Priority based efficient data scheduling technique for VANETs

As vehicular networks are gaining popularity, large number of vehicles want to take advantage of these networks, by utilizing the information they have, in order to take decision. Vehicle receives data from other vehicles or from the road side units (RSUs) available across the road. Since RSUs act as router to connect with the external world as well as it is a high capacity storage place where important data (e.g. data used in traffic safety, location dependent query, etc.) can be stored for download purpose for other vehicles moving through the service area. Since the RSUs have limited communication range and vehicles usually moves at very high speed in the service area, they have limited time to serve data to vehicles moving in the service area. For this purpose RSUs have to schedule data in such a way that maximum vehicles can get benefit from the data available with the RSUs. There are many algorithms proposed in the past to schedule data at RSUs. This paper proposes a mechanism to schedule data of those vehicles which are in the coverage range of the RSU. The proposed algorithm outperforms to serve requests whose deadline is about to expire i.e. vehicles which have left the service area after forwarding request to RSU. This scheme performs well in dense network and has good results in highway scenario.     

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。     

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.     

Data dissemination scheduling algorithm for V2R/V2V in multi-channel VANET

Considering that the data dissemination in multi-channel VANET (vehicular ad hoc network),a cooperative data dissemination scheduling algorithm was introduced for V2R(vehicle to roadside unit) and V2V(vehicle to vehicle).The algorithm created initial scheduling operators according to data requisition of vehicles.Then,initial collision graph and collision matrix were generated based on the conflict among initial scheduling operators.After proving the positive semidefinite of collision matrix,SDP (semidefinite programming) was used to channel allocation and collision graph creation.The algorithm then assigned weights for each data requisition according to dwell time and data volume of vehicles in RSU service region.Furthermore,it selected maximum weighted independent set of collision graph.The goal was to satisfy the most urgent data requisitions by V2R/V2V cooperate transmission.Transportation simulation results demonstrate that the proposed solution effectively promotes the service capacity by utilizes the multichannel of VANET and V2R/V2V transmission scheduling.     

Generating routes for autonomous driving in vehicle-to-infrastructure communications

The study of vehicular networks has attracted considerable interest in academia and the industry. In the broad area, connected vehicles and autonomous driving are technologies based on wireless data communication between vehicles or between vehicles and infrastructures. A Vehicle-to-Infrastructure (V2I) system consists of communications and computing over vehicles and related infrastructures. In such a system, wireless sensors are installed in some selected points along roads or driving areas. In autonomous driving, it is crucial for a vehicle to figure out the ideal routes by the communications between its equipped sensors and infrastructures then the vehicle is automatically moving along the routes. In this paper, we propose a Bezier curve based recursive algorithm, which effectively creates routes for vehicles through the communication between the On-Board Unit (OBU) and the Road-Side Units (RSUs). In addition, this approach generates a very low overhead. We conduct simulations to test the proposed algorithm in various situations. The experiment results demonstrate that our algorithm creates almost ideal routes.     

基于车辆成组的V2V协同计算卸载策略研究

在车联网中引入V2V计算卸载技术可以缓解当前车载计算卸载热点地区路边单元(RSU)计算资源不足的问题.然而,在计算卸载过程中,服务车辆可能因故障离组或自主选择离开车组.如何返回任务结果并高效地分配计算任务是需要进一步研究的关键问题.提出了一个车组内计算任务分配算法,考虑了可能导致车辆离开车组的因素影响,以及组中每辆车能...     

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.     

Developments and Constraints in 802.11-Based Roadside-to-Vehicle Communications

Vehicular communication has recently become popular for delivering traffic information and broadband services to the commuters. The feasibility of using the opportunistic short interval connections between vehicles and between vehicles and the roadside infrastructure is under scrutiny. The main motivation behind writing this review is that several survey works addressing inter-vehicle communications are available in literature but hardly any survey article on roadside-to-vehicle (R2V) communication is known to the authors. Here, we discuss the latest standards and protocols which can allow the use of already available WLAN infrastructure in the vehicular context. The use of roadside WLAN APs would provide the same services as those envisaged by the intelligent transportation systems using the dedicated roadside base stations. In this paper, we give an overview of the recent developments, limitations, standards and protocols that can facilitate 802.11-based R2V communication.     

