1,716 research outputs found
On hidden Markov chains and finite stochastic systems
In this paper we study various properties of finite stochastic systems or
hidden Markov chains as they are alternatively called. We discuss their
construction following different approaches and we also derive recursive
filtering formulas for the different systems that we consider. The key tool is
a simple lemma on conditional expectations
The Dynamics of Retail Oligopolies
Dynamic Models, Retail Indusry, Markov perfect equilibrium, Oligopoly
Power vs. Spectrum 2-D Sensing in Energy Harvesting Cognitive Radio Networks
Energy harvester based cognitive radio is a promising solution to address the
shortage of both spectrum and energy. Since the spