Privacy preserving broadcast message authentication protocol for VANETs

Vehicular Ad-hoc Networks (VANETs) will start becoming deployed within the next decade. Among other benefits, it is expected that VANETs will support applications and services targeting the increase of safety on the road, and assist in improving the efficiency of the road transportation network. However, several serious challenges remain to be solved before efficient and secure VANET technology becomes available, one of them been efficient authentication of messages in a VANET. There is a significant body of research work addressing this issue, however, while progress has been made, the challenge is still far from having been resolved and reliable and secure systems ready for deployment becoming available. In this paper, we propose the Privacy Preserving Broadcast Message Authentication (PPBMA) scheme, which, instead of performing asymmetric verification, uses Message Authentication Code (MAC) functionality and HASH operations to authenticate messages. Moreover, we use two-level key hash chain, which assists avoiding message losses. Simulation results demonstrate that PPBMA has superior performances in terms of packet loss rate and message delivery latency when compared to existing solutions. Due to this advantage, it can support emergency and routine messages alike, while existing solutions can only support routine messages.     

基于密度和距离的多跳广播转发节点选择方案

多数车联网VANET(Vehicular Ad Hoc Network)的安全应用均采用多跳广播方式分发安全消息。现已提出了许多的多跳广播转发节点选择方案,但它们以减少转发节点数为目的。为此,提出基于密度和距离的多跳广播转发节点选择方案DDBFS(Density-Distance based multi-hop Broadcast Forwarder Selection scheme),记为DDBFS。DDBFS方案主要解决两个问题：密集区域的冗余广播和稀疏区域的高的传输时延。在提出的DDBFS方案中,节点在决策是否转播接收的消息前,依据距离和网络密度设置定时器,一旦定时完毕,且在定时期间,没有其他节点转发该消息,该节点就成为下一跳转发节点。仿真结果表明,与现有的方案相比,提出的DDBFS协议在重播次数和传输时延性能得到显著提高。在密集区域,消息重播次数下降了约57%,在稀疏区域,传输时延缩短了约82%。     

车载自组织网络中的数据分发机制

车载自组织网络（vehicular ad-hoc network,简称VANET）作为一种新型的移动自组织网络,应用前景广阔.鉴于长距离数据分发机制是支撑VANET应用的一个不可或缺的机制,提出了一种VANET下路边单元（roadsideunit,简称RSU）辅助的数据分发机制Ara,并在不同的交通场景下对其性能进行了评估.实验结果表明,即使在有RSU出现故障的情况下,Ara也可以保证较高的数据到达率、较小的延迟和较低的消息开销.同时,通过建立分析模型对Ara的数据传递延迟进行了理论分析.该分析模型建立在车辆的微观流模型之上,可以推导出不同RSU 部署场景下的数据传递延迟.模拟实验结果验证了模型的正确性,因此该分析模型可以对Ara数据传递的性能进行预测.     

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.     

车联网中beacon消息传输频率研究

车联网(VANETs)提供车与车之间的车间通信(V2V)和车与路旁设施(V2I)间的通信。VANETs中存在两类消息:beacon消息和安全消息。车辆周期地交互车辆的beacon消息,仅在紧急情况下才广播安全消息;而beacon消息的传输频率受多个因素影响。为此,提出基于模糊逻辑的自适应beacon传输频率方案,利用模糊逻辑系统处理多输入决策系统的优势,将信道忙碌因子、车辆移动因子和数据包传递率作为系统输入,通过模糊逻辑系统决策算出最优的beacon传输频率。使用NS-3仿真软件分析VAB方案的平均等待时间,总体传输时延和平均邻居数等参数。仿真实验表明,VAB方案的性能明显优于JSRC和BRAIN-F方案。     

