A baseband wireless spectrum hypervisor for multiplexing concurrent OFDM signals

The next generation of wireless and mobile networks will have to handle a significant increase in traffic load compared to the current ones. This situation calls for novel ways to increase the spectral efficiency. Therefore, in this paper, we propose a wireless spectrum hypervisor architecture that abstracts a radio frequency (RF) front-end into a configurable number of virtual RF front ends. The proposed architecture has the ability to enable flexible spectrum access in existing wireless and mobile networks, which is a challenging task due to the limited spectrum programmability, i.e., the capability a system has to change the spectral properties of a given signal to fit an arbitrary frequency allocation. The proposed architecture is a non-intrusive and highly optimized wireless hypervisor that multiplexes the signals of several different and concurrent multi-carrier-based radio access technologies with numerologies that are multiple integers of one another, which are also referred in our work as radio access technologies with correlated numerology. For example, the proposed architecture can multiplex the signals of several Wi-Fi access points, several LTE base stations, several WiMAX base stations, etc. As it able to multiplex the signals of radio access technologies with correlated numerology, it can, for instance, multiplex the signals of LTE, 5G-NR and NB-IoT base stations. It abstracts a radio frequency front-end into a configurable number of virtual RF front ends, making it possible for such different technologies to share the same RF front-end and consequently reduce the costs and increasing the spectral efficiency by employing densification, once several networks share the same infrastructure or by dynamically accessing free chunks of spectrum. Therefore, the main goal of the proposed approach is to improve spectral efficiency by efficiently using vacant gaps in congested spectrum bandwidths or adopting network densification through infrastructure sharing. We demonstrate mathematically how our proposed approach works and present several simulation results proving its functionality and efficiency. Additionally, we designed and implemented an open-source and free proof of concept prototype of the proposed architecture, which can be used by researchers and developers to run experiments or extend the concept to other applications. We present several experimental results used to validate the proposed prototype. We demonstrate that the prototype can easily handle up to 12 concurrent physical layers

An Efficient FPGA-Based Frequency Shifter for LTE/LTE-A Systems

The Physical Random Access Channel plays an important role in LTE and LTE-A systems. Through this channel, the user equipment aligns its uplink transmissions to the eNodeB’s uplink and gains access to the network. One of the initial operations executed by the receiver at eNodeB side is the translation of the channel’s signal back to base-band. This operation is a necessary step for preamble detection and can be executed through a time-domain frequency-shift operation. Therefore, in this paper, we present the hardware architecture and design details of an optimised and configurable FPGA-based time-domain frequency shifter. The proposed architecture is based on a customised Numerically Controlled Oscillator that is employed for creating complex exponential samples using only plain logical resources. The main advantage of the proposed architecture is that it completely removes the necessity of saving in memory a huge number of long complex exponentials by making use of a Look-Up Table and exploiting the quarter-wave symmetry of the basis waveform. The results demonstrate that the proposed architecture provides high Spurious Free Dynamic Range signals employing only a minimal number of FPGA resources. Additionally, the proposed architecture presents spur-suppression ranging from 62.13 to 153.58 dB without employing any correction

On the distribution of an effective channel estimator for multi-cell massive MIMO

Accurate channel estimation is of utmost importance for massive MIMO systems to provide significant improvements in spectral and energy efficiency. In this work, we present a study on the distribution of a simple but yet effective and practical channel estimator for multi-cell massive MIMO systems suffering from pilot-contamination. The proposed channel estimator performs well under moderate to aggressive pilot contamination scenarios without previous knowledge of the inter-cell large-scale channel coefficients and noise power, asymptotically approximating the performance of the linear MMSE estimator as the number of antennas increases. We prove that the distribution of the proposed channel estimator can be accurately approximated by the circularly-symmetric complex normal distribution, when the number of antennas, M, deployed at the base station is greater than 10

Investimentos públicos em pesquisa e desenvolvimento (P&D) de Etanol no Brasil e nos Estados Unidos de 2001 até 2008

Identifica os projetos de Pesquisa & Desenvolvimento (P&D) voltados para a produção de bioetanol realizados no Brasil e nos Estados Unidos, a partir de 2001, até o ano de 2008. Para a análise, serão levadas em conta as peculiaridades e características dos países citados. O Brasil, para a produção de etanol, tem como principal insumo a cana-de-açúcar, e esta por enquanto tem se mostrado a alternativa mais eficiente em termos de geração de energia e custos. Já os Estados Unidos produzem a maior parte do seu bioetanol a partir do milho, porém, recentemente, um grande volume dos projetos de P&D está relacionado à geração de álcool a partir da celulose. Adicionalmente, pretende-se investigar os montantes investidos em P&D em bioetanol em ambos os países com o propósito de estabelecer uma comparação não só entre as trajetórias da pesquisa como também nos valores aplicados

The opportunity cost of preserving the Brazilian Amazon forest.

