1,720,956 research outputs found
Frequency offset estimation and multiuser detection for MC-CDMA systems
No full textWe propose a joint scheme for multicarrier code-division multiple access (MC-CDMA) systems; it jointly estimates the frequency offset for the desired user and eliminates multiuser interference (MUI). In the proposed scheme, the well-known constrained minimum output energy (MOE) detector is designed under the condition that the frequency offset estimate of the desired user is known. Then, the frequency offset estimate is obtained by searching for the value which maximizes the output energy of the conditional MOE detector. Finally, the frequency offset estimate is used for the conditional MOE weight vector, and the joint work is completed. The analytical expression for the estimation error of the proposed frequency offset estimator is derived and compared with simulation results. Other simulation results show that the frequency offset estimate is very close to the true value and the bit error rate (BER) of the proposed scheme is comparable to that of the MOE detector with perfect frequency offset compensation
Channel estimation and multiuser detection for MC-DS/CDMA systems
No full textWe propose a joint channel and data estimation scheme which does not require the training data in multicarrier direct-sequence multiple access (MC-DS/CDMA) systems. In order to eliminate the multiple access interference (MAI), the minimum output energy (MOE) filter is first used on each subcarrier because it can be implemented without the knowledge of the channel coefficients. Then, the channel coefficients of the subcarriers are estimated using the MOE filter output signals, and they are used to combine the MOE filter output signals to maximize the output signal-to-interference plus noise ratio (SINR). Simulation results show that the proposed scheme is much superior to the previous schemes especially in the near-far environment
Fast Convergent LMS Adaptive Receiver for MC-CDMA Systems with Space-Time Block Coding
No full textFor multicarrier code-division multiple access (MC-CDMA) systems employing Alamouti's simple space-time block coding (STBC), a special relationship between two minimum mean-square error (MMSE) filter weight vectors is derived in which one filter is for detecting odd-indexed symbols and the other for even-indexed symbols. Using this relationship, a modified MSE cost function is presented and an improved least mean-square (LMS) adaptive receiver is proposed. Since the number of filter taps independently updated in the proposed adaptive receiver is only half that of the conventional LMS adaptive receiver, the proposed adaptive receiver has a faster convergence rate than the conventional LMS adaptive receiver while keeping the same steady-state MSE performance. This is verified through the simulation
Transmission Scheme for D2D Multicast Communication in LTE-Advanced Networks
Get PDFWe consider D2D multicast communication whichreuses cellular uplink frequency resources in LTE-Advancednetworks. In this case, the cellular uplink signal will interfere tothe D2D link communication. The data transmission rate of D2Dmulticast communication is determined by the user having theworst signal-to-interference plus noise (SINR) condition.Conventional schemes assume that the D2D transmitter employsSC-FDMA transmission scheme because it is already used forcellular uplink transmission in LTE-Advanced system. However,if SC-FDMA is employed in D2D transmitter, it is very difficultto reduce the interference from the cellular user in D2D receiverand D2D multicast transmission is allowed only when theinterference from the cellular user is very small in all userswithin the D2D multicast group. In this paper, we propose toemploy MC-CDMA transmission scheme in D2D multicasttransmitter. The interference signal from the cellular user can beeliminated by applying the interference cancellation schemes inthe D2D multicast receivers and D2D communication becomespossible even in the high interference cases. Through simulation,we show that the proposed scheme has better SINR performancethan the conventional scheme
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
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