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Browsing by Issue Date, starting with "2020-10-09"

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  • Exploring the use of control packets in LoRa medium access: a scalability analysis
    Publication . Fernandes, Rui; Oliveira, Rui; Luís, Miguel; Sargento, Susana
    LoRa technology has been attesting itself as one of the most prominent and widely adopted low power wide area technologies. Highly compatible with Internet of Things (IoT) applications and urban environments, this technology enables large range communications although with small bandwidths and duty cycle restrictions. In this work, we propose a distinct way of dealing with the Medium Access Control (MAC) in LoRa, through the use of control packets to enhance the technology performance in urban city scenarios, where a large number of nodes is expected. The proposed protocol is asynchronous and takes into account the energy expenditure. We compare this scheme with the standard (LoRaWAN) by considering different network densities and packet sizes, and through different LoRa collision models. Performance results, such as network throughput and fairness index, show that, depending on the ratio between data and control packet lengths, it is possible to greatly improve the bit rate and overall network performance, even if increasing the duty-cycle restriction time due to the addition of overhead.
    2020-10-09Conference object Open access Show more
  • Anomalies in B-meson decays and the muon g-2 from dark loops
    Publication . Huang, Da; Morais, António P.; Santos, Rui
    We explore a class of models which can provide a common origin for the recently observed evidence for lepton flavor universality violation in b -> sl(+)l(-) decays, the dark matter (DM) problem, and the long-standing muon (g - 2) anomaly. In particular, both anomalies in the B meson decays and the muon (g - 2) can be explained by the additional one-loop diagrams with DM candidates. We first classify several simple models according to the new fields' quantum numbers. We then focus on a specific promising model and perform a detailed study of both DM and flavor physics. A random scan over the relevant parameter space reveals that there is indeed a large parameter space which can explain the three new physics phenomena simultaneously, while satisfying all other flavor and DM constraints. Finally, we discuss some of the possible new physics signatures at the Large Hadron Collider.
    2020-10-09Journal article Restricted access Show more