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.     

Perception for collision avoidance and autonomous driving

The Navlab group at Carnegie Mellon University has a long history of development of automated vehicles and intelligent systems for driver assistance. The earlier work of the group concentrated on road following, cross-country driving, and obstacle detection. The new focus is on short-range sensing, to look all around the vehicle for safe driving. The current system uses video sensing, laser rangefinders, a novel light-stripe rangefinder, software to process each sensor individually, a map-based fusion system, and a probability based predictive model. The complete system has been demonstrated on the Navlab 11 vehicle for monitoring the environment of a vehicle driving through a cluttered urban environment, detecting and tracking fixed objects, moving objects, pedestrians, curbs, and roads.     

A Resilient and Scalable Flocking Scheme in Autonomous Vehicular Networks

Vehicular Ad hoc NETworks (VANET) is emerging as a highly promising technology, which aims to provide road safety, environment protection and personal-oriented services. The vehicle ad hoc wireless communications form an indispensable part of truly ubiquitous communications networking. VANET is formed by spontaneously moving autonomous vehicles with the self-organization and self-management capability. In this paper, we focus on the decentralized coordination of multiple unmanned vehicles such that they can freely move and adaptively cooperate in a complex environment. During this procedure, flocking is one of the key operations and requirements. Here, flocking refers to the formation and maintenance of a desired pattern by a group of mobile vehicles without collision during movement. We propose a resilient and scalable flocking scheme for a group of vehicles, which follows the leader–followers moving pattern. In the absence of obstacles, a collision avoidance algorithm is presented to maintain a desired distance among vehicles. This will ensure information completeness and is significant in certain mission critical situations without collision between a unmanned vehicle and its neighboring vehicles. In the presence of obstacles in an environment, this algorithm is able to avoid collision between a vehicle and its neighbor (either a neighboring vehicle or a neighboring obstacle). Theoretical proof has been presented to demonstrate the effectiveness and correctness of the algorithm to guarantee collision-free. In addition, with increasing number of vehicles, the performance of the proposed flocking scheme performs without increasing the processing overhead, which demonstrates the desirable scalability.     

A Mobicast Routing Protocol in Vehicular Ad-Hoc Networks

In this paper, we present a “spatiotemporal multicast”, called a “mobicast”, protocol for supporting applications which require spatiotemporal coordination in vehicular ad hoc networks (VANETs). The spatiotemporal character of a mobicast is to forward a mobicast message to vehicles located in some geographic zone at time t, where the geographic zone is denoted as zone of relevance (ZOR). Vehicles located in ZOR at the time t must keep the connectivity to maintain the real-time data communication between all vehicles in ZOR. The connectivity is kept of all vehicles in ZOR through the vehicular ad hoc networks (VANETs). The connectivity of ZOR is lost if any vehicle in ZOR suddenly accelerates or decelerates its velocity. The temporal network fragmentation problem is occurred such that vehicle in ZOR cannot successfully receive the mobicast messages. To solve the problem, a new mobicast protocol is presented in this work to successfully disseminate mobicast messages to all vehicles in ZOR via a special geographic zone, called as zone of forwarding (ZOF). The main contribution of this work is to develop a new mobicast routing protocol to dynamically estimate the accurate ZOF to successfully disseminate mobicast messages to all vehicles in ZOR. To illustrate the performance achievement, simulation results are examined in terms of dissemination successful rate, packet overhead multiplication, packet delivery delay, and throughput.     

