车间通信技术的研究

近年来,随着汽车的日益普及和汽车电子产业的迅速发展,人们利用车间通信技术来解决驾车安全问题,并帮助建立智能交通系统,提高交通管理效率.然而,高速移动、变化的汽车行驶环境,需要与之相应的通信和网络技术的支持.本文将介绍车间通信的主要应用以及实现车间通信的主流技术.     

Improving vehicular safety message delivery through the implementation of a cognitive vehicular network

The Wireless Access in Vehicular Environments (WAVE) protocol stack has been recently defined to enable vehicular communication on the Dedicated Short Range Communication (DSRC) frequencies. Some recent studies have demonstrated that the WAVE technology might not provide sufficient spectrum for reliable exchange of safety information over congested urban scenarios. In this paper, we address this issue, and present a novel cognitive network architecture in order to dynamically extend the Control Channel (CCH) used by vehicles to transmit safety-related information. To this aim, we propose a cooperative spectrum sensing scheme, through which vehicles can detect available spectrum resources on the 5.8 GHz ISM band along their path, and forward the data to a fixed infrastructure known as Road Side Units (RSUs). We design a novel Fuzzy-Logic based spectrum allocation algorithm, through which the RSUs infer the actual CCH contention conditions, and dynamically extend the CCH bandwidth in network congestion scenarios, by using the vacant frequencies detected by the sensing module. The simulation results reveal the effectiveness of our architecture in providing dynamic and scalable allocation of spectrum resources, and in increasing the performance of safety-related applications.     

Machine learning based cluster formation in vehicular communication

Telecommunication Systems - Nowadays vehicular communication has become a widespread phenomenon, which will cause spectrum scarcity. By utilizing the cognitive radio in vehicular communication can...     

Secure vehicular communication systems: design and architecture

Significant developments have taken place over the past few years in the area of vehicular communication systems. Now, it is well understood in the community that security and protection of private user information are a prerequisite for the deployment of the technology. This is so precisely because the benefits of VC systems, with the mission to enhance transportation safety and efficiency, are at stake. Without the integration of strong and practical security and privacy enhancing mechanisms, VC systems can be disrupted or disabled, even by relatively unsophisticated attackers. We address this problem within the SeVeCom project, having developed a security architecture that provides a comprehensive and practical solution. We present our results in a set of two articles in this issue. In this first one, we analyze threats and types of adversaries, identify security and privacy requirements, and present a spectrum of mechanisms to secure VC systems. We provide a solution that can be quickly adopted and deployed. In the second article we present our progress toward the implementation of our architecture and results on the performance of the secure VC system, along with a discussion of upcoming research challenges and our related current results.     

Secure vehicular data communication in Named Data Networking

Vehicular data misuse may lead to traffic accidents and even loss of life, so it is crucial to achieve secure vehicular data communications. This paper focuses on secure vehicular data communications in the Named Data Networking (NDN). In NDN, names, provider IDs and data are transmitted in plaintext, which exposes vehicular data to security threats and leads to considerable data communication costs and failure rates. This paper proposes a Secure vehicular Data Communication (SDC) approach in NDN to supress data communication costs and failure rates. SCD constructs a vehicular backbone to reduce the number of authenticated nodes involved in reverse paths. Only the ciphtertext of the name and data is included in the signed Interest and Data and transmitted along the backbone, so the secure data communications are achieved. SCD is evaluated, and the data results demonstrate that SCD achieves the above objectives.     

Mitigating adjacent channel interference in vehicular communication systems

In the last few decades, dedicated wireless channels were specifically allocated to enable the development and implementation of vehicular communication systems. The two main protocol stacks, the WAVE standards proposed by the IEEE in the United States and the ETSI ITS-G5 in Europe, reserved 10 MHz wide channels in the 5.9 GHz spectrum band. Despite the exclusive use of these frequencies for vehicular communication purposes, there are still cross channel interference problems that have been widely reported in the literature. In order to mitigate these issues, this paper presents the design of a two-stage FIR low-pass filter, targeting the integration with a digital baseband receiver chain of a custom vehicular communications platform. The filter was tested, evaluated and optimized, with the simulation results proving the effectiveness of the proposed method and the low delay introduced in the overall operation of the receiver chain.     

