1,720,963 research outputs found
Joint source-channel iterative decoding of arithmetic codes
No full textIn this paper an innovative joint source channel coding scheme is presented. The system is based on iterative soft decoding of arithmetic codes, by means of a novel soft-in soft-out decoder based on suboptimal search and pruning of a binary tree. An error resilient arithmetic coder with a forbidden symbol is used in order to improve the performance of the joint source/channel scheme. The performance in the case of transmission across the AWGN channel is evaluated in terms of frame error rate, and compared to a traditional separated approach. Finally the convergence property of the system is analyzed by means of the EXIT chart technique
Iterative decoding of serially concatenated arithmetic and channel codes with JPEG 2000 applications
No full text
Nonsystematic turbo codes
No full textIn this paper, we introduce the concept of nonsystematic turbo codes and compare them with classical systematic turbo codes. Nonsystematic turbo codes can achieve lower error floors than systematic turbo codes because of their superior effective free distance properties. Moreover, they can achieve comparable performance in the waterfall region if the nonsystematic constituent encoder has a low-weight feedforward inverse. A uniform interleaver analysis is used to show that rate R=1/3 turbo codes using nonsystematic constituent encoders have larger effective free distances than when systematic constituent encoders are used. Also, mutual information-based transfer characteristics and extrinsic information transfer charts are used to show that rate R=1/3 turbo codes with nonsystematic constituent encoders having low-weight feedforward inverses achieve convergence thresholds comparable to those achieved with systematic constituent encoders. Catastrophic encoders, which do not possess a feedforward inverse, are shown to be capable of achieving low convergence thresholds by doping the code with a small fraction of systematic bits. Finally, we give tables of good nonsystematic turbo codes and present simulation results comparing the performance of systematic and nonsystematic turbo codes
On the capacity comparison of multi-user access techniques for fourth generation cellular TDD OFDM-based systems
No full text
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
Cross-layer design of packet scheduling and resource allocation algorithms for 4G cellular systems
No full textAdaptive radio resource management in next generation
wireless cellular networks is a key issue to attain efciency and complexity
trade-offs with full edged exibility. Cross-layer algorithms encompassing
the view of MAC and physical layer are needed to exploit at best radio
resource. Two main stochastic drivers need be considered: trafc prole,
along with fairness and QoS constraint, and radio channel for mobile
terminals. We consider a time division OFDMA/TDD based wireless
interface where frequency carriers and OFDM symbols are grouped into
resource chunks, that can be individually and dynamically assigned to
active trafc ows. We take a loose coupling approach and dene a
clear-cut interface between the packet scheduling module, in charge of
trafc policies, and the radio resource allocator, aiming at an optimized
assignment of resource chunks autonomously performed within each cell.
A detailed multi-cell simulation software is used to evaluate the obtained
performance in a number of scenarios, as dened during the PRIMO
project, where the reported research activity has been developed
- …
