Cooperative and Opportunistic Channel Access for Vehicle to Roadside (V2R) Communications

This paper focuses on vehicle to roadside (V2R) communications in vehicular networks based on the IEEE 802.11 DCF MAC protocol. In vehicular networks, roadside units (RSUs) are typically spaced apart along the road and each vehicle can be connected to an RSU only when the vehicle is within its transmission range. Due to the high relative speed between a moving vehicle and a stationary RSU, the residence time of the vehicle within the coverage of each RSU is very short. Thus it is hard for the system to reach a steady state. With multi-hop forwarding, in which a vehicle may be connected to an RSU through relaying over other vehicles, the connection time of each V2R access may be extended. But this is at the expense of introducing wireless interference among vehicles, which may dramatically degrade the system performance. To tackle these challenges, we propose a new mechanism called Proxy-based Vehicle to RSU access (PVR) for V2R communications. This protocol is designed to exploit cooperative and opportunistic forwarding between any two distant RSUs and to emulate back-to-back transmissions within the coverage of an RSU. As a result, it can shorten the access delay by taking advantage of opportunistic forwarding and mitigate the interference problem during the short residence time within the coverage of an RSU. The simulation results show that PVR achieves excellent performance and outperforms all existing solutions for V2R communications in vehicular networks.     

ROAMER: Roadside Units as message routers in VANETs

Vehicular Ad hoc Networks, also known as VANETs, enable vehicles that are not necessarily within the same radio transmission range to communicate with each other. VANETs also allow vehicles to connect to Roadside Units (RSUs). The latter are connected to the Internet, forming a fixed infrastructure that offers them the capability of communicating with each other and with roaming vehicles. RSUs support cooperative and distributed applications in which vehicles and RSUs work together to coordinate actions and to share and process several types of information. RSUs have so far been used for different roles such as data disseminators, traffic directories, location servers, security managers, and service proxies. In this paper, we focus on routing; namely we exploit RSUs to route packets between any source and destination in the VANET. To our knowledge, this is the first attempt to use the RSU backbone to efficiently route packets to very far locations in VANETs by using geographic forwarding. We evaluate the RSU backbone routing performance via the ns2 simulation platform. We compare our scheme to existing solutions and prove the feasibility and efficiency of our scheme in terms of query delay, packet success delivery ratio, and total generated traffic.     

Reducing wireless multi‐hop delay via RSU re‐routing in vehicular wireless networks

Vehicular wireless networks offer wireless multi‐hop communications between vehicles and roadside units (RSUs). To reduce deployment cost, the distance between two RSUs could be long; that is, the communications between an RSU and a vehicle may be carried out through multi‐hops among intermediate vehicles. When a vehicle is driven from one RSU to another, the wireless multi‐hop delay becomes more serious as the number of multi‐hop relays increases. The wireless multi‐hop delay is critical for some emergency service. For instance, in a traffic accident, when a patient was sent to the hospital by ambulance, the life information of the patient must be transmitted to the hospital on time through the multi‐hop wireless network. If the ambulance is moved from one RSU to another, the wireless multi‐hop delay becomes more and more serious as the ambulance is closing to another RSU. In this paper, we propose an RSU re‐routing strategy that dynamically alters multi‐hop communications until the best RSU with the shortest path using location information is found. Moreover, we compare the proposed strategy with the existing strategy in terms of broadcasting costs, re‐routing delay, and wireless multi‐hop delay of data transmission. Performance results show that the proposed strategy can reduce the wireless multi‐hop delay significantly. Copyright © 2014 John Wiley & Sons, Ltd.     

