1,721,013 research outputs found
Automatic Emergency Braking: Realistic Analysis of Car Dynamics and Network Performance
No full textSafety applications are among the key drivers in VANET research, and their true performance can be assessed only if the application and the communication network are jointly considered. This work presents a simulation study of an emergency braking application accomplished by embedding mobility, cars’ dynamic, and drivers’ behavior models into a detailed networking simulator (ns-3). The overall system allows capturing the interactions of the communications with the car’s automated braking mechanism and the driver’s behavior. At the same time yields very detailed information on the communication level. Besides the integrated tool, the paper presents a novel and simple message aggregation mechanism to empower message re-propagation while controlling the network congestion during the peak load due to the emergency braking. Next it discusses the effectiveness of such applications as a function of the market penetration rate, showing that even cars that are not equipped with communication devices benefit from the smoother and earlier reaction of the cars that can communicate. Fading phenomena and sensitivity to the radio transmitted power are analyzed, while fine grained dynamics of cars’ collisions as taking into account different masses and different elastic coefficients are introduced to evaluate the severity of impacts
Vehicles or Pedestrians: On the gNB Placement in Ultradense Urban Areas
Full text linkThis paper tackles the problem of base stations placement to guarantee line of sight connectivity to vehicles in urban areas, when high frequency communications (mmWave or TeraHertz) are used. We introduce a novel methodology mixing vehicular networks simulations and show that the density of base stations per squared km is low enough to be feasibly reached. However, optimizing the placement for vehicles coverage provides an advantage but may not be enough for pedestrians coverage
Estimating coverage and capacity of high frequency mobile networks in ultradense urban areas
No full textHigh frequency communications (mmWave and TeraHz) in urban areas require a higher density of base stations compared to pre-5G mobile networks, but open the way to a quantum leap in increased throughput and reduced latency. However, we currently have no indication of how much we need to densify the deployment, and on the trade-off between the density of base stations and the performance improvement. This paper studies the problem of base stations placement to guarantee coverage to vehicles and pedestrians in urban areas when using high frequency communications. Our novel methodology takes advantage of vehicular traffic simulations and precise urban maps to generate a realistic demand model for vehicles and pedestrians in urban areas. We use a bounded error heuristic to find the maximal coverage that can be achieved with a given density of base stations, primarily using line-of-sight communications. We implemented the heuristic using CUDA libraries on Nvidia GPUs and evaluated the coverage in an urban area in the city of Luxembourg, for which vehicular traffic patterns are available. We focus on coverage and capacity analysis for the mmWave frequency, but the results are easily extended to TeraHz communications. Our results are the first to show that a reasonably low density (15 base stations per km) is sufficient to provide coverage for vehicles in urban environments. However, optimizing on vehicles or on pedestrians are competing objectives: the operator needs to choose which one to target based on its business model when designing the network infrastructure. Our algorithms, code and open data can be used to perform this task and reproduce our results in different setting
Communication-based Collision Avoidance between Vulnerable Road Users and Cars
No full textThe advent of wireless communication for vehicles paves the road for a bounty of cooperative applications: The most interesting being cooperative safety awareness. By exchanging information vehicles can become aware of each other and prevent dangerous situations that can lead to crashes either by early warning drivers or by automatic vehicle control, a solution particularly appealing for self-driving cars. While research on vehicular safety mainly focuses on vehicle-to-vehicle safety, we can exploit communication to implement applications aimed at protecting vulnerable road users, such as pedestrians or cyclists. In this paper, we start by exploiting a probability framework for estimating the likelihood of collision between a vehicles approaching an intersection and a cyclist, in light of the feasibility of communication between the two. On top of this framework, we design a simple application that, under certain conditions, informs the car driver (assumed to have to yield precedence) of the possible collision. We model the reaction of the driver to the warning and analyze possible benefits and drawbacks of such an application. The contribution is not the application itself, which is obvious, but the insights in the results in light of communication capabilities and human reaction that provide a specific set of aspects that should be considered in the design of such a safety system
Let's talk in groups: A distributed bursting scheme for cluster-based vehicular applications
No full textCooperative Driving and the Tactile Internet
No full textThe trend towards autonomous driving and the recent advances in vehicular networking led to a number of very successful proposals towards cooperative driving. Maneuvers can be coordinated among participating vehicles and controlled by means of wireless communications. One of the most challenging scenario or application in this context is Cooperative Adaptive Cruise Control (CACC) or platooning. When it comes to realizing safety gaps between the cars of less than 5m, very strong requirements on the communication system need to be satisfied. The underlying distributed control system needs regular updates of sensor information from the other cars in the order of about 10 Hz. This leads to message rates in the order of up to 10 kHz for large networks, which, given the possibly unreliable wireless communication and the critical network congestion, is beyond the capabilities of current vehicular networking concepts. In this article, we summarize the concepts of networked control systems and revisit the capabilities of current vehicular networking approaches. We then present opportunities of Tactile Internet concepts that integrate interdisciplinary approaches from both control theory, mechanical engineering, and communication protocol design. This way, it becomes possible to solve the high reliability and latency issues in this context
A Joint Network/Control Design for Cooperative Automatic Driving: Extended Version
No full textCooperative automatic driving, or platooning, is a promising solution to improve traffic safety, while reducing congestion and pollution. The design of a control system for this application is a challenging, multi-disciplinary problem, as cooperation between vehicles is obtained through wireless communication. So far, control and network issues of platooning have been investigated separately. In this work we design a cooperative driving system from a joint network and control perspective, determining worst-case upper bounds on the safety distance subject to network losses, so the actual inter-vehicle gap can be tuned depending on vehicle or network performance. By means of simulation, we show that the system is very robust to packet losses and that the derived bounds are never violated
Simulation of 802.11 PHY/MAC: The quest for accuracy and efficiency
No full textThe goal of this work is to highlight and explain the limitations of traditional physical channel models used in network simulators for wireless LANs, with particular reference to VANETs, where these limitations may jeopardize the validity of results, specially for safety applications. The fundamental tradeoff is between simulation time and realism. Indeed, a simulator should provide realistic results as fast as possible, even if several nodes (i.e., hundreds) are considered. Our final goal, beyond this initial contribution, is the development of a stochastic channel model which improves reliability of simulations while increasing computational complexity only marginally. The design of our model is based on the representation of the packet decoding procedure as a Markov Decision (Stochastic) Process (MDP), thus avoiding the computational complexity of the simulation of the entire transmission - propagation - decoding chain bit-by-bit, which can surely provide enough accuracy, but at the price of unacceptable computational (and model) complexity. The paper identifies the key phenomena such as preamble detection, central-frequency misalignment, channel captures, vehicles relative speed, that represent the `state' of the MDP modeling the transmission chain, and propose an MDP structure to exploit it. The focus is on 802.11p and OFDM-based PHY layers, but the model is extensible to other transmission techniques easily. The design is tailored for implementation in ns-3, albeit the modeling principle is general and suitable for every event-driven simulator
Emergency braking: a study of network and application performance
No full textSafety applications are among the key drivers in VANET research. Their study is complex as it encompasses different disciplines, from wireless networking to car dynamics, to drivers' behavior, not to mention the economic and legal aspects. This work presents a simulative study of emergency braking applications tackled by embedding a mobility, cars' dynamic, and driver's behavior model into a detailed networking simulator (ns-3). The results, derived both at the network and at the application level, capture correctly the interactions of the communications and protocols with the car's adaptive cruise control system and the driver's behavior for cars that are not equipped with communication devices. The paper presents in detail the improvements we contribute in simulation techniques and model completeness. It introduces a novel and easy message aggregation technique to empower message re-propagation while controlling the network load during the peak due to the emergency braking. Finally it discusses the effectiveness of such applications as a function of the market penetration rate, showing that even cars that are not equipped with communication devices benefit from the smoother and earlier reaction of those cars that can communicate and whose adaptive cruise control implements a correct deceleration strategy
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