智能汽车技术发展趋势

机电信息系统的高性能化发展使智能汽车成为可能。智能汽车可以通过感知驾驶环境(人-车-路)并提供信息和车辆控制,帮助或替代驾驶员进行最安全、最高效、最舒适的车辆操控。本文从交通安全、节能减排、城市/交通规划这几个角度入手,分析了当前智能汽车技术对汽车产业乃至整个社会的影响,对自动驾驶汽车技术的发展现状进行了综述。基于以上分析对智能汽车技术的发展趋势和前景进行了讨论。     

双卡技术在涉车系统中的实现研究

机动车被盗正日益成为人们关心的社会问题,超高频(UHF)频段射频识别(RFID)双卡技术迎合需求,不仅实现机动车的主动防盗,还能防止运营车辆的违规驾驶。双卡技术包括固定式配对和弹性绑定配对,在整个涉车管理中将机动车与驾驶员作为两个对象分别采用车卡与驾驶员卡两种证件进行管理。固定式配对可在双卡发行时实现,而弹性配对可通过计算机电话集成(CTI)技术、网页(WEB)技术等手段实现。双卡技术的上述功能在应用示范中得到了很好的印证,为涉车管理提供一条新途径。     

一种基于RTRL的神经网络驾驶员巡航模型

针对大多数巡航模型未能充分考虑驾驶员的行为特性,文中设计了以实时递归学习算法的神经网络为核心的驾驶员巡航模型。该模型选取前车车速、本车车速、前车加速度和安全车间距共4个参数作为模型输入,以驾驶员控制自车所期望的加速度值为输出,通过真实环境下的巡航实验获取数据样本对RTRL的神经网络进行训练,并对该模型进行仿真验证。仿真实验结果表明,本车期望加速度的预测值与实际真实值基本一致,误差控制在005以内,说明该模型能较准确的模拟驾驶员的巡航行为。     

Adaptive on-line parameter identification of a steer-by-wire system

Adaptive compliance control strategy can be a significant advantage for control of steer-by-wire systems. Initially the method is proposed for robotic applications where the main concern is the interaction forces between the robot and its environment. There are several studies about cooperative working of a robot and a human. As long as the steering system is a part of the vehicle where driver interaction is involved, it is reasonable to think that compliance control strategies can be adapted to steer-by-wire systems. Compliance control is a model reference control (MRC) strategy where the measured external force/torque is used as an input to a reference model to calculate its output and where the real system is controlled appropriately to track the reference system output. If a sensor is available to measure the external force/torque, system parameters need not to be estimated. A constant gain feedback controller can be used in such a case. However, if the parameter variations of the system are not within certain bounds, a model reference adaptive controller (MRAC) is needed. In addition to this, examining the change in the dynamics of the system due to the compliance of the driver arms is not possible by direct MRAC, because the driver effect is considered as a disturbance in this strategy. Therefore, in this study, instead of estimating controller parameters using direct MRAC where the main concern is the tracking performance, it is considered to use indirect MRAC in which the system parameters are estimated to observe their variations in the presence of parametric uncertainty and disturbances and to further examine the change in the dynamics of the system due to the compliance of the driver arms forming a closed kinematic structure by constraining the steering wheel. Hence, a steer-by-wire experimental setup including driver interaction and vehicle directional control units has been developed and three well-known adaptive on-line estimation methods, which are output-error method, equation-error method and modified recursive least squares method are evaluated on the driver interaction unit. These three methods are compared in terms of computational complexity, convergence, stability and applicability to real vehicles.     

Cooperation Enhancement for Message Transmission in VANETs

As one special case of the Mobile Ad Hoc Networks (MANET), vehicular ad-hoc networking (VANET) is featured by its high mobility and constantly changing topology. In VANET, nodes can work properly only if the participating vehicles cooperate with each other during communications. However, as a distributed network, individual vehicles might be non-cooperative for their own benefits. In order to prevent non-cooperative vehicles from tampering packet relaying in the network, we propose a cooperation enhancement mechanism using “Neighborhood WatchDog” to generate “Trust Token” based on the first-hand observation. Therefore, trust relationships and packet-acceptance decisions of the receiving nodes are based on the instant observation and the token-proved relaying behavior of the benign neighboring vehicles. With the inherit mapping between the Electronic ID of one vehicle and its public key, keys can be distributed on-the-fly. As a network layer solution, the cooperation enhancement mechanism proposed in this paper is built on the top of our previous proposed Media Access Control (MAC) protocol: Relative Position Based-MAC (RPB-MAC).     

