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Browsing by Author "Pinto, Luís"

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  • 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 Show more
  • Wireless radio link design to improve nearshore communication with surface nodes on tidal waters
    Publication . Gutiérrez Gaitán, Miguel; d'Orey, Pedro; Santos, Pedro Miguel; Ribeiro, Manuel; Pinto, Luís; Almeida, Luís; Sousa, J. Borges de
    Wireless radio links deployed over aquatic areas (e.g., sea, estuaries or harbors) are affected by the conductive properties of the water surface, strengthening signal reflections and increasing interference effects. Recurrent natural phenomena such as tides or waves cause shifts in the water level that, in turn, change the interference patterns and cause varying impairments to propagation over water surfaces. In this work, we aim at mitigating the detrimental impact of tides on the quality of a line-of-sight over-water link between an onshore station and a surface node, targeting mission data transfer scenarios. We consider different types of surface nodes, namely, autonomous underwater vehicles, unmanned surface vehicles and buoys, and we use WiFi technology in both 2.4 GHz and 5 GHz frequency bands. We propose two methods for link distance/height design: (i) identifying a proper Tx-Rx distance for improved link quality at each point of the tidal cycle; (ii) defining the height/distance that minimizes the path loss averaged during the whole tidal cycle.Experimental results clearly show the validity of our link quality model and the interest of method (i). Analytical results confirm method (ii) and show that it outperforms, in both frequency bands, the common practice of placing onshore antennas at the largest possible height and/or surface nodes at a short but arbitrary distance.
    2021-09-23Conference object Open access Show more