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Inter-vehicle communications (IVC) has the potential to play an important role in many future vehicle and traffic applications. Much of this will occur in the automated vehicle control and safety systems (AVCSS) arena, and to a lesser extent in the advanced transportation management and information systems (ATMIS) arena. One such ATMIS application...
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... evaluate the effectiveness of the dissemination scheme across a larger, real-world network with calibrated travel demand, Southern California's Inland Empire freeway network was used as shown in Fig. 7. This network includes the I-10, I-15, CA-60, CA-91 and I-215 freeways, consisting of approximately 500 roadway links. In the simulation runs, origin-destination travel demand values are calibrated from the region's travel demand model, specified for a typical morning peak period from 7AM to 8AM. In the simulation, the traffic ...
Citations
... During indicators creation, the existing indicators suitable to defined sub-criteria could be applied directly. For example, for the criteria mentionedthe function of a road network, the indicators presented in the study of Xu and Barth (2006) could be borrowed. It refers to three indicators, Speed, Flow, and Density, whose references 240 involve six levels of service for Basic Freeway Section (see Table 1). ...
Criteria and indicators are frequently used for assessing the resilience of Critical Infrastructures (CIs). However, the application of the concept of CIs resilience in practical disaster management is challenged by the lack of operational tools. An operational tool should enable the establishment of an organized system of indicators and optimising operational practice. Therefore, to address the operationalisation of resilience assessment, the main objective of this study is to develop a step-by-step guide for the creation of specific indicators aimed at different practical situations. This guide can assist CIs managers in their decision-making as it is structured based on a multi-criteria framework that considers the various interests of stakeholders. This guide includes the methods for Criteria and indicators setting, reference definition, and data collection. Furthermore, this study presents an example of the application of the guide. This example is based on a given scenario focusing on the Nantes Ring Road (NRR) network: when it is flooded and closed, the road network manager suggests alternative roads to citizens. The created indicators, based on this scenario and involved 62 676 data, relate to potential damages and costs-benefit and involve technical, social, and environmental dimensions.
... The studies in [3][4][5][6][7][8]show that typical endto-end delay requirements can easily be met but achieving high level of PDR is extremely difficult in single-hop V2V safety communication broadcast. Typical methods applied to enhance communication performance such as higher PDR of VANET include the Beacon Generation Interval (BGI) control [9][10][11] and the Transmission power/Range (TR) control [12][13][14][15][16]. Joint or hybrid of both seems suitable for optimal performance of periodic safety communications [4][8] [17]. However, the maximum achievable PDR resulting from such a combination is still lacking extensive proof for worst-case traffic scenarios. ...
... In the literature, different techniques for content dissemination in VSNs are described, such as flooding and geocasting (Tonguz et al., 2007;Bronsted & Kristensen, 2006), request/reply (Zhao & Cao, 2007;Wegener et al., 2007), broadcasting, sharing (Seskar et al., 1992), and beaconing (Xu & Barth, 2006;Fujiki et al., 2007). In the D4V system, we combine the DGT scheme with the opportunistic and spatiotemporal dissemination approach proposed by Leontiadis & Mascolo (2007), which is based on the publish/subscribe paradigm and allows message distribution to all interested receivers in a given region, by keeping messages alive in that region for a specific period of time. ...
Vehicular data collection applications are emerging as an appealing technology to monitor urban areas, where a high concentration of connected vehicles with onboard sensors is a near future scenario. In this context, smartphones are, on one side, effective enablers of Vehicle-to-Vehicle (V2V) and Vehicle-to-Infrastructure (V2I) applications and, on the other side, highly sophisticated sensing platforms. In this paper, we introduce an effective and efficient system, denoted as D4V, to disseminate vehicle-related information and sensed data using smartphones as V2I devices. D4V relies on a Peer-to-Peer (P2P) overlay scheme, denoted as Distributed Geographic Table (DGT), which unifies the concepts of physical and virtual neighborhoods in a scalable and robust infrastructure for application-level services. First, we investigate the discovery procedure of the DGT overlay network, through analytical and simulation results. Then, we present and discuss an extensive simulation-based performance evaluation (considering relevant performance indicators) of the D4V system, in a 4G wireless communication scenario. The simulation methodology combines DEUS (an application-level simulation tool for the study of large-scale systems) with ns-3 (a well-known network simulator, which takes into account lower layers), in order to provide a D4V proof-of-concept. The observed results show that D4V-based information sharing among vehicles allows to significantly reduce risks and nuisances (e.g., due to road defects and congestions).