A code-pattern-driven digital background calibration technique for SAR ADCs

The article presents the buck converter for the application on headlights of vehicle with chip-level design. The LED components are used as for lighting source, which near/far lights are controlled with high-current switching circuit in the chip. The level-shift circuit and its current driver is proposed to control the input of high-voltage power MOS. The bypass method is presented to reduce the transient time as load current changes suddenly. The input voltage widely ranges from 8 to 21 V while keeping a stable output voltage with 6 V. The chip current can output from 20 to 1500 mA with excellent regulation. This chip had been implemented with TSMC0.25 µm HV- process, and the size of the circuit layout is about 8.6 mm², where includes power switch and far/near lighting switches. Measurements show that peak efficiency can achieve 86.3%. The power regulation is excellent, where the load regulation is only 0.3%, and the line regulation is only 0.5%.

     

Mixing greedy and predictive approaches to improve geographic routing for VANET

In recent years, thanks to the development and popularization of wireless network technologies, the issue of vehicular ad hoc network (VANET) has received great attention, and more and more VANET‐related researches have been brought up. Generally speaking, the biggest difference between VANET and traditional ad hoc network is the velocity of carriers because in VANET, the velocity of vehicles, the carriers, is much higher than those in traditional ad hoc. Therefore, it would be a great challenge to forward data efficiently in VANETs and many researches proposed have focused on the development of routing protocols. The current proposed routing protocols are all assumed to simulate in a distributed and ideal environment. As for the complex geographic environments, such as urban scenarios, extra amendments must be needed to improve the efficiency of the routing protocols. Thus, the main purpose of this paper is to design a suitable routing protocol for urban scenarios with better performance and adaptability. For this reason, greedy on straight roads and predictive at the intersections (GSPI) routing protocol is proposed to use greedy mode on straight roads and to use predictive mode at the intersections. In greedy mode, we choose the next hop according to the weight value that combines the distances and multi‐rate. In predictive mode, we predict the directions of the vehicles to determine the next hop. The simulation results reveal that our proposed algorithm indeed proves its feasibility. Copyright © 2010 John Wiley & Sons, Ltd.     

On the characteristics of routing paths and the performance of routing protocols in vehicle‐formed mobile ad hoc networks on highways

Recently, intelligent transportation systems (ITS) is becoming an important research topic. One goal of ITS is to exchange information among vehicles in a timely and efficient manner. In the ITS research community, inter‐vehicle communications (IVC) is considered a way that may be able to achieve this goal. An information network built on the top of vehicles using IVC can be viewed as a type of mobile ad hoc networks (MANETs). In the past, several unicast routing protocols for MANET have been proposed. However, most of them are designed for general MANETs rather than for IVC networks. In this paper, we first used more realistic vehicle mobility traces generated by a microscopic traffic simulator (VISSIM) to understand the characteristics of routing paths in an IVC network. Based on the insights gained from the derived path characteristics, we designed and implemented an intelligent flooding‐based routing protocol for small‐scale IVC networks. Via several field trials conducted on highways, we compared the performance of ad hoc on‐demand distance vector (AODV) and our protocol. Our experimental results show that (1) our protocol outperforms AODV greatly in IVC networks and (2) our protocol can provide text, image, audio, and video services for small‐scale IVC networks (e.g., a platoon) quite well. Copyright © 2009 John Wiley & Sons, Ltd.     

