Defense against misbehavior in anonymous vehicular ad hoc networks

Vehicular ad hoc network (VANET) can offer various services and benefits to VANET users and thus deserves deployment effort. Misusing such network could cause destructive consequences. It is therefore necessary to discourage misbehavior and defend VANET systems against it, in order to ensure correct and smooth operations of the network. In this paper, we review the techniques for handling misbehavior in VANETs, particularly where anonymous communications are desired to conserve user privacy since it adds more complexity to the defense against misbehavior. A new scheme is proposed to punish misbehaving users and can be employed in both inter-vehicle and vehicle-to-infrastructure anonymous communications. Our scheme leverages some threshold authentication technique that dynamically revokes a user’s credential, while providing the flexibility of whether to reveal the user’s identity and tolerating unintentional misbehavior such as hardware malfunctioning.     

基于演化图论的可靠的VANETs路由协议

车载网络（VANETs）属于移动无线网络的特例,具有鲜明的特性。传统无线网络的路由协议难以直接应用于VANETs。节点的高速移动,引起网络拓扑动态变化,导致VANETs的通信链路频繁断裂。高动态网络的链路可靠性问题引起广泛的关注。为此,针对高速公路VANETs的路由可靠性进行分析,对演化图论进行扩展,建立扩展后的演化图论模型（EEGM）,并利用EEGM获取VANETs拓扑的动态信息,从而预先获取可靠路由的信息。在此基础上,提出基于演化图论的可靠路由协议（EG-RAODV）。仿真结果表明,与同类的其他协议相比,提出的路由协议在分组传输率、端到端传输时延、路由请求消息率以及链路断裂数方面得到了提升。     

Robust geocast routing protocols for safety and comfort applications in VANETs

Routing in cooperative vehicular networks is a challenging task because of high mobility of vehicles and difficulty of localization. In this paper, we study the geocast routing problem in Vehicular Ad‐hoc NETworks (VANETs), which aims at delivering data to a specific group of mobile vehicles identified by their geographical location. Although many geocast routing protocols have been proposed, only partial inherent constraints of VANETs (such as mobility, internal network fragmentation problem, external network fragmentation problem, and overload) are taken into account. Therefore, we propose two novel and robust geocast routing protocols: the first one, called Robust Geocast Routing Protocol for Safety Applications (RGRP‐SA), is dedicated to road safety applications, while the second, namely, Robust Geocast Routing Protocol for Comfort Applications (RGRP‐CA), is designed for comfort applications. Simulations conducted in NS‐2 demonstrate that our safety‐oriented RGRP‐SA protocol outperforms Inter‐Vehicle Geocast protocol and Mobicast Routing Protocol in VANETs by sending up to 25% more packets, cutting the end‐to‐end delay in half, and solving the internal network fragmentation problem. Besides, it is also shown that our comfort‐oriented RGRP‐CA protocol serves well comfort applications with only light overhead by solving internal and external network fragmentation problems and providing more reliable data delivery (with a 25% higher packet delivery ratio) and higher network throughput utilization in comparison with Mobicast with Carry‐and‐Forward protocol. Copyright © 2015 John Wiley & Sons, Ltd.     

车联网环境下基于Cuckoo过滤器的轻量V2I认证算法

基于假名认证机制是保护车与路边设施间通信(V2I)隐私的有效方法,传统的基于证书撤销清单(CRL)方法存在通信和计算开销大的问题。为此,提出基于布谷鸟(Cuckoo)过滤器的轻量V2I认证算法(CFLA)。CFLA算法通过局部信任中心(LTA)给其覆盖内的车辆分配假名,并利用Merkle散列树(MHT)存储车辆假名,每辆车维持一棵独立MHT。同时,采用布谷鸟过滤器(CF)数据结构,降低存储、计算和通信开销。安全性能分析表明,提出的CFLA算法能够具有防御中间攻击、重放攻击的能力。相比于相关的同类算法,CFLA算法降低了认证开销。     

An Improved Cooperative Adaptive Cruise Control （CACC） Algorithm Considering Invalid Communication

For the Cooperative Adaptive Cruise Control （CACC） Algorithm, existing research studies mainly focus on how inter-vehicle communication can be used to develop CACC controller, the influence of the communication delays and lags of the actuators to the string stability. However, whether the string stability can be guaranteed when inter-vehicle communication is invalid partially has hardly been considered. This paper presents an improved CACC algorithm based on the sliding mode control theory and analyses the range of CACC controller parameters to maintain string stability. A dynamic model of vehicle spacing deviation in a platoon is then established, and the string stability conditions under improved CACC are analyzed. Unlike the traditional CACC algorithms, the proposed algorithm can ensure the functionality of the CACC system even if inter-vehicle communication is partially invalid. Finally, this paper establishes a platoon of five vehicles to simulate the improved CACC algorithm in MATLAB/Simulink, and the simulation results demonstrate that the improved CACC algorithm can maintain the string stability of a CACC platoon through adjusting the controller parameters and enlarging the spacing to prevent accidents. With guaranteed string stability, the proposed CACC algorithm can prevent oscillation of vehicle spacing and reduce chain collision accidents under real-world circumstances. This research proposes an improved CACC algorithm, which can guarantee the string stability when inter-vehicle communication is invalid.     

