A Centrality-based RSU Deployment Approach for Vehicular Ad Hoc Networks

International audienceThis paper studies the RSU deployment problem in a 2-D road scenario of a vehicular ad hoc network. To optimize RSU deployment, we introduce the notion of centrality in a social network to RSU deployment, and use it to measure the importance of an RSU position candidate in RSU deployment. Based on the notion of centrality, we propose a centrality-based RSU deployment approach and formulate the RSU deployment problem as a linear programing problem with the objective to maximize the total centrality of all position candidates selected for RSU deployment under the constraint of a given deployment budget. To solve the formulated problem, we analogize the problem to a 0-1 Knapsack problem and thus employ a 0-1 Knapsack algorithm to solve the problem. In the analogy, the budget in the RSU deployment problem is analogous to the bag's capacity in the Knapsack problem, the cost of deploying an RSU is analogous to an item's weight, and the centrality of a position candidate is analogous to an item's value. Simulation results show that the proposed centrality-based deployment approach can effectively improve the efficiency of the RSU deployment in terms of the coverage time ratio as compared to a random deployment approach

Road side unit deployment: a density-based approach

© 2013 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Currently, the number of vehicles increases every year, raising the probability of having accidents. When an accident occurs, wireless technologies enable vehicles to share warning messages with other vehicles by using vehicle to vehicle (V2V) communications, and with the emergency services by using vehicle to infrastructure (V2I) communications. Regarding vehicle to infrastructure communications, Road Side Units (RSUs) act similarly to wireless LAN access points, and can provide communications with the infrastructure. Since RSUs are usually very expensive to install, authorities limit their number, especially in suburbs and areas of sparse population, making RSUs a precious resource in vehicular environments. In this paper, we propose a Density-based Road Side Unit deployment policy (D-RSU), specially designed to obtain an efficient system with the lowest possible cost to alert emergency services in case of an accident. Our approach is based on deploying RSUs using an inverse proportion to the expected density of vehicles. The obtained results show how D-RSU is able to reduce the required number of RSUs, as well as the accident notification time.This work was partially supported by the Ministerio de Educacion y Ciencia, Spain, under Grant TIN2011-27543-C03-01, as well as by the Fundacion Universitaria Antonio Gargallo (FUAG), and the Caja de Ahorros de la Inmaculada (CAI).Barrachina, J.; Garrido, P.; Fogue, M.; Martínez, FJ.; Cano Escribá, JC.; Tavares De Araujo Cesariny Calafate, CM.; Manzoni, P. (2013). Road side unit deployment: a density-based approach. IEEE Intelligent Transportation Systems Magazine. 5(3):30-39. https://doi.org/10.1109/MITS.2013.2253159S30395

Routing protocol for V2X communications for Urban VANETs

Intelligent Transportation Systems (ITSs) have been attracting tremendous attention in both academia and industry due to emerging applications that pave the way towards safer enjoyable journeys and inclusive digital partnerships. Undoubtedly, these ITS applications will demand robust routing protocols that not only focus on Inter-Vehicle Communications but also on providing fast, reliable, and secure access to the infrastructure. This thesis aims mainly to introduce the challenges of data packets routing through urban environment using the help of infrastructure. Broadcasting transmission is an essential operational technique that serves a broad range of applications which demand different restrictive QoS provisioning levels. Although broadcast communication has been investigated widely in highway vehicular networks, it is undoubtedly still a challenge in the urban environment due to the obstacles, such as high buildings. In this thesis, the Road-Topology based Broadcast Protocol (RTBP) is proposed, a distance and contention-based forwarding scheme suitable for both urban and highway vehicular environments. RTBP aims at assigning the highest forwarding priority to a vehicle, called a mobile repeater, having the greatest capability to send the packet in multiple directions. In this way, RTBP effectively reduces the number of competing vehicles and minimises the number of hops required to retransmit the broadcast packets around the intersections to cover the targeted area. By investigating the RTBP under realistic urban scenarios against well-known broadcast protocols, eMDR and TAF, that are dedicated to retransmitting the packets around intersections, the results showed the superiority of the RTBP in delivering the most critical warning information for 90% of vehicles with significantly lower delay of 58% and 70% compared to eMDR and TAF. The validation of this performance was clear when the increase in the number of vehicles. Secondly, a Fast and Reliable Hybrid routing (FRHR) protocol is introduced for efficient infrastructure access which is capable of handling efficient vehicle to vehicle communications. Interface to infrastructure is provided by carefully placed RoadSide Units (RSUs) which broadcast beacons in a multi-hop fashion in constrained areas. This enables vehicles proactively to maintain fresh minimum-delay routes to other RSUs while reactively discovering routes to nearby vehicles. The proposed protocol utilizes RSUs connected to the wired backbone network to relay packets toward remote vehicles. A vehicle selects an RSU to register with according to the expected mean delay instead of the device’s remoteness. The FRHR performance is evaluated against established infrastructure routing protocols, Trafroute, IGSR and RBVT-R that are dedicated to for urban environment, the results showed an improvement of 20% to 33% in terms of packet delivery ratio and lower latency particularly in sparse networks due to its rapid response to changes in network connectivity. Thirdly, focusing on increasing FRHR’s capability to provide more stable and durable routes to support the QoS requirements of expected wide-range ITS applications on the urban environment, a new route selection mechanism is introduced, aiming at selecting highly connected crossroads. The new protocol is called, Stable Infrastructure Routing Protocol (SIRP). Intensive simulation results showed that SIRP offers low end-to-end delay and high delivery ratio with varying traffic density, while resolving the problem of frequent link failures

