1,720,957 research outputs found
A performance analysis of LDPC code decoding under finite-precision arithmetics
No full textWhile several implementations of LDPC codes decoders are available, the effects of fixed-point quantisation are still somewhat obscure. This paper aims at defining a systematic and general methodology to attack the LDPC decoding problem under finite–precision arithmetic. Statistical analysis is completed with Monte Carlo simulations to deploy the basics of the quantisation problem; the key aspect of this work is the independent study of channel reliability and extrinsic messages. As a case example, a short block, structured LDPC code is considered, and the results are shown. The extension to different codes confirms the validity of our method in relating design parameters and performance. This study is at the basis of the exploration of the trade-off between system performance and hardware complexity and can be easily extended to other applications
On the implementation of quadraphonic data recording
No full textA recent patent in the acoustics field introduced a new approach to quadraphonic data recording and playback. Based on fixed objective criteria, this method seems a promising technique to be used in high-fidelity systems where a characterization of the recording environment is needed. This may be useful for instance when documenting "sound events" such as music performances in real acoustic spaces or when composing virtual acoustic environments as for cinema sound tracks. A major bottleneck for real-time application of this system is represented by the physical implementation, which has to cope both with feasible implementation and no detriment to the high-end performances offered by the quadraphonic technique. This paper presents the architectural design issues for implementation of the quadraphonic recording algorithm: after the algorithm profiling, the hardware/software architecture is derived as a trade-off between complexity, performance and flexibility among different target technologies ranging from Digital Signal Processor (DSP) throughApplication Specific Instruction set Processor (ASIP) up to Field ProgrammableGate Arrays (FPGA) and Application Specific Integrated Circuit (ASIC). As a conclusion, preliminary implementation results for the most promising technology will be provided
Adaptive Single Phase Decoding of LDPC Codes
No full textA new "memory-aware" Low-Density Parity-Check codes decoding is presented. The proposed algorithm performs a single-phase update in which the variable node elaboration is embedded in the check node phase. This reduces the memory size to the number of bits in the codeword, for a saving of 70-80% depending on the code in use. Despite these rough approximations, simulation results on AWGN channel provide almost the same BER/FER performance of the exact belief propagation (only about 0.2 dB is lost in the transmission SNR) thanks to the introduction of stabilising factors driving the algorithm, which are adaptively updated through the decoding process. Remarkably, the decoding throughput is roughly doubled at high SNR and the computational complexity is also lower than current 2-phase serial implementations
High-Precision LDPC Codes Decoding at the Lowest Complexity
Full text linkThis paper presents a simplified, low-complexity check node processor for a decoder of LDPC codes. This is conceived as the combination of the modified Min-Sum decoding with the reduction of the number of computed messages to only P+1 different values. The simulations with a random code used as a case study show that this technique performs excellently even when only two different values are propagated (P = 1). This result is assumed as the basement to the design of an optimised serial architecture. The logic synthesis on 0.18 μm CMOS technology shows that our design outperforms in complexity similar state-of-the-art solutions and makes the check node operations no longer critical to the complexity of the whole decoder
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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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