Search results for "Automobile"

Quasi-nash equilibria for non-convex distributed power allocation games in cognitive radios

2013

In this paper, we consider a sensing-based spectrum sharing scenario in cognitive radio networks where the overall objective is to maximize the sum-rate of each cognitive radio user by optimizing jointly both the detection operation based on sensing and the power allocation, taking into account the influence of the sensing accuracy and the interference limitation to the primary users. The resulting optimization problem for each cognitive user is non-convex, thus leading to a non-convex game, which presents a new challenge when analyzing the equilibria of this game where each cognitive user represents a player. In order to deal with the non-convexity of the game, we use a new relaxed equilib…

Distributed Resource Allocation in Underlay Multicast D2D Communications

2021

Multicast device-to-device communications operating underlay with cellular networks is a spectral efficient technique for disseminating data to nearby receivers. However, due to the critical challenge of having an intelligent interference coordination between multicast groups along with the cellular network, it is necessary to judiciously perform resource allocation for the combined network. In this work, we present a framework for a joint channel and power allocation strategy to maximize the sum rate of the combined network while guaranteeing minimum rate to individual groups and cellular users. The objective function is augmented by an austerity function that penalizes excessive assignmen…

Energy-Efficient Resource Optimization with Wireless Power Transfer for Secure NOMA Systems

2018

In this paper, we investigate resource allocation algorithm design for secure non-orthogonal multiple access (NOMA) systems empowered by wireless power transfer. With the consideration of an existing eavesdropper, the objective is to obtain secure and energy efficient transmission among multiple users by optimizing time, power and subchannel allocation. Moreover, we also take into consideration for the practical case that the statistics of the channel state information of the eavesdropper is not available. In order to address the optimization problem and its high computational complexity, we propose an iterative algorithm with guaranteed convergence to deliver a suboptimal solution for gene…

A Highly Flexible Trajectory Model Based on the Primitives of Brownian Fields—Part II: Analysis of the Statistical Properties

2016

In the first part of our paper, we have proposed a highly flexible trajectory model based on the primitives of Brownian fields (BFs). In this second part, we study the statistical properties of that trajectory model in depth. These properties include the autocorrelation function (ACF), mean, and the variance of the path along each axis. We also derive the distribution of the angle-of-motion (AOM) process, the incremental traveling length process, and the overall traveling length. It is shown that the path process is in general non-stationary. We show that the AOM and the incremental traveling length processes can be modeled by the phase and the envelope of a complex Gaussian process with no…

Youngtimers : a sociology of contemporary relations to oldcars

2022

If this was not still the case 50 years ago, the automobile is today an essential capital good for a majority of French households. For a majority of individuals, and in a context of increasing urbanization, mobility is in fact essential for individuals who have to move here for their work, there for their leisure, or even to multiple places of consumption or sociability. . Everywhere, in cities as in the countryside, the automobile has established itself as the main mode of daily transport. The generalization of car ownership has thus modified the way of life of individuals as well as all the stages of professional and family life, and to put it simply, contemporary urban society presuppos…

L’autodrome du Morvan (1907-1909) : projet et abandon d’une infrastructure au début de l’âge automobile

2022

De la vente au conseil : l'irréstible évolution du commercial du secteur automobile

2013

Dans les contextes mouvementés du secteur de l'automobile, de la concurrence exacerbée, de l'émergence du e-commerce, du développement de stratégies marketing par les constructeurs visant à attirer le maximum de clients, que deviennent les vendeurs? Quelles sont aujourd'hui leur place et leurs pratiques professionnelles? Et comment ces évolutions sont-elles soutenues par les employeurs en termes de politiques et de pratiques gestionnaires ? Pour apporter des éléments de réponses à ces questions, ce texte s'appuie sur une vingtaine d'entretiens de salariés et de leurs responsables hiérarchiques (supérieurs directs, dirigeants) menées dans deux entreprises de nature et de taille très différen…

Direct ELISA kits as a sensitive and selective screening method for abstinence control in urine.

2011

In 2009 cutoff values of assessment criteria to testify abstinence control in order to estimate driving ability were standardized in Germany. The cutoff values are lower than required in existing guidelines like SAMHSA and there is critical discussion about detection of low concentrations by using immunoassay, especially concerning amphetamines in urine (50 ng/ml). In this study Direct ELISA kits were tested for their applicability to identify the absence of amphetamines, cannabinoids, opiates, cocaine, methadone and benzodiazepines in urine. Results were confirmed by LC/MS or GC/MS analyses. Sensitivity, specificity, predictive values (positive as well as negative) and overall misclassific…

Adapting Downlink Power in Fronthaul-Constrained Hierarchical Software-Defined RANs

2017

Abstract The proof-of-concept software-defined radio access network (RAN) is not flexible enough due to the inherent delay and the necessity of high-capacity fronthaul links. We are hence motivated to propose a hierarchical software-defined RAN architecture, over which the base stations (BSs) are abstracted into multiple virtual local controllers while these local controllers are administered by a high-level controller. Under such a hierarchical network architecture, we particularly investigate in this paper how to adapt the BS transmit power over a long term according to the network dynamics under the constraints of mobile user queue stability and limited fronthaul capacity. We first formu…

Efficient Steering Mechanism for Mobile Network-Enabled UAVs

2022

HTTP Adaptive Streaming (HAS) is becoming the de-facto video delivery technology over best-effort networks nowadays, thanks to the myriad advantages it brings. However, many studies have shown that HAS suffers from many Quality of Experience (QoE)-related issues in the presence of competing players. This is mainly caused by the selfishness of the players resulting from the decentralized intelligence given to the player. Another limitation is the bottleneck link that could happen at any time during the streaming session and anywhere in the network. These issues may result in wobbling bandwidth perception by the players and could lead to missing the deadline for chunk downloads, which result …