Performance of beacon safety message dissemination in Vehicular Ad hoc NETworks (VANETs)

Currently, there is a growing belief that putting an IEEE 802.11-like radio into road vehicles can help the drivers to travel more safely. Message dissemination protocols are primordial for safety vehicular applications. There are two types of safety messages which may be exchanged between vehicles: alarm and beacon. In this paper we investigate the feasibility of deploying safety applications based on beacon message dissemination through extensive simulation study and pay special attention to the safety requirements. Vehicles are supposed to issue these messages periodically to announce to other vehicles their current situation and use received messages for preventing possible unsafe situations. We evaluate the performance of a single-hop dissemination protocol while taking into account the quality of service (QoS) metrics like delivery rate and delay. We realize that reliability is the main concern in beacon message dissemination. Thus, a new metric named effective range is defined which gives us more accurate facility for evaluating QoS in safety applications specifically. Then, in order to improve the performance, the effects of three parameters including vehicle's transmission range, message transmission's interval time and message payload size are studied. Due to special characteristics of the safety applications, we model the relationship between communication-level QoS and application-level QoS and evaluate them for different classes of safety applications. As a conclusion, the current technology of IEEE 802.11 MAC layer has still some challenges for automatic safety applications but it can provide acceptable QoS to driver assistance safety applications.

Software Defined Networking Based On-Demand Routing Protocol in Vehicle Ad-Hoc Networks

This paper comes up with a SDN Based Vehicle Ad-Hoc On-Demand Routing Protocol(SVAO),which separates the data forwarding layer and network control layer,as in software defined networking(SDN),to enhance data transmission efficiency within vehicle ad-hoc networks(VANETs).The roadside service unit plays the role of local controller and is in charge of selecting vehicles to forward packets within a road segment.All the vehicles state in the road.Correspondingly,a two-level design is used.The global level is distributed and adopts a ranked query scheme to collect vehicle information and determine the road segments along which a message should be forwarded.On the other hand,the local level is in charge of selecting forwarding vehicles in each road segment determined by the global level.We implement two routing algorithms of SVAO,and compare their performance in our simulation.We compare SVAO with popular ad-hoc network routing protocols,including Optimized Link State Routing(OLSR),Dynamic Source Routing(DSR),Destination Sequence Distance Vector(DSDV),and distance-based routing protocol(DB)via simulations.We consider the impact of vehicle density,speed on data transmission rate and average packet delay.The simulation results show that SVAO performs better than the others in large-scale networks or with high vehicle speeds.

A Self-Adaptive Back-off Optimization Scheme Based on Beacons Probability Prediction for Vehicle Ad-Hoc Networks

In order to improve the broadcast reception rates of beacon messages in vehicle ad-hoc networks,a conclusion that the relationship between collision probability and minimum contention window size and the relationship between expiration probability and minimum window size was reached by building a Markov model. According to this conclusion, a back-off algorithm based on adjusting the size of minimum contention window called CEB is proposed, and this algorithm is on the basis of the differential size between the number of expiration beacons and preset threshold. Simulations were done to compare the performance of CEB with that of RBEB and BEB, and the results show that the performance of the new proposed algorithm is better than that of RBEB and BEB.

Mobility Aware Zone-Based Routing in Vehicle Ad hoc Networks Using Hybrid Metaheuristic Algorithm

Vehicle Ad hoc Networks(VANETs)have high mobility and a rando-mized connection structure,resulting in extremely dynamic behavior.Several challenges,such as frequent connection failures,sustainability,multi-hop data transfer,and data loss,affect the effectiveness of Transmission Control Protocols(TCP)on such wireless ad hoc networks.To avoid the problem,in this paper,mobility-aware zone-based routing in VANET is proposed.To achieve this con-cept,in this paper hybrid optimization algorithm is presented.The hybrid algo-rithm is a combination of Ant colony optimization(ACO)and artificial bee colony optimization(ABC).The proposed hybrid algorithm is designed for the routing process which is transmitting the information from one place to another.The optimal routing process is used to avoid traffic and link failure.Thefitness function is designed based on Link stability and Residual energy.The validation of the proposed algorithm takes solution encoding,fitness calculation,and updat-ing functions.To perform simulation experiments,NS2 simulator software is used.The performance of the proposed approach is analyzed based on different metrics namely,delivery ratio,delay time,throughput,and overhead.The effec-tiveness of the proposed method compared with different algorithms.Compared to other existing VANET algorithms,the hybrid algorithm has proven to be very efficient in terms of packet delivery ratio and delay.

