322,853 research outputs found
On optimal and near-optimal turbo decoding using generalized max operator
No full textMotivated by a recently published robust geometric programming approximation, a generalized approach for approximating efficiently the max* operator is presented. Using this approach, the max* operator is approximated by means of a generic and yet very simple max operator, instead of using additional correction term as previous approximation methods require. Following that, several turbo decoding algorithms are obtained with optimal and near-optimal bit error rate (BER) performance depending on a single parameter, namely the number of piecewise linear (PWL) approximation terms. It turns out that the known max-log-MAP algorithm can be viewed as special case of this new generalized approach. Furthermore, the decoding complexity of the most popular previously published methods is estimated, for the first time, in a unified way by hardware synthesis results, showing the practical implementation advantages of the proposed approximations against these method
Simplified Log-MAP Algorithm for Very Low-Complexity Turbo Decoder Hardware Architectures
No full textMotivated by the importance of hardware implementation in practical turbo decoders, a simplified, yet effective, n-input max∗ approximation algorithm is proposed with the aim being its efficient implementation for very low-complexity turbo decoder hardware architectures. The simplification is obtained using an appropriate digital circuit for finding the first two maximum values in a set of n data that embeds the computation of a correction term. Various implementation results show that the proposed architecture is simpler by 30%, on average, than the constant logarithmic-maximum
a posteriori (Log-MAP) one, in terms of chip area with the same delay. This comes at the expense of very small performance degradation, in the order of
0.1 dB for up to moderate bit error rates, e.g., 10e−5, assuming binary turbo codes. However, when applying scaling to the extrinsic information, the proposed algorithm achieves almost identical Log-MAP turbo code performance for both binary and double-binary turbo codes, without increasing noticeably the implementation complexity
On Practical Implementation and Generalizations of max* Operator for Turbo and LDPC Decoders
No full textNon-recursive max* operator with reduced implementation complexity for turbo decoding
No full textIn this study, the authors deal with the problem of how to effectively approximate the max?? operator when having n > 2 input values, with the aim of reducing implementation complexity of conventional Log-MAP turbo decoders. They show that, contrary to previous approaches, it is not necessary to apply the max?? operator recursively over pairs of values. Instead, a simple, yet effective, solution for the max?? operator is revealed having the advantage of being in non-recursive form and thus, requiring less computational effort. Hardware synthesis results for practical turbo decoders have shown implementation savings for the proposed method against the most recent published efficient turbo decoding algorithms by providing near optimal bit error rate (BER) performance
Comments on "Bitwise Log-Likelihood Ratios for Quadrature Amplitude Modulations"
No full textWith reference to a recently published letter, the purpose of our contribution is two-fold. Firstly, to point out that, what is referred to as a new approximation function MinC (see Eqs. (5)-(8) of Park, 2015) has been previously published (see Eq. (12) of Papaharalabos et al., 2009). Secondly, we present additional related published works of ours, which have further investigated the subject of bitwise log-likelihood ratio (LLR) simplification in soft-output decoding, but have not been mentioned in Park, 2015. © 1997-2012 IEEE
Waste to real energy: The first MFC powered mobile phone
No full textThis communication reports for the first time the charging of a commercially available mobile phone, using Microbial Fuel Cells (MFCs) fed with real neat urine. The membrane-less MFCs were made out of ceramic material and employed plain carbon based electrodes. This journal i
Autonomous energy harvesting and prevention of cell reversal in MFC stacks
No full text© The Author(s) 2016. This study presents a novel method for avoiding cell reversal whilst optimising energy harvesting from stacked Microbial Fuel Cells (MFCs) by dynamically reconfiguring the electrical connections between them. The sequential changing of in-parallel and in-series electrical connections in an 8-MFC stack resulted in energy being transferred twice as fast into a super-capacitor avoiding cell reversal in MFCs as opposed to a fixed in-series configuration. This approach, allows for a lower internal resistance state within the stack compared to a fixed electrical configuration. This is critical in the initial stages of energy extraction from MFCs connected electrically in-series where the impedance of the capacitor is drawing high levels of current and cell reversals are likely to occur and hinder performance. Automation of electrical connections doubled the extracted power from the stack whilst halving the charging times without any cell reversal occurrence. The electrical reconfiguring of MFCs was performed by a USB-powered switch-box that modulated the stack's connections. This lead to the development of an energy autonomous switch-box circuitry powered solely by the MFC stack with negligible impact on the overall energy harvesting efficiency (i.e. above 90%)
2nd International Conference on Advances in Satellite and Space Communications, SPACOMM 2010: Preface
No full textDiffusive author(s), cohesive author: Analysis of S/N (1994)
No full textThis study indicates the ways in which various aspects of the author(s) are brought forth in Dumb type’s performance art, the S/N production. Previous research has suggested a non-hierarchical organization of Dumb type and the absence of a “privileged author” in Dumb type’s collaborative work, S/N. However, the results that I have investigated from member’s interviews on the creative process of S/N along with my analysis of the recorded images of S/N, indicate a different aspect of the author(s). First, S/N was created through, so to speak, the collective ideas of the members of Dumb type. Further, S/N has at least nine quotations from previous performances, installations, and printed writings, besides the work-in-progress technique. Explicating one of the “author functions” as given by Michel Foucault, each text has plural subjects of the author. However, it has been revealed from members’ interviews that Teiji Furuhashi had a decision-making role in selecting the members’ ideas within the performance. Since then, S/N has had plural subjects of creation; however, Furuhashi is one of the subjects of creation along with the “privileged author.” S/N has plural authors (diffusive authors) yet at the same time, it has a “privileged author,” Teiji Furuhashi (cohesive author)
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
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