ALCA: agent learning–based clustering algorithm in vehicular ad hoc networks

Vehicular ad hoc network (VANET) is an emerging technology which can be used in various applications such as intelligent transport technology, safety applications, etc. But one of the major issues in VANETs is how to cluster the vehicles on the road for efficient operations such as routing, mobility management and generating safety alarms. Clustering of vehicles has been widely used for routing and data dissemination in VANETs. But due to the high mobility of the vehicles/nodes on the road, it is quite difficult to find the exact route in VANETs. Keeping in view of the above issue, in this paper, we propose a new agent learning–based clustering and routing in VANETs. Agents learn from the environment in which they are deployed, and accordingly, their action performed is rewarded or penalized with certain values. Each agent performs its task in collaboration with the other agents, i.e. agents communicate with each other in collaborative manner for information sharing. The deployed agents estimate the mobility of the vehicles, and based upon their learning, clustering of vehicles is performed. An Agent Learning–based Algorithm for Clustering is proposed. The performance of the proposed scheme is evaluated using extensive simulation with respect to the various metrics such as message transmission ratio, percentage of connectivity, node participation, cluster head duration, and connectivity preservation ratio. The results obtained show that the proposed scheme is effective in performing fast clustering and converges quickly to the final solution.     

车载自组织网络中基于停车骨干网络的数据传输

车载自组织网络(vehicular ad hoc networks,简称VANETs)具有网络间歇连通、节点高速移动及动态的网络拓扑结构等特性,如何有效地实现车辆间的数据传输,成为VANETs的重大挑战.现有研究工作基于历史交通流量或历史延迟预测路段当前交通状况的方法并不可靠.此外,要实现高效的数据路由传输,配置大量路边基础设施节点(deploying roadside unit,简称RSU)是一种可行方案,但通常需要额外开销.基于城市区域长时间拥有大量地上停放车辆这一事实,提出了基于停车骨干网络的数据传输策略PBBD(parking backbone based data delivery),不需要配置任何地面基础设施,而是把地面的停放车辆组成一个虚拟的停车覆盖网络,通过该停车覆盖网实现数据的传输.为此,首先,对于每一条道路,把路边和非路边停放车辆组成一个尽可能长的停车簇,并基于这些停车簇组织城市停车骨干网络.其次,设计基于停车覆盖网络的全新数据传输算法来实现车辆间的有效数据传输.基于真实城市地图和交通数据的模拟实验结果表明,与现有的几种数据传输算法相比,PBBD能够以较低的网络传输开销和较小的传输延迟获得较高的数据传输成功率.     

Game theoretic approach for real-time data dissemination and offloading in vehicular ad hoc networks

Due to high velocity of the vehicles, data dissemination and mobile data offloading are most difficult tasks to be performed in vehicular ad hoc networks (VANETs). In recent years, due to an exponential increase in the data generated from various sources such as smart devices, gadgets, and actuators, there arises a need of usage of an efficient communication infrastructure to handle the aforementioned issues. Most of the earlier solutions reported in the literature for data offloading problem have used the cellular communication, which may be congested in handing a large number of requests from community of users. This may result a performance bottleneck in terms of call drops and data dissemination to the other vehicles in the VANET environment. Also, these schemes lack a comprehensive approach of data dissemination to meet the quality of service (QoS) in real time. Hence, to overcome this problem, some of the mobile data can be disseminated using the existing vehicular infrastructure and Wi-Fi access points (APs). In this paper, we propose a new schedule based on game theoretic approach where the APs and vehicles act as players in a game and compete for offloading the cellular data. The proposed scheme is based on the selection of the best vehicle or AP based on the utility of the players (vehicles and APs) in the game. The utility of vehicle and AP is decided based on the parameters such as distance, velocity, connectivity to destination, bandwidth, and area of the network. A novel algorithm has been designed using the proposed game theoretic approach for handling mobile data offloading and data dissemination. The proposed solution not only successfully offloads the data but also maintains QoS with respect to the parameters such as end-to-end delay, message progress, and message dissemination speed. Results obtained confirm the superiority of the proposal in comparison with the other existing schemes. Specifically, the proposed scheme achieves improvement of 4.16 and 20.5 % in message progress, 18.91 and 4.75 % in extra messages generated, 11.26 and 54.94 % in message dissemination speed, and 78.71 and 87.94 % in end-to-end delay in sparse network as compared to GyTAR and GPCR, respectively.     