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.     

Medium Access Control for QoS Provisioning in Vehicle-to-Infrastructure Communication Networks

The emerging vehicular networks are targeted to provide efficient communications between mobile vehicles and fixed roadside units (RSU), and support mobile multimedia applications and safety services with diverse quality of service (QoS) requirements. In this paper, we propose a busy tone based medium access control (MAC) protocol with enhanced QoS provisioning for life critical safety services. By using busy tone signals for efficient channel preemption in both contention period (CP) and contention free period (CFP), emergency users can access the wireless channel with strict priority when they compete with multimedia users, and thus achieve the minimal access delay. Furthermore, through efficient transmission coordination on the busy tone channel, contention level can be effectively reduced, and the overall network resource utilization can be improved accordingly. We then develop an analytical model to quantify the medium access delay of emergency messages. Extensive simulations with Network Simulator (NS)-2 validate the analysis and demonstrate that the proposed MAC can guarantee reliable and timely emergency message dissemination in a vehicular network.     

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.     

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.     

Stochastic modeling and performance analysis in balancing load and traffic for vehicular ad hoc networks: A review

The rapid growth of vehicular applications has resulted in high demand for Internet technology, which demands an unprecedented network capacity and a high quality of service (QoS). In vehicular ad hoc networks (VANETs), since nodes (vehicles) are highly mobile. The dynamic nature of the network topology in the VANET system changes due to frequent changes in link connectivity. The vehicles-to-vehicles (V2V), vehicles-to-infrastructure (V2I), and QoS, as well as the heterogeneity of applications within the VANET. VANETs have been introduced to make driving comfortable by providing safety and support to drivers. Due to the flexibility and offloading schemes available in-vehicle applications, there are some limitations. However, there are many issues in providing optimum service provisioning and scheduling in the vehicular environment. In VANETs, BSs and roadside units (RSUs) improve QoS. However, Internet services transmit packets to vehicles using stochastic models, and it predicts the traffic on a VANET. We provide open challenges to drive stochastic models in this direction.     

车联网中整合移动边缘计算与内容分发网络的移动性管理策略

由于车载应用的普及和车辆数量的增加,路边基础设施的物理资源有限,当大量车辆接入车联网时能耗与时延同时增加,通过整合内容分发网络(CDN)和移动边缘计算(MEC)的框架可以降低时延与能耗。在车联网中,车辆移动性对云服务的连续性提出了重大挑战。因此,该文提出了移动性管理(MM)来处理该问题。采用开销选择的动态信道分配(ODCA)算法避免乒乓效应且减少车辆在小区间的切换时间。采用基于路边单元(RSU)调度的合作博弈算法进行虚拟机迁移并开发基于学习的价格控制机制,以有效地处理MEC的计算资源。仿真结果表明,所提算法相比于现有的算法能够提高资源利用率且减少开销。     

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.     

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.     

An Efficient Message Authentication Scheme for Vehicular Communications

In this paper, we introduce a novel roadside unit (RSU)-aided message authentication scheme named RAISE, which makes RSUs responsible for verifying the authenticity of messages sent from vehicles and for notifying the results back to vehicles. In addition, RAISE adopts the $k$- anonymity property for preserving user privacy, where a message cannot be associated with a common vehicle. In the case of the absence of an RSU, we further propose a supplementary scheme, where vehicles would cooperatively work to probabilistically verify only a small percentage of these message signatures based on their own computing capacity. Extensive simulations are conducted to validate the proposed scheme. It is demonstrated that RAISE yields a much better performance than previously reported counterparts in terms of message loss ratio (LR) and delay.      

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.