A Comparative Survey of VANET Clustering Techniques

© 2016 Crown. A vehicular ad hoc network (VANET) is a mobile ad hoc network in which network nodes are vehicles - most commonly road vehicles. VANETs present a unique range of challenges and opportunities for routing protocols due to the semi-organized nature of vehicular movements subject to the constraints of road geometry and rules, and the obstacles which limit physical connectivity in urban environments. In particular, the problems of routing protocol reliability and scalability across large urban VANETs are currently the subject of intense research. Clustering can be used to improve routing scalability and reliability in VANETs, as it results in the distributed formation of hierarchical network structures by grouping vehicles together based on correlated spatial distribution and relative velocity. In addition to the benefits to routing, these groups can serve as the foundation for accident or congestion detection, information dissemination and entertainment applications. This paper explores the design choices made in the development of clustering algorithms targeted at VANETs. It presents a taxonomy of the techniques applied to solve the problems of cluster head election, cluster affiliation, and cluster management, and identifies new directions and recent trends in the design of these algorithms. Additionally, methodologies for validating clustering performance are reviewed, and a key shortcoming - the lack of realistic vehicular channel modeling - is identified. The importance of a rigorous and standardized performance evaluation regime utilizing realistic vehicular channel models is demonstrated

A Hybrid (Active-Passive) VANET Clustering Technique

Clustering serves a vital role in the operation of Vehicular Ad hoc Networks (VANETs) by continually grouping highly mobile vehicles into logical hierarchical structures. These moving clusters support Intelligent Transport Systems (ITS) applications and message routing by establishing a more stable global topology. Clustering increases scalability of the VANET by eliminating broadcast storms caused by packet flooding and facilitate multi-channel operation. Clustering techniques are partitioned in research into two categories: active and passive. Active techniques rely on periodic beacon messages from all vehicles containing location, velocity, and direction information. However, in areas of high vehicle density, congestion may occur on the long-range channel used for beacon messages limiting the scale of the VANET. Passive techniques use embedded information in the packet headers of existing traffic to perform clustering. In this method, vehicles not transmitting traffic may cause cluster heads to contain stale and malformed clusters. This dissertation presents a hybrid active/passive clustering technique, where the passive technique is used as a congestion control strategy for areas where congestion is detected in the network. In this case, cluster members halt their periodic beacon messages and utilize embedded position information in the header to update the cluster head of their position. This work demonstrated through simulation that the hybrid technique reduced/eliminated the delays caused by congestion in the modified Distributed Coordination Function (DCF) process, thus increasing the scalability of VANETs in urban environments. Packet loss and delays caused by the hidden terminal problem was limited to distant, non-clustered vehicles. This dissertation report presents a literature review, methodology, results, analysis, and conclusion

Fixed Cluster Based Cluster Head Selection Algorithm in Vehicular Adhoc Network

The emergence of Vehicular Adhoc Networks (VANETs) is expected support variety of applications for driver assistance, traffic efficiency and road safety. For proper transmission of messages in VANET, one of the proposed solutions is dividing the network into clusters and then selecting a cluster head (CH) in each cluster. This can decrease the communication overhead between road side units (RSUs) and other components of VANETs, because instead of every node communicating with RSU, only CH communicates with RSU and relays relevant messages. In clustering, an important step is the selection of CH. In this thesis, we implemented vehicle to vehicle (V2V), cluster head to road side unit and road side unit to trusted authority authentication for the clustered network. We also presented a heuristic algorithm for selecting a suitable vehicle as the cluster head in a cluster. For the selection of head vehicle, we used weighted fitness values based on three parameters; trust value, position from the cluster boundary and absolute relative average speed. Simulation results indicate that the proposed approach can lead to improvements in terms of QoS metrics like delay, throughput and packet delivery ratio

A survey on pseudonym changing strategies for Vehicular Ad-Hoc Networks

The initial phase of the deployment of Vehicular Ad-Hoc Networks (VANETs) has begun and many research challenges still need to be addressed. Location privacy continues to be in the top of these challenges. Indeed, both of academia and industry agreed to apply the pseudonym changing approach as a solution to protect the location privacy of VANETs'users. However, due to the pseudonyms linking attack, a simple changing of pseudonym shown to be inefficient to provide the required protection. For this reason, many pseudonym changing strategies have been suggested to provide an effective pseudonym changing. Unfortunately, the development of an effective pseudonym changing strategy for VANETs is still an open issue. In this paper, we present a comprehensive survey and classification of pseudonym changing strategies. We then discuss and compare them with respect to some relevant criteria. Finally, we highlight some current researches, and open issues and give some future directions