... Another question especially for anticipatory assistance is the transmission quality at high distances. Figure 2.10 shows the reception probability between two network nodes for optimal conditions (see Xu et al. [XB06]). Using the IEEE 802.11p wireless standard the reception probability is still above 95% at a distance of 400m. ...
... Reception probability in an IEEE 802.11p based Car2X network depending on the distance. The plot represents ideal conditions without interferences (based on[XB06]). ...
Modern Cities must deal with vastly growing road traffic volumes. As available space for new streets is limited the use of Intelligent Transportation Systems (ITS) becomes more and more inevitable. As a result there is currently a transition phase in which Advanced Driver Assistance Systems (ADAS) can support human drivers with their wide-ranging electronic horizon. This is made possible with the help of new sensor types and in the future Car2X Communication.
This book covers the identification of relevant traffic situations for anticipatory driving, the development of an assistance system and user studies to assess acceptance, impact etc. of different system variants. The studies are carried out in various experimental environments with real drivers. Finally several approaches to developing a driver model that resembles the behavior of assisted and reference drivers are presented. These provide a way to estimate the potential impact of the assistance system on a larger scale with the help of traffic simulations.
... Obviously, packets for probing and propagating route information induce massive overheads. By contrast, [5,11] employ a reactive route discovery approach with the help of the relay nodes. However, the routing tables are out of date quickly because of the mobility of the relay nodes. ...
... It is clear that the maximum waiting time is a critical parameter to Algorithm 1, which closely relies on the one-hop (1) //Definition: denotes a vehicle in a VANET, ( ) denotes a neighbor list of ; (2) // denotes the last intersection passed by; dist ( , ) denotes the length from to ; (3) // denotes wireless transmission radius; (4) // denotes the data packet which needs to be delivered, and consists of ID, data, sender node , a neighbor list of ( ), the coordinates of , and the distance between and (5) On receiving a data packet at node (6) Extract dist( , ), coordinates of and ( ) from ; (7) I f has been received before or ∉ ( ) then (8) D r o pd a t ap a c k e t ; (9) If exists any defer timer on then (10) Cancel all the timers; (11) return; (12) Ifdist( , ) ≤ dist( , ) then (13) D r o pd a t ap a c k e t ; (14) If ( ) ⊆ ( ) then (15) D r o pd a t ap a c k e t ; (16) Set defer timer 1 time to ; (17) On expiration of deferred timer 1 (18) Broadcast data packet ; (19) Set equals to ( − (dist( , ) mod )) * / ; (20) Set defer timer 2 with ; ...
... Additionally, in order to avoid the expanding of the neighbor list in the packet when the vehicle density is high, the probabilistic data structure (e.g., bloom filter) can be used. Meanwhile, the interval of beacon messages can be dynamically adjusted according to the vehicle density to reduce the communication overheads [11]. ...
Many attractive applications over vehicular ad hoc networks (VANETs) need data to be transmitted to the remote destinations through multihop data forwarding, but some unique characteristics of VANETs (i.e., high node mobility, dynamic topology changes with frequent link breakage, and unstable quality of wireless transmission) incur unstable data delivery performance. In order to reliably and quickly disseminate the data, we present Dubhe which includes a delay model and an improved greedy broadcast algorithm embedded with a coverage elimination rule. The former is used for making decisions for path selection with the aim of minimizing the transmission latency, while the latter focuses on boosting the reliability of one-hop data transmission. We also analyze the necessity and effectiveness of Dubhe and the retransmission overheads theoretically. It is shown from the experiments that Dubhe can achieve high-reliability and low-latency data delivery in comparison with the epidemic-based protocol and the static-node-assisted adaptive data delivery protocol.
... Bayesian inference for general data model problems can be implemented by exact methods, by Monte Carlo sampling, or by deterministic approximate methods. The methods that make Gaussian approximations [1] using Laplace's method [2,3] or variation methods [4]. For neural networks there are few exact methods. ...
... Hopfeld networks [2,8] have two applications. First, they can act as associative memories. ...
A coding and decoding scheme controlling run length is presented. The proposed scheme limits the run length of data 0 in digital communication systems. We present a transformation approach to reduce the implementation complexity. The new adaptive scheme is implemented by combining the tree structure model and the candidate space model.
... For studying certain problems, it is possible to simulate only simple road networks (e.g. sections of limited-access highways) [10], or artificial ones (e.g., loops, Manhattan layouts) [28] [8] [25] [34]. For applications where a much larger-scale simulation is necessary, a frequent practice is to associate two separate simulators: one for the traffic, the other for the communication network. ...