Fault tolerant time synchronization using offsets table robust broadcasting protocol for vehicular ad hoc networks

The requirement of time synchronization emerged in distributed systems remains one of the most significant issues that should be addressed to the extent of that systems evolve. As clock synchronization is important for any type of network, Vehicular Ad hoc networks (VANETs) are being considered for their basic communication platforms, but also for providing the ability to detect movement, location, proximity, and other network capabilities. The intrinsic characteristics of VANETs like: the high speed of nodes and the lack of permanent network connectivity generated by an instable environment, which make communication difficult or temporarily impossible, have created new challenges. These challenges make solutions that have been already proposed for classical networks no longer appropriate. Therefore, to overcome this deficiency, new and adaptive clock synchronization mechanisms should be devised and implemented, dealing so with communication and scalability issues. In this paper, we propose “Offsets Table Robust Broadcasting” (OTRB) algorithm. In this algorithm, instead to each node communicates with its vicinity, a set of nodes is selected to spread the time information over the entire network. The proposed time synchronization protocol is well-adapted to random network topology changes, high nodal velocity while offering good precision and robustness against nodal failure and packet loss. The analytical study and protocol simulation for evaluating the system performance, carried out by a combination of VanetMobiSim and NS2 simulators, have yielded convincing results, outperforming those exhibited by the basic referred protocols.     

A rate control video dissemination solution for extremely dynamic vehicular ad hoc networks

Video dissemination to a group of vehicles is one of the many fundamental services envisioned for Vehicular Ad hoc Networks, especially as a building block for entertainment applications. For this purpose, in this paper we describe VoV, a video dissemination protocol that operates under extremely dynamic road traffic conditions. Contrary to most existing approaches that focus exclusively on always-connected networks and tackle the broadcast storm problem inherent to them, VoV is designed to operate under any kind of road traffic condition. We propose a new geographic-based broadcast suppression mechanism that gives a higher priority to rebroadcast to vehicles inside especial forwarding zones. Furthermore, vehicles store and carry received messages in a local buffer in order to forward them to vehicles that were not covered by the first dissemination process, probably as a result of collisions or intermittent disconnections. Finally, VoV employs a rate control mechanism that sets the pace at which messages must be transmitted according to the perceived network data traffic, thus avoiding channel overloading. Therefore, VoV adapts not only to the perceived road traffic condition, but also to the perceived channel quality. When compared to two related and well-accepted solutions–ABSM and AID–under Manhattan grid and real city scenarios, we show that, overall, our proposal is more efficient in terms of message delivery, delay and overhead.     

An intelligent hybrid prairie dog optimization algorithm-based stable cluster reliable routing scheme for VANETs

Vehicular ad hoc network (VANET) is most significant for supporting intelligent transportation system (ITS)-based technologies, but it gets hurdled by sparse distribution of vehicles on highways, and dynamically challenging topology that arises due to increase in traffic. Hence, energy stable and optimized cluster construction maximizes the network lifetime. In this paper, Hybrid Prairie Dogs and Beluga Whale Optimization-based Node Clustering (HPDBWOA-NC) mechanism is proposed with the parameters of highway route, node velocity, number of vehicular nodes, and communication for achieving stable cluster construction in VANETs. It is proposed with the balanced exploration and exploitation potential of Prairie Dog Optimization Algorithm (PDOA) and Beluga Whale Optimization Algorithm (BWOA) for establishing optimal clusters that increase the network stability during the routing process. It integrated the exploration and exploitation capabilities of PDOA and BWOA and confirmed better optimized clusters which confirmed reliable data delivery by preventing the issue of premature convergence. It constructed clusters and selected cluster heads (CHs) depending on the fitness factors of energy, interdistance between vehicles, communication range, and vehicular density. The results of the proposed HPDBWOA-NC generated optimal number of CHs in the network which is comparatively 34.21% better than the benchmarked mechanisms. The mean throughput and packet delivery ratio (PDR) achieved by the proposed HPDBWOA-NC are identified to be significantly improved by 25.48% and 28.91% better than the investigated metaheuristic clustering protocols. The statistical study also guaranteed an increased factor of 81, during the processing of optimizing the clusters during the employment of ITS applications in VANETs.     

基于区块链的车联网信任机制

车联网（VANETs）中虚假的共享信息会导致负面影响。针对车辆间的信任缺失现象,提出了一种基于区块链的信任解决方案。通过引入贝叶斯推理,基于先验概率进行信任评估,综合考虑了消息可信度和源节点自身可信度。通过超级账本实现信任管理,路侧单元（RSU）将汇聚车辆提交的评价形成信任值并创建区块,利用智能合约进行信任值初始化、查询和更新操作。仿真结果显示,提出方案能有效进行信任评估,准确识别虚假消息。同时与现有方案对比表明,该方案具有更高吞吐量和更低时延,适用于车联网的轻量级资源消耗环境。     

IGR:面向车载网的基于地理信息的数据传输协议

由于车辆的高速移动和拓扑的动态变化,基于地理信息的数据传输协议被广泛应用于车载网.然而,现存的多数协议在路由决定时并没有考虑链路的质量,导致数据包丢失率升高,增加了传输时延.为此,提出了新的基于地理信息的数据包传输协议(IGR).IGR协议在路由决策时充分考虑车辆的移动方向、位置和链路质量3项信息.其中,利用beacon接收率体现链路质量.将这3项信息融合成节点权值.源节点择优选择权值高的节点作为下一跳转发节点.与同类协议相比,提出的IGR协议具有低的传输时延和高的传输率.