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

CGT Method of Message forwarding

In vehicular ad hoc networks (VANETs), because of the nonexistence of end-to-end connections, it is essential that nodes take advantage of connection opportunities to forward messages to make end-to-end messaging possible. Thus, it is crucial to make sure that nodes have incentives to forward messages for others, despite the fact that the routing protocols in VANETs are different from traditional end-to-end routing protocols. In this paper, stimulation of message forwarding in VANETs is concerned. This approach is based on coalitional game theory, particularly, an incentive scheme for VANETs is proposed and with this scheme, following the routing protocol is in the best interest of each node. In addition, a lightweight approach is proposed for taking the limited storage space of each node into consideration

Investigating seamless handover in VANET systems

Wireless communications have been extensively studied for several decades, which has led to various new advancements, including new technologies in the field of Intelligent Transport Systems. Vehicular Ad hoc Networks or VANETs are considered to be a long-term solution, contributing significantly towards Intelligent Transport Systems in providing access to critical life-safety applications and infotainment services. These services will require ubiquitous connectivity and hence there is a need to explore seamless handover mechanisms. Although VANETs are attracting greater commercial interest, current research has not adequately captured the realworld constraints in Vehicular Ad hoc Network handover techniques. Due to the high velocity of the vehicles and smaller coverage distances, there are serious challenges in providing seamless handover from one Road Side Unit (RSU) to another and this comes at the cost of overlapping signals of adjacent RSUs. Therefore, a framework is needed to be able to calculate the regions of overlap in adjacent RSU coverage ranges to guarantee ubiquitous connectivity. This thesis is about providing such a framework by analysing in detail the communication mechanisms in a VANET network, firstly by means of simulations using the VEINs framework via OMNeT++ and then using analytical analysis of the probability of successful packet reception. Some of the concepts of the Y-Comm architecture such as Network Dwell Time, Time Before Handover and Exit Times have been used to provide a framework to investigate handover issues and these parameters are also used in this thesis to explore handover in highly mobile environments such as VANETs. Initial investigation showed that seamless communication was dependant on the beacon frequency, length of the beacon and the velocity of the vehicle. The effects of each of these parameters are explored in detail and results are presented which show the need for a more probabilistic approach to handover based on cumulative probability of successful packet reception. In addition, this work shows how the length of the beacon affects the rate of change of the Signal-to-Noise ratio or SNR as the vehicle approaches the Road-Side Unit. However, the velocity of the vehicle affects both the cumulative probability as well as the Signal-to-Noise ratio as the vehicle approaches the Road-Side Unit. The results of this work will enable systems that can provide ubiquitous connectivity via seamless handover using proactive techniques because traditional models of handover are unable to cope with the high velocity of the vehicles and relatively small area of coverage in these environments. Finally, a testbed has been set-up at the Middlesex University, Hendon campus for the purpose of achieving a better understanding of VANET systems operating in an urban environment. Using the testbed, it was observed that environmental effects have to be taken into considerations in real-time deployment studies to see how these parameters can affect the performance of VANET systems under different scenarios. This work also highlights the fact that in order to build a practical system better propagation models are required in the urban context for highly mobile environments such as VANETs

On The Security And Quality Of Wireless Communications In Outdoor Mobile Environment