Avaliação por simulação da comunicação entre veículos

Mestrado em Engenharia Electrónica e TelecomunicaçõesNuma rede veicular, a densidade de veículos (com o tipo de comunicação IEEE 802.11p) que formam a rede veicular será um dos pontos chave para o sucesso da comunicação entre os mesmos. Nos cenários de auto-estrada, o caso mais estudado ao longo desta dissertação, existe uma grande probabilidade de a rede veicular se encontrar desligada, ou seja, de não existir um caminho entre veículos sempre ao alcance, o que diminuirá a viabilidade e qualidade das comunicações. Para melhorar a comunicação nestes cenários podem ser integradas na rede estações fixas, conhecidas por Road Side Units (RSUs). A utilização de RSUs permite melhorar as comunicações entre veículos conseguindo reduzir, essencialmente, o atraso na entrega das mensagens, pois pretende-se que essa inserção diminua a probabilidade de partição da rede entre os veículos. Nesta Dissertação são idealizados e implementados no simulador ns-3 cenários diferentes, com diferentes densidades de veículos, que permitem avaliar a influência das RSUs nas comunicações veiculares. Pelos resultados apresentados, verifica-se que existe uma melhoria significativa nas comunicações quando as RSUs estão ligadas através de rede fixa, por exemplo a Ethernet. Com RSUs ligadas por redes sem fios, existe uma melhoria significativa das comunicações, mas esta melhoria é inferior à existente em cenários de RSUs ligadas por uma rede com fios. Quando as RSUs se encontram desligadas, verifica-se que não existe grande melhoria e as comunicações ficam mais instáveis. Cada RSU tem um custo bastante elevado. Sendo assim, um dos desafios desta Dissertação é o de conseguir melhorar, de facto, a comunicação entre os veículos, mas reduzindo ao máximo o número de RSUs necessárias no cenário, garantindo sempre essa melhoria nas comunicações. Ao longo do trabalho desenvolvido verificou-se que o espaçamento ideal entre as RSUs, para os testes realizados, é de 1800m.In a Vehicular network, the density of vehicles (enabled with the standard IEEE 802.11p) that form the network is one of the keys to the success of intervehicular communication. In highway scenarios, which will be the focus of this Master dissertation, the probability of having a disconnected vehicular network can be very high — in other words, the probability of having no paths within reach between vehicles can be very high, which hinders communication reliability. To improve the communication in these scenarios we can use infrastructure known as Road Side Units (RSUs). When we use RSUs as fixed points for communication in highways, we expect an enhancement on the network performance with an improvement on the propagation delay of messages between the disconnected vehicles. In this Dissertation, we idealized and implemented different scenarios in a network simulator (ns-3), with different densities of vehicles used to evaluate the influence of RSUs in inter-vehicular communication. The results show that, with RSUs interconnected by Ethernet, we have a significant improvement on the network performance. With RSUs interconnected by Wi-Fi, we also see improvements on the network performance, albeit less significant than those of the scenarios with RSUs connected by a wired network. When the RSUs are disconnected, we observe that there is no improvement and communications become unstable. Each RSU has a high cost; therefore, in this Dissertation, we need to minimize the distribution of RSUs while still providing a significant improvement on communications. In this work we have shown that the ideal spacing between the RSUs, in our tests, was of approximately 1800m