基于BP和RBF神经网络的C-V2X无线资源管理

为了提升蜂窝车联网（Cellular Vehicle-to-Everything,C-V2X）资源复用的有效性和降低终端间的干扰，提出通过神经网络对未来时刻车流量的预测辅助无线资源管理方案。依据车载单元（On Board Unit,OBU）与路侧单元（Road Side Unit,RSU）间的车联网消息，获取RSU覆盖区域内各时刻的车流情况，分别采用BP（Back Propagation）神经网络和RBF（Radial Basis Function）神经网络进行短时交通流预测。RSU根据预测结果进行自适应分簇，簇间复用相同资源，簇内进行资源池的划分，RSU覆盖内的OBU在划分的资源池中选择发送资源，从而减少终端间的干扰，并保证热点区域车辆拥有更多的资源。仿真结果表明，在道路交通拥塞的场景下，所提方案的数据包接收率较标准中的方案提升14%，较典型文献方案提升10%，保证了通信的可靠性。     

车载自组织网络中基于连接时长的RSU部署方案

针对目前城市场景下车载自组织网络中的RSU部署问题,提出了一种基于连接时长的RSU部署方案.该方案在RSU数量受限的情况下,以保证通信连接时长为前提,以最大化服务车辆数目为目的,将部署问题建模成最大覆盖问题,设计了二进制粒子群算法进行求解,并结合真实的北京市路网地图和出租车GPS数据进行仿真实验.仿真结果表明,该算法是收敛、稳定及可行的,相比贪心算法,该算法求得的部署方案能为更多的车辆提供持续性的网络服务.     

A roadside unit‐based localization scheme for vehicular ad hoc networks

Vehicular Ad Hoc Networks (VANETs), designed to ensure the safety and comfort of passengers via the exchange of information amongst nearby vehicles or between the vehicles and Roadside Units (RSUs), have attracted particular attention. However, the success of many VANET applications depends on their ability to estimate the vehicle position with a high degree of precision, and thus, many vehicle localization schemes have been proposed. Many of these schemes are based on vehicle‐mounted Global Positioning System (GPS) receivers. However, the GPS signals are easily disturbed or obstructed. Although this problem can be resolved by vehicle‐to‐vehicle communication schemes, such schemes are effective only in VANETs with a high traffic density. Accordingly, this paper presents a VANET localization scheme in which each vehicle estimates its location on the basis of beacon messages broadcast periodically by pairs of RSUs deployed on either side of the road. In addition, three enhancements to the proposed scheme are presented for the RSU deployment, RSU beacon collisions, and RSU failures. Overall, the ns‐2 simulation results show that the localization scheme achieves a lower localization error than existing solutions on the basis of vehicle‐to‐vehicle communications and is robust toward changes in the traffic density and the vehicle speed. Copyright © 2012 John Wiley & Sons, Ltd.     

Improving RSU service time by Distributed Sorting Mechanism

In recent years, Vehicle Ad Hoc Networks (VANETs) have become very popular. A VANET network is mainly constructed with an infrastructure composed of mobile vehicles and fixed Road Site Units (RSUs). RSUs are usually very expensive to install, this limits their number, especially in suburbs and areas of sparse population. Therefore, RSUs are precious resource in VANET. In order to promote the utility of RSUs, we propose a novel mechanism, Distributed Sorting Mechanism (DSM), to improve the efficiency of communication between vehicles and RSUs (Vehicle to Infrastructure, V2I). In DSM, every vehicle can individually calculate its own priority of communication, and the time to compete and obtain the channel can be reduced. We further consider the vehicles moving away from the coverage of communication and adjust their priorities of communication appropriately. Moreover, DSM owns the characteristic of “Deadline First” in specific situations. Using DSM not only simplifies the handoff procedure and reduces the network overhead, but also achieves adequate utilization of RSU resources.     

Broadcast-First Service Scheduling Scheme for Vehicle-Roadside Communication

In recent years, the research of vehicular ad-hoc networks (VANET) has become increasingly popular. More and more vehicles want their requests to be served from roadside units (RSU) in VANET, thus the service scheduling of RSU becomes an important task, especially when a large number of vehicles drive past the RSU and access data. Obviously, different kinds of request messages have different degrees of emergency, in other words, request messages have different priorities while scheduling. In order to provide a more effective and appropriate scheme, in this paper we study the scheduling of service algorithm in VANET, and proposed a novel broadcast-first service scheduling scheme. That scheme is on the basis of existing priority schemes, and takes channel bandwidth and processing capability of RSU into consideration so as to cope with the challenges in vehicle-roadside data access. Finally we conduct our experimental scenario, and simulation results show that our algorithm performs better than other existing algorithms by the comparison.     