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。     

Transparent and conformal wheel-shaped fractal antenna for vehicular communication applications

In this article, a low cost, compact conformal antenna is proposed for vehicular communications applications. The concept of fractal geometry is applied in this design to make the model more attractive in its appearance as well as to attain desired bands in the vehicular communication spectrum. It is fabricated on a transparent and flexible poly vinyl chloride material of size 55 mm × 40 mm × 3 mm. The proposed antenna is intended to operate in GSM-1800/1900, Digital Communication System (DCS-1800), Personal Communication Service (PCS-1900), Universal Mobile Telecommunications System (UMTS), Long-Term Evolution (LTE2600), Industrial, Scientific, and Medical radio band (ISM 2.4G), Wireless local area network (WLAN), Bluetooth, World Interoperability for Microwave Access (WiMAX), IEEE802.11p protocol based Vehicle-to-everything, Dedicated short-range communications (DSRC) and Wireless Access in Vehicular Environments (WAVE) communications bands. The prototype of the antenna in its planar and conformal versions exhibit the wideband characteristics and their measured results show good agreement with that of obtained simulation results. The virtual analysis of platform mounted characteristics of the proposed antenna at two different locations of the vehicle (vehicle roof-top and on side-view mirror) are performed in ANSYS Savant simulation tool and the corresponding far-field radiation performance is characterized.     

大型多媒体网络通信中的安全监测平台设计

由于受到大型多媒体网络通信中不安全因素更新迅速的影响,导致以往设计出的大型多媒体网络通信安全监测平台监测能力和响应效果均不高。因而,设计监测能力强、响应效果好的大型多媒体网络通信安全监测平台。该平台的监控中心为数据采集模块,数据采集模块利用RTL8019AS控制器采集大型多媒体网络通信中的节点传输数据和通信节点安全状态数据,为处理模块提供统一格式的待测数据。处理模块利用MSP430处理器对待测数据进行安全检测,其与传输模块直接相连。传输模块会对已处理过的待测数据进行错误检测和传输,其处理流程在软件中给出,软件还给出平台功能图。实验结果表明,所设计的平台监测能力强、响应效果好。     

宽带高速车载环境中的分布式空时频编码

利用高速车载终端与基站宽带通信时信道的多径时变特性,提出一种分布式空时频编码方法.该方法通过选择车内空闲终端构成虚拟天线阵列进行协同编码,在不降低传输速率的前提下,能够获得信道中潜在的协同分集、时间分集和频率分集增益.理论分析表明:车载速度的提高使时间分集增益得以增强,正确解码中继个数的增加使协同分集增益得以增加.仿真...     

Design considerations of satellite-based vehicular broadband networks

Convergence between wireless networks is the main trend in current and future wireless communications. The distinct advantage of satellite and terrestrial network integration is the possibility to provide ubiquitous multimedia services in vehicles at any location. The key design considerations of mobile broadband satellite access technologies are given in this article. After presenting the conceptual models of a system and services, the design issues of satellite network synchronization and burst demodulation are described. The design considerations of medium access control, resource management, capacity, and buffer controls for internetworking are given. Also, the active antenna issues are provided along with a sample design.     

Information-centric dissemination protocol for safety information in vehicular ad-hoc networks

In vehicular networks, efficient safety information dissemination is a crucial issue. Unique characteristics of such an environment like highly mobility, fast topology changing, short-lived and intermittent connectivity pose challenges for safety information dissemination. Although IEEE 802.11p is standardized as an amendment to the IEEE 802.11 for connection-based wireless communication in vehicular environments (WAVE), it is still an open topic and a challenge to efficiently handle high mobility, intermittent connectivity, and spontaneous characteristics of vehicles on the roadway during wireless communication. This paper exploits information centric networking approach to design an efficient information dissemination protocol for such a challenging environment. The protocol is designed for both communication schemes in vehicular networks including vehicles-to-vehicles and vehicle-to-road. By focusing on information object itself, instead of end-to-end connection, the proposed mechanism supports fast and efficient data dissemination among multiple content consumers and multiple content providers, removing dependence on end-to-end connection between two nodes, thus improve the overall network performance. Through experimental results over different scenarios, we show that the proposed protocol achieves a significant improvement in term of the network performance compared to the conventional approach (WAVE).     

Broadcasting safety information in vehicular networks: issues and approaches

A primary goal of intelligent transportation systems is to improve road safety. The ability of vehicles to communicate is a promising way to alleviate traffic accidents by reducing the response time associated with human reaction to nearby drivers. Vehicle mobility patterns caused by varying traffic dynamics and travel behavior lead to considerable complexity in the efficiency and reliability of vehicular communication networks. This causes two major routing issues: the broadcast storm problem and the network disconnection problem. In this article we review broadcast communication in vehicular communication networks and mechanisms to alleviate the broadcast storm problem. Moreover, we introduce vehicular safety applications, discuss network design considerations, and characterize broadcast protocols in vehicular networks.     

