3,886 research outputs found
Cooperative vehicular networks for intelligent transportation systems
University of Technology Sydney. Faculty of Engineering and Information Technology.Transportation systems are fundamental for the human society as they allow people and goods to move from one location to another. With an increasing volume of population and vehicles, current transportation systems are now facing a number of disruptive challenges such as congestion, crashes, air pollution and noise throughout the world. However, traditional solutions like expanding the present transportation systems by increasing the number of roads are recognized to be expensive, disruptive and involve protracted effort. Instead, intelligent transportation systems (ITS), with the goal of building a safer, more efficient and environmentally sustainable transportation system by incorporating state-of-the-art sensing, computing and communication technologies, is expected to be a better solution.
ITS are complex systems and they function in a broad range of areas through smartly sensing, analysing and disseminating different kinds of traffic information. Vehicular networks, which incorporate advanced communication technology with intelligent vehicles equipped with on-board units (OBUs) and intelligent roadside infrastructure, realise the function of large scale traffic information dissemination for ITS through vehicle to vehicle (V2V), vehicle to infrastructure (V2I) and infrastructure to infrastructure (I2I) communications. Therefore, as one of the most enabling tools to support ITS, vehicular networks play a crucial role in improving road safety, relieving traffic congestion, enhancing driving experience and reducing pollution.
Considering the critical impact information exchange poses on the transportation systems, vehicular network applications require particularly fast, reliable and secure message dissemination in the network. However, depending only on V2V or V2I communications may fail to meet these requirements. On one hand, the frequently changing topology of vehicular networks caused by the highly dynamic nature of vehicles and the lossy vehicular wireless channels resulting from fading, path loss and the fast movement of vehicles, would result in unreliable and intermittent V2V communications. On the other hand, V2I communications may have limited availability, especially in rural areas and in the initial deployment phase of vehicular networks due to the high cost of implementation and maintenance of infrastructure. These make research on employing cooperative communications within vehicular networks both interesting and important.
In this thesis, we focus on the design of cooperative vehicular networks for ITS to satisfy the requirement of disseminating data quickly, reliably and securely, in the conditions of sparse roadside infrastructure, high mobility, and intermittent connectivity. Firstly, we propose a cooperative communication strategy that explores the combined use of V2I communications, V2V communications, mobility of vehicles, and cooperation among vehicles and infrastructure, to facilitate data dissemination in vehicular networks. The network performance, measured by the achievable throughput when there exists only one vehicle with a download request in the network, and the achievable capacity when there exist multiple vehicles with download requests in the network respectively, are analysed. The results show that the proposed cooperative communication strategy significantly boosts the throughput (or capacity) of vehicular networks. Secondly, to protect secure message dissemination, we investigate topological approaches to keep the message dissemination in vehicular networks robust against insider attackers who may tamper with the message content. As a novel approach, we take the network topology into consideration when designing algorithms to check the integrity and consistency of messages. Overall, our work provides guidance on the optimum design of cooperative vehicular networks for ITS to achieve fast, reliable and secure message dissemination
CMD: A Multi-Channel Coordination Scheme for Emergency Message Dissemination in IEEE 1609.4
In the IEEE 1609.4 legacy standard for multi-channel communications in
vehicular ad hoc networks(VANETs), the control channel (CCH) is dedicated to
broadcast safety messages while the service channels (SCH's) are dedicated to
transmit infotainment service content. However, the SCH can be used as an
alternative to transmit high priority safety messages in the event that they
are invoked during the service channel interval (SCHI). This implies that there
is a need to transmit safety messages across multiple available utilized
channels to ensure that all vehicles receive the safety message. Transmission
across multiple SCH's using the legacy IEEE 1609.4 requires multiple channel
switching and therefore introduces further end-to-end delays. Given that safety
messaging is a life critical application, it is important that optimal
end-to-end delay performance is derived in multi-channel VANET scenarios to
ensure reliable safety message dissemination. To tackle this challenge, three
primary contributions are in this article: first, a channel coordinator
selection approach based on the least average separation distance (LAD) to the
vehicles that expect to tune to other SCH's and operates during the control
channel interval (CCHI) is proposed. Second, a model to determine the optimal
time intervals in which CMD operates during the CCHI is proposed. Third, a
contention back-off mechanism for safety message transmission during the SCHI
is proposed. Computer simulations and mathematical analysis show that CMD
performs better than the legacy IEEE 1609.4 and a selected state-of-the-art
multi-channel message dissemination schemes in terms of end-to-end delay and
packet reception ratio.Comment: 15 pages, 10 figures, 7 table
V2X Content Distribution Based on Batched Network Coding with Distributed Scheduling
Content distribution is an application in intelligent transportation system
to assist vehicles in acquiring information such as digital maps and
entertainment materials. In this paper, we consider content distribution from a
single roadside infrastructure unit to a group of vehicles passing by it. To
combat the short connection time and the lossy channel quality, the downloaded
contents need to be further shared among vehicles after the initial
broadcasting phase. To this end, we propose a joint infrastructure-to-vehicle
(I2V) and vehicle-to-vehicle (V2V) communication scheme based on batched sparse
