4 research outputs found

    Reliable and efficient data dissemination schemein VANET: a review

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    Vehicular ad-hoc network (VANET), identified as a mobile ad hoc network MANETs with several added constraints. Basically, in VANETs, the network is established on the fly based on the availability of vehicles on roads and supporting infrastructures along the roads, such as base stations. Vehicles and road-side infrastructures are required to provide communication facilities, particularly when enough vehicles are not available on the roads for effective communication. VANETs are crucial for providing a wide range of safety and non-safety applications to road users. However, the specific fundamental problem in VANET is the challenge of creating effective communication between two fast-moving vehicles. Therefore, message routing is an issue for many safety and non-safety of VANETs applications. The challenge in designing a robust but reliable message dissemination technique is primarily due to the stringent QoS requirements of the VANETs safety applications. This paper investigated various methods and conducted literature on an idea to develop a model for efficient and reliable message dissemination routing techniques in VANET

    Boltzmann-type description with cutoff of Follow-the-Leader traffic models

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    In this paper we consider a Boltzmann-type kinetic description of Follow-the-Leader traffic dynamics and we study the resulting asymptotic distributions, namely the counterpart of the Maxwellian distribution of the classical kinetic theory. In the Boltzmann-type equation we include a non-constant collision kernel, in the form of a cutoff, in order to exclude from the statistical model possibly unphysical interactions. In spite of the increased analytical difficulty caused by this further non-linearity, we show that a careful application of the quasi-invariant limit (an asymptotic procedure reminiscent of the grazing collision limit) successfully leads to a Fokker-Planck approximation of the original Boltzmann-type equation, whence stationary distributions can be explicitly computed. Our analytical results justify, from a genuinely model-based point of view, some empirical results found in the literature by interpolation of experimental data.Comment: 18 pages, 7 figure

    Fast propagation of messages in VANETs and the impact of vehicles as obstacles on signal propagation

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    Vehicular Ad hoc NETworks (VANETs), an emerging technology, use vehicles as nodes to form a mobile ad hoc network for the dissemination of safety and entertainment messages. The thesis provides a scheme for the fast propagation of messages in VANETs and evaluates the impact of vehicles as obstacles on signal propagation. An improved scheme for intermediate node selection in DBA-MAC (Dynamic Backbone Assisted MAC) is proposed, which consists of a CW (Contention Window) constraint scheme and an updated criterion of suitability. A performance comparison shows that messages in the proposed scheme propagate faster than in DBA-MAC. The CW constraint scheme is also applicable in VANET protocols which adapt the CW mechanism to communicate the suitability of vehicles for acting as intermediate nodes. Additionally, the mathematical models for DBAMAC and the proposal are established, which indicate the probability of candidates to be chosen over alternatives in the intermediate node selection. A novel metric - delay taking into account the effect of formation time(DEFT) - is proposed. DEFT combines the network formation time and propagation delay. It shows the impact of network formation on propagation latency. The configuration for optimal performance can be acquired using the proposed DEFT. In order to evaluate the proposals, a novel distribution of vehicle location is proposed. In the proposed distribution, the security distances between adjacent vehicles in the same lane are considered. The estimation of vehicles’ location can be more practical and accurate using the proposed distribution. In the wide body of the VANET literature, it is assumed that all the vehicles within the radio range of a transmitter are able to receive the signal. Yet, in practice, the vehicles as obstacles between the transmitter and the receiver affect the signal propagation significantly. This thesis presents the impact of these obstacles on the network connectivity and system performance of the protocols. The results and the analysis show that neglecting obstacles in practice leads to a significant degree of error in the estimation of system performance. In practice, tall vehicles forward messages in a more efficient way than do lower vehicles since they are free from the obstacle effect. An improved scheme is proposed, in which the height of vehicles is used as a factor to determine their suitability for message forwarding
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