Vehicle Positioning Method Based on RFID in Vehicular Ad-Hoc Networks

With the rapid development of vehicular ad hoc network( VANET) technology,VANET applications such as safe driving and emergency rescue demand high position accuracy,but traditional GPS is difficult to meet new accuracy requirements. To overcome this limitation,a new vehicle positioning method based on radio frequency identification( RFID) is proposed. First RFID base stations are divided into three categories using fuzzy technology,and then Chan algorithm is used to calculate three vehicles' positions,which are weighed to acquire vehicles' accurate position. This method can effectively overcome the problem that vehicle positioning accuracy is not high resulting from the factors such as ambient noise and base distribution when Chan algorithm is used. Experimental results show that the performance of the proposed method is superior to Chan algorithm and 2-step algorithm based on averaging method,which can satisfy the requirements of vehicle positioning in VANETs.

Adaptive 3D Routing Protocol for Flying Ad Hoc Networks Based on Prediction-Driven Q-Learning

The routing protocols are paramount to guarantee the Quality of Service(QoS)for Flying Ad Hoc Networks(FANETs).However,they still face several challenges owing to high mobility and dynamic topology.This paper mainly focuses on the adaptive routing protocol and proposes a Three Dimensional Q-Learning(3DQ)based routing protocol to guarantee the packet delivery ratio and improve the QoS.In 3DQ routing,we propose a Q-Learning based routing decision scheme,which contains a link-state prediction module and routing decision module.The link-state prediction module allows each Unmanned Aerial Vehicle(UAV)to predict the link-state of Neighboring UAVs(NUs),considering their Three Dimensional mobility and packet arrival.Then,UAV can produce routing decisions with the help of the routing decision module considering the link-state.We evaluate the various performance of 3DQ routing,and simulation results demonstrate that 3DQ can improve packet delivery ratio,goodput and delay of baseline protocol at most 71.36%,89.32%and 83.54%in FANETs over a variety of communication scenarios.

A Secured Message Transmission Protocol for Vehicular Ad Hoc Networks

Vehicular Ad hoc Networks(VANETs)become a very crucial addition in the Intelligent Transportation System(ITS).It is challenging for a VANET system to provide security services and parallelly maintain high throughput by utilizing limited resources.To overcome these challenges,we propose a blockchain-based Secured Cluster-based MAC(SCB-MAC)protocol.The nearby vehicles heading towards the same direction will form a cluster and each of the clusters has its blockchain to store and distribute the safety messages.The message which contains emergency information and requires Strict Delay Requirement(SDR)for transmission are called safety messages(SM).Cluster Members(CMs)sign SMs with their private keys while sending them to the blockchain to confirm authentication,integrity,and confidentiality of the message.A Certificate Authority(CA)is responsible for physical verification,key generation,and privacy preservation of the vehicles.We implemented a test scenario as proof of concept and tested the safety message transmission(SMT)protocol in a real-world platform.Computational and storage overhead analysis shows that the proposed protocol for SMT implements security,authentication,integrity,robustness,non-repudiation,etc.while maintaining the SDR.Messages that are less important compared to the SMs are called non-safety messages(NSM)and vehicles use RTS/CTS mechanism for NSM transmission.Numerical studies show that the proposed NSM transmission method maintains 6 times more throughput,2 times less delay and 125%less Packet Dropping Rate(PDR)than traditional MAC protocols.These results prove that the proposed protocol outperforms the traditional MAC protocols.