The rapid advancement in wireless technology along with their low cost and ease of deployment have been attracting researchers academically and commercially. Researchers from private and public sectors are investing into enhancing the reliability, robustness, and security of radio frequency (RF) communications to accommodate the demand and enhance lifestyle. RF base communications -by nature- are slower and more exposed to attacks than a wired base (LAN). Deploying such networks in various cutting-edge mobile platforms (e.g. VANET, IoT, Autonomous robots) adds new challenges that impact the quality directly. Moreover, adopting such networks in public outdoor areas make them vulnerable to various attacks (regardless of the attacker motive). Therefore, the quality and security of the communications cannot be neglected especially when developing outdoor wireless applications/networks. While some wireless applications and platforms aim to provide comfort and infotainment, others are more critical to protect and save lives. Thus, the need for mobile broadband connections has been increased to accommodate such applications. The FCC took the first step to regulate and assure the quality when using these technologies by allocating spectrums and issuing standards and amendments (e.g. IEEE802.11a, b, g, n, and p) to deliver reliable and secure communications. In this dissertation, we introduce several problems related to the security and quality of communications in outdoor environments. Although we focus on the ISM-RF bands UHF and SHF (licensed and unlicensed) and their applications when solving quality and security issues nevertheless, the concept of propagating signals through the air for communications remain the same across other ISM bands. Therefore, problems and their solutions in this work can be applied to different wireless technologies with respect to environment and mobility

A fast, reliable and lightweight distributed dissemination protocol for safety messages in Urban Vehicular Networks

It is foreseeable that in the few upcoming years, real time traffic information, including road incidents notifications, will be collected and disseminated by mobile vehicles, thanks to their plethora of embedded sensors. Each vehicle can thus actively participate in sharing the collected information with the other peers forming an infrastructure-less self-organising network of vehicles. However, the fast development of applications in ITS field may result in an excessive load on such a network; therefore an efficient use of the available bandwidth is highly required. Not only should the size of the data inserted in the network be properly controlled, but also the extent of each message should be accurately defined. In this paper, we propose a distributed dissemination protocol for safety messages in urban areas, dubbed “Road-Casting Protocol (RCP)”, which is based on a novel cooperative forwarding mechanism. Moreover, an accurate definition of the Region of Interest (RoI) (i.e. the geographical scope) of each broadcasted safety message is also devised to ensure better control of the network load. We have evaluated the efficiency of the RCP along with the proposed RoI definition using realistic simulations, based on an accurate propagation loss model for urban vehicular ad hoc network communications, and the obtained results show a substantial improvement, compared to state of the art schemes, in terms of enhanced packet delivery ratio up to higher than 95%, lower end-to-end delay and reduced network load

Deadline constrained optimal periodic broadcasting under hidden terminals in vehicular networks

Dissertação (mestrado)—Universidade de Brasília, Faculdade de Tecnologia, 2015.Este trabalho faz uma análise para o acesso aleatório ótimo na transmissão de mensagens com prazo de entrega final em uma rede de rádio cognitivo, considerando que a mensagem deve ser entregue para todos os nós da rede em um prazo de entrega definido. O transmissor é um usuário secundário (SU) que acessa o canal usado pelos usuários primários de forma oportunista. O protocolo de controle de acesso ao meio usado é o Slotted-Aloha onde uma transmissão por difusão tem sucesso se todos os nós receptores, dentro do alcance de transmissão do emissor, recebem a mensagem dentro do prazo de entrega definido previamente. Uma abordagem com re-transmissão de mensagens é utilizada para melhorar a confiabilidade da entrega, que necessita ter uma taxa de sucesso maior ou igual a 99,9 %, com uma latência máxima de 100 ms para cumprir as regulamentações de segurança das redes veiculares. Além disso, um novo método de análise de transmissão periódica é proposto usando uma abordagem com coeficientes multinomiais e outra baseada na função de distribuição de probabilidade geométrica.This work analyses an optimal random access for broadcasting messages with deadline in a cognitive radio (CR) network considering that the message must be delivery to all nodes in the network in a strict known delivery time. The transmitter is a secondary user (SU) that accesses the primary users (PUs) channel opportunistically. The slotted-Aloha medium access control (MAC) protocol is considered assuming that a successful broadcast transmission from a SU happens if all the receiver nodes within the SU transmission range receive the SU message within a given deadline. A re-broadcast approach is used to improve the reliability of the message delivery which requires a probability of success greater than or equal to 99.9% with a latency of 100 ms. Also a novel method of analysis for periodic broadcast using multinomial coeficients is introduced, as well as a method that considers a geometric distribution approach