Recently, the IEEE 1609.4 protocol has been defined to enable multi-channel operations in a vehicular environment, and to guarantee interference-free co-existence of safety-related and non-safety related applications ...
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ISBN:
(纸本)9781450316231
Recently, the IEEE 1609.4 protocol has been defined to enable multi-channel operations in a vehicular environment, and to guarantee interference-free co-existence of safety-related and non-safety related applications in the same network. To meet these goals, the protocol assumes strict time synchronization among vehicles, and time/frequency separation in the Dedicated Short Range Communication (DSRC) band. However, recent studies have demonstrated that this approach might not be suitable for safety-related broadcast applications with strict Quality-of-Service (QoS) requirements. In this paper, we investigate the potentials of Cognitive Radio (CR) technology to enhance the delivery ratio of safety-related broadcast applications in a multi-channel vehicular scenario. In this research field, we propose three novel contributions: (i) we introduce an analytical model to study the delivery ratio of broadcast applications in IEEE 802.11p/1609.4 multi-channel vehicular networks, and the impact of MAC and PHY parameters on the system performance;(ii) we propose a framework to jointly decide the optimal values of the Contention Window size (CW) at the MAC layer and of the control CHannel (CCH) bandwidth at PHY layer, so that each vehicle is able to transmit all its safety data during the CCH interval with a minimum MAC collision probability, and (iii) we discuss the framework implementation in a realistic vehicular scenario. Our on-demand bandwidth allocation algorithm utilizes vacant frequencies in the DSRC band to increase the bandwidth of the CCH, leveraging the spectrum agile capabilities offered by the CR technology. Simulation results confirm the effectiveness of our proposal in enhancing the delivery rate of broadcast applications under varying network scenarios and load conditions. Copyright 2012 acm.
Learning opportunities play an important role in the vision of curriculum favored by the Bologna Process. this paper proposes an ontology intended for representing learning opportunities. the ontology is designed in a...
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the proceedings contain 67 papers. the topics discussed include: estimating wireless network properties with spatial statistics and models;should we use the default protocol settings for networks of constrained device...
ISBN:
(纸本)9783901882456
the proceedings contain 67 papers. the topics discussed include: estimating wireless network properties with spatial statistics and models;should we use the default protocol settings for networks of constrained devices?;a population model based on a Poisson line tessellation;a benchmark for channel assignment algorithms in wireless testbeds;on the feasibility of measuring the Internet through marathoner-based crowdsourcing;Energino: a hardware and software solution for energy consumption monitoring;floating information with stationary nodes;walking around in a changing world: understanding random walks over dynamic graphs;optimizing practical adaptive frequency hopping and medium accesscontrol in ad hoc networks;fair scheduling in common-pool games by aspiration learning;power control in random networks: the effect of disorder in user positions;and analysis of multicell cooperation with random user locations via deterministic equivalents.
the proceedings contain 19 papers. the topics discussed include: a model of triangulating environments for policy authoring;towards analyzing complex operating system accesscontrol configurations;monitoring security ...
ISBN:
(纸本)9781450300490
the proceedings contain 19 papers. the topics discussed include: a model of triangulating environments for policy authoring;towards analyzing complex operating system accesscontrol configurations;monitoring security policies with metric first-order temporal logic;on the definition of role mining;mining roles with noisy data;StateMiner: an efficient similarity-based approach for optimal mining of role hierarchy;role mining based on weights;accesscontrol in practice: pain points;automated management of network accesscontrol from design to enforcement;role-based accesscontrol (RBAC) in Java via proxy objects using annotations;role updating for assignments;enforcing spatial constraints for mobile RBAC systems;capability-based delegation model in RBAC;and a card requirements language enabling privacy-preserving accesscontrol.
accesscontrol is one of key aspects of computer security. Current accesscontrolmodels do not take into account the context of the system and its environment. In this paper, we present a particular context model for...
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accesscontrol is one of key aspects of computer security. Current accesscontrolmodels do not take into account the context of the system and its environment. In this paper, we present a particular context model for the accesscontrol system primarily-intended for business processes accesscontrol. By using a context-sensitive accesscontrol, it is possible to define more sophisticated accesscontrol policies that cannot be implemented by existing accesscontrolmodels. the proposed context is modeled using Web Ontology Language (OWL) in order to provide: formal representation of context, rich representation of different contextual information, semantic interoperability between different context-aware systems and high degree of inference making.
this work investigates the approximate verification of probabilistic specifications expressed as any non-nested PCTL formula over Markov processes on general state spaces. the contribution puts forward new algorithms,...
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