1,720,983 research outputs found
On the Cramer-Rao bound for carrier frequency estimation in the presence of phase noise
No full textWe consider the carrier frequency offset estimation in a digital burst-mode satellite transmission affected by phase noise. The corresponding Cramer-Rao lower bound is analyzed for linear modulations under a Wiener phase noise model and in the hypothesis of knowledge of the transmitted data. Even if we resort to a Monte Carlo average, from a computational point of view the evaluation of the Cramer-Rao bound is very hard. We introduce a simple but very accurate approximation that allows to carry out this task in a very easy way. As it will be shown, the presence of the phase noise produces a remarkable performance degradation of the frequency estimation accuracy. In addition, we provide asymptotic expressions of the Cramer-Rao bound, from which the effect of the phase noise and the dependence on the system parameters of the frequency offset estimation accuracy clearly result. Finally, as a by-product of our derivations and approximations, we derive a couple of estimators specifically tailored for the phase noise channel that will be compared with the classical Rife and Boorstyn algorithm, gaining in this way some important hints on the estimators to be used in this scenario
On the information rate and repeat-accumulate code design for phase noise channels
No full textWe investigate the information rate of channels affected by phase noise, aiming at predicting the ultimate performance limits in this scenario. Moreover, a closed-form upper bound is also derived for phase shift keying (PSK) modulations. Finally, we consider the design of nonsystematic irregular repeat-accumulate (RA) codes for this channel trying to give new insights on the codes to be employed for such an application
Da terreira para os views: a midiatização da Umbanda e a emergência da religiosidade on-line no canal do sacerdote Alan Barbieri no Youtube
Full text linkO presente trabalho consiste no estudo da religiosidade on-line por meio da divulgação de conhecimentos teológicos e ritualísticos apresentado no canal de vídeos do sacerdote umbandista Alan Barbieri no Youtube. Para o debate trouxemos os conceitos de religião e religiosidade (BARROS, 2011; BELLOTTI, 2004; FEITOSA, 2014; SBARDELOTTO, 2018 e WILGES, 1994). Em seguida, discutimos sobre a origem da religião Umbanda e sua matriz religiosa (CUMINO, 2019; JARDIM, 2017 e JUNIOR, 2014). Na sequência abordamos a midiatização como um quadro referencial teórico com base nos apontamentos dos autores da área (BORELLI, 2010; FAUSTO NETO, 2004, 2009 e 2010; GOMES, 2016; HJARVARD, 2014, 2014a e 2016; LEMES, 2017; SGORLA, 2014, 2015; VERÓN, 1997) a midiatização da religião, a religiosidade on-line e a Umbanda Midiatizada (CUNHA, 2014; FAUSTO NETO, 2004; FEITOSA, 2014; TEIXEIRA FILHO; AZEVEDO JUNIOR, 2020; HJARVARD, 2014; 2014a; MARTINO, 2016; SANTANA 2021a, 2021b e SBARDELOTTO, 2014). O objetivo geral da pesquisa é reconhecer a religiosidade on-line que emerge a partir dos vídeos produzidos pelo sacerdote umbandista Alan Barbieri em seu canal no Youtube. Os objetivos específicos são a) identificar o conteúdo apresentado por Alan Barbieri em dois vídeos disponibilizado em seu canal no Youtube, b) investigar as reações de espectadores-usuários que comentam sobre os vídeos produzidos pelo Alan Barbieri em seu canal no Youtube e c) reconhecer sinais de apropriações de práticas ritualísticas e de conhecimentos teológicos da doutrina umbandista pelos espectadores-usuários. Adotamos como metodologia a pesquisa qualitativa (BRESLER, 2007) e empregamos as técnicas de pesquisa bibliográfica (GIL, 2002) e a análise de conteúdo (BARDIN, 2006 e MORAES, 1999). O corpus de estudo integra dois vídeos e 19 comentários. Entre os vídeos, um com teor de tutorial ritualístico (2016) e outro de cunho teológico umbandista (2017). De forma geral, os conteúdos dos vídeos e os comentários investigados neste trabalho nos levou a compreender que há uma emergência da religiosidade on-line a partir dos vídeos produzidos por Alan Barbieri em seu canal no qual ele ensina conhecimentos teológicos e ritualísticos da religião Umbanda. As características desse fenômeno são: 1) a reconfiguração do ambiente sagrado que não limita-se a um ambiente físico e, sim, passam a perpetuar-se em espaços midiáticos, 2) a ressignificação de práticas ritualísticas, dando a elas novas formas de confecção e novos significados à experiências e a relação profética com determinada religião e 3) a autonomia dos indivíduos que podem apropriarem-se de conhecimentos teológicos e realizem as práticas ritualísticas em qualquer ambiente, reconfigurando os aspectos comunicacionais da religião.This paper consists of the study of online religiosity through the dissemination of theological and ritualistic knowledge presented in the YouTube video channel of the umbandist priest Alan Barbieri. The debate includes the concepts of religion and religiosity (BARROS, 2011; BELLOTTI, 2004; FEITOSA, 2014; SBARDELOTTO, 2018 and WILGES, 1994). Then, we discuss the origin of the Umbanda religion and its religious matrix (CUMINO, 2019; JARDIM, 2017 and JUNIOR, 2014). Following, we address the mediatization as a theoretical referential framework based on the studies of authors in the area (BORELLI, 2010; FAUSTO NETO, 2004, 2009 and 2010; GOMES, 2016; HJARVARD, 2014, 2014a and 2016; LEMES, 2017; SGORLA, 2014, 2015; VERÓN, 1997), the mediatization of religion, online religiosity and Mediatized Umbanda (CUNHA, 2014; FAUSTO NETO, 2004; FEITOSA, 