In this letter we demonstrate a mapper that enables all waveforms of OFDM with Index Modulation (OFDM-IM) while preserving polynomial time and space computational complexities. Enabling all OFDM-IM waveforms maximizes the spectral efficiency (SE) gain over the classic OFDM but, as far as we know, the computational overhead of the resulting mapper remains conjectured as prohibitive across the OFDM-IM literature. For an N -subcarrier symbol, we show that OFDM-IM needs a Θ(2 N / √ N )entry LUT to ensure that any sequence of N/2 + ⌊log 2 N N/2 ⌋ bits can be mapped in the same asymptotic time of the classic OFDM mapper i.e., O(N ). We demonstrate this trade-off between SE and computational complexity can be improved if one stores Θ(N 2 ) binomial coefficients (the so-called Pascal's triangle) instead of the classic LUT. With this, we show the OFDM-IM mapper can achieve its maximal SE in the same time complexity of the OFDM's mapper under polynomial (rather than exponential) space resources.
Making the evaluation of learning adherent to the students in order to allow a real characterization of the classroom is a common challenge for teachers. When working with many students, the use of self-assessment and peer review supported by technological tools increases the possibility of perceiving individual challenges. This paper presents a self-assessment and peer review approach integrated with a distance learning platform. We describe a procedure for tracing learning profiles by analyzing the correlation of the students' evaluations among themselves and the teacher. In doing so, we demonstrate the usefulness of the statistical set of tools to highlight the students who came close to the expected teacher's evaluation and those who did not achieve the goal.
Stream of real-time video among mobile phones is expected to play a huge role in near future software. The diversity of industries that may benefit of it and its usefulness are most likely the main reason for that. The purpose of this paper is to show a new concept of content sharing within social networks, where the real time video is streamed among other mobile devices. Typically, the middle is a 3G/UMTS compliant network, with an Internet server acting as a proxy and providing the whole support for the system. The mobile devices interact with this proxy in order to the video to be routed. The approach for this paper is to show how the system will work, its architecture, technical issues like codec and data compression, user interface design and main flow, that includes recording and sharing of online and on demand multimedia content.
Resumo-O algoritmo de cancelamento cooperativo por divisão da densidade espectral de potência com dobramento circular (circular folding cooperative power spectral density split cancellation, CFCPSC) é um algoritmo baseado em periodogramas projetado para detectar sinais primários, via rádios cognitivos (cognitive radios, CRs), no sensoriamento espectral cooperativo centralizado com fusão de dados. Suas principais vantagens são: i) baixa complexidade de implementação e robustez em cenários sob ii) ruído dinâmico e iii) ruído não uniforme. Além disso, o CFCPSC mostrou-se efetivo em cenários sob iv) canais seletivos em frequência e/ou v) com sombreamento correlacionado e vi) ruído impulsivo. O algoritmo weighted CFCPSC, ou WCFCPSC, é a nova versão ponderada do CFCPSC com maior poder estatístico de detecção, contudo ainda não analisado nos cenários supracitados. Portanto, este artigo avalia os desempenhos do WCFCPSC nos cenários iii, iv e v e os resultados mostram que seu maior poder estatístico se mantem também nestes cenários.Palavras-Chave-sensoriamento espectral, rádios cognitivos, sombreamento correlacionado, canais seletivos em frequência, CFCPSC, WCFCPSC.
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