220605

This work presents a capacity analysis of Space-Time Block Codes (STBC) for Vehicle-to-Vehicle (V2V) communication in Line-of-Sight (LOS). The aim is to assess how this type of coding performs when the V2V LOS channel is influenced by ground reflections. STBCs of various coding rates are evaluated using antenna elements distributed over the surface of two contiguous vehicles. A multi-ray tracing tool is used to model the multiple constructive/destructive interference patterns of the transmitted/received signals by all pairs of Tx-Rx antenna links. Simulation results show that STBCs are capable of counteracting fades produced by the destructive self-interference components across a range of inter-vehicle distances. Notably, the effectiveness in deep fades is shown to outperform schemes with exclusive receive diversity. Higher-order STBCs with rate losses are also evaluated, showing interesting gains even for low coding rate performance, particularly, when accompanied by a multiple antenna receiver. Overall, these results can shed light on how to exploit transmit diversity in slow fading vehicular channels.info:eu-repo/semantics/publishedVersio

Real-Time Communication Support for Over-water Wireless Multi-hop Networks

https://www.bsc.es/education/predoctoral-phd/doctoral-symposium/7th-bsc-so-doctoral-symposiumThe prospect scenario for wireless communications and networking technologies in aquatic environments is nowadays promising. The growing interest around this subject in the last decades has recently been accelerated due to the more powerful capabilities of a number of sensing, control and communication devices. Moored, fixed, drifting, and vehicular nodes form now a rich ecosystem of autonomous embedded systems potentially connected in a multi-hop (and over-water) fashion, which demand innovative solutions to satisfy the ever-increasing requirements of reliability, bandwidth, latency and cost. The efforts in this direction, mostly as a result of the push from the Internet-of-Thing (IoT) and related communication paradigms, are now at an early stage, and thus still pose significant, technical and research challenges, especially from the perspective of communication and networking for applications involving real-time and/or multimedia networking traffic. In this research, we focus on the communication and networking aspects of over-water multi-hop networks aiming at support real-time and/or multimedia (audio/video) traffic using IEEE 802.11 (WiFi) commodity technologies. Special attention is devoted to the impact of cyclic water-level variations (such as tides and waves) on the overall network performance, and how an integrated approach to (i) network design, (ii) protocol adaptation and (iii) routing can contribute to mitigating such an issue.info:eu-repo/semantics/publishedVersio

231202

This work presents the performance analysis of space-time block codes (STBCs) for vehicle-to-vehicle (V2V) fast-fading channels in scenarios with modified line-of-sight (LOS). The objective is to investigate how the V2V MIMO (multiple-input multiple-output) system performance is influenced by two important impairments: deterministic ground reflections and an increased Doppler frequency (time-variant channels). STBCs of various coding rates (using an approximation model) are evaluated by assuming antenna elements distributed over the surface of two contiguous vehicles. A multi-ray model is used to study the multiple constructive/destructive interference patterns of the transmitted/received signals by all pairs of Tx–Rx antenna links considering ground reflections. A double scattering model is used to include the effects of stochastic channel components that depend on the Doppler frequency. The results show that STBCs are capable of counteracting fades produced by destructive self-interference components across a range of inter-vehicle distances and for a range of Doppler frequency values. Notably, the effectiveness of STBCs in deep fades is shown to outperform schemes with exclusive receive diversity, despite the interference created by the loss of orthogonality in time-varying channels with a moderate increase of Doppler frequency (mainly due to higher vehicle speeds, higher frequency or shorter time slots). Higher-order STBCs with rate losses are also evaluated using an approximation model, showing interesting gains even for low coding rate performance, particularly when accompanied by a multiple antenna receiver. Overall, these results can shed light on how to exploit transmit diversity in time-varying vehicular channels with modified LOS.info:eu-repo/semantics/publishedVersio

211002

This work introduces LibreDTE, an initiative providing software tools and support for electronic invoicing in Chile. LibreDTE is mainly built upon libredte-lib, a free software library that directly connects with the Chilean Internal Revenue Service, thus enabling automatic emissions of official e-invoices and other electronic tax documents. LibreDTE is either: (1) the first (and so far, the only one) Chilean framework for free-software-driven e-invoicing, and (2) an official software solution with featured e-business capabilities. In this paper, we describe both, the community (or free software) version, and the official (or commercial) version of LibreDTE. We focus on their primary building blocks and major technical differences, and we show, in a tutorial way, some of the key design considerations behind their common e-invoice generation. We also discuss some lessonslearned from earlier implementations, as well as the latest (and promising) features incorporated within the official version.This paper was partially supported by National Funds through FCT/MCTES (Portuguese Foundation for Science and Technology), within the CISTER Research Unit (UIDP/UIDB/04234/2020) and by FCT through the European Social Fund (ESF) and the Regional Operational Programme (ROP) Norte 2020, under grant 2020.06685.BDinfo:eu-repo/semantics/publishedVersio

On the Two-Ray Model Analysis for Overwater Links with Tidal Variations

Atas do 11º Simpósio de Informática (INForum 2019)This work explores the impact of antenna heights and polarization on overwater links during the cycle of tidal variations. We focus our attention on links of short-to-medium-range distances with antenna heights near-to-the-water-surface. The typical use-case for such a scenario is an overwater, water quality monitoring wireless sensor network. The radio propagation is simulated using a featured two-ray model that considers the relative permittivity of the water surface and the antenna polarization. The results show that the performance of overwater links may be better with lower antennas than higher antennas as well as with one polarization or the other, intuitively, during part of the tidal cycle.info:eu-repo/semantics/publishedVersio

An Analysis of the Two-Ray Propagation Model to Support Near-Surface Overwater Wireless Sensor Networks Design

3rd Doctoral Congress in Engineering will be held at FEUP on the 27th to 28th of June, 2019In this work, a thorough analysis based on the two-ray model in the presence of tides is performed. The study aims to provide a tool to guide the deployment of near-surface overwater wireless sensor networks, and thus improve its overall link quality regardless of the variations of the tides. We consider realistic parameters, such as the distance between the nodes and the tide-levels range taken from the mouth of the Douro river, Porto and the Seixal Bay, Lisbon. In future works, we will complement the theoretical analysis with network level simulations and an extended experimental campaign.info:eu-repo/semantics/publishedVersio

Wi-Fi-based network systems design over freshwater: Experimental evaluation using COTS devices

To experimentally assess the impact of surface reflection on the received signal strength of a set of short-andmedium-range shore-to-shore links (<200 m) that use antennas installed at two heights, at a few meters above surface (<3 m).info:eu-repo/semantics/publishedVersio

220604

This research proposes a novel minimal-overlap centrality-driven gateway designation method for real-time wireless sensor networks (WSNs). The goal is to enhance network schedulability by design, particularly, by exploiting the relationship between path node-overlaps and gateway designation. To this aim, we define a new metric termed minimal-overlap network centrality which characterizes the overall overlapping degree between all the active flows in the network when a given node is selected as gateway. The metric is then used to designate as gateway the node which produces the least overall number of path overlaps. For the purposes of evaluation, we assume a time-synchronized channel-hopping (TSCH) WSN under centralized earliest-deadline-first (EDF) scheduling and shortest-path routing. The assessment of the WSN traffic schedulability suggests our approach is dominant over classical network centrality metrics, namely, eigenvector, closeness, betweenness, and degree. Notably, it achieves up to 50% better schedulability than a degree centrality benchmark.This work was partially supported by National Funds through FCT/MCTES (Portuguese Foundation for Science and Technology), within the CISTER Research Unit (UIDB/04234/2020); by the Operational Competitiveness Programme and Internationalization (COMPETE 2020) under the PT2020 Agreement, through the European Regional Development Fund (ERDF); also by FCT and the ESF (European Social Fund) through the Regional Operational Programme (ROP) Norte 2020, under PhD grant 2020.06685.BDN/

Multiprocessor Scheduling meets the Industrial Wireless

This survey covers schedulability analysis approaches that have been recently proposed for multi-hop and multi-channel wireless sensor and actuator networks in the industrial control process domain. It reviews results with a focus on WirelessHART-like networks. The paper address the mapping of multi-channel transmission scheduling to multiprocessor scheduling theory, and recognize it as the key aspect of the research direction covered by this survey. It also provides a taxonomy of the existing approaches concerning this direction, and discuss its main features and evolution. The survey identifies open issues, key research challenges, and future directions