TDMA Slot Reservation in Cluster-Based VANETs

Vehicular Ad Hoc Networks (VANETs) are a form of Mobile Ad Hoc Networks (MANETs) in which vehicles on the road form the nodes of the network. VANETs provide several services to enhance the safety and comfort of drivers and passengers. These services can be obtained by the wireless exchange of information among the vehicles driving on the road. In particular, the transmission of two different types of messages, safety/update and non-safety messages. The transmission of safety/update message aims to inform the nearby vehicles about the sender\u27s current status and/or a detected dangerous situation. This type of transmission is designed to help in accident and danger avoidance. Moreover, it requires high message generated rate and high reliability. On the other hand, the transmission of non-safety message aims to increase the comfort on vehicles by supporting several non-safety services, from notifications of traffic conditions to file sharing. Unfortunately, the transmission of non-safety message has less priority than safety messages, which may cause shutting down the comfort services. The goal of this dissertation is to design a MAC protocol in order to provide the ability of the transmission of non-safety message with little impact on the reliability of transmitting safety message even if the traffic and communication densities are high. VANET is a highly dynamic network. With lack of specialized hardware for infrastructure and the mobility to support network stability and channel utilization, acluster-based MAC protocol is needed to solve these overcomes. This dissertation makes the following contributions: 1. A multi-channel cluster-based TDMA MAC protocol to coordinate intracluster communications (TC-MAC) 2. A CH election and cluster formation algorithm based on the traffic flow and a cluster maintenance algorithm that benefits from our cluster formation algorithm 3. A multi-channel cluster-based CDNIA/TDMA hybrid MAC protocol to coordinate inter-cluster communications I will show that TC-MAC provides better performance than the current WAVE standard in terms of safety/update message reliability and non-safety message delivery. Additionally, I will show that my clustering and cluster maintenance protocol provides more stable clusters, which will reduce the overhead of clusterhead election and re-clustering and leads to an efficient hierarchical network topology

Un protocole de diffusion des messages dans les réseaux véhiculaires

De nos jours, la voiture est devenue le mode de transport le plus utilisé, mais malheureusement, il est accompagné d’un certain nombre de problèmes (accidents, pollution, embouteillages, etc.), qui vont aller en s’aggravant avec l’augmentation prévue du nombre de voitures particulières, malgré les efforts très importants mis en œuvre pour tenter de les réduire ; le nombre de morts sur les routes demeure très important. Les réseaux sans fil de véhicules, appelés VANET, qui consistent de plusieurs véhicules mobiles sans infrastructure préexistante pour communiquer, font actuellement l’objet d'une attention accrue de la part des constructeurs et des chercheurs, afin d’améliorer la sécurité sur les routes ou encore les aides proposées aux conducteurs. Par exemple, ils peuvent avertir d’autres automobilistes que les routes sont glissantes ou qu’un accident vient de se produire. Dans VANET, les protocoles de diffusion (broadcast) jouent un rôle très important par rapport aux messages unicast, car ils sont conçus pour transmettre des messages de sécurité importants à tous les nœuds. Ces protocoles de diffusion ne sont pas fiables et ils souffrent de plusieurs problèmes, à savoir : (1) Tempête de diffusion (broadcast storm) ; (2) Nœud caché (hidden node) ; (3) Échec de la transmission. Ces problèmes doivent être résolus afin de fournir une diffusion fiable et rapide. L’objectif de notre recherche est de résoudre certains de ces problèmes, tout en assurant le meilleur compromis entre fiabilité, délai garanti, et débit garanti (Qualité de Service : QdS). Le travail de recherche de ce mémoire a porté sur le développement d’une nouvelle technique qui peut être utilisée pour gérer le droit d’accès aux médias (protocole de gestion des émissions), la gestion de grappe (cluster) et la communication. Ce protocole intègre l'approche de gestion centralisée des grappes stables et la transmission des données. Dans cette technique, le temps est divisé en cycles, chaque cycle est partagé entre les canaux de service et de contrôle, et divisé en deux parties. La première partie s’appuie sur TDMA (Time Division Multiple Access). La deuxième partie s’appuie sur CSMA/CA (Carrier Sense Multiple Access / Collision Avoidance) pour gérer l’accès au medium. En outre, notre protocole ajuste d’une manière adaptative le temps consommé dans la diffusion des messages de sécurité, ce qui permettra une amélioration de la capacité des canaux. Il est implanté dans la couche MAC (Medium Access Control), centralisé dans les têtes de grappes (CH, cluster-head) qui s’adaptent continuellement à la dynamique des véhicules. Ainsi, l’utilisation de ce protocole centralisé nous assure une consommation efficace d’intervalles de temps pour le nombre exact de véhicules actifs, y compris les nœuds/véhicules cachés; notre protocole assure également un délai limité pour les applications de sécurité, afin d’accéder au canal de communication, et il permet aussi de réduire le surplus (overhead) à l’aide d’une propagation dirigée de diffusion.Nowadays, the car has become the most popular mode of transport, but unfortunately its use is accompanied by a number of problems (accidents, pollution, congestion, etc.). These problems will get worse with the increase in the number of passenger cars, despite very significant efforts made to reduce the number of road deaths, which is still very high. Wireless networks for vehicles called VANET (Vehicle Ad Hoc Networks), were developed when it became possible to connect several mobile vehicles without relying on pre existing communication infrastructures. These networks have currently become the subject of increased attention from manufacturers and researchers, due to their potential for improving road safety and/or offering assistance to drivers. They can, for example, alert other drivers that roads are slippery or that an accident has just occurred. In VANETs, broadcast protocols play a very important role compared to unicast protocols, since they are designed to communicate important safety messages to all nodes. Existing broadcast protocols are not reliable and suffer from several problems: (1) broadcast storms, (2) hidden nodes, and (3) transmission failures. These problems must solved if VANETs are to become reliable and able to disseminate messages rapidly. The aim of our research is to solve some of these problems while ensuring the best compromise among reliability, guaranteed transmission times and bandwidth (Quality of Service: QoS). The research in this thesis focuses on developing a new technique for managing medium access. This protocol incorporates the centralized management approach involving stable clusters. In this technique, time is divided into cycles; with each cycle being shared among the control and service channels, and is divided into two segments. The first is based on TDMA (Time Division Multiple Access) while the second is based on CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) to manage access to the medium. Furthermore, our protocol adaptively adjusts the time consumed in broadcasting safety messages, thereby improving channel capacity. It is implemented in the MAC (Medium Access Control), and centralized in stable cluster heads that are able to adapt to the dynamics of vehicles. This protocol provides a centralized and efficient use of time intervals for an exact number of active vehicles, including hidden nodes/vehicles. Our protocol also provides time intervals dedicated to security applications for providing access to communication channels, and also reduces overhead via directed diffusion of data. Keywords: Ad-hoc networks, VANET, Vehicle, Periodic Safety Messages, broadcast protocols, contention-free