We estimate the trade-off between forest preservation and agricultural production for the Legal Amazon region, using census and deforestation data for municipalities in 2006.We use a directional distance function to represent the production possibility frontier, and then calculate the shadow price of reducing deforestation in terms of agricultural income foregone. Results indicate that, on average, to preserve 1 ha of forest, $797 in annual agricultural GDP must be foregone. Using a discount rate of 10average shadow price of$16 per ton of CO2 permanently sequestered

The Cost of Forest Preservation in the Brazilian Amazon: The “Arc of Deforestation”

We estimate the trade-off between agricultural production and forest preservation for the municipalities in Brazil’s agricultural frontier, the so-called “arc of deforestation,” using census and deforestation data for 2006. We use a nonparametric directional output distance function that allows us to identify the gradients of the production possibility frontier, which are the trade-offs of interest. We found that, on average, $979 is forgone in annual livestock, timber, and grain revenues to conserve 1 hectare of forest. This translates, ceteris paribus, to an average present value of costs to permanently sequester CO2 of$16.36/t, higher than most previous estimates

THE EFFECT OF THE EARLY ENTRANCE TO JOB MARKET ON THE HEALTH STATUS OF THE BRAZILIANS IN 2008

The early entrance to the job market has, among other consequences, a negative effect on the health status of the individual. In 2008, nearly a sixth of the Brazilian population claimed to have started working before the age of 10 and over a third reported to have started working between 10 and 15 years old. This paper aims to investigate the effect of early entrance to the job market on the current health status of the individual. The database provided by the National Survey by Household Sampling (PNAD) for 2008 was used to reach the objective of this paper. The analysis was conducted at national and regional extent using Ordered Logit method. It was evident that delaying entrance to the job market impacts positively on the current state of health. Moreover, it was found that the educational level and personal income increase the likelihood of the individual presenting a better state of health. Distinct effects of these variables on health status were also found when we took into account the regional context. The Southeast and South showed the most severe impacts of child labor on health, as well as the best results in terms of the impact of education and personal income on health status. In contrast, the North and Northeast regions showed the greatest gender disparities related to health status

Agricultural Production and Forest Preservation in the Brazilian Amazon

Brazil has become a strong competitor in world soybean production. In 2014, Brazil produced 28% of the world’s soybeans, while the United States produced 34%. Brazil increased its production sharply during the 1990s and 2000s, partly due to the expansion into the Amazon forest region. Soybean was one of the main commodities that led to this expansion. In 2016, the Legal Amazon region produced 33% of the Brazilian soybean production compared to 15% in 1990 (Figure 1)

Da episteme à áskesis: notas sobre aspectos éticos no método cartesiano / From Episteme to Áskesis: Remarks on Ethical Aspects in Cartesian Method

A antiga ideia de êthos, no âmbito da filosofia grega, antes mesmo de ter se tornado (com Aristóteles) objeto de um interesse especulativo e teórico, jamais esteve desvinculada da de áskesis - no sentido de exercício, prática, treino, modo de vida (mais do que no de ascetismo, tal como esta palavra passou a soar para nós depois do cristianismo). É lugar comum se afirmar que essa vinculação mais originária se desvaneceu abruptamente a partir do “momento cartesiano”: que o racionalismo moderno e as ditas teorias do conhecimento que lhe sucederam submeteram todas as dimensões antigas do filosofar a exigências estritamente epistemológicas. Isso, de maneira a reduzir o domínio da ação racional (ou da razão prática) aos termos de teorias gerais de Filosofia Moral, Política ou do Direito (à questão de fundamentar e sistematizar a ação em termos universalistas). Na contramão desses dados, este artigo objetiva redescobrir alguns aspectos éticos no método cartesiano. No escritos de Descartes, é possível identificar elementos de filosofia prática em dois sentidos distintos, mais ou menos independentes entre si: por um lado, encontramos reflexões avulsas sobre moral e ética (as quais Descartes faz interagir com a sua cogitatio); por outro, é possível demonstrar como o próprio procedimento metódico ele mesmo não é outra coisa senão uma reorientação da ação que precede a aquisição do conhecimento e que é pré-condição para o aparecimento do verdadeiro. Isto, de maneira que a adoção de um método - de um caminho que vise a um fim (meta - hodos) - implicou para Descartes em uma conversão de si, na adoção de um modo de vida em constante exercício. Concluímos que a história da filosofia, tal como narrada hegemonicamente entre nós, acaba encobrindo esta espécie de áskesis que está implícita no método cartesiano. O que pretendemos neste artigo não foi senão apresentar algumas passagens da obra de Descartes que nos ajudam a enxergar de que maneira a atividade do pensamento (das Cogitationes) é, ao mesmo tempo, um incessante exercício de aprimoramento no modo de ser e de se conduzir no mundo imanente