The Pontifícia Universidade Católica do Rio de Janeiro is a major private and non-profit Catholic university, located in Rio de Janeiro, the second largest city of Brazil. It is maintained by the Catholic Archdiocese of Rio de Janeiro and the Society of Jesus. Wikipedia.
De Lamare R.C.,University of York |
Sampaio-Neto R.,Pontifical Catholic University of Rio de Janeiro
IEEE Transactions on Vehicular Technology | Year: 2011
This paper presents a novel adaptive reduced-rank multiple-input-multiple- output (MIMO) equalization scheme and algorithms based on alternating optimization design techniques for MIMO spatial multiplexing systems. The proposed reduced-rank equalization structure consists of a joint iterative optimization of the following two equalization stages: 1) a transformation matrix that performs dimensionality reduction and 2) a reduced-rank estimator that retrieves the desired transmitted symbol. The proposed reduced-rank architecture is incorporated into an equalization structure that allows both decision feedback and linear schemes to mitigate the interantenna (IAI) and intersymbol interference (ISI). We develop alternating least squares (LS) expressions for the design of the transformation matrix and the reduced-rank estimator along with computationally efficient alternating recursive least squares (RLS) adaptive estimation algorithms. We then present an algorithm that automatically adjusts the model order of the proposed scheme. An analysis of the LS algorithms is carried out along with sufficient conditions for convergence and a proof of convergence of the proposed algorithms to the reduced-rank Wiener filter. Simulations show that the proposed equalization algorithms outperform the existing reduced- and full- algorithms while requiring a comparable computational cost. © 2011 IEEE.
Street A.,Pontifical Catholic University of Rio de Janeiro
Theory and Decision | Year: 2010
The Expected Shortfall or Conditional Value-at-Risk (CVaR) has been playing the role of main risk measure in the recent years and paving the way for an enormous number of applications in risk management due to its very intuitive form and important coherence properties. This work aims to explore this measure as a probability-dependent utility functional, introducing an alternative view point for its Choquet Expected Utility representation. Within this point of view, its main preference properties will be characterized and its utility representation provided through local utilities with an explicit dependence on the assessed revenue's distribution (quantile) function. Then, an intuitive interpretation for the related probability dependence and the piecewise form of such utility will be introduced on an investment pricing context, in which a CVaR maximizer agent will behave in a relativistic way based on his previous estimates of the probability function. Finally, such functional will be extended to incorporate a larger range of risk-averse attitudes and its main properties and implications will be illustrated through examples, such as the so-called Allais Paradox. © 2009 Springer Science+Business Media, LLC.
De Lamare R.C.,Pontifical Catholic University of Rio de Janeiro |
De Lamare R.C.,University of York
IEEE Transactions on Wireless Communications | Year: 2013
In this work, decision feedback (DF) detection algorithms based on multiple processing branches for multi-input multi-output (MIMO) spatial multiplexing systems are proposed. The proposed detector employs multiple cancellation branches with receive filters that are obtained from a common matrix inverse and achieves a performance close to the maximum likelihood detector (MLD). Constrained minimum mean-squared error (MMSE) receive filters designed with constraints on the shape and magnitude of the feedback filters for the multi-branch MMSE DF (MB-MMSE-DF) receivers are presented. An adaptive implementation of the proposed MB-MMSE-DF detector is developed along with a recursive least squares-type algorithm for estimating the parameters of the receive filters when the channel is time-varying. A soft-output version of the MB-MMSE-DF detector is also proposed as a component of an iterative detection and decoding receiver structure. A computational complexity analysis shows that the MB-MMSE-DF detector does not require a significant additional complexity over the conventional MMSE-DF detector, whereas a diversity analysis discusses the diversity order achieved by the MB-MMSE-DF detector. Simulation results show that the MB-MMSE-DF detector achieves a performance superior to existing suboptimal detectors and close to the MLD, while requiring significantly lower complexity. © 2013 IEEE.
Costa E.,Pontifical Catholic University of Rio de Janeiro
IEEE Transactions on Intelligent Transportation Systems | Year: 2011
A simulation model is proposed to represent the channel of the Global Positioning System (GPS). Initially, a digital elevation model, building databases, and a vegetation model are processed to generate azimuth-elevation maps of path states (clear, shadowed, and blocked) for a large number of observers. At each simulation step, satellite positions are updated, and azimuths and elevations of paths from observers to satellites are calculated. Signal strengths and range errors are assigned to paths with the aid of random number generators for each path state. This information is processed to determine the statistics of the channel. It will be shown that model predictions are able to display good agreement with the results from an experimental campaign carried out for validation purposes. The simulation model will then be applied to a large number of observers deployed along two routes in densely urbanized areas in the city of Rio de Janeiro, Brazil (22.8° S, 43.3° W), with buildings displaying different height distributions to quantitatively show how the most probable number of available satellites, the probability that four or more satellites are simultaneously available (that is, that positions can be fixed), and the position errors change with the average building height and for vehicles in static and kinematic modes. In combination with the comparison between measurement and prediction results, this indicates that the simulation model is an efficient and flexible tool for studying and planning satellite-based location and navigation applications with accuracy and sensitivity, which will be used in future developments of mitigation techniques of multipath effects, leading to improved performance of intelligent transportation systems. © 2006 IEEE.
Godoy-Matos A.F.,Pontifical Catholic University of Rio de Janeiro
Diabetology and Metabolic Syndrome | Year: 2014
The opposite effects of insulin and glucagon in fuel homeostasis, the paracrine/endocrine inhibitory effects of insulin on glucagon secretion and the hyperglucagonemia in the pathogenesis of type 2 diabetes (T2D) have long been recognized. Inappropriately increased alpha-cell function importantly contributes to hyperglycemia and reflects the loss of tonic restraint normally exerted by high local concentrations of insulin on alpha-cells, possibly as a result of beta-cell failure and alpha-cell insulin resistance, but additional mechanisms, such as the participation of incretin hormones in this response, have also been suggested. Three classes of drugs already available for clinical use address the abnormalities of glucagon secretion in T2D, namely, the GLP-1 receptor agonists (GLP-1RA), the inhibitors of dipeptidyl peptidase-4 (DPP-4i) and the amylin agonist pramlintide; it has been proposed that the glucagonostatic and insulinotropic effects of GLP-1RA equally contribute to their hypoglycemic efficacy. In this review, the control of glucagon secretion and its participation in T2D pathogenesis are summarized. © 2014 Godoy-Matos; licensee BioMed Central Ltd.