MPC: A RSUs deployment strategy for VANET

A Vehicle AdHoc Network is mainly composed of mobile vehicles and fixed Road Site Units (RSUs). The latter is usually very expensive to deploy and has a crucial role in maintaining the network connectivity. Therefore, the design of an efficient RSU deployment strategy that enables a high coverage ratio and a lower deployment cost has been of paramount importance. In this respect, we introduce in this paper a new spatiotemporal coverage strategy for nonsafety Vehicle AdHoc Network applications like driving assistance and business promotion, called Minimal Mobility Patterns Coverage (MPC). The main thrust of MPC is to (1) depict the mobility patterns of moving vehicles from their trace files and then (2) compute the adequate RSU locations in order to cover the extracted mobility patterns by the minimal possible number of RSUs. To this end, we firstly provide a new method to depict the mobility patterns of vehicles by mining the correlations between the kept track connections of vehicle trajectories versus crossed junctions. Secondly, we introduce a new way to compute the adequate RSU locations through the instantiation of the well‐known problem of extracting minimal transversals of a hypergraph. Experimental results show that our RSUs deployment strategy performs better than baseline strategies.     

RVCloud: a routing protocol for vehicular ad hoc network in city environment using cloud computing

Routing in Vehicular Ad hoc Network (VANET) is a challenging task due to high mobility of vehicles. In this paper, a RVCloud routing protocol is proposed for VANET to send the data efficiently to the destination vehicle using cloud computing technology. In this protocol, vehicle beacon information is send to the cloud storage through the Road Side Unit (RSU). As vehicles have less storage and computing facility, the information of all the vehicles moving in the city is maintained by the cloud. Source vehicle sends the data to the destination by sending the data to the nearby RSU. After receiving the data, RSU sends a request to the cloud for an optimal RSU information, that takes minimum packet forwarding delay to send the data to the destination. Cloud provides location service by providing destination location and optimal RSU information. Then RSU sends the data to the optimal RSU using internet. By using the internet facility, packet forwarding delay and link disruption problem are reduced. Simulation results show that, RVCloud performs better than VehiCloud, P-GEDIR, GyTAR, A-STAR, and GSR routing protocols.     

A moving cluster architecture and an intelligent resource reuse protocol for vehicular networks

Real-time data transmission, especially video delivery over high-speed networks have very stringent constraints in terms of network connectivity and offered data rate. However, in high-speed vehicular networks, direct communication between vehicles and road side units (RSU) often breaks down, resulting in loss of information. On the other hand, a peer-to-peer based multihop network topology is not sufficient for efficient data communication due to large packet loss and delay. In this paper, a novel ‘moving cluster multiple forward’ (MCMF) architecture is proposed and investigated for efficient real-time data communication in high speed vehicular networks. MCMF involves novel aspects in relation to the formation of clusters and managing the communication between groups of vehicles and introduction of a hierarchical multiple forwarding mechanism which enables communication between any vehicle and RSU via other vehicles. Additionally, a novel protocol called ‘alternate cluster resource reuse’ (ACRR) is proposed and its detailed communication mechanism is presented. Simulation tests show how the use of MCMF and the ACRR protocol results in superior bit-rate performance—around three times that obtained in peer-to-peer multihop communications and twice that of MCMF with no ACRR protocol. Further, the average delay in MCMF-based transmissions from vehicle to RSU is around 50 % that of a peer-to-peer multihop communication mechanism. MCMF/ACRR has the potential to support multimedia traffic according to the IEEE 802.11p standard, even with a sparse investment in the infrastructure.     

