Departamento de Teoría de la Señal y Comunicaciones
http://hdl.handle.net/10016/1590
2014-04-24T15:19:05ZFilter optimization and complexity reduction for video coding using graph-based transforms
http://hdl.handle.net/10016/18793
Filter optimization and complexity reduction for video coding using graph-based transforms
Martínez Enríquez, Eduardo; Díaz-de-María, Fernando; Cid Sueiro, J.; Ortega, Antonio
The basis functions of lifting transform on graphs are completely
determined by finding a bipartition of the graph and defining the
prediction and update filters to be used. In this work we consider the
design of prediction filters that minimize the quadratic prediction error
and therefore the energy of the detail coefficients, which will give
rise to higher energy compaction. Then, to determine the graph bipartition,
we propose a distributed maximum-cut algorithm that significantly
reduces the computational cost with respect to the centralized
version used in our previous work. The proposed techniques
show improvements in coding performance and computational cost
as compared to our previous work.
2013-01-01T00:00:00ZMean Achievable Rates in Clustered Coordinated Base Station Transmission with Block Diagonalization
http://hdl.handle.net/10016/17420
Mean Achievable Rates in Clustered Coordinated Base Station Transmission with Block Diagonalization
Corvaja, Roberto; García Fenández, Juan José; García-Armada, Ana
We focus on the mean achievable rate per user of the coordinated base station downlink transmission in a clustered cellular environment, with transmit power constraints at the base stations. Block Diagonalization is employed within the cluster to remove interference among users while the interference from other clusters remains. The average achievable rate per user is evaluated considering the effects of the propagation channel and the interference and a theoretical framework is presented to provide its analytical expression, validated by simulation results with different power allocation schemes. As an application, the number of cells of the cluster that maximizes the mean achievable rate per user is investigated. It can be seen that in most of the cases a reduced cluster size, close to seven cells, guarantees a rate very close to the maximum achievable
2013-07-16T00:00:00ZTwo adaptive rejection sampling schemes for probability density functions log-convex tails
http://hdl.handle.net/10016/17200
Two adaptive rejection sampling schemes for probability density functions log-convex tails
Martino, Luca; Míguez Arenas, Joaquín
Monte Carlo methods are often necessary for the implementation of optimal Bayesian estimators. A fundamental technique that can be used to generate samples from virtually any target probability distribution is the so-called rejection sampling method, which generates candidate samples from a proposal distribution and then accepts them or not by testing the ratio of the target and proposal densities. The class of adaptive rejection sampling (ARS) algorithms is particularly interesting because they can achieve high acceptance rates. However, the standard ARS method can only be used with log-concave target densities. For this reason, many generalizations have been proposed. In this work, we investigate two different adaptive schemes that can be used to draw exactly from a large family of univariate probability density functions (pdf's), not necessarily log-concave, possibly multimodal and with tails of arbitrary concavity. These techniques are adaptive in the sense that every time a candidate sample is rejected, the acceptance rate is improved. The two proposed algorithms can work properly when the target pdf is multimodal, with first and second derivatives analytically intractable, and when the tails are log-convex in a infinite domain. Therefore, they can be applied in a number of scenarios in which the other generalizations of the standard ARS fail. Two illustrative numerical examples are shown.
Documento depositado en el repositorio arXiv.org. Versión: arXiv:1111.4942v1 [stat.CO]
2011-11-21T00:00:00ZOn the Generalized Ratio of Uniforms as a Combination of Transformed Rejection and Extended Inverse of Density Sampling
http://hdl.handle.net/10016/17175
On the Generalized Ratio of Uniforms as a Combination of Transformed Rejection and Extended Inverse of Density Sampling
Martino, Luca; Luengo García, David; Míguez Arenas, Joaquín
In this work we investigate the relationship among three classical sampling techniques: the inverse of density (Khintchine's theorem), the transformed rejection (TR) and the generalized ratio of uniforms (GRoU). Given a monotonic probability density function (PDF), we show that the transformed area obtained using the generalized ratio of uniforms method can be found equivalently by applying the transformed rejection sampling approach to the inverse function of the target density. Then we provide an extension of the classical inverse of density idea, showing that it is completely equivalent to the GRoU method for monotonic densities. Although we concentrate on monotonic probability density functions (PDFs), we also discuss how the results presented here can be extended to any non-monotonic PDF that can be decomposed into a collection of intervals where it is monotonically increasing or decreasing. In this general case, we show the connections with transformations of certain random variables and the generalized inverse PDF with the GRoU technique. Finally, we also introduce a GRoU technique to handle unbounded target densities.
Documento depositado en el repositorio arXiv.org. Versión: arXiv:1205.0482v6 [stat.CO]
2012-08-11T00:00:00Z