming over vehicular networks

Because of of the characteristics of high mobility, time varying and dynamic topology, how to provide multimedia streaming service for connected vehicles becomes one emerging and popular technical research. The motivation of this paper is to utilize cooperation among neighboring vehicles for video streaming's quality improvement over vehicular networks. In the proposed cooperative streaming scenario, a connected vehicle requests a video stream from the Internet by using its 3G/3.5G interface, which may not have enough bandwidth to receive good quality of video. Thus, the vehicle is suggested to ask neighboring members belonging to the same fleet to download the requested video data by using their 3G/3.5G interfaces. Then, neighboring members should forward video data to the requested vehicle by using another wireless technique, for example, dedicated short range communication (DSRC). Regarding the differentiation between the two access networks, that is, 3G/3.5G network and DSRC network, a buffer‐aware scheduling mechanism based on layered streaming is designed in this paper to adapt to the networking situation of the vehicular networks. Two selection algorithms are proposed to select neighboring vehicles from the fleet. According to our simulation results, the 3G/3.5G‐based selection algorithm is suitable to improve video quality for vehicles at low speeds. On the other hand, the DSRC‐based selection algorithm can get better performance when vehicles move at high speeds or too many data are transmitted among vehicles.Copyright © 2013 John Wiley & Sons, Ltd.     

Seismic source model for moving vehicles

We develop a method for the loading of ground by moving vehicles in large finite-difference time-domain simulations of seismic wave propagation. The objective is to realistically produce two distinct types of ground loading for either wheeled or tracked vehicles in our propagation models: lower frequency loading associated with suspension dynamics and higher frequency impulsive loading associated with tire treads or wheels rolling over individual track blocks. These loading characteristics are important because field measurements show that vehicle ground forcing in both frequency bands produces seismic surface waves that networked sensors can remotely process for security applications. The method utilizes a vehicle-dynamics model to calculate a response to vehicle acceleration and ground features such as bumps; calculates forces transmitted to the ground; distributes these forces to staggered points of a finite-difference model; and simulates seismic wave propagation away from the vehicle. We demonstrate the method using bounce-and-pitch models of wheeled and tracked vehicles. We show that by carefully preprocessing force inputs, we can accurately simulate wave propagation and seismic signatures in finite-difference analyses of vehicles moving continuously over terrain.     

TOPVISOR: Two‐level controller‐based approach for service advertisement and discovery in vehicular cloud network

Vehicular cloud is a kind of mobile cloud in which vehicles share their resources and provide services for each other. The first step in establishing a vehicular cloud network is the service advertisement and discovery. Due to the dynamic nature of vehicular cloud networks, services are not continuous and the service location may vary at any time depending on the vehicle location. Therefore, higher network traffic is generated to access the consistent and up‐to‐date information. In this paper, a two‐level hierarchical approach is proposed for service advertisement and discovery in vehicular cloud networks. To register the services' specification in this approach, the distributed directories in RSUs and central controllers are used. Moreover, a method is used to avoid extra update packets by localizing the updates. The simulation results show improvement in the packet delivery rate as well as a reduction in transmission bandwidth preventing the network congestion.     

High capacity personal rapid transit system developments

High capacity personal rapid transit (HCPRT) is a system concept which utilizes small, 4 to 6 passenger, vehicles at very short headways on exclusive guideway networks. The automatic operation of small vehicles at headways of 1 s or less presents a major technical problem which is amenable to a combination of design approaches. This paper explores the effect of basic parameters such as vehicle length, reaction time, emergency and failed vehicle deceleration rates, and emergency jerk rate on potential minimum operating headway. The results of this analysis are then discussed in the context of five HCPRT programs.     

Traffic models for wireless communication networks

Introduces a deterministic fluid model and two stochastic traffic models for wireless networks. The setting is a highway with multiple entrances and exits. Vehicles are classified as calling or noncalling, depending upon whether or not they have calls in progress. The main interest is in the calling vehicles; but noncalling vehicles are important because they can become calling vehicles if they initiate (place or receive) a call. The deterministic model ignores the behavior of individual vehicles and treats them as a continuous fluid, whereas the stochastic traffic models consider the random behavior of each vehicle. However, all three models use the same two coupled partial differential equations (PDEs) or ordinary differential equations (ODEs) to describe the evolution of the system. The call density and call handoff rate (or their expected values in the stochastic models) are readily computable by solving these equations. Since no capacity constraints are imposed in the models, these computed quantities can be regarded as offered traffic loads. The models complement each other, because the fluid model can be extended to include additional features such as capacity constraints and the interdependence between velocity and vehicular density, while the stochastic traffic model can provide probability distributions. Numerical examples are presented to illustrate how the models can be used to investigate various aspects of time and space dynamics in wireless networks     

