1,720,961 research outputs found
Hybrid Vehicular Communications based on V2V-V2I Protocol Switching
No full textIn this paper, a hybrid communication paradigm for vehicular networking is presented in which connectivity is provided by both existing network infrastructure (e.g. wireless network access points) through a vehicle-to-infrastructure protocol and traditional vehicle-to-vehicle networking. Preexisting infrastructure can provide seamless connectivity, especially when vehicles are sparse or travelling in disconnected neighbourhoods, while vehicular communications are available for dense traffic scenarios. In this vision, we depict a novel heterogeneous vehicular network scenario, in which overlapping wireless networks partially cover the vehicular grid. Vehicle-to-X (V2X) is based on a protocol switching decision, which is achieved in a distributed fashion by each vehicle based on a cost function using path alternatives. An analytical model for protocol switching in V2X is described. Moreover, we analyse how messages are forwarded by vehicles communicating via V2X. We characterise the maximum and minimum bounds of information propagation and compare performance with traditional message propagation based on opportunistic networking
Modeling of Intermittent Connectivity in Opportunistic Networks: The Case of Vehicular Ad hoc Networks
No full textQoSHVCP: Hybrid Vehicular Communications Protocol with QoS Priorization for Safety Applications
No full textThis paper introduces a hybrid communication paradigm for achieving seamless connectivity in Vehicular Ad hoc Networks
(VANETs), wherein the connectivity is often affected by changes in the dynamic topology, vehicles’ speed, as well as the traffic
density. Our proposed technique named QoS-oriented Hybrid Vehicular Communications Protocol (QoSHVCP) exploits both
existing network infrastructure through a Vehicle-to-Infrastructure (V2I), as well as a traditional Vehicle-to-Vehicle (V2V)
connection that could satisfy Quality-of-Service requirements. QoSHVCP is based on a V2V-V2I protocol switching algorithm,
executed in a distributed fashion by each vehicle and is based on the cost function for alternative paths each time it needs to
transmit a message. We utilize time delay as a performance metric and present the delay propagation rates when vehicles are
transmitting high priority messages via QoSHVCP. Simulation results indicate that simultaneous usage of preexisting network
infrastructure along with inter-vehicular communication provide lower delays, while maintaining the level of user’s performance.
Our results show a great promise for their future use in VANETs
LAT Indoor MIMO-VLC —Localize, Access and Transmit—
No full textVisible Light Communications (VLC) is an innovative technology that uses the visible spectrum for high-speed data communications. In this paper we investigate the use of MIMO in the design of luminaires supporting VLC and, specifically, in enabling localization and high data rate services. Localization and transmission appear as two different problems in the communication system; however, the former is helpful to understand which is the diversity degree that the system can adopt, in order to achieve the required performance in terms of BER and data rate. Finally, we consider also how different users can access the Internet by means of a TDMA-like access scheme. © 2012 IEEE
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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