1,834 research outputs found
EVEREST IST - 2002 - 00185 : D23 : final report
Deliverable pĂşblic del projecte europeu EVERESTThis deliverable constitutes the final report of the project IST-2002-001858 EVEREST. After its successful completion, the project presents this document that firstly summarizes the context, goal and the approach objective of the project. Then it presents a concise summary of the major goals and results, as well as highlights the most valuable lessons derived form the project work. A list of deliverables and publications is included in the annex.Postprint (published version
Methodologies for Future Vehicular Digital Twins
The role of wireless communications in various domains of intelligent
transportation systems is significant; it is evident that dependable message
exchange between nodes (cars, bikes, pedestrians, infrastructure, etc.) has to
be guaranteed to fulfill the stringent requirements for future transportation
systems. A precise site-specific digital twin is seen as a key enabler for the
cost-effective development and validation of future vehicular communication
systems. Furthermore, achieving a realistic digital twin for dependable
wireless communications requires accurate measurement, modeling, and emulation
of wireless communication channels. However, contemporary approaches in these
domains are not efficient enough to satisfy the foreseen needs. In this
position paper, we overview the current solutions, indicate their limitations,
and discuss the most prospective paths for future investigation.Comment: Submitted to IEEE Intelligent Transportation Systems Magazin
Algorithms for propagation-aware underwater ranging and localization
MenciĂłn Internacional en el tĂtulo de doctorWhile oceans occupy most of our planet, their exploration and conservation are one of
the crucial research problems of modern time. Underwater localization stands among the
key issues on the way to the proper inspection and monitoring of this significant part of our
world. In this thesis, we investigate and tackle different challenges related to underwater
ranging and localization. In particular, we focus on algorithms that consider underwater
acoustic channel properties. This group of algorithms utilizes additional information
about the environment and its impact on acoustic signal propagation, in order to improve
the accuracy of location estimates, or to achieve a reduced complexity, or a reduced
amount of resources (e.g., anchor nodes) compared to traditional algorithms.
First, we tackle the problem of passive range estimation using the differences in the
times of arrival of multipath replicas of a transmitted acoustic signal. This is a costand
energy- effective algorithm that can be used for the localization of autonomous
underwater vehicles (AUVs), and utilizes information about signal propagation. We study
the accuracy of this method in the simplified case of constant sound speed profile (SSP)
and compare it to a more realistic case with various non-constant SSP. We also propose
an auxiliary quantity called effective sound speed. This quantity, when modeling acoustic
propagation via ray models, takes into account the difference between rectilinear and
non-rectilinear sound ray paths. According to our evaluation, this offers improved range
estimation results with respect to standard algorithms that consider the actual value of
the speed of sound.
We then propose an algorithm suitable for the non-invasive tracking of AUVs or
vocalizing marine animals, using only a single receiver. This algorithm evaluates the
underwater acoustic channel impulse response differences induced by a diverse sea
bottom profile, and proposes a computationally- and energy-efficient solution for passive
localization.
Finally, we propose another algorithm to solve the issue of 3D acoustic localization
and tracking of marine fauna. To reach the expected degree of accuracy, more sensors
are often required than are available in typical commercial off-the-shelf (COTS) phased
arrays found, e.g., in ultra short baseline (USBL) systems. Direct combination of multiple
COTS arrays may be constrained by array body elements, and lead to breaking the optimal array element spacing, or the desired array layout. Thus, the application of
state-of-the-art direction of arrival (DoA) estimation algorithms may not be possible. We
propose a solution for passive 3D localization and tracking using a wideband acoustic
array of arbitrary shape, and validate the algorithm in multiple experiments, involving
both active and passive targets.Part of the research in this thesis has been supported by the EU H2020 program under
project SYMBIOSIS (G.A. no. 773753).This work has been supported by IMDEA Networks InstitutePrograma de Doctorado en IngenierĂa Telemática por la Universidad Carlos III de MadridPresidente: Paul Daniel Mitchell.- Secretario: Antonio Fernández Anta.- Vocal: Santiago Zazo Bell
Wireless Channel Models for Indoor Environments
Wireless networks have made significant advancement in recent times by adding a new dimension to theway people communicate. Development of wireless standards have constantly aimed at providing higher datarates even under complex environments using smart antennas, multiple-input, and multiple-output systems.This has necessitated an understanding of the indoor propagation channel. Channel models describe acommunication channel and are essential in developing efficient wireless communication networks. This papersurveys different channel models used to characterise wireless indoor environment. This survey may be usefulfor the army, where the communication over wide areas during wargames that they hold periodically, isnecessary. Moreover, it may also be useful for communication near the border areas for surveillance operations.Defence Science Journal, 2008, 58(6), pp.771-777, DOI:http://dx.doi.org/10.14429/dsj.58.170
