2,122 research outputs found
Agile Data Offloading over Novel Fog Computing Infrastructure for CAVs
Future Connected and Automated Vehicles (CAVs) will be supervised by
cloud-based systems overseeing the overall security and orchestrating traffic
flows. Such systems rely on data collected from CAVs across the whole city
operational area. This paper develops a Fog Computing-based infrastructure for
future Intelligent Transportation Systems (ITSs) enabling an agile and reliable
off-load of CAV data. Since CAVs are expected to generate large quantities of
data, it is not feasible to assume data off-loading to be completed while a CAV
is in the proximity of a single Road-Side Unit (RSU). CAVs are expected to be
in the range of an RSU only for a limited amount of time, necessitating data
reconciliation across different RSUs, if traditional approaches to data
off-load were to be used. To this end, this paper proposes an agile Fog
Computing infrastructure, which interconnects all the RSUs so that the data
reconciliation is solved efficiently as a by-product of deploying the Random
Linear Network Coding (RLNC) technique. Our numerical results confirm the
feasibility of our solution and show its effectiveness when operated in a
large-scale urban testbed.Comment: To appear in IEEE VTC-Spring 201
Mobility and connectivity in highway vehicular networks: a case study in Madrid
The performance of protocols and architectures for upcoming vehicular networks is commonly investigated by means of computer simulations, due to the excessive cost and complexity of large-scale experiments. Dependable and reproducible simulations are thus paramount to a proper evaluation of vehicular networking solutions. Yet, we lack today a reference dataset of vehicular mobility scenarios that are realistic, publicly available, heterogeneous, and that can be used for networking simulations straightaway. In this paper, we contribute to the endeavor of developing such a reference dataset, and present original synthetic traces that are generated from high-resolution real-world traffic counts. They describe road traffic in quasi-stationary state on three highways near Madrid, Spain, for different time-spans of several working days. To assess the potential impact of the traces on networking studies, we carry out a comprehensive analysis of the vehicular network topology they yield. Our results highlight the significant variability of the vehicular connectivity over time and space, and its invariant correlation with the vehicular density. We also underpin the dramatic influence of the communication range on the network fragmentation, availability, and stability, in all of the scenarios we consider.The research leading to these results has received funding from the People Programme (Marie Curie Actions) of the European Unions Seventh Framework Programme (FP7/2007-2013) under REA grant agreement n.630211 ReFleX. This research was also funded by Spanish MICINN through the ADAS-ROAD Project (TRA2013-48314-C3-1-R). Funding for D. Naboulsi was provided by a grant from Rhône-Alpes Region. This work was carried out while Marco Gramaglia was at CNR-IEIIT.Publicad
Outage in motorway multi-lane VANETs with hardcore headway distance using synthetic traces
In this paper we analyze synthetic mobility traces generated for three-lane
unidirectional motorway traffic to find that the locations of vehicles along a
lane are better modeled by a hardcore point process instead of the
widely-accepted Poisson point process (PPP). In order to capture the repulsion
between successive vehicles while maintaining a level of analytical
tractability, we make a simple extension to PPP: We model the inter-vehicle
distance along a lane equal to the sum of a constant hardcore distance and an
exponentially distributed random variable. We calculate the J-function and the
Ripley's K-function for this hardcore point process. We fit its parameters to
the available traces, and we illustrate that the higher the average speed along
a lane, the more prominent the hardcore component becomes. In addition, we
consider a transmitter-receiver link on the same lane, and we generate simple
formulae for the moments of interference under reduced Palm measure for that
lane, and without conditioning for other lanes. We illustrate that under
Rayleigh fading a shifted-gamma approximation for the distribution of
interference per lane provides a very good fit to the simulated outage
probability using the synthetic traces, while the fit using the PPP is poor.Comment: to be publishe
Investigation of Wireless Channel Asymmetry in Indoor Environments
Asymmetry is unquestionably an important characteristic of the wireless
propagation channel, which needs to be accurately modeled for wireless and
mobile communications, 5G networks, and associated applications such as
indoor/outdoor localization. This paper reports on the potential causes of
propagation asymmetry. Practical channel measurements at Khalifa University
premises proved that wireless channels are asymmetric in realistic scenarios.
Some important conclusions and recommendation are also summarized.Comment: Accepted in IEEE International Symposium on Antennas and Propagation
(APS17), San Diego, California, 9-14 Jul. 2017. arXiv admin note: substantial
text overlap with arXiv:1704.0687
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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