An Efficient Message Dissemination Scheme for Minimizing Delivery Delay in Delay Tolerant Networks

Delay tolerant networks (DTNs) are a kind of sparse and highly mobile wireless networks, where no stable connectivity guarantee can be assumed. Most DTN users have several points of interest (PoIs), and they enjoy disseminating messages to the other users of the same PoI through WiFi. In DTNs, some time-sensitive messages (disaster warnings, search notices, etc.) need to be rapidly propagated among specific users or areas. Therefore, finding a path from the source to the destination with the shortest delay is the key problem. Taking the dissemination cost into consideration, we propose an efficient message dissemination strategy for minimizing delivery delay (MDMD) in DTNs, which first defines the user’s activeness according to the transiting habit among different PoIs. Furthermore, depending on the activeness, an optimal user in each PoI is selected to constitute the path with the shortest delay. Finally, the MDMD with inactive state (on the way between PoIs) is further proposed to enhance the applicability. Simulation results show that, compared with other dissemination strategies, MDMD achieves the lowest average delay, and the comparable average hopcounts, on the premise that the delivery ratio is guaranteed to be 100% by the sufficient simulation time.     

A scalable group communication mechanism for mobile agents

Many multi-agent applications based on mobile agents require message propagation among group of agents. A fast and scalable group communication mechanism can considerably improve performance of these applications. Unfortunately, most of the existing approaches do not scale well and disseminate messages slowly when the number of agents grows.In this paper, we propose Sama, a new group communication mechanism, to speed up message delivery for a group of mobile agents on a heterogeneous internetwork. The main contribution of Sama is distribution and parallelization of message propagation in an efficient way to achieve scalability and high-speed of message delivery to group members. Sama uses message dispatcher objects (MDOs), which are stationary agents on each host, to propagate messages concurrently. The proposed mechanism is independent of agent locations and transparently delivers messages to the group using constant number of remote messages. It also transparently recovers from host failures. We also present a Hop-Ring protocol that considerably improves the performance of message dissemination in Sama. Our experimental results show that message propagation in Sama is significantly fast compared to the previously proposed methods.     

The insights of message delivery delay in VANETs with a bidirectional traffic model

Message delivery delay is mainly caused by mobility and sparse distribution of vehicles in Vehicular Ad hoc NETworks (VANETs). It directly impacts the application design and deployments for VANETs. In this paper, we conduct an in-depth study on the insights of message delivery delay in VANETs towards the identified two major factors: (1) message delivery distance, (2) density of vehicles, based on a bidirectional vehicle traffic model. The bidirectional vehicle traffic was modeled as a combination of multiple Poisson point processes. Based on the sub-additive ergodic theory, theoretically, we found that the message delivery delay has a linear relationship with the message delivery distance. Furthermore, the upper bound of the coefficient of the linear relationship has an exponential polynomial relationship with the density of vehicles on the road and decreases with the increase of the velocity of the traffic.     

Distributed route selection for establishing real-time channels

To guarantee the delivery of real-time messages before their deadline, a real-time channel or connection must be established before the transmission of any message belonging to the connection. During this channel establishment phase, one must first select a route between the source and destination of this channel and then reserve sufficient resources along this route so that the worst-case end-to-end delay over the selected route may not exceed the user-specified delay bound. We propose an efficient distributed route selection scheme that is guaranteed to find a “qualified” route, if any, satisfying the performance requirement of the requested channel without compromising any of the existing guarantees. The proposed scheme can also eliminate the common reliability/performance bottleneck of a centralized route selection scheme while improving efficiency over the centralized and other distributed schemes. Although the proposed solution starts with searching all possible routes in parallel, it prunes infeasible routes quickly, and its worst-case operational overhead is shown to be only a linear function of the number of links in the network. Several examples and simulation results are presented to demonstrate the effectiveness of the proposed distributed route selection scheme as compared to sequential route-search schemes     

车载自组织网络基于簇的协作MAC协议研究

随着无线通信技术的发展,车载自组织网络(Vehicular Ad Hoc Network,VANET)已经成为一个新型的研究领域。针对VANET中车辆行驶的特征以及车辆间安全信息传输严格的时延限制和高可靠性要求,提出了一种基于簇的协作MAC(CCB-MAC)协议用于安全信息的传输。当在广播期间节点没有接收到安全信息时,被选择的辅助节点重传先前侦听到的安全信息到目的节点,并且重传是在未被预留的时隙中进行的,这将不会中断正常的传输。数值分析和仿真结果表明,CCB-MAC明显提高了安全信息传输成功的概率,降低了传输时延和丢包率。     

An efficient joint channel assignment and QoS routing protocol for IEEE 802.11 multi-radio multi-channel wireless mesh networks

With the emerging of video, voice over IP (VoIP) and other real-time multimedia services, more and more people pay attention to quality of service (QoS) issues in terms of the bandwidth, delay and jitter, etc. As one effective way of broadband wireless access, it has become imperative for wireless mesh networks (WMNs) to provide QoS guarantee. Existing works mostly modify QoS architecture dedicated for ad hoc or sensor networks, and focus on single radio and single channel case. Meanwhile, they study the QoS routing or MAC protocol from view of isolated layer. In this paper, we propose a novel cross-layer QoS-aware routing protocol on OLSR (CLQ-OLSR) to support real-time multimedia communication by efficiently exploiting multi-radio and multi-channel method. By constructing multi-layer virtual logical mapping over physical topology, we implement two sets of routing mechanisms, physical modified OLSR protocol (M-OLSR) and logical routing, to accommodate network traffic. The proposed CLQ-OLSR is based on a distributed bandwidth estimation scheme, implemented at each node for estimating the available bandwidth on each associated channel. By piggybacking the bandwidth information in HELLO and topology control (TC) messages, each node disseminates information of topology and available bandwidth to other nodes in the whole network in an efficient way. From topology and bandwidth information, the optimized path can be identified. Finally, we conduct extensive simulation to verify the performance of CLQ-OLSR in different scenarios on QualNet platform. The results demonstrate that our proposed CLQ-OLSR outperforms single radio OLSR, multi-radio OLSR and OLSR with differentiated services (DiffServ) in terms of network aggregate throughput, end-to-end packet delivery ratio, delay and delay jitter with reasonable message overheads and hardware costs. In particular, the network aggregate throughput for CLQ-OLSR can almost be improved by 300% compared with the single radio case.     

LAMR: learning automata based multicast routing protocol for multi-channel multi-radio wireless mesh networks

Multicast routing is a crucial issue in wireless networks in which the same content should be delivered to a group of recipients simultaneously. Multicast is also considered as a key service for audio and video applications as well as data dissemination protocols over the last-mile backhaul Internet connectivity provided by multi-channel multi-radio wireless mesh networks (MCMR WMNs). The multicast problem is essentially related to a channel assignment strategy which determines the most suitable channel-radio associations. However, channel assignment brings about its own complications and hence, solving the multicast problem in MCMR WMNs will be more complicated than that of traditional networks. This problem has been proved to be NP-hard. In the major prior art multicast protocols developed for these networks, channel assignment and multicast routing are considered as two separate sub-problems to be solved sequentially. The work in this article is targeted at promoting the adoption of learning automata for joint channel assignment and multicast routing problem in MCMR WMNs. In the proposed scheme named LAMR, contrary to the existing methods, these two sub-problems will be solved conjointly. Experimental results demonstrate that LAMR outperforms the LCA and MCM proposed by Zeng et al. (IEEE Trans. Parallel. Distrib. Syst. 21(1):86–99, 2010) as well as the genetic algorithm-, tabu search-, and simulated annealing-based methods by Cheng and Yang (Int. J. Appl. Soft Comput. 11(2):1953–1964, 2011) in terms of achieved throughput, end-to-end delay, average packet delivery ratio, and multicast tree total cost.     