Vehicular Communication in Obstructed and Non Line-of-Sight Scenarios
Since the invention of the first car available to masses, the 1908 Ford Model T, technology has advanced towards making car travel safer for occupants and bystanders. In recent years, wireless communication has been introduced in the vehicular industry as a means to avoid accidents and save lives.Wireless communication may sometimes be challenging due to obstacles in the physical world that interact with wireless signals. Such obstacles may be dynamic, e.g. other vehicles in the traffic flow, or static, e.g. nearby buildings. Two scenarios are defined to describe those cases. The obstructed line-of-sight (OLOS) scenario is described as the case where a smaller obstacle, usually a vehicle, is placed in-between a transmitter and a receiver. This obstacle usually partially blocks communication and the receiver often moves in an out of the line-of-sight. The non line-of-sight (NLOS) scenario is described as the case where a larger obstacle completely blocks communication between a transmitter and a receiver. An example would be a building at an intersection which shadows the communication between two vehicles. In this thesis the OLOS and NLOS scenarios are investigated from different points of view.In chapter 2, a road side unit (RSU) that has been constructed and evaluated for integrating older vehicles without wireless communication with newer vehicles using wireless communication is described. Older vehicles are being detected using a universal medium-range radar and their position and speed vectors are broadcasted wirelessly to newer vehicles. Tests have been performed by using the system in parallel with wireless enabled vehicles; by comparing the content in the messages obtained from both systems, the RSU has been found to perform adequately. Accuracy tests have been performed on the system and Kalman filtering has been applied to improve the accuracy even further.Chapter 3 focuses on the OLOS scenario. A truck as an obstacle for wireless vehicular communication is being investigated. Real life measurements have been performed to characterize and model the wireless channel around the truck. The distance dependent path loss and additional shadowing loss due to the truck is analyzed through dynamic measurements. The large scale fading, delay and Doppler spreads are characterized as a measure of the channel dispersion in the time and frequency domains. It has been found that a truck as an obstacle reduces the received power by 12 and 13 dB on average in rural and highway scenarios, respectively. Also, the dispersion in time and frequency domains is highly increased when the line-of-sight is obstructed by the truck. A model for power contributions due to diffraction around the truck has also been proposed and evaluated using the previously mentioned real life measurements. It has been found that communication may actually be possible using solely diffraction around a truck as a propagation mechanism.Finally, in chapter 4 a wireless channel emulator that has been constructed and evaluated is described. Modem manufacturers face a challenge when designing and implementing equipment for highly dynamic environments found in vehicular communication. For testing and evaluation real-life measurements with vehicles are required, which is often an expensive and slow process. The channel emulator proposed is designed and implemented using a software defined radio (SDR). The emulator together with the proposed test methodology enables quick on-bench evaluation of wireless modems. It may also be used to evaluate modem performance in different NLOS and OLOS scenarios
Cooperative Radio Communications for Green Smart Environments
The demand for mobile connectivity is continuously increasing, and by 2020 Mobile and Wireless Communications will serve not only very dense populations of mobile phones and nomadic computers, but also the expected multiplicity of devices and sensors located in machines, vehicles, health systems and city infrastructures. Future Mobile Networks are then faced with many new scenarios and use cases, which will load the networks with different data traffic patterns, in new or shared spectrum bands, creating new specific requirements. This book addresses both the techniques to model, analyse and optimise the radio links and transmission systems in such scenarios, together with the most advanced radio access, resource management and mobile networking technologies. This text summarises the work performed by more than 500 researchers from more than 120 institutions in Europe, America and Asia, from both academia and industries, within the framework of the COST IC1004 Action on "Cooperative Radio Communications for Green and Smart Environments". The book will have appeal to graduates and researchers in the Radio Communications area, and also to engineers working in the Wireless industry. Topics discussed in this book include: • Radio waves propagation phenomena in diverse urban, indoor, vehicular and body environments• Measurements, characterization, and modelling of radio channels beyond 4G networks• Key issues in Vehicle (V2X) communication• Wireless Body Area Networks, including specific Radio Channel Models for WBANs• Energy efficiency and resource management enhancements in Radio Access Networks• Definitions and models for the virtualised and cloud RAN architectures• Advances on feasible indoor localization and tracking techniques• Recent findings and innovations in antenna systems for communications• Physical Layer Network Coding for next generation wireless systems• Methods and techniques for MIMO Over the Air (OTA) testin
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