A mobicast routing protocol with carry‐and‐forward in vehicular ad hoc networks

In vehicular networks, safety and comfort applications are two quite different kinds of applications to avoid the emergency traffic accident and enjoy the non‐emergency entertainment. The comfort application drives the challenges of new non‐emergency entertainments for vehicular ad hoc networks (VANETs). The comfort application usually keeps the delay‐tolerant capability; that is, messages initiated from a specific vehicle at time t can be delivered through VANETs to some vehicles within a given constrained delay time λ. In this paper, we investigate a new mobicast protocol to support comfort applications for a highway scenario in VANETs. All vehicles are located in a geographic zone (denoted as zone of relevance (ZOR)) at time t; the mobicast routing must disseminate the data message initiated from a specific vehicle to all vehicles that have ever appeared in ZOR at time t. This data dissemination must be performed before time t + λ through the carry‐and‐forward technique. In addition, the temporary network fragmentation problem is considered in our protocol design. Also, the low degree of channel utilization is kept to reserve the resource for safety applications. To illustrate the performance achievement, simulation results are examined in terms of message overhead, dissemination success rate, and accumulative packet delivery delay. Copyright © 2012 John Wiley & Sons, Ltd.     

SiLK™ etch optimization and electrical characterization for 0.13 μm interconnects

This paper is focused on the optimization of reactive ion etching (RIE) process of low-k polymeric spin-on dielectric (SOD) material, SiLK™ (Trade mark of Dow Chemical, USA), for 0.13 μm Cu-low-k interconnects technology and subsequent electrical characterization of the metallization. Damascene metallization of SiLK™ film was integrated with dual hardmask scheme and “trench first” approach. Etch processes for single damascene metal trench and dual damascene via and metal2 trench structures were developed and evaluated. Effect of SiN and SiC films used as one of the hard mask layers and copper cap layers for single and dual damascene formation were also evaluated. The advantages of using SiC over SiN layer as one of the (bottom) dual hardmask layers were demonstrated through the results of electrical performance. Integration issues related to process development were analyzed and discussed. Electrical and reliability performance of testing vehicles associated to different etch criteria were studied. Electrical yield of >90% was obtained for the structures under study, which indicated the wide process margin. The consistency of processes was further demonstrated through the successful integration of eight metal layers with SiLK™ dielectric film.     

Temperature profile effects in accelerated thermal cycling of SnPb and Pb-free solder joints

Accelerated thermal cycling (ATC) has been widely used in the microelectronics industry for reliability assessment. ATC testing decreases life cycle test time by one or more of the following means: increasing the heating and cooling rate, decreasing the hold time, or increasing the range of the applied temperature. The relative effect of each of these cycle parameters and the failure mechanisms they induce has been the subject of many studies; however uncertainty remains, particularly regarding the role of the heating and cooling rate. In this research, three conditions with two ramp rates (14 °C/min and 95 °C/min) and two temperature ranges (ΔT = 0–100 °C and −40 to 125 °C) were applied to resistor 2512 and PBGA 256 test vehicles assembled with SnPb and Pb-free solders. The test results showed that the higher ramp rate reduced the testing time while retaining the same failure modes, and that the damage per cycle increased with the temperature difference. For the resistors, the Pb-free solder joints lasted longer than the SnPb joints at the smaller ΔT, but were inferior at the larger ΔT. In contrast, the Pb-free solder joints in the PBGA test vehicles lasted longer than the SnPb solder under both conditions.     

Consumer Vehicle Telematics — An Emerging Market Where Web Services

This paper examines how Web Services can be used to provide a shared infrastructure in an emerging area of consumer communications, namely consumer vehicle telematics. The paper reviews the key advantages which Web Services offer from a service provider's viewpoint — namely openness, reuse and ease of integration with legacy systems. The paper then goes on to examine why the consumer vehicle telematics industry is an area where point solutions have been developed. It then explores why legislation, changes in industry dynamics and the growing use of electronics in vehicles make the use of Web Services, in the software platform supporting the applications, an attractive proposition. Using a scenario-driven approach, it is shown how Web Services can be employed to provide reusable components which can make applications available for vehicle manufacturers, vehicle dealers, legislators and third-party service providers. These applications can be used to provide information to drivers, occupants and vehicles themselves. The paper also presents a brief review of the emerging competitive environment. This revised version was published online in July 2006 with corrections to the Cover Date.     