2014; TEIXEIRA FILHO; AZEVEDO JUNIOR, 2020; HJARVARD, 2014; 2014a; MARTINO, 2016; SANTANA 2021a, 2021b and SBARDELOTTO, 2014). The general objective of the research is to recognize the online religiosity that emerges from the videos produced by the umbandist priest Alan Barbieri on his Youtube channel. The specific objectives are a) to identify the content presented by Alan Barbieri in two videos made available on his Youtube channel, b) to investigate the reactions of viewers-users who comment on the videos produced by Alan Barbieri on his Youtube channel and c) to recognize signs of appropriation of ritualistic practices and theological knowledge of Umbanda doctrine by viewers-users. The chosen methodology was the qualitative research (BRESLER, 2007), using the techniques of bibliographic research (GIL, 2002) and content analysis (BARDIN, 2006 and MORAES, 1999). The study corpus includes two videos and 19 comments. Among the videos, one including ritualistic tutorial content (2016) and the second Umbanda theological content (2017). In general, the contents of the videos and the comments investigated in this paper led us to understanding there is an emergence of online religiosity from the videos produced by Alan Barbieri in his channel, in which he teaches theological and ritualistic knowledge of the Umbanda religion. The characteristics of this phenomenon are: 1) the reconfiguration of the sacred environment, which is not limited to a physical environment, but perpetuates itself in media spaces, 2) the re-signification of ritualistic practices, giving them new forms of confection and new meanings to the experiences and the prophetic relationship with a certain religion and 3) the autonomy of individuals who can appropriate theological knowledge and perform the ritualistic practices in any environment, reconfiguring the communicational aspects of religion
Joint iterative detection and decoding in the presence of phase noise and frequency offset
No full textWe present a new algorithm for joint detection and decoding of iteratively decodable codes transmitted over channels affected by a time-varying phase noise (PN) and a constant frequency offset. The proposed algorithm is obtained as an application of the sum-product algorithm to the factor graph representing the joint a posteriori distribution of the information symbols and the channel parameters given the channel output. The resulting algorithm employs the soft-output information on the coded symbols provided by the decoder and performs forward-backward recursions, taking into account the joint probability distribution of phase and frequency offset. We present simulation results for high-order coded modulation schemes based on low-density parity-check codes and serially concatenated convolutional codes, showing that, despite its low complexity, the algorithm is able to cope with a strong PN and a significant uncompensated frequency offset, thus avoiding the use of complicated data-aided frequency-estimation schemes operating on a known preamble. The robustness of the algorithm in the presence of a time-varying frequency offset is also discussed
Soft-output decoding of rotationally invariant codes over channels with phase noise
No full textWe consider rotationally invariant (RI) trellis-coded modulations (TCMs) transmitted over channels affected by phase noise. To describe the main ideas of this paper, we first concentrate, as a case study, on the simplest RI scheme, namely the differentially encoded M-ary phase-shift keying (M-PSK) signal. For this problem, we use the framework based on factor graphs (FGs) and the sum-product algorithm (SPA), to derive the exact maximum a posteriori (MAP) symbol detection algorithm. By analyzing its properties, we demonstrate that it can be implemented by a forward-backward estimator of the phase probability density function, followed by a symbol-by-symbol completion to produce the a posteriori probabilities of the information symbols. To practically implement the forward-backward phase estimator, we propose a couple of schemes with different complexity. The resulting algorithms exhibit an excellent performance and, in one case, only a limited complexity increases with respect to the algorithm that perfectly knows the channel phase. The properties of the optimal decoder and the proposed practical decoding schemes are then extended to the case of a generic RI code. The proposed soft-output algorithms can also be used in iterative decoding schemes for concatenated codes employing RI inner components. Among them, in the numerical results, we consider repeat-accumulate (RA) codes and other serially concatenated schemes recently proposed in the technical literature
On MAP symbol detection for ISI channels using the Ungerboeck observation model
No full textIn this letter, the well-known problem of a transmission over an additive white Gaussian noise channel affected by known intersymbol interference is considered. We show. that the maximum a posteriori (MAP) symbol detection strategy usually implemented by using the Forney observation model, can be equivalently implemented based on the samples at the output of a filter matched to the received pulse, i.e., based on the Ungerboeck observation model. Although interesting from a conceptual viewpoint, the derived algorithm has a practical relevance in turbo equalization schemes for partial response signalling, where the implementation of a whitening filter can be avoided
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
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