RIALS: RSU/INS‐aided localization system for GPS‐challenged road segments

This paper introduces a new vehicle localization approach for global positioning system‐challenged road segments (e.g., tunnels), which takes advantage of roadside units (RSUs) and in‐vehicle inertial navigation system (INS). In the proposed approach, namely RSU/INS‐aided localization system (RIALS), vehicles only need one RSU in their transmission range for an accurate positioning. The beacons received from the RSU along with the information provided by the INS system are used for establishing and maintaining particular locus circles. After linearization, the system of locus circle equations is solved using the linear least square estimation technique, and the estimated vehicle's position is obtained. In the presence of speed variations and existing ranging and INS estimation errors, the proposed RIALS adaptively sets the sufficient number of required locus circles, aiming at keeping the localization error below a given threshold. We study the effects of ranging and INS estimation errors on localization accuracy of RIALS from analytical and simulation perspectives. Results of extensive simulations show that the localization error is more sensitive to the ranging error than the INS error. Moreover, the network traffic overhead of the proposed method is considerably lower than other competitive localization approaches. Copyright © 2015 John Wiley & Sons, Ltd.     

关于S1240远端模块话务统计及疏忙方法

根据S1240远端用户模块(RSU)在天津本地网中被广泛地应用，且目前还没有完整的话务统计方法的情况，在介绍RSU工作原理的基础上，提出了一个全新的解决RSU话务统计的方法，建议在实际工作中对这一方法予以应用。     

Cooperative caching for content dissemination in vehicular networks

The explosive growth of mobile data traffic has made cellular operators to seek low‐cost alternatives for cellular traffic off‐loading. In this paper, we consider a content delivery network where a vehicular communication network composed of roadside units (RSUs) is integrated into a cellular network to serve as an off‐loading platform. Each RSU subjecting to its storage capacity caches a subset of the contents of the central content server. Allocating the suitable subset of contents in each RSU cache such that maximizes the hit ratio of vehicles requests is a problem of paramount value that is targeted in this study. First, we propose a centralized solution in which, we model the cache content placement problem as a submodular maximization problem and show that it is NP‐hard. Second, we propose a distributed cooperative caching scheme, in which RSUs in an area periodically share information about their contents locally and thus update their cache. To this end, we model the distributed caching problem as a strategic resource allocation game that achieves at least 50% of the optimal solution. Finally, we evaluate our scheme using simulation for urban mobility simulator under realistic conditions. On average, the results show an improvement of 8% in the hit ratio of the proposed method compared with other well‐known cache content placement approaches.     

Performance enhancement of traffic information gathering (PEnTInG) algorithm for vehicular ad‐hoc networks

Vehicular ad‐hoc networks (VANETs) play a vital role in today's context of vehicular traffic. In this paper, clusters of vehicles are created on the basis of average speed of the vehicles. One cluster communicates with the next cluster through a cluster head and also share the same information with next cluster heads and installed road side units (RSUs). By using this technique, we can solve the problem of rough driving behavior and road terrorism which is due to speed variation of vehicles and fake information dissemination by the drivers. Many a times, drivers may spread fake accident‐related information into the network which is a serious cause of concern in VANETs. It is ensured that such drivers are not allowed to spread wrong information in the network to avoid accidents. To solve this problem, we developed performance enhancement of traffic information gathering (PEnTInG) algorithm that selects only those drivers/vehicles as cluster heads in a cluster who has maximum value of the cluster head factor (CHF). The CHF is derived by considering different weights in range of 0 to 1 of relative average speed, time to leave, trust factor, and neighborhood degree. Further, the elected cluster head shares and stores the same information with the RSUs. In case, a driver wants to disseminate fake or wrong information in a network, then that vehicle driver can be easily tracked by the local authority by accessing RSU data. Simulation results show that the stability of PEnTInG is increased by 25% against the existing schemes viz. lowest‐ID, MCMF, and cluster‐based technique.     

