2,019 research outputs found
Spatio-Temporal Motifs for Optimized Vehicle-to-Vehicle (V2V) Communications
Caching popular contents in vehicle-to-vehicle (V2V) communication networks
is expected to play an important role in road traffic management, the
realization of intelligent transportation systems (ITSs), and the delivery of
multimedia content across vehicles. However, for effective caching, the network
must dynamically choose the optimal set of cars that will cache popular content
and disseminate it in the entire network. However, most of the existing prior
art on V2V caching is restricted to cache placement that is solely based on
location and user demands and does not account for the large-scale
spatio-temporal variations in V2V communication networks. In contrast, in this
paper, a novel spatio-temporal caching strategy is proposed based on the notion
of temporal graph motifs that can capture spatio-temporal communication
patterns in V2V networks. It is shown that, by identifying such V2V motifs, the
network can find sub-optimal content placement strategies for effective content
dissemination across a vehicular network. Simulation results using real traces
from the city of Cologne show that the proposed approach can increase the
average data rate by for different network scenarios
A review of traffic simulation software
Computer simulation of tra c is a widely used method in research of tra c modelling,
planning and development of tra c networks and systems. Vehicular tra c systems are of
growing concern and interest globally and modelling arbitrarily complex tra c systems is a
hard problem. In this article we review some of the tra c simulation software applications,
their features and characteristics as well as the issues these applications face. Additionally, we
introduce some algorithmic ideas, underpinning data structural approaches and quanti able
metrics that can be applied to simulated model systems
Providing over-the-horizon awareness to driver support systems
Vehicle-to-vehicle communications is a promising technique for driver support systems to increase traffic safety and efficiency. A proposed system is the Congestion Assistant [1], which aims at supporting drivers when approaching and driving in a traffic jam. Studies have shown great potential for the Congestion Assistant to reduce the impact of congestion, even at low penetration. However, these studies assumed complete and instantaneous availability of information regarding position and velocity of vehicles ahead. In this paper, we introduce a system where vehicles collaboratively build a so-called TrafficMap, providing over-the-horizon awareness. The idea is that this TrafficMap provides highly compressed information that is both essential and sufficient for the Congestion Assistant to operate. Moreover, this TrafficMap can be built in a distributed way, where only a limited subset of the vehicles have to alter it and/or forward it in the upstream direction. Initial simulation experiments show that our proposed system provides vehicles with a highly compressed view of the traffic ahead with only limited communication
Models and Performance of VANET based Emergency Braking
The network research community is working in the field of automotive to provide VANET based safety applications to reduce the number of accidents, deaths, injuries and loss of money. Several approaches are proposed and investigated in VANET literature, but in a completely network-oriented fashion. Most of them do not take into account application requirements and no one considers the dynamics of the vehicles. Moreover, message repropagation schemes are widely proposed without investigating their benefits and using very complicated approaches. This technical report, which is derived from the Master Thesis of Michele Segata, focuses on the Emergency Electronic Brake Lights (EEBL) safety application, meant to send warning messages in the case of an emergency brake, in particular performing a joint analysis of network requirements and provided application level benefits. The EEBL application is integrated within a Collaborative Adaptive Cruise Control (CACC) which uses network-provided information to automatically brake the car if the driver does not react to the warning. Moreover, an information aggregation scheme is proposed to analyze the benefits of repropagation together with the consequent increase of network load. This protocol is compared to a protocol without repropagation and to a rebroadcast protocol found in the literature (namely the weighted p-persistent rebroadcast). The scenario is a highway stretch in which a platoon of vehicles brake down to a complete stop. Simulations are performed using the NS_3 network simulation in which two mobility models have been embedded. The first one, which is called Intelligent Driver Model (IDM) emulates the behavior of a driver trying to reach a desired speed and braking when approaching vehicles in front. The second one (Minimizing Overall Braking Induced by Lane change (MOBIL)), instead, decides when a vehicle has to change lane in order to perform an overtake or optimize its path. The original simulator has been modified by - introducing real physical limits to naturally reproduce real crashes; - implementing a CACC; - implementing the driver reaction when a warning is received; - implementing different network protocols. The tests are performed in different situations, such as different number of lanes (one to five), different average speeds, different network protocols and different market penetration rates and they show that: - the adoption of this technology considerably decreases car accidents since the overall average maximum deceleration is reduced; - network load depends on application-level details, such as the implementation of the CACC; - VANET safety application can improve safety even with a partial market penetration rate; - message repropagation is important to reduce the risk of accidents when not all vehicles are equipped; - benefits are gained not only by equipped vehicles but also by unequipped ones
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