Based on traffic data acquisition by the vehicles and inter-vehicle wireless communications, road traffic self-organization has been studied for several years. In this paper we propose a generic model of cooperation among vehicles, which is designed not to saturate the communication medium and to be insensitive to information loss among vehicles. We also propose an original software simulator, which helps us to show how this model can be used in realistic traffic situations. In the simulation, we evaluate one instance of our model, which features an algorithm for limiting the risks of information storms. This feature is particularly interesting in urban settings, where radio communication must fit within the traditional IEEE-802.11 traffic. We show that this algorithm can considerably reduce the amount of communication, without affecting the quality of traffic self-organization.
... Based on VANETs, recent research4567 18] has introduced zero-infrastructure systems where information is exchanged only between the vehicles themselves. Data delivery between vehicles can be classified into two models: push and pull [12]. ...
... Vehicles only receive/broadcast information from/to the vehicles moving in the opposite direction [4], since such vehicles may carry useful information with higher probability. In [7,18], several methods are proposed to save communication resources caused by periodical broadcasting. The principle is to dynamically adjust the broadcast period according to vehicle density. ...
Traffic congestion is a very serious problem in large cities. With the number of vehicles increasing rapidly, especially in cities whose economy is booming, the situation is getting even worse. In this paper, by leveraging the techniques of Vehicular Ad hoc Networks (VANETs) we present a dynamic navigation protocol called VAN for individual vehicles to find the shortest-time paths toward their given destinations. Specifically, a vehicle initiates a number of queries, which are routed by VANETs along different paths toward its destination. During query forwarding, the real-time road traffic information in each road segment is aggregated from multiple participating vehicles and returned to the source after the query reaches the destination. This information enables the source to calculate the shortest-time path. We also propose two forwarding optimization methods to reduce communication costs and an error handling mechanism to deal with abnormal circumstances. To evaluate its performance, we use the real traffic data of Beijing, including 2,308 road segments at two different times. Our simulation results demonstrate that our protocol, on average, could save around 30% driving time, compared to traveling along the shortest distance paths.
... It also encompasses the selection of the optimal subset of the knowledge base to be incorporated into a transmission of limited size. Work in this area can, for example, be found in [11, 12, 13, 14, 15]. When speaking about applications for VANETs in a real environment, questions about security arise. ...
We propose an algorithm for the hierarchical aggregation of observations in dissemination-based, distributed traffic information systems. Instead of transmitting observed parameters directly, we propose soft-state sketches—an extension of Flajolet–Martin sketches—as a probabilistic approximation. This data representation is duplicate insensitive, a trait that overcomes two central problems of existing aggregation schemes for VANET applications. First, when multiple aggregates of observations for the same area are available, it is possible to combine them into an aggregate containing all information from the original aggregates. This is fundamentally different from existing approaches where typically one of the aggregates is selected for further use while the rest is discarded. Second, any observation or aggregate can be included into higher-level aggregates, regardless if it has already been previously—directly or indirectly—added. Those characteristics result in a very flexible aggregate construction and a high quality of the aggregates. We demonstrate these traits of our approach by a simulation study.
... By contrast, our approach is able to handle numerous data units in parallel, even when they are disseminated at the same time to arbitrary directions and created at arbitrary positions in the network. Approaches that concentrate on disseminating traffic conditions, like [Wischhof et al. 2003; Xu and Barth 2006], focus on the adaptation of broadcast interval, e.g., according to the vehicle's speed. The proposed techniques are closely bound to specific applications with fixed sized road segments and distinguish only between regular communication and emergency data. ...
In recent years, tremendous progress has been made in understanding the dynamics of vehicle traffic flow and traffic congestion by interpreting traffic as a multiparticle system. This helps to explain the onset and persistence of many undesired phenomena, for example, traffic jams. It also reflects the apparent helplessness of drivers in traffic, who feel like passive particles that are pushed around by exterior forces; one of the crucial aspects is the inability to communicate and coordinate with other traffic participants.
We present distributed methods for solving these fundamental problems, employing modern wireless, ad-hoc, multi-hop networks. The underlying idea is to use these capabilities as the basis for self-organizing methods for coordinating data collection and processing, recognizing traffic phenomena, and changing their structure by coordinated behavior. The overall objective is a multi-level approach that reaches from protocols for local wireless communication, data dissemination, pattern recognition, over hierarchical structuring and coordinated behavior, all the way to large-scale traffic regulation.
In this article, we describe three types of results: (i) self-organizing and distributed methods for maintaining and collecting data (using our concept of Hovering Data Clouds ); (ii) adaptive data dissemination for traffic information systems; (iii) methods for self-recognition of traffic jams. We conclude by describing higher-level aspects of our work.