Adaptive rate control algorithm based on logarithmic R–Q model for MPEG-1 to MPEG-4 transcoding

This paper proposes an adaptive rate control algorithm for MPEG-1 to MPEG-4 transcoder for video internetworking where a compressed video is transmitted through networks of different capacities. It is based on an adaptive logarithmic R–Q (rate-quantization) model for controlling the new target bit-rate of a transcoded MPEG-4 bitstream. In R–Q modeling, the R–Q characteristics predicted from a previous picture of the same picture type are used in combination with the R–Q data measured for the current picture. The proposed adaptive model takes into account the effect of picture dependencies arising in motion-compensated video coding. Furthermore, full advantage is taken of the special situation related to transcoding where a priori knowledge of the current R–Q data can be obtained by just counting the number of bits in the input bitstream without re-encoding. It is shown by simulation that the adaptive R–Q model-based rate control can efficiently control the output bit-rate to match the target bit-budget.     

GOLD: a parallel real-time stereo vision system for genericobstacle and lane detection

This paper describes the generic obstacle and lane detection system (GOLD), a stereo vision-based hardware and software architecture to be used on moving vehicles to increment road safety. Based on a full-custom massively parallel hardware, it allows to detect both generic obstacles (without constraints on symmetry or shape) and the lane position in a structured environment (with painted lane markings) at a rate of 10 Hz. Thanks to a geometrical transform supported by a specific hardware module, the perspective effect is removed from both left and right stereo images; the left is used to detect lane markings with a series of morphological filters, while both remapped stereo images are used for the detection of free-space in front of the vehicle. The output of the processing is displayed on both an on-board monitor and a control-panel to give visual feedbacks to the driver. The system was tested on the mobile laboratory (MOB-LAB) experimental land vehicle, which was driven for more than 3000 km along extra-urban roads and freeways at speeds up to 80 km/h, and demonstrated its robustness with respect to shadows and changing illumination conditions, different road textures, and vehicle movement.     

New challenges to the modelling and electrical characterisation of ohmic contacts for ULSI devices

Continuing developments in semiconductor process and materials technology have enabled significant reductions to be achieved in the contact resistance R_c of devices. This reduction is commonly assessed in terms of the specific contact resistance (SCR) parameter ρ_c (Ω cm²) of the metal–semiconductor interface. Such a reduction in SCR is essential, for as device dimensions decrease, then so also must ρ_c and the corresponding contact resistance in order not to compromise the down-scaled ULSI device performance. Thus the ability to accurately model contacts and measure ρ_c is essential to ohmic contact development. The cross kelvin resistor (CKR) test structure is commonly used to experimentally measure the Kelvin resistance of an ohmic contact and obtain the specific contact resistance ρ_c. The error correction curves generated from computer modelling of the CKR test structure are used to compensate for the semiconductor parasitic resistance, thus giving the SCR value. In this paper the increased difficulty in measuring lower ρ_c values, due to trends in technology, is discussed. The challenges presented by the presence of two interfaces in silicided contacts (metal-silicide–silicon) is also discussed. Experimental values of the SCR of an aluminium–titanium silicide interface is determined using multiple CKR test structures.     

基于车车通信的车辆防碰撞算法

为了提前预测车辆碰撞事故和降低碰撞事故发生概率,提出了基于车车通信的车辆防碰撞算法（VACA）。VACA根据自身和周围邻居车辆的北斗位置坐标,在水平和垂直两个方向上分别采用Kalman预测算法预测下一时刻的车辆行驶状态,采用数据预判断方法直接确定一定发生碰撞或不发生碰撞的情况。当不能直接判断时,则计算加速度可变下的安全距离,建立和求解碰撞状态预测模型,获得碰撞预测时间最小值。如果该最小值小于阈值,则发出报警信号提醒驾驶员。仿真结果表明,与基于车辆间通信的智能防碰撞报警模型（IVCWM）和车辆提前预警的防碰撞算法（ECWA）比较,VACA可提前发现碰撞情况,而且更准确,有一定的应用价值。