A Comprehensive Approach to WSN-Based ITS Applications: A Survey

In order to perform sensing tasks, most current Intelligent Transportation Systems (ITS) rely on expensive sensors, which offer only limited functionality. A more recent trend consists of using Wireless Sensor Networks (WSN) for such purpose, which reduces the required investment and enables the development of new collaborative and intelligent applications that further contribute to improve both driving safety and traffic efficiency. This paper surveys the application of WSNs to such ITS scenarios, tackling the main issues that may arise when developing these systems. The paper is divided into sections which address different matters including vehicle detection and classification as well as the selection of appropriate communication protocols, network architecture, topology and some important design parameters. In addition, in line with the multiplicity of different technologies that take part in ITS, it does not consider WSNs just as stand-alone systems, but also as key components of heterogeneous systems cooperating along with other technologies employed in vehicular scenarios

Performance analysis of vehicular networks for motorway scenario.

Abstract Not Provided

TDMA-based MAC Protocols for Vehicular Ad Hoc Networks: A Survey, Qualitative Analysis and Open Research Issues

International audience—Vehicular Ad-hoc NETworks (VANETs) have attracted a lot of attention in the research community in recent years due to their promising applications. VANETs help improve traffic safety and efficiency. Each vehicle can exchange information to inform other vehicles about the current status of the traffic flow or a dangerous situation such as an accident. Road safety and traffic management applications require a reliable communication scheme with minimal transmission collisions, which thus increase the need for an efficient Medium Access Control (MAC) protocol. However, the design of the MAC in a vehicular network is a challenging task due to the high speed of the nodes, the frequent changes in topology, the lack of an infrastructure, and various QoS requirements. Recently several Time Division Multiple Access (TDMA)-based medium access control protocols have been proposed for VANETs in an attempt to ensure that all the vehicles have enough time to send safety messages without collisions and to reduce the end-to-end delay and the packet loss ratio. In this paper, we identify the reasons for using the collision-free medium access control paradigm in VANETs. We then present a novel topology-based classification and we provide an overview of TDMA-based MAC protocols that have been proposed for VANETs. We focus on the characteristics of these protocols, as well as on their benefits and limitations. Finally, we give a qualitative comparison, and we discuss some open issues that need to be tackled in future studies in order to improve the performance of TDMA-based MAC protocols for vehicle to vehicle (V2V) communications