A Cyber–Physical Routing Protocol Exploiting Trajectory Dynamics for Mission-Oriented Flying Ad Hoc Networks

As a special type of mobile ad hoc network(MANET),the flying ad hoc network(FANET)has the potential to enable a variety of emerging applications in both civilian wireless communications(e.g.,5G and 6G)and the defense industry.The routing protocol plays a pivotal role in FANET.However,when designing the routing protocol for FANET,it is conventionally assumed that the aerial nodes move randomly.This is clearly inappropriate for a mission-oriented FANET(MO-FANET),in which the aerial nodes typically move toward a given destination from given departure point(s),possibly along a roughly deterministic flight path while maintaining a well-established formation,in order to carry out certain missions.In this paper,a novel cyber–physical routing protocol exploiting the particular mobility pattern of an MO-FANET is proposed based on cross-disciplinary integration,which makes full use of the missiondetermined trajectory dynamics to construct the time sequence of rejoining and separating,as well as the adjacency matrix for each node,as prior information.Compared with the existing representative routing protocols used in FANETs,our protocol achieves a higher packet-delivery ratio(PDR)at the cost of even lower overhead and lower average end-to-end latency,while maintaining a reasonably moderate and stable network jitter,as demonstrated by extensive ns-3-based simulations assuming realistic configurations in an MO-FANET.

Navigation Route Based Stable Clustering for Vehicular Ad Hoc Networks

Due to high node mobility, stability has been always one of the major concerns of vehicle clustering algorithms in vehicular ad hoc networks. In this paper, we propose a novel clustering algorithm based on the information of routes planned by vehicular navigation systems. In the clustering algorithm, we design a residual route time function to quantitatively calculate the overlapping time among vehicles based on route information, with which a novel clusterhead selection metric is presented. We further design a mechanism of future-clusterhead, which can help avoid message exchanges at intersections and reduce the overhead of cluster maintenance. The simulation results show that, compared with previous works, our clustering algorithm can achieve higher stability and at the same time lower communication cost.

Review of the Security Issues in Vehicular Ad Hoc Networks (VANET)

There is a significant increase in the rates of vehicle accidents in countries around the world and also the casualties involved ever year. New technologies have been explored relating to the Vehicular Ad Hoc Network (VANET) due to the increase in vehicular traffic/congestions around us. Vehicular communication is very important as technology has evolved. The research of VANET and development of proposed systems and implementation would increase safety among road users and improve the comfort for the corresponding passengers, drivers and also other road users, and a great improvement in the traffic efficiency would be achieved. This research paper investigates the current and existing security issues associated with the VANET and exposes any slack amongst them in order to lighten possible problem domains in this field.

Connectivity of sparse vehicular ad hoc networks with channel randomness

In this paper, we investigate the connectivity of vehicular ad hoc networks in free-flow traffic situation with channel randonmess. In order to illustrate the realistic environment, we consider that vehicles are distributed in free-flow highway according to a Poisson point process, and signal propagation between connected vehicles is subjected to log-normal shadowing effects. We obtain the distribution of the space headway between successive vehicles and the distribution of signal coverage, which allows us to use the equivalent M/G/z~ queue theory to model the connectivity of VANETs in the form of average broadcast percolation distance and average number of connected nodes. Then, extensive simulation studies are conducted to evaluate the obtained results. The analytical model presented here is able to describe the impact of various system parameters, including traffic parameters and signal propagation parameters on the con- nectivity. We use our analytical results, along with the common signal propagation data, to understand impact of channel randomness on the connectivity of VANETs.

Effective Life and Area Based Data Storing and Deployment in Vehicular Ad-Hoc Networks

In vehicular ad-hoc networks (VANETs), store-carry-forward approach may be used for data sharing, where moving vehicles carry and exchange data when they go by each other. In this approach, storage resource in a vehicle is generally limited. Therefore, attributes of data that have to be stored in vehicles are an important factor in order to efficiently distribute desired data. In VANETs, there are different types of data which depend on the time and location. Such kind of data cannot be deployed adequately to the requesting vehicles only by popularity-based rule. In this paper, we propose a data distribution method that takes into account the effective life and area in addition to popularity of data. Our extensive simulation results demonstrate drastic improvements on acquisition performance of the time and area specific data.