浅析车载自组织网络通信系统的设计与实现

车载自组织是构成职能交通的重要组成部分,能够实现道路上的车辆之间、车辆与道路之间状况的互相通信。其通过车载自组织网络通信系统能够显著降低交通事故,为交通部分提供办案依据。文章主要对车载自组织网络通信系统的设计进行分析,并进一步探讨了车载应用系统实用化。     

Location- and delay-aware cross-layer communication in V2I multihop vehicular networks

Intelligent transportation systems are targeted to improve the traffic safety and driving experience of passengers. Vehicular ad hoc networks are wireless communication networks proposed to be used as parts of ITS. VANETs facilitate communication among vehicles, and between vehicles and roadside equipment. A key challenge in developing such systems is to design routing and MAC protocols that not only provide good end-to-end packet delay but can also quickly adapt to changes in the network topology due to vehicular mobility. In this article we outline a new framework for location- and delayaware cross-layer communication that addresses these challenges. Our framework provides an efficient V2I data delivery system that relays packets over low-delay paths to a fixed base station or access point. Furthermore, an instance of this framework is also presented as a protocol. Our preliminary evaluations show that our design approach is promising, and provides delay predictability, fairness, and a good packet delivery ratio.     

时变信道下ADF协作车载通信误码率分析

智能车载协作系统中车辆快速移动使得无线通信信道具有时变特性,为有效评估系统的误码性能,给出了符合车载时变信道的一阶自回归(AR1)模型,提出了一种基于AR1模型的自适应解码转发(ADF)协作误码率分析方法.该方法通过AR1模型的多普勒频偏相关系数来刻画时变信道特性,根据中继译码结果自适应选择是否协作转发,提升了智能交通系统的可靠性.此外,利用矩生成函数(MGF)推导出ADF协作下多进制正交幅度调制(M-QAM)信号误码率封闭表达式,并分析了车载移动速度和信道状态信息(CSI)估计精度对误码性能的影响.数值仿真结果表明,车载系统能通过增加CSI估计精度,有效地减少车载快速移动引起的误码平顶值.该方法相对于放大转发(AF)协作通信方式,平均误码性能提高约8.7 dB.     

Adapting contention-based forwarding to urban vehicular topologies for active safety applications

Contention-based forwarding (CBF) is a broadcasting technique used to disseminate emergency messages for traffic safety applications in intelligent transportation systems. Its design hypotheses have however been based on three major assumptions: uniform vehicular topology, nonfading channels and homogeneous communication capabilities. Realistic vehicular urban topologies do not comply with any of them, making CBF select relays, which may not exist, may not be reached or may not be optimal due to heterogeneous transmit capabilities. In this paper, we propose to adapt CBF to such challenging environment by first employing two different mechanisms as a function of the topology and second by considering the dissemination capabilities of the relays, allowing for example road-side units or tall vehicles to preferably act as relays when necessary. Our protocol, called Bi-Zone Broadcast, is evaluated in a realistic urban environment and showed to provide around 46 % improvement in dissemination delay and 40 % reduction in overhead compared to plain CBF or flooding. We finally shed light to other aspects of CBF that remain unsolved and should be addressed in future work to further improve the reliability of dissemination protocols for traffic safety protocols.     

Secure vehicular communication systems: implementation, performance, and research challenges

Vehicular communication systems are on the verge of practical deployment. Nonetheless, their security and privacy protection is one of the problems that have been addressed only recently. In order to show the feasibility of secure VC, certain implementations are required. In [1] we discuss the design of a VC security system that has emerged as a result of the European SeVe- Com project. In this second article we discuss various issues related to the implementation and deployment aspects of secure VC systems. Moreover, we provide an outlook on open security research issues that will arise as VC systems develop from today?s simple prototypes to fullfledged systems.     

车载鲨鱼鳍式超宽带多功能天线的研制

设计了一种用于车载应用的新型超宽带鲨鱼鳍天线。该天线工作频域覆盖了应用于车载通信的四个宽频带(824~960 MHz、 1 710~ 2 170 MHz、 2 300~ 2 690 MHz 以及3 300~ 5 000 MHz ),使得该天线系统集卫星导航、移动通信、WiFi、蓝牙、FM收音等多功能性于一体。主集天线尺寸为50 mm ×42 mm ×1.6 mm ,且由1/4椭圆单极子枝节和矩形单极子枝节组成,并将天线垂直放置在鲨鱼鳍式金属板上,从而方便了天线的制作和加工。仿真结果表明,全频段驻波比小于4 dB,全频段天线隔离度小于-15 dB ,且包络相关系数(Envelope Correlation Coefficient,ECC)小于0.1。与最大增益和辐射效率方面的实测值相比,该天线的模拟结果显示出良好的一致性,可广泛应用于车载通信系统中。