Supporting Real-time Communications in Over-water Multi-hop Networks

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Outage Probability of V2V Multiple-Antenna Rice Fading Links with Explicit Ground Reflection

Publication . Gutiérrez Gaitán, Miguel; Samano-Robles, Ramiro; Rodriguez, Jonathan

This paper investigates the improvement in terms of outage probability of a vehicle-to-vehicle (V2V) communication link with respect to the density of antennas used at each vehicle end. The objective is to find a trade-off between system complexity and communication performance considering that the deterministic component of the link is affected explicitly by multiple ground reflections (self-interference). The antennas are assumed to be located at regularly distributed positions across the surface of contiguous vehicles. Part of the work assumes symbol repetition at the transmitter side, and different signal combining mechanisms at the receiver side, namely, maximum-ratio and equal-gain combining (MRC and EGC, respectively). The objective is to minimize outage probability of the link with deterministic and stochastic channel components (Rice-distributed), where the line-of-sight (LOS) is affected by multi-ray ground reflections as an extension of the well-known two-ray model. This scenario is considered more realistic for V2V scenarios due to the potential proximity of ground to the antenna elements. The outage probability is calculated over a range of inter-vehicle distances with respect to the free-space loss solution. The results show that performance is improved even for a relatively small number of antennas and that a critical point is reached beyond which improvement is only differential. This suggests that an optimum trade-off can be obtained to ensure a value of outage probability with a complexity constraint over a range of inter-vehicle distances.

2023-01-11Conference object

Restricted access

Improving WiFi communication with surface nodes at near-shore on tidal waters

Publication . Gutiérrez Gaitán, Miguel; d'Orey, Pedro; Santos, Pedro Miguel; Ribeiro, Manuel; Pinto, Luis; Almeida, Luís; de Sousa, J. Borges

Wireless radio links deployed in aquatic areas (e.g., sea, rivers, lakes, estuaries) are affected by the conductive properties of the water surface, strengthening signal reflections and increasing destructive interference. Recurrent natural phenomena (e.g. tides or waves) cause shifts in water levels further impairing propagation over water surfaces. In this work, we aim to mitigate the detrimental impact of tides on link quality by providing tailored link distance/height-design regions that minimize average path losses. We focus on line-of-sight (LOS) over-water links between onshore stations and different types of surface nodes, namely AUVs, buoys, or USVs, using 2.4 GHz and 5 GHz frequency bands. Analytical results targeting mission data transfer scenarios demonstrate that the proposed method outperforms, in both frequency bands, the common practice of placing (i) onshore antennas at the largest possible height and/or (ii) surface nodes at a short but arbitrary distance from the shore. A longer version of this summary was presented at IEEE/MTS OCEANS 2021.

2022-02-04Other

Open access

Minimal-Overlap Centrality for Multi-Gateway Designation in Real-Time TSCH Networks

Publication . Gutiérrez Gaitán, Miguel; Almeida, Luis; D'Orey, Pedro; Santos, Pedro M.; Watteyne, Thomas

This article presents a novel centrality-driven gateway designation framework for the improved real-time performance of low-power wireless sensor networks (WSNs) at system design time. We target time-synchronized channel hopping (TSCH) WSNs with centralized network management and multiple gateways with the objective of enhancing traffic schedulability by design. To this aim, we propose a novel network centrality metric termed minimal-overlap centrality that characterizes the overall number of path overlaps between all the active flows in the network when a given node is selected as gateway. The metric is used as a gateway designation criterion to elect as a gateway the node leading to the minimal number of overlaps. The method is then extended to multiple gateways with the aid of the unsupervised learning method of spectral clustering. Concretely, after a given number of clusters are identified, we use the new metric at each cluster to designate as cluster gateway the node with the least overall number of overlaps. Extensive simulations with random topologies under centralized earliest-deadline-first (EDF) scheduling and shortest-path routing suggest our approach is dominant over traditional centrality metrics from social network analysis, namely, eigenvector, closeness, betweenness, and degree. Notably, our approach reduces by up to 40% the worst-case end-to-end deadline misses achieved by classical centrality-driven gateway designation methods.

2023-07-25Journal article

Open access

LibreDTE: Software Tools and Support for Electronic Invoicing in Chile

Publication . De la Fuente, Esteban; Gutiérrez Gaitán, Miguel

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.

2021-11-16Journal article

Open access

Demonstrating RA-TDMAs+ for robust communication in WiFi mesh networks

Publication . Almeida, Diogo; Gutiérrez Gaitán, Miguel; D'Orey, Pedro; Santos, Pedro M.; Pinto, Luís; Almeida, Luis

This work will demonstrate a new flavor of the RA-TDMA set of protocols, namely RA-TDMAs+, which uses IEEE-802.11 (WiFi) COTS hardware in ad-hoc mode to set up a dynamic mesh network of mobile nodes with highbandwidth. The protocol uses topology tracking to configure the TDMA frame and robust relative synchronization to define the TDMA slots without resorting to a global clock and in the presence of interfering traffic. The demo will set up a small-scale testbed using COTS hardware, thus evidencing the feasibility of the approach, and it will show 1clive plots 1d of the temporal (synchronization) and topological views of the network.

2021-12-07Journal article

Open access