面向智能网联汽车边缘网络的分布式端-边协同算法

车联网高级安全服务中,智能网联车辆配备了摄像头,可以拍摄周围的视频,用于安全、交通监控和监视等目的。车辆将获取的视频上传到边缘计算节点后,可以对视频进行分析和备份,以满足不同的安全驾驶需求。然而,车辆连续直接向边缘计算节点上传生成的视频内容会非常消耗带宽,并消耗大量的能量。基于该问题,提出一种面向智能网联汽车边缘网络的分布式端-边协同算法。针对车联网高可靠低时延内容传输的特点,引入有限块长度编码机制。同时,引入车辆视频信息源的压缩编码功率消耗,建立车辆能耗模型。根据车辆视频信息源的视频质量要求,通过调整视频编码码率、信息源传输速率,以及车辆多路径路由的决策,提出一种完全分布式的优化算法,以提高网络资源利用率,并保证单个车辆的能耗公平性。     

An efficient adaptive intelligent routing system for multi‐intersections

With the rapid development of wireless technologies and the growing emphasis on vehicle safety, many vehicular ad hoc network applications have been extensively used. This study attempts to use vehicular ad hoc network technologies for autonomous driving to improve and reduce traffic congestion and vehicle waiting time. Therefore, this study proposes an adaptively intelligent routing system, which uses V2V communications to increase vehicle speed, allows vehicles to communicate with traffic control systems, arranges appropriate vehicle routes based on queuing theory, and uses traffic signals for information exchange. The timing of traffic signals is decided according to road traffic density. To decrease vehicle waiting time at intersections, every vehicle's speed is adjusted based on the distance between the vehicle and the traffic signals. In the simulation, automated vehicles and a more realistic car‐following model are taken into consideration and vehicle speeds are regulated based on speed limits and safe following distance on most roads. The simulation result reveals that our proposed adaptively intelligent routing system outperforms periodic system in average vehicle speed and average waiting time at both single and double cross intersections. Copyright © 2016 John Wiley & Sons, Ltd.     

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。     

基于动态评估模型的基站传输受限问题识别方法研究

本文提出一种基于基站传输带宽动态评估模型实现基站传输带宽受限问题识别的方法。该方法根据基站的实际业务模型建立基站动态传输带宽评估模型,并通过定义FEGE接收最大速率峰均比作为基站带宽受限问题的识别方法,该方法可以代替传统逐站灌包测试的验证方法,可实现对全网基站传输带宽的受限问题的快速识别和高效发现,极大地降低的人力物力及时间成本。     

HIMALIS-VI: Fast and Secure Mobility Management Scheme Based on HIMALIS for V2I Services in Future Networks

To overcome the inherent limitations of the current Internet architecture, such as lack of mobility support and security mechanism, research has begun on future Internet based on ID/locator split architecture. For the realization of future networks, it is necessary to consider the characteristics of their services and applications, as well as research on their basic architectures. The representative services include Cooperative Intelligent Transportation System (C-ITS) applications based on vehicle-to-vehicle/vehicle-to-infrastructure (V2V/V2I) communication which can prevent vehicular accidents, increase the efficiency of transportation systems, and reduce environmental pollution, all while improving passenger convenience. Since C-ITS services using V2I communication are tightly connected to both passenger and pedestrian safety, they require not only continuous network access but also secure communication regardless of the vehicle mobility. To provide continuous network access and secure communication to moving vehicles in future networks based on an ID/locator split approach, authentication and location updates of moving vehicles should be frequently performed, which results in significant signaling overhead. Therefore, to integrate V2I communication with an ID/locator split approach based on the (R1) HIMALIS architecture, in this paper we propose a novel mobility management scheme, called HIMALIS-VI, which can contribute to a delay reduction for the authentication and mitigating handover procedures at both the mobile hosts and network entities in an edge network.     

Profit-Based Routing for Multihop Coverage Extension in Wireless Networks

In future wireless systems, the coverage of a base station will decrease due to the characteristics of the channel at high-frequency bands. To expand the service coverage, a hybrid network that combines an ad hoc network with a cellular (or wireless LAN) network, appears to have great potential. In such systems, some mobile users outside the service area can access the network with the aid of other intermediate mobiles. However, this method incurs energy consumption in routing users, which could be a serious obstacle for wide-spread deployment of multihop wireless networks. Therefore we consider a revenue-cost model and propose a profit-based routing strategy that encourages routing users to actively participate in the relaying service because they are compensated for their energy consumption cost. Our strategy enables each mobile node to find an appropriate multihop path to a base station (or access point) that satisfies the interests of the service provider and the users. Numerical results show that our model successfully expands the network coverage area while ensuring the profit of each system involved.     

On minimizing the system information age in vehicular ad-hoc networks via efficient scheduling and piggybacking

Recent advances in vehicular networks have enforced researchers to focus on various information dissemination techniques. Exchanging information among the vehicles is imperative due to the ever-changing network topology in vehicular networks. However, random transmitter selection in traditional CSMA based channel access mechanism limits the delay performance. Data, such as state information, is often time critical, and hence, efficient information dissemination techniques to improve delay performance are essential. In this work, we aim to minimize the average system age which is the mean number of time slots old a vehicle’s information is at all other vehicles in the network. To achieve this, we explore the benefits of simultaneous transmission along with piggybacking of information for multi-hop communication. While allowing simultaneous transmission guarantees faster dissemination of information, piggybacking facilitates dissemination of more information per transmission, thereby keeping the network more updated. We have also analysed the relationship between piggybacked information and number of vehicles in the network. Simulation results show improvement in network performance. Our analytical results are in good agreement with the simulation results.