无线IEEE 802.11网络多信道MAC性能建模与分析

IEEE 802.11动态频谱接入网络是当前协议和模型在无线网络研究中一直受到广泛的关注.虽然它的物理层支持多信道,但其MAC层对多信道的支持仍面临挑战.目前的多信道MAC研究大多基于仿真实验,缺乏性能分析模型.本文设计了一种简单通用的信道切换机制,将IEEE802.11MAC扩展成为一种多信道MAC.本文提出了三维马尔可夫链分析模型描述多信道MAC性能,刻画单信道内重传次数和多信道间切换对性能的影响,支持基本和RTS/CTS两种接入方式.仿真结果表明,该多信道MAC模型能够很好地预测系统的饱和吞吐量,系统性能随着重传次数的增加能得到提高,而切换信道数量的增加并不能总是带来性能的提高.     

Channel time allocation scheme based on feedback information in IEEE 802.11e wireless LANs

The IEEE 802.11e standard defines a set of quality of service (QoS) enhancements for wireless local area network (WLAN) applications such as voice and streaming multimedia traffic. In the standard, a new medium access control (MAC) protocol is called the hybrid coordinator function (HCF), and also a channel access scheme to transmit multimedia traffic is called the HCF controlled channel access (HCCA). In the IEEE 802.11e WLANs, to satisfy the stringent real-time constraints of multimedia services it is very important to provide an efficient method of allocating network resources. In this regard, we propose a feedback-assisted dynamic channel time allocation scheme considering the application layer information in order to achieve better performance of multimedia traffic over IEEE 802.11e HCCA under the constrained QoS requirements. Performance of the proposed scheme is investigated by simulation. Our results show that under typical channel error conditions, the proposed scheme is very effective regardless of the variation of station numbers and service intervals. Also, it yields high performances while guaranteeing the delay bound.     

车载自组织网络中的数据传递

基于车载自组织网络(Vehicular Ad Hoc Network,VANET)的数据传递为 VANET 应用提供数据传输服务,是车辆主动安全、城市生活服务、应急救援等应用不可或缺的组成部分。然而,由于网络拓扑变化快、网络分区频繁、信道容量有限,VANET 数据传递面临诸多挑战。文章分析了 VANET 特点,指出了影响 VANET 数据传递的主要因素,进而综述了已有的 VANET 数据传递技术,包括数据传递的基本实现方法和提高数据传递能力的优化策略。     

Augmenting Vehicle-to-Roadside connectivity in multi-channel vehicular Ad Hoc Networks

Vehicle-to-Roadside (V2R) wireless communication is a cornerstone for providing a wide plethora of intelligent transportation system (ITS) applications in the near future. Initial investment costs could discourage the deployment of a ubiquitous roadside infrastructure to support on-the-road networks; this would imply discontinuous coverage and short-lived connectivity.The purpose of this paper is to design techniques that make the best of sparse road-side unit (RSU) placement by supporting the spreading of network initialization advertisements from RSUs, when considering the multichannel features of the recently published IEEE 802.11p/IEEE 1609.4 standards for wireless access in vehicular environment (WAVE). The proposed techniques leverage time, space and channel diversity to improve efficiency and robustness of the network advertisement procedure in a urban scenario where obstructions to signal propagation due to buildings and traffic jam could hinder successful message spreading. Simulation under different RSU density, vehicular networking technology penetration rate, data rate, and packet size, aims at assessing effectiveness and efficiency of the proposed solutions.     

Synchronous bandwidth allocation in FDDI networks

It is well known that an FDDI token ring network provides a guaranteed throughput for synchronous messages and a bounded medium access delay for each node/station. However, this fact alone cannot effectively support many real-time applications that require the timely delivery of each critical message. The reason for this is that the FDDI guarantees a medium access delay bound to nodes, but not to messages themselves. The message-delivery delays may exceed the medium-access delay bound even if a node transmits synchronous messages at a rate not greater than the guaranteed throughput. We solve this problem by developing a synchronous bandwidth allocation (SEA) scheme which calculates the synchronous bandwidth necessary for each application to satisfy its message-delivery delay requirement. The result obtained in this paper is essential for effective use of the FDDI token ring networks in supporting such real-time communication as digital video/audio transmissions, and distributed control/monitoring