9,101 research outputs found
Implicit Cooperative Positioning in Vehicular Networks
Absolute positioning of vehicles is based on Global Navigation Satellite
Systems (GNSS) combined with on-board sensors and high-resolution maps. In
Cooperative Intelligent Transportation Systems (C-ITS), the positioning
performance can be augmented by means of vehicular networks that enable
vehicles to share location-related information. This paper presents an Implicit
Cooperative Positioning (ICP) algorithm that exploits the Vehicle-to-Vehicle
(V2V) connectivity in an innovative manner, avoiding the use of explicit V2V
measurements such as ranging. In the ICP approach, vehicles jointly localize
non-cooperative physical features (such as people, traffic lights or inactive
cars) in the surrounding areas, and use them as common noisy reference points
to refine their location estimates. Information on sensed features are fused
through V2V links by a consensus procedure, nested within a message passing
algorithm, to enhance the vehicle localization accuracy. As positioning does
not rely on explicit ranging information between vehicles, the proposed ICP
method is amenable to implementation with off-the-shelf vehicular communication
hardware. The localization algorithm is validated in different traffic
scenarios, including a crossroad area with heterogeneous conditions in terms of
feature density and V2V connectivity, as well as a real urban area by using
Simulation of Urban MObility (SUMO) for traffic data generation. Performance
results show that the proposed ICP method can significantly improve the vehicle
location accuracy compared to the stand-alone GNSS, especially in harsh
environments, such as in urban canyons, where the GNSS signal is highly
degraded or denied.Comment: 15 pages, 10 figures, in review, 201
Optimal Content Downloading in Vehicular Networks
We consider a system where users aboard communication-enabled vehicles are interested in downloading different contents from Internet-based servers. This scenario captures many of the infotainment services that vehicular communication is envisioned to enable, including news reporting, navigation maps and software updating, or multimedia file downloading. In this paper, we outline the performance limits of such a vehicular content downloading system by modelling the downloading process as an optimization problem, and maximizing the overall system throughput. Our approach allows us to investigate the impact of different factors, such as the roadside infrastructure deployment, the vehicle-to-vehicle relaying, and the penetration rate of the communication technology, even in presence of large instances of the problem. Results highlight the existence of two operational regimes at different penetration rates and the importance of an efficient, yet 2-hop constrained, vehicle-to-vehicle relaying
Proactive TCP mechanism to improve Handover performance in Mobile Satellite and Terrestrial Networks
Emerging standardization of Geo Mobile Radio (GMR-1) for satellite system is
having strong resemblance to terrestrial GSM (Global System for Mobile
communications) at the upper protocol layers and TCP (Transmission Control
Protocol) is one of them. This space segment technology as well as terrestrial
technology, is characterized by periodic variations in communication properties
and coverage causing the termination of ongoing call as connections of Mobile
Nodes (MN) alter stochastically. Although provisions are made to provide
efficient communication infrastructure this hybrid space and terrestrial
networks must ensure the end-to-end network performance so that MN can move
seamlessly among these networks. However from connectivity point of view
current TCP performance has not been engineered for mobility events in
multi-radio MN. Traditionally, TCP has applied a set of congestion control
algorithms (slow-start, congestion avoidance, fast retransmit, fast recovery)
to probe the currently available bandwidth on the connection path. These
algorithms need several round-trip times to find the correct transmission rate
(i.e. congestion window), and adapt to sudden changes connectivity due to
handover. While there are protocols to maintain the connection continuity on
mobility events, such as Mobile IP (MIP) and Host Identity Protocol (HIP), TCP
performance engineering has had less attention. TCP is implemented as a
separate component in an operating system, and is therefore often unaware of
the mobility events or the nature of multi-radios' communication. This paper
aims to improve TCP communication performance in Mobile satellite and
terrestrial networks.Comment: 5 pages, 2 figure
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