1,720,972 research outputs found
On discrete-time modeling of the filtered and symbol-rate sampled continuous-time signal affected by Wiener phase noise
Get PDFStrategic Network Slicing Management in Radio Access Networks
Get PDFNetwork slicing might radically change the relations among different actors of the telecommunications ecosystem, where new players, active in different markets, could benefit of tailored connectivity services based on different business strategies. We argue that for fully exploiting the opportunities offered by network slicing, dynamic sharing of resources is crucial not only for efficiency and cost savings, but also for enabling a resource negotiation that can unleash the potential of new business relations. We develop an automated mechanism that allows tenants to take strategic decisions to optimize the management of their slices based on their instantaneous demands and model their interaction as in marketplace. We integrate our solution, based on game theory, on a 3GPP calibrated system level simulator, where a slice-aware scheduler enforces the tenants' decisions at the Nash Equilibrium (NE). We compare our proposal with a static baseline, that assigns a fixed share of resources to each slice, and show that, by dynamically trading resources in the market, tenants achieve lower costs, and, therefore, higher profits. We provide an algorithmic implementation that guarantees the convergence to a single NE and test the computational complexity of our algorithm to an increasing number of slices in the system
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Analysis of Wiener phase noise issues in optical transmission systems
Get PDFNelle comunicazioni ottiche, gli oscillatori locali e la propagazione introducono rumore di fase moltiplicativo che devono essere presi in considerazione, stimati e compensati al ricevitore. In letteratura tali canali sono trattati considerando un modello a tempo di simbolo dove il simbolo trasmesso è disturbato sia da rumore AWGN che da rumore di fase moltiplicativo, modellato come un processo di Wiener del primo ordine. Le problematiche introdotte da questi canali sono oggetto di diverse opere in letteratura. Lo scopo di questa tesi è di discutere alcuni di loro e cercare di estendere tali dissertazioni.
Prima di tutto, in letteratura tale modello è assunto considerando un “piccolo” rumore di fase, ma nessuno ha mai discusso quanto “piccolo” questo deve essere. Una analisi statistica e matematica e una soglia di validità del modello discreto è stato elaborato, dimostrando che l'ipotesi è corretta in quasi tutti gli scenari pratici ed è conservativa in termini di simulazione delle prestazioni. L'analisi dei canali affetti da rumore di fase viene poi approfondita studiando tecniche di stima Bayesiana per estrarre tutte le informazioni sui simboli trasmessi. Uno schema di demodulazione e decodifica iterativa è stato proposto e confrontato con altri presenti in letteratura. Il maggiore guadagno dello schema della tesi è dato dalla maggiore efficienza spettrale ottenuta non trasmettendo Simboli pilota e mantenendo comunque prestazioni migliori di altri sistemi analoghi considerati. La stima Bayesiana permette anche di ricavare l’informazione mutua del canale dato dal modello discreto considerato e verificare che l'algoritmo proposto può raggiungerla.
L'attenzione viene quindi spostata all’analisi di scenari di accesso ottici su tratte brevi in cui, per massimizzare l’efficienza spettrale del ricevitore, OFDM è stato considerato invece di sistemi di trasporto a singola portante. Per costi, requisiti di ingombro e di potenza, la rivelazione diretta ha diversi vantaggi rispetto ai sistemi coerenti poiché il rumore di fase moltiplicativo introdotto dal laser al trasmettitore può essere trascurato. Tuttavia, se non si utilizzano le fibre per la compensazione della dispersione cromatica, essa ostacola il segnale e il rumore di fase non può essere completamente cancellato. L'autore ha analizzato gli studi già presenti su questo fenomeno, sottolineandone le debolezze e confrontando i nuovi risultati della tesi sia con misure sperimentali, sia con lavori di altri autori.In optical communications, local oscillators and propagation introduce multiplicative phase noise
that must be taken in consideration, estimated and compensated at the receiver.
In the literature such channels are dealt with by considering
a symbol-spaced discrete-time model where the transmitted symbol is impaired by both
AWGN and a multiplicative phase noise given by a first order Wiener process.
The issues given by such channels are objects of several works in the literature.
The aim of this thesis is to discuss some of them and try to extend those
dissertations.
First of all, in the literature this model is assumed by considering ``small'' phase noise
but nobody has ever discussed how much ``small'' it must be.
A statistical and mathematical analysis is derived by the author, and a threshold of validity of the
so called Discrete Model is worked out, proving that the assumption is correct in almost
all practical scenario and it is conservative in term of performance simulation.
The analysis of phase noise channels is then deepened by studying Bayesian tracking
techniques to extract all the information about the transmitted symbols.
An iterative demodulation and decoding scheme is proposed and compared to others in the literature.
The major gain is given by the greater spectral efficiency obtained by not transmitting
Pilot Symbols and still working better than other considered similar schemes.
Bayesian tracking allows also to derive the information rate of the considered Discrete Model channel
and to verify that the proposed algorithm can achieve it.
The focus is then moved to analyze short reach access optical scenarios where,
for spectral efficiency and receiver sensitivity, OFDM has been considered instead
of single carrier systems.
For cost, footprint and power consumptions requirements, Direct Detection has several advantages compared
to Coherent schemes since the multiplicative phase noise introduced by the transmitting laser
can be neglected. However, if dispersive compensating fibers are not used, Chromatic Dispersion
impairs the signal and the phase noise cannot be canceled. The author has proposed the literature
analysis of this phenomenon, enlightening its weaknesses and comparing the new results of the thesis
with experimental measurements given by other authors.DIPARTIMENTO DI ELETTRONICA, INFORMAZIONE E BIOINGEGNERIATelecommunications28MONTI-GUARNIERI, ANDREA VIRGILIOBONARINI, ANDRE
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