车载Ad Hoc网络中基于移动网关的数据传输

由于车载Ad hoc网络拓扑的动态变化及车载节点的快速移动,应用现有传输方法在其上进行Internet接入点向移动车辆(Infrastructure-to-Vehicle,I2V)数据传输时成功率较低,而且传输延迟高、延迟抖动大.为了解决这一问题,文中利用公交车路线固定、运行特征可预测、节点及线路分布稠密等特性,将公交车作为移动网关(Mobile Gateway,MG),提出了一种新的基于MG转发的I2V数据传输方法(Mobile Gateway based Forwarding,MGF).文中首先将公路网模型化为状态-空间图,再运用马尔可夫决策方法建立了一种基于MG转发的I2V数据传输优化模型,然后通过对模型求解得出I2V数据传输的最优转发决策,最优转发决策指的就是每个状态下对应的最优动作序列,最后在目的车辆行驶轨迹上选取满足传输成功率阈值,并使I2V传输延迟最小的路口节点作为数据包与目的车辆的最优汇聚节点,即目标节点.应用MGF方法,MG节点将以最优概率转发序列向目标节点转发数据包.文中利用模拟平台对MGF方法的传输性能进行了评估,结果表明该方法在满足传输成功率阈值前提下,能够获得最小传输延迟期望.理论分析同样也证明了该方法的有效性.

车载Ad Hoc网络

车载自组织网络(VANET)作为移动自组织网络(MANET)的特殊子类,因其在智能交通和车载娱乐方面的广阔应用前景,目前受到业界的普遍关注。VANET的主要特点是车辆高速行驶、信道快速衰落、多普勒效应严重、网络拓扑变化快,由此将带来许多传输和组网的问题。

基于OPNET的车用Ad hoc网可靠性评估研究

通过搭建车用Ad hoc网络(VANET)的仿真平台,将一个真实的车辆节点移动模型与标准的无线移动Ad hoc网络模型进行结合来对车用网络的可靠性进行评估。反映了车辆的移动特性对整个VANET可靠性的影响,利于更详细、更直观地刻画VANET的重要特性,为将来VANET相关协议的设计提供具体、详实的参考数据和建议。

无人飞行器Ad hoc网络中基于容错的中继节点配置

针对无人飞行器Ad hoc网络的容错设计需求,采用增加中继节点的方法实现。在二维平面同构网络中,将容错问题转化为边长受限条件下最少数量Steiner点的Steiner树问题。提出了两种基于最小成本子图的中继节点配置算法,以求解最少数量的中继节点及其位置,使改变后的网络拓扑图为顶点2-连通,实现容错。第一种为多项式时间的8-近似算法;第二种为随机近似算法,采用文化基因算法,搜索需要新增加的最小成本强化边组合。仿真结果表明了所提算法的有效性,当网络规模较小和中等时,随机近似算法得到的中继节点数量较少,平均情况下性能较优。

一种基于AD HOC网络的车辆定位系统的组网框架设计

本文提出了一种基于ADHOC网络的车辆定位系统的组网框架,着重分析了该网络的路由协议选择及优化措施。它能通过车载设备自动组成一个网络来传送系统的位置信息、控制指令和语音信息等信息,可以取得灵活的组网模式,降低系统的运行费用。

大城市环境下移动Ad Hoc网络通信技术的研究

结合实际应用场景,对大城市环境下面向车辆通信的移动ad hoc网络通信技术进行了分析与研究,分析了车辆运动行为特征,总结车辆运动的规律性,结合该规律提出了改进的ad hoc路由协议以及适用该协议的网络结构。利用实测的车辆运行数据对改进的网络性能进行评估,取得了一定效果。

一种基于方向优先的车载Ad hoc路由策略

针对城市车载网络在十字路口路由选择效率低下的问题,结合已有的地理位置路由协议,提出一种基于方向优先的地理位置路由策略。该策略通过信标的广播信息确定节点的类型,是属于普通节点、预测节点或者十字路口节点;然后再判断采取什么样的方式转发数据包,普通节点采取贪婪转发的方式,预测节点采取受限的贪婪转发,而十字路口节点决定路由策略的方向。通过NS2仿真分析,该路由策略能够以更少的跳数、更短的路径成功传递数据包。

基于移动ad-hoc网络的车辆定位

当车辆不能通过GPS接收机获得自身位置信息时,就难以获得有用的交通提示风险服务.提出了一种新的基于车载移动ad-hoc网络车辆定位方法,该方法能够获取作为网络节点车辆的大致位置,并结合一种改进的警报信息优化传播算法,向即将处于危险或拥堵区域的不能通过GPS接收机定位的车辆发送警报信息.仿真实验表明只要车辆自组织网络中有40%的车辆可以获得GPS的定位信息,就可以将警报信息准确完整地送达处于网络中的所有车辆.当遇到浓雾天气、交通事故或者是其他拥塞时,该方法会防止车辆进一步拥堵并能提醒驾驶员防范危险.