DESCV—A Secure Wireless Communication Scheme for Vehicle ad hoc Networking

As an indispensable part of intelligent transportation system (ITS), inter-vehicle communication (IVC) emerges as an important research topic. The inter-vehicle communication works based on vehicular ad hoc networking (VANET), and provides communications among different vehicles. The wide applications of VANET helps to improve driving safety with the help of traffic information updates. To ensure that messages can be delivered effectively, the security in VANET becomes a critical issue. Conventional security systems rely heavily on centralized infrastructure to perform security operations such as key assignment and management, which may not suit well for VANET due to its high mobility and ad hoc links. Some works suggested that vehicles should be connected to fixed devices such as road side units (RSUs), but this requires deployment of a large number of costly RSUs in a specific area. This paper is focused on the issues on decentralized IVC without fixed infrastructure and proposes a method for Dynamic Establishment of Secure Communications in VANET (DESCV), which works in particular well for VANET communication key management when centralistic infrastructure or RSU is not available. We will demonstrate through synergy analysis and simulations that DESCV performs well in providing secure communications among vehicles traveling at a relative velocity as high as 240 km/h.     

车载边缘计算中多任务部分卸载方案研究

现有车载应用设备对时延有更严苛的要求,车载边缘计算(VEC)能够充分利用网络边缘设备,如路边单元(RSU)进行协作处理,可有效地降低时延。现有研究多假设RSU计算资源充足,可提供无限的服务,但实际其计算资源会随着所需处理任务数量的增加而受限,对时延敏感的车载应用造成限制。该文针对此问题,提出一种车载边缘计算中多任务部分卸载方案,该方案在充分利用RSU的计算资源条件下,考虑邻近车辆的剩余可用计算资源,以最小化总任务处理时延。首先在时延限制和资源约束下分配各任务在本地、RSU和邻近车辆的最优卸载决策变量比例,其次以最小处理时延为目的在一跳通信范围内选择合适的空闲车辆作为处理部分任务的邻近车辆。仿真结果表明所提车载边缘计算中多任务部分卸载方案相较现有方案能较好地降低时延。     

Optimal solution for malicious node detection and prevention using hybrid chaotic particle dragonfly swarm algorithm in VANETs

Vehicular ad hoc networks (VANETs) have the ability to make changes in travelling and driving mode of people and so on, in which vehicle can broadcast and forward the message related to emergency or present road condition. The safety and efficiency of modern transportation system is highly improved using VANETs. However, the vehicular communication performance is weakened with the sudden emergence of distributed denial of service (DDoS) attacks. Among other attacks, DDoS attack is the fastest attack degrading the VANETs performance due to its node mobility nature. Also, the attackers (cyber terrorists, politicians, etc.) have now considered the DDoS attack as a network service degradation weapon. In current trend, there is a quick need for mitigation and prevention of DDoS attacks in the exploration field. To resolve the conflict of privacy preservation, we propose a fast and secure HCPDS based framework for DDoS attack detection and prevention in VANETs. The Road Side Units (RSUs) have used HCPDS algorithm to evaluate the fitness values of all vehicles. This evaluation process is done for effective detection of spoofing and misbehaving nodes by comparing the obtained fitness value with the statistical information (packet factors, RSU zone, and vehicle dynamics) gathered from the vehicles. The credentials of all worst nodes are cancelled to avoid further communication with other vehicles. In HCPDS algorithm, the PSO updation strategy is added to Dragon fly algorithm to improve the search space. In addition, Chaos theory is applied to tune the parameters of proposed HCPDS algorithm. From the experimental results, it proved that the HCPDS based proposed approach can efficiently meet the requirements of security and privacy in VANETs.

     

Research on adaptive dual task offloading decision algorithm for parking space recommendation service

In order to improve the efficiency of tasks processing and reduce the energy consumption of new energy vehicle (NEV), an adaptive dual task offloading decision-making scheme for Internet of vehicles is proposed based on information-assisted service of road side units (RSUs) and task offloading theory. Taking the roadside parking space recommendation service as the specific application Scenario, the task offloading model is built and a hierarchical self-organizing network model is constructed, which utilizes the computing power sharing among nodes, RSUs and mobile edge computing (MEC) servers. The task scheduling is performed through the adaptive task offloading decision algorithm, which helps to realize the available parking space recommendation service which is energy-saving and environmental-friendly. Compared with these traditional task offloading decisions, the proposed scheme takes less time and less energy in the whole process of tasks. Simulation results testified the effectiveness of the proposed scheme.