(BATS) coding to minimize the traffic overhead and reduce the total
transmission delay. In the I2V phase, the roadside unit (RSU) encodes the
original large-size file into a number of batches in a rateless manner, each
containing a fixed number of coded packets, and sequentially broadcasts them
during the I2V connection time. In the V2V phase, vehicles perform the network
coded cooperative sharing by re-encoding the received packets. We propose a
utility-based distributed algorithm to efficiently schedule the V2V cooperative
transmissions, hence reducing the transmission delay. A closed-form expression
for the expected rank distribution of the proposed content distribution scheme
is derived, which is used to design the optimal BATS code. The performance of
the proposed content distribution scheme is evaluated by extensive simulations
that consider multi-lane road and realistic vehicular traffic settings, and
shown to significantly outperform the existing content distribution protocols.Comment: 12 pages and 9 figure
Hybrid-Vehfog: A Robust Approach for Reliable Dissemination of Critical Messages in Connected Vehicles
Vehicular Ad-hoc Networks (VANET) enable efficient communication between
vehicles with the aim of improving road safety. However, the growing number of
vehicles in dense regions and obstacle shadowing regions like Manhattan and
other downtown areas leads to frequent disconnection problems resulting in
disrupted radio wave propagation between vehicles. To address this issue and to
transmit critical messages between vehicles and drones deployed from service
vehicles to overcome road incidents and obstacles, we proposed a hybrid
technique based on fog computing called Hybrid-Vehfog to disseminate messages
in obstacle shadowing regions, and multi-hop technique to disseminate messages
in non-obstacle shadowing regions. Our proposed algorithm dynamically adapts to
changes in an environment and benefits in efficiency with robust drone
deployment capability as needed. Performance of Hybrid-Vehfog is carried out in
Network Simulator (NS-2) and Simulation of Urban Mobility (SUMO) simulators.
The results showed that Hybrid-Vehfog outperformed Cloud-assisted Message
Downlink Dissemination Scheme (CMDS), Cross-Layer Broadcast Protocol (CLBP),
PEer-to-Peer protocol for Allocated REsource (PrEPARE), Fog-Named Data
Networking (NDN) with mobility, and flooding schemes at all vehicle densities
and simulation times
SDDV: scalable data dissemination in vehicular ad hoc networks
An important challenge in the domain of vehicular ad hoc networks (VANET) is the scalability of data dissemination. Under dense traffic conditions, the large number of communicating vehicles can easily result in a congested wireless channel. In that situation, delays and packet losses increase to a level where the VANET cannot be applied for road safety applications anymore. This paper introduces scalable data dissemination in vehicular ad hoc networks (SDDV), a holistic solution to this problem. It is composed of several techniques spread across the different layers of the protocol stack. Simulation results are presented that illustrate the severity of the scalability problem when applying common state-of-the-art techniques and parameters. Starting from such a baseline solution, optimization techniques are gradually added to SDDV until the scalability problem is entirely solved. Besides the performance evaluation based on simulations, the paper ends with an evaluation of the final SDDV configuration on real hardware. Experiments including 110 nodes are performed on the iMinds w-iLab.t wireless lab. The results of these experiments confirm the results obtained in the corresponding simulations
The Dynamics of Vehicular Networks in Urban Environments
Vehicular Ad hoc NETworks (VANETs) have emerged as a platform to support
intelligent inter-vehicle communication and improve traffic safety and
performance. The road-constrained, high mobility of vehicles, their unbounded
power source, and the emergence of roadside wireless infrastructures make
VANETs a challenging research topic. A key to the development of protocols for
inter-vehicle communication and services lies in the knowledge of the
topological characteristics of the VANET communication graph. This paper
explores the dynamics of VANETs in urban environments and investigates the
impact of these findings in the design of VANET routing protocols. Using both
real and realistic mobility traces, we study the networking shape of VANETs
under different transmission and market penetration ranges. Given that a number
of RSUs have to be deployed for disseminating information to vehicles in an
urban area, we also study their impact on vehicular connectivity. Through
extensive simulations we investigate the performance of VANET routing protocols
by exploiting the knowledge of VANET graphs analysis.Comment: Revised our testbed with even more realistic mobility traces. Used
the location of real Wi-Fi hotspots to simulate RSUs in our study. Used a
larger, real mobility trace set, from taxis in Shanghai. Examine the
implications of our findings in the design of VANET routing protocols by
implementing in ns-3 two routing protocols (GPCR & VADD). Updated the
bibliography section with new research work
A Stochastic Hybrid Framework for Driver Behavior Modeling Based on Hierarchical Dirichlet Process
Scalability is one of the major issues for real-world Vehicle-to-Vehicle
network realization. To tackle this challenge, a stochastic hybrid modeling
framework based on a non-parametric Bayesian inference method, i.e.,
hierarchical Dirichlet process (HDP), is investigated in this paper. This
framework is able to jointly model driver/vehicle behavior through forecasting
the vehicle dynamical time-series. This modeling framework could be merged with
the notion of model-based information networking, which is recently proposed in
the vehicular literature, to overcome the scalability challenges in dense
vehicular networks via broadcasting the behavioral models instead of raw
information dissemination. This modeling approach has been applied on several
scenarios from the realistic Safety Pilot Model Deployment (SPMD) driving data
set and the results show a higher performance of this model in comparison with
the zero-hold method as the baseline.Comment: This is the accepted version of the paper in 2018 IEEE 88th Vehicular
Technology Conference (VTC2018-Fall) (references added, title and abstract
modified
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