1,721,017 research outputs found
On single-tap equalization for an FBMC multicarrier system in wireless channels
No full textThis paper deals with single-tap equalization for the recently introduced FBMC-PAM system, a multicarrier scheme able to meet the requirements of cognitive radio such as high level of adjacent channel leakage ratio and asynchronous communications. The optimum single-tap gain in the minimum mean square error (MMSE) sense is derived and its performance is compared with that of previously considered receivers. It is shown that, when the zero-mean output of the standard matched filter is noncircular, the proposed equalizer is superior to the existing single-tap alternative solution and comes close in performance to a more advanced previously considered structure
CFO sensitivity and efficient joint estimation for the short filter multicarrier system FBMC-PAM
No full textSensitivity to carrier frequency offset, due to oscillator inaccuracy and terminal mobility, is a key issue that modern multicarrier systems have to face. In that respect, FBMC-PAM holds a specific position due to its short prototype filter: the overlapping factor is K=2 and the width of the main lobe of its frequency response is 3 times the sub-carrier spacing, while OFDM and FBMC-OQAM schemes have frequency response whose main lobe width is 2 times the sub-carrier spacing. As a consequence, it is shown in the present paper that FBMC-PAM outperforms other multicarrier techniques in terms of CFO sensitivity. In order to best exploit this property in burst transmission, an efficient and accurate approach for joint symbol timing and CFO estimation is proposed, based on a specific preamble. A theoretical in-depth analysis of the scheme is provided as well as performance validation in multipath channel through simulations
On blind CFO estimation for FBMC-PAM systems
No full textThis paper deals with the problem of blind carrier-frequency offset (CFO) estimation for filter bank multicarrier systems with pulse amplitude modulation (FBMC-PAM). In FBMC-PAM a sequence of real-valued symbols can be transmitted over 2 M spectrally separated subcarriers operating at the same symbol rate as OFDM. This recently proposed system does not require a cyclic prefix and, in the multi-user context, it provides a high level of spectral separation among users. In this paper is derived the maximum likelihood (ML) blind CFO estimator for AWGN channel under the assumption of low SNR conditions. Since the FBMC-PAM signal is a noncircular random process, the obtained ML estimator exploits both the unconjugate and the conjugate correlation (or relation function). The performance of the derived CFO estimator is compared with that of the two estimators obtained by separately maximizing the contribution to the ML cost function exploiting the unconjugate correlation or the conjugate correlation, and with the modified Cramér-Rao bound
On the performance of FBMC-PAM systems in frequency-selective Rayleigh fading channels
No full textFilter bank multicarrier (FBMC) techniques are emerging alternatives to the widely used orthogonal frequency division multiplexing (OFDM) schemes for applications such as machine type communications or cognitive radio. Recently an FBMC scheme based on a sine prototype filter with overlapping factor K=2 termed FBMC-PAM has been introduced. It assures an interesting performance, a reduced system latency and is robust to carrier-frequency offset. After presentation of the system model, an analytical expression of the BER of the single-tap sub-channel equalizer for the considered FBMC-PAM system operating in frequency-selective Rayleigh fading channel is obtained and compared with simulation results. Moreover, a performance comparison with an approximate single-tap sub-channel equalizer and with the previously proposed FBMC-PAM-2M, is presented
Comparing the performance of OFDM and FBMC multicarrier systems in doubly-dispersive wireless channels
No full textIn mobile communications, the most widely used multicarrier technique, namely OFDM, is known to exhibit performance limitations in high speed scenarios. FBMC is an alternative approach and, among FBMC techniques, the recently introduced FBMC-PAM scheme has emerged as the most robust to CFO. Therefore, it is chosen here as the challenger of OFDM for performance comparison in doubly dispersive channels. After presentation of the system model, multicarrier scheme and wireless channel, an analytical evaluation of the BER in the particular case of single path time-varying channel is provided for FBMC-PAM and validated through simulations. Then, simulation results are reported for both OFDM and FBMC-PAM, using the 3GPP multipath channel models. It appears that FBMC-PAM can outperform OFDM in highly time-varying frequency-selective channels
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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