1,720,987 research outputs found
Improved ultra wide band-based tracking of twin-receiver automated guided vehicles
No full textIn this paper, we present the design and performance analysis of an innovative system for tracking Automated Guided Vehicles (AGVs) in indoor industrial scenarios. An on-board odometer provides information about the dynamic state of the AGV, allowing to predict its pose (i.e., its position and orientation). At the same time, an external Ultra-Wide Band (UWB) wireless network provides the information necessary to compensate for the error drift accumulated by the odometer. Two novel alternative solutions for AGV tracking are proposed: (i) a classical Time Differences Of Arrivals (TDOA) approach with a single receiver; (ii) a “Twin-receiver” TDOA (TTDOA) approach, that requires the presence of two independent receivers on the AGV. The TTDOA configuration allows to indirectly estimate the orientation of the vehicle, thus increasing the estimation accuracy. Moreover, this allows direct estimation of the vehicle’s movement even when the odometer is not working properly (e.g., temporary failure) or when the AGV is not moving (e.g., at the start-up). The system performance with the two proposed tracking algorithms is evaluated in realistic conditions, by considering a consolidated UWB channel model and a simple on-board energy detector receiver. The impact of the wireless network architecture and of the presence of moving obstacles is analyzed. The obtained results show clearly that the implementation of a tracking system with a sub-centimeter accuracy can be realized by means of low-complexity UWB receiver and commercial odometers. The automatic movement of goods within a warehouse is one of the most appealing application of the proposed tracking system
Efficient broadcasting, through Irresponsible Forwarding, in intelligent transportation systems
No full textPerformance analysis of broadcast protocols in VANETs with Poisson spatial vehicle distribution
No full textSurface Modes in Antiresonant Reflecting Optical Waveguides with Rectangular Hollow Core
No full textCluster-Based Irresponsible Forwarding
No full text"Proc. of the 20th Tyrrhenian International Workshop on Digital Communications" (Tyrrhenian 2009), Pula, Sardinia, Italy, September 200
On the effects of mobility for efficient broadcast data dissemination in I2V networks
No full textIn this paper, we consider the problem of disseminating data in Infrastructure-to-Vehicular (I2V) networks. In particular, given a fixed Road Side Unit (RSU) we evaluate the maximum amount of data that can be reliably transferred from the RSU to the vehicles passing in its proximity through a recently proposed multihop probabilistic broadcasting protocol, namely Irresponsible Forwarding (IF). In particular, referring to highway-like Vehicular Ad-Hoc Networks (VANETs), we first characterize a mobile scenario in such a way to make a direct comparison with a static scenario meaningful, taking into account a physical characterization of the network (e.g., in terms of vehicle spatial density). Then, we carry out a comparative investigation considering mobile and static IEEE 802.11 networking scenarios. Our results show that from a single packet perspective, the vehicles' mobility does not affect the behavior of the IF protocol, at least in the considered highway scenarios. However, different conclusions are reached when an information flow (i.e., a series of consecutive packets) is considered. In this context, we determine the maximum amount of data that can be transferred from the RSU to the mobile vehicles passing through a certain region of interest around the RSU
Efficient broadcasting in IEEE 802.11 networks through irresponsible forwarding
No full textIn a self-organizing vehicular network, vehicles share and distribute information by rebroadcasting a received information packet to their neighbors. An efficient broadcast technique can offer a high reactivity without sacrificing the communication reliability. Therefore, broadcast techniques are particularly suitable for safety-related vehicular transmissions, whose goal is reaching reliably the widest area in the shortest time. Among the numerous solutions appeared in the literature, the probabilistic broadcast approaches seem to be promising and not yet accurately analyzed. Since the interaction between a high level broadcasting protocol with the lower layers cannot be ignored, in this work we analyze the behavior of a recently proposed broadcast technique, denoted as the Irresponsible Forwarding (IF), in IEEE 802.11 networks. Our attention concentrates on the Medium Access Control (MAC) layer, which is affected by some critical impairments for broadcasting, such as the hidden terminal problem and self-interference. In this work, we evaluate the benefits brought by the use of IF to perform efficient broadcasting in IEEE 802.11 networks
Short-lived key management for secure communications in VANETs
No full textVehicular Ad-hoc NETworks (VANETs) are witnessing an ever increasing interest. Security is a key aspect to pave the road to commercial deployments, as malicious attacks may increase the risk of accidents. Key management in VANETs poses further problems, as connectivity is limited and communication with a central certification authority might be problematic. In this paper, we propose a novel approach to key management for securing VANET communications. In particular, a general framework for key group multicast is proposed, with specific application to a VANET communication scenario
Recursive analytical performance evaluation of broadcast protocols with silencing: application to VANETs
No full textIn this article, we present a novel theoretical framework suitable for analytical performance evaluation of a family of multihop broadcast protocols. The framework allows to derive several average performance metrics, including reliability, latency, and efficiency, and it is targeted to Vehicular Ad-hoc NETworks (VANETs) applications based on an underlying IEEE 802.11 protocol. It builds on the assumption that the positions of the nodes of a VANET can be statistically modeled as Poisson points. However, the proposed approach holds for any spatial vehicle distribution with constant average distance between consecutive vehicles. In this work, the proposed analytical framework is applied to the class of probabilistic broadcast multihop protocols with silencing, but can be generalized to nonprobabilistic protocols as well. More specifically, this work considers a few broadcast protocols with silencing, differing for the probability assignment function. The validity of the proposed analytical approach is assessed by means of numerical simulations in a highway-like scenario
Information Dissemination in Urban VANETs: Single-hop or Multi-hop?
No full textIn recent years, Vehicular Ad-hoc NETworks (VANETs) have experienced an intense development phase, driven by academia, industry, and public authorities. On the basis of the obtained results, it is reasonable to expect that VANETs will finally hit the market in the near future. In order to reach commercial success, VANETs must effectively operate during the first years of deployment, when the market penetration rate will be unavoidably low, and, consequently, only a small number of suitably equipped vehicles (VANET- enabled) will be present on the roads. Among the possible strategies to face the initial sparse VANET scenarios, the deployment of an auxiliary network constituted by fixed Road Side Units (RSUs), either Dissemination Points (DPs) or relays, is certainly one of the most promising. In order to maximize the benefits offered by this support infrastructure, the placement of RSUs needs to be carefully studied. In this chapter, the authors analyze, by means of numerical simulations, the performance of an application that leverages on a finite number of DPs for disseminating information to the transiting vehicles. The positions of the DPs are determined through a recently proposed family of optimal placement algorithms, on the basis of proper vehicular mobility traces. The analysis is carried out considering two realistic urban scenarios. In both cases, the performance improvement brought by the use of multi-hop broadcast protocols, with respect to classical single-hop communications with DPs, is investigated
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