The Mobility Impact in IEEE 802.11p Infrastructureless Vehicular Networks

Vehicular ad hoc networks (VANETs) are an extreme case of mobile ad hoc networks (MANETs). High speed and frequent network topology changes are the main characteristics of vehicular networks. These characteristics lead to special issues and challenges in the network design, especially at the medium access control (MAC) layer. Due to high speed of nodes and their frequent disconnections, it is difficult to design a MAC scheme in VANETs that satisfies the quality-of-service requirements in all networking scenarios. In this thesis, we provide a comprehensive evaluation of the mobility impact on the IEEE 802.11p MAC performance. The study evaluates basic performance metrics such as packet delivery ratio, throughput, and delay, as well as the impact of mobility factors. The study also presents a relation between the mobility factors and the respective medium access behavior. Moreover, a new unfairness problem according to node relative speed is identified for both broadcast and unicast scenarios. To achieve better performance, we propose two dynamic contention window mechanisms to alleviate network performance degradation due to high mobility. Extensive simulation results show the significant impact of mobility on the IEEE 802.11p MAC performance, an identification of a new unfairness problem in the vehicle-to-vehicle (V2V) communications, and the effectiveness of the proposed MAC schemes

Performance comparison between 802.11 and 802.11p for high speed vehicle in VANET

Vehicular ad-hoc networks (VANETs) technology has been emerged as a critical research area. Being ad-hoc in nature, VANET is a type of networks that is created from the concept of establishing a network of cars for a specific need or situation. Communication via routing packets over the high-speed vehicles is a challenging task. Vehicles mobility, speed can vary depending on the road specification. However, on highway, the speed can be increase up to 120 – 200 Km/H. Moving at high speed can affect the efficiency of data delivery. In particular V2I traffic where moving car trying to deliver data to fixed space units which are designed to collect and process data from vehicles. Different protocols have been proposed to be implemented for VANET infrastructure, including 802.11 and 802.11p. In this paper, the performance of the most widely deployed MAC protocols for handling wireless communication which is 802.11 and the 802.11p have been compared, which is a customized version for high speed modes. Performance is investigated in term of data delivery evaluation metrics including network throughput, delay and packet delivery ration. Results show that 802.11p has efficiently enhanced the network performance where network throughput is increased, delay is decreased, and packet delivery ratio is increased as well

Available bandwidth-aware routing in urban vehicular ad-hoc networks

Vehicular communication for intelligent transportation systems will provide safety, comfort for passengers, and more efficient travels. This type of network has the advantage to warn drivers of any event occurred in the road ahead, such as traffic jam, accidents or bad weather. This way, the number of traffic accidents may decrease and many lives could be saved. Moreover, a better selection of non-congested roads will help to reduce pollution. Some other interesting services, such as downloading of multimedia services, would be possible and available through infrastructure along the roadside. Providing multimedia services over VANETs may require a QoS-aware routing protocol that often need to estimate available resources. In this paper, we study the performance, in realistic VANET urban scenarios, of an extension of AODV that includes the available bandwidth estimator ABE [1]. AODV-ABE establishes forwarding paths that satisfy the bandwidth required by the applications. The results, obtained on the NCTUns simulator [2], show that AODVABE could be used in urban-VANETs where vehicles’ speed is moderate.Peer ReviewedPostprint (author’s final draft

Enhancing the Physical Layer in V2V Communication Using OFDM - MIMO Techniques

Vehicular Ad hoc network (VANET) has recently been attracting the attention of researchers as a new technology in the wireless communication system. Vehicle-to-vehicle V2V communication can be considered an important way to help the drivers to satisfy requirements such as less congestion, accident warning, road exploration, etc. The propagation issues such as multipath fading significantly affect the reliability of V2V communication. The goal of this work is to enhance the performance of the physical layer PHY in V2V communication. However, the cellular phone channel has been used to evaluate the possibility of apply it in the vehicular communication V2V. The simulation results observed that the transmitted signal is affected by a multipath fading channel. In order to overcome this problem two techniques are used: Orthogonal Frequency Division Multiplexing (OFDM) technique and Multiple-Input-MultipleOutput (MIMO) diversity technique. The simulation results showed that the OFDM technique overcomes the multipath fading with high transmission power. On the other hand, MIMO diversity technique called Alamouti Space-Time Code for two transmitters and two receivers (MIMO 2x2) is used to improve the error degradation with less transmission power

Modeling Enhancements in DSR, FSR, OLSR under Mobility and Scalability Constraints in VANETs

Frequent topological changes due to high mobility is one of the main issues in Vehicular Ad-hoc NETworks (VANETs). In this paper, we model transmission probabilities of 802.11p for VANETs and effect of these probabilities on average transmission time. To evaluate the effect of these probabilities of VANETs in routing protocols, we select Dynamic Source Routing (DSR), Fish-eye State Routing (FSR) and Optimized Link State Routing (OLSR). Framework of these protocols with respect to their packet cost is also presented in this work. A novel contribution of this work is enhancement of chosen protocols to obtain efficient behavior. Extensive simulation work is done to prove and compare the efficiency in terms of high throughput of enhanced versions with default versions of protocols in NS-2. For this comparison, we choose three performance metrics; throughput, End-to-End Delay (E2ED) and Normalized Routing Load (NRL) in different mobilities and scalabilities. Finally, we deduce that enhanced DSR (DSR-mod) outperforms other protocols by achieving 16% more packet delivery for all scalabilities and 28% more throughput in selected mobilities than original version of DSR (DSR-orig)

A novel real-time traffic information system based on wireless mesh networks

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Improving Performance of IEEE 802.11p MAC Layer for Emergency Message Dissemination

Vehicular ad-hoc networking is the most promising subfield of mobile ad-hoc networks, which may become the ad-hoc networking technology in near future for vehicles communicating amongst themselves on road. It uses IEEE 802.11p MAC protocol as wireless networking technology. The IEEE 802.11p MAC protocol has inherent problems in wireless ad-hoc networking environment due its heterogeneous, infrastructureless and highly dynamic nature. The performance of IEEE 802.11p MAC layer for vehicular ad-hoc networking is based on performance of one-hop broadcasting. The performance of IEEE 802.11p one-hop broadcasting is of major concern regarding emergency message dissemination. The CSMA/CA protocol used in IEEE 802.11p is far from optimal solution for emergency message dissemination due to inherent properties of random access, higher delivery delays and retransmissions. Techniques to improve emergency message dissemination delivery rate and minimize time latency of message dissemination, such as, disabling backoff and synchronous transmission, have been mentioned in this thesis out of which one technique such as disabling backoff is being evaluated through simulation results. The goal of this thesis work is to evaluate a technique, modifying the IEEE 802.11p MAC layer protocol using Network Simulator 3 (NS3). The technique is based on introducing a separate EDCA queue and a separate EDCAF function for emergency messages in QoS EDCA priority queues, disabling backoff for emergency messages and giving highest priority to emergency messages in a station having different AC queues seeking for transmission opportunity. Disabling backoff for emergency messages may reduce time latency arising from exponential backoff algorithm. As the backoff is disabled, more than one station may start transmitting emergency message at the same time. So, it can be deduced that such technique could be beneficial for simple emergency applications. The simulation results show that this technique could be useful for emergency applications utilizing a buzz signal for hazardous warnings on road

Benchmarking the cooperative awareness service at application layer with IEEE 802.11p and LTE-PC5 Mode-4

© 2021 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. Al document ha d’aparèixer l’enllaç a la publicació original a IEEE, o bé al Digital Object Identifier (DOI).Vehicular communications hold the promise of disrupting mobility services and supporting the mass adoption of future autonomous vehicles. Regulators have set aside specific spectrum at the 5.9 GHz band to support Intelligent Transport Systems (ITS) safety applications, for which a world-wide adoption of a standardized radio technology is a key factor to deliver on this promise. Two technologies are currently positioned to begin its commercial path, IEEE 802.11p and LTE-PC5 Mode-4. The main differences between these technologies lie on the design of their channel access mechanisms. This paper provides an analysis of the impact that the Medium Access Control (MAC) mechanisms included in 802.11p and LTE-PC5 Mode-4 will have on the performance of the applications using the Cooperative Awareness Service, applying two new application-level metrics used by safety applications: Neighborhood Awareness Ratio and Position Error. We have found that, even with an equivalent physical layer performance, the MAC layer of LTE-PC5 Mode-4 will mostly outperform the MAC layer of IEEE 802.11p (or its not yet ready enhanced version 802.11bd). However, IEEE 802.11p/bd results in slightly better vehicle positioning accuracy at lower distances.Peer ReviewedPostprint (author's final draft

Adaptive Mechanisms to Improve Message Dissemination in Vehicular Networks

En el pasado, se han dedicado muchos recursos en construir mejores carreteras y autovías. Con el paso del tiempo, los objetivos fueron cambiando hacia las mejoras de los vehículos, consiguiendo cada vez vehículos más rápidos y con mayor autonomía. Más tarde, con la introducción de la electrónica en el mercado del automóvil, los vehículos fueron equipados con sensores, equipos de comunicaciones, y otros avances tecnológicos que han permitido la aparición de coches más eficientes, seguros y confortables. Las aplicaciones que nos permite el uso de las Redes Vehiculares (VNs) en términos de seguridad y eficiencia son múltiples, lo que justifica la cantidad y recursos de investigación que se están dedicando en los últimos años. En el desarrollo de esta Tesis, los esfuerzos se han centrado en el área de las Vehicular Ad-hoc Networks, una subclase de las Redes Vehiculares que se centra en las comunicaciones entre los vehículos, sin necesidad de que existan elementos de infraestructura. Con la intención de mejorar el proceso de diseminación de mensajes de alerta, imprescindibles para las aplicaciones relacionadas con la seguridad, se ha propuesto un esquema de difusión adaptativo, capaz de seleccionar automáticamente el mecanismo de difusión óptimo en función de la complejidad del mapa y de la densidad actual de vehículos. El principal objetivo es maximizar la efectividad en la difusión de mensajes, reduciendo al máximo el número de mensajes necesarios, evitando o mitigando las tormentas de difusión. Las propuestas actuales en el área de las VANETs, se centran principalmente en analizar escenarios con densidades típicas o promedio. Sin embargo, y debido a las características de este tipo de redes, a menudo se dan situaciones con densidades extremas (altas y bajas). Teniendo en cuenta los problemas que pueden ocasionar en el proceso de diseminación de los mensajes de emergencia, se han propuesto dos nuevos esquemas de difusión para bajas densidades: el \emph{Junction Store and Forward} (JSF) y el \emph{Neighbor Store and Forward} (NSF). Además, para situaciones de alta densidad de vehículos, se ha diseñado el \emph{Nearest Junction Located} (NJL), un esquema de diseminación que reduce notablemente el número de mensajes enviados, sin por ello perder prestaciones. Finalmente, hemos realizado una clasificacion de los esquemas de difusión para VANETs más importantes, analizando las características utilizadas en su diseño. Además hemos realizado una comparación de todos ellos, utilizando el mismo entorno de simulación y los mismos escenarios, permitiendo conocer cuál es el mejor esquema de diseminación a usar en cada momento