Search results for "Telecommunication"
showing 10 items of 1769 documents
Achieving Ultra Reliable Communication in 5G Networks: A Dependability Perspective Availability Analysis in the Space Domain
2017
As part of the 5G communication paradigm, ultra reliable communication (URC) is envisaged as an important technology pillar for providing anywhere and anytime services to end users. While most existing studies on reliable communication do not investigate this problem from a dependability theory perspective, those dependability-based studies tend to define reliability merely in the time domain. In this letter, we advocate extending the concept of URC from the dependability perspective also in the space domain . We initiate definitions on cell availability and system availability. The availability and the probability of providing a guaranteed level of availability in a network are analyzed bo…
Combined IT and power supply infrastructure sizing for standalone green data centers
2021
International audience; In this work, we propose a two-step methodology for designing and sizing a data center solely powered by local renewable energy. The first step consists in determining the necessary IT equipment for processing a given IT workload composed of batch and service tasks. We propose an adapted binary search algorithm and prove its optimality to find the minimum number of servers to handle the IT workload. When the IT sizing is computed, the second step consists in defining the supplying electrical infrastructure using wind turbines and photovoltaic panels as primary sources. Batteries and a hydrogen system are added as secondary sources for short- and long-term energy stor…
Characterization of Radio Frequency Echo using frequency sweeping and power analysis
2014
International audience; Coupling between repeater's antennas, called Radio Frequency Echo (RFE) deteriorates signal quality and compromises system stability. If the channel insulation is insufficient, the power in the closed-loop raises with time according to the gain margin value. Multiple methods of echo cancellation exists. Generally, these techniques are based on correlation calculation and adaptive filtering. However, their efficiency and algorithm's convergence speed are calling into question under signal's modulation and real-time constraints, specially with narrow band signals having frequency hopping as GSM or TETRA. This paper describes a real time method of RFE detection and esti…
Waiting time in quantum repeaters with probabilistic entanglement swapping
2019
The standard approach to realize a quantum repeater relies upon probabilistic but heralded entangled state manipulations and the storage of quantum states while waiting for successful events. In the literature on this class of repeaters, calculating repeater rates has typically depended on approximations assuming sufficiently small probabilities. Here we propose an exact and systematic approach including an algorithm based on Markov chain theory to compute the average waiting time (and hence the transmission rates) of quantum repeaters with arbitrary numbers of links. For up to four repeater segments, we explicitly give the exact rate formulae for arbitrary entanglement swapping probabiliti…
An experimental testbed of an Internet of Underwater Things
2020
A number of critical features have so far slowed down the realization of an Internet of Underwater Things. The most relevant of these aspects are related to the unreliability of the communication channel, the long propagation delay and the effect of severe multi-path and fading. This paper presents the design and development of a hybrid underwater-terrestrial IoT where different underwater sensors collect heterogeneous data and use marine acoustic modems to send information to a gateway device; this is able to set up a long distance link, implemented through a LoRaWAN connection, to forward data to a remote cloud for further processing. Performance of this system has been tested in a real s…
Design of a narrow-band filter based on the Brewster phenomenon for microwave applications
2017
A high-efficiency narrow-band filter based on a Dielectric Frequency-Selective Surface (DFSS) has been predicted theoretically for oblique plane-wave incidence. A DFSS showing total reflection at a frequency of 10.5 GHz, based on the Brewster phenomenon for TM polarization, has been designed with a single dielectric grating, showing extremely low-reflectance sidebands adjacent to the resonance peak. The angular and spectral response of the designed filter has been studied. In addition, dielectric ohmic losses have been accounted for in this structure. This work was supported by the Agencia Estatal de Investigación (AEI) and by the Unión Europea through the Fondo Europeo de Desarrollo Region…
Delivering Services to Residential Appliances by Utilizing Remote Resource Awareness
2008
Service providers are nowadays offering a variety of services, and in particular multimedia content delivery. Besides, consumer appliances are increasingly becoming digitalized including support for communication networks. However, it is difficult, and in many cases impossible, to use these services with standard consumer appliances, such as TV and media player devices. Rather, usage is often restricted so that they can only be accessed through web browsers from PCs, mobile phones and similar terminals. This is unfortunate, because dedicated consumer appliances are often better suited to handle the content and thereby give consumers a better experience. Within this paper, three design appro…
A Design Methodology for Low-Power MCML Ring Oscillators
2007
In this paper, a low-power design method for MCML based ring oscillators is presented. The proposed method takes into account the parasitic capacitances of the MOS transistors. To validate it, some ring oscillators with different oscillation frequencies were designed in a 0.18 mum CMOS technology. SPICE simulations demonstrate the effectiveness of the design method.
A non-stationary one-ring scattering model
2013
This paper introduces a non-stationary one-ring scattering model in which the mobile station (MS) can move along a straight line from the ring's center to the border of the ring. This movement results in a time-variant angle-of-arrival (AOA), which is modeled by a stochastic process. We derive the first-order density of the AOA process in closed form. Subsequently, a closed-form expression is provided for the local power spectral density (PSD) of the channel. We also formulate the local autocorrelation function (ACF) of the complex channel gain in integral form, from which a highly accurate closed-form approximation is derived. Furthermore, the average Doppler shift and the Doppler spread o…
Mobility and Spatio-Temporal Exposure Control
2013
Modern risk assessment methods cover many issues and encompass both risk analysis and corresponding prevention/mitigation measures.However, there is still room for improvement and one aspect that may benefit from more work is “exposure control”.The “exposure” an asset experiences plays an important part in the risks facing the asset.Amongst the aspects that all too regularly get exposed is user identities and user location information,and in a context with mobile subscriber and mobility in the service hosting (VM migration/mobility) the problems associated with lost identity/location privacy becomes urgent.In this paper we look at “exposure control” as a way for analyzing and protecting use…