Search results for "Networks"

Making WiFi work in multi-hop topologies: Automatic negotiation and allocation of airtime

2015

We propose a solution for mitigating the performance impairments of CSMA/CA protocols in multi-hop topologies based on the dynamic adaptation of the contention process experienced by nodes in a wireless network. A distributed protocol is used to negotiate the channel airtime for a node as a function of the traffic requirements of its neighbourhood, taking into account bandwidth reserved for the control operations. A mechanism is provided for a node to tune its contention window depending on its allocated airtime. Different from previous schemes, a node's contention window is fixed in size unless the traffic requirements of its neighbourhood change. The scheme is implemented on legacy commer…

Power consumption analysis for mobile stations in hybrid relay-assisted wireless networks

2010

While Internet access using mobile or wireless technologies has become ubiquitous these days, the energy consumption aspect of such connections has not been studied in-depth yet. In this paper, a hybrid wireless network, which consists of a cellular component and a relay-assisted ad hoc component, is studied focusing on energy consumption by mobile stations with respect to the amount of data communicated and achieved battery lifetime. Four alternative paths are considered, including both pure cellular and hybrid ad hoc/cellular links for uplink and downlink traffic. The effects of each alternative connection on energy consumption of the involved mobile stations are analyzed in terms of the …

Wittgenstein, Turing, and Neural Networks

2018

The main task of this paper is grounding the socio-anthropological “naturalization” of meaning operated by the later Wittgenstein in his remarks on rule-following in the Philosophical Investigations in considerations relating to models of low-level (biological) processes of imitation, training, and learning. If the operation suggested above is successful, two of its immediate consequences are that the social aspect of language can no longer be considered as a primitive notion, but needs to be placed upon, if not reduced to, a biological foundation; and that the study of thought, and, actually, of certain brain processes, becomes prior in the order of explanation to the study of language. Th…

Mobile information systems - executives' view

1997

The concepts of travelling executive and executives' mobile information system are first defined in this paper. The main findings are in the form of collected data and opinions concluded from our personal discussions with 49 executives in the United Kingdom, France, Italy and Finland concerning the nature of the work of executives and the usage of information technology (IT) to support their work today. The near future expectations of the executives are also analysed, especially concerning the mobile use of IT services in order to construct executives' holistic view of mobile computing. The use of IT services was found to be very widespread. Big differences were found: some of the executive…

Effect of disorder on Majorana localization in topological superconductors: a quasiclassical approach

2020

Two-dimensional (2D) topological superconductors (TS) host chiral Majorana modes (MMs) localized at the boundaries. In this work, we study the effect of disorder on the localization length of MMs in two-dimensional spin-orbit (SO) coupled superconductors within quasiclassical approximation. We find nonmonotonic behavior of the Majorana localization length as a function of disorder strength. At weak disorder, the Majorana localization length decreases with an increasing disorder strength. Decreasing the disorder scattering time below a crossover value ${\ensuremath{\tau}}_{c}$, the Majorana localization length starts to increase. The crossover scattering time depends on the relative magnitud…

Guest Editorial

2011

Las redes sociales y la innovación educativa. La experiencia del Geoforo. Balance anual de 2012

2012

El aumento de la participación en los foros ha facilitado el intercambio de opiniones y argumentos sobre la innovación educativa. Podemos definir este momento como la creación de una red social con intereses profesionales coincidentes: la mejora del aprendizaje de los hechos sociales, en especial los que tienen una característica geográfica. Los datos que se aportan en este balance anual nos indican que se está asentando el Geoforo allí donde hay grupos locales, lo que nos confirma que este blog es una red de redes.

The social perspective of the main MOOC platforms through Facebook

2017

Facebook, como red social, ofrece un medio potente de comunicación social a través de la Red, conectando usuarios con intereses comunes. En este estudio se analizan las cuentas de Facebook de 7 de las principales plataformas de MOOC: Coursera, EdX, Future Learn, Harvard Extension, Miríada X, Stanford Online y Udacity, con el fin de describir el modo en que estas emplean sus cuentas de Facebook como espacio digital de comunicación, información e interacción social con sus usuarios. Para ello, se han utilizado herramientas de medición online sobre el crecimiento y la visibilidad de las cuentas, el contenido publicado y la interactividad con los seguidores. Los resultados evidencian que el núm…

An Inter-Technology Communication Scheme for WiFi/ZigBee Coexisting Networks

2017

In this paper we show how inter-technology interference can be exploited to set-up a low-rate bi-directional communication channel between heterogeneous technologies, which coexist in ISM bands. In particular, we focus on WiFi and ZigBee networks, whose high density deployments make coexistence a critical issue. We monitor the transmission duration of the interference and, after recognizing ZigBee interference from WiFi off-the-shelf receivers, we precisely measure the channel busy intervals to map time duration to communication symbols. A similar approach is used on the ZigBee receivers for making the communication channel bidirectional. Extensive experimental results show the feasibility …

Chemical Bath Deposition as a Simple Way to Grow Isolated and Coalesced ZnO Nanorods for Light-Emitting Diodes Fabrication

2018

A way to grow and characterize isolated and coalesced ZnO nanorods on $p$ -GaN/sapphire structure is presented. Chemical bath deposition can be used to grow ZnO nanorods of device-quality, simply controlling the duration time of the growth process and the concentration of the nutrient solution in the bath. Increasing the duration of the process, as well as the concentration of the solution, leads to compact and sound layers instead of separated nanorods. However, too high concentrations stop the growth process. Light-emitting diodes fabricated on these ZnO-p-GaN heterostructure have a peak of electroluminescence at 400 nm and exhibit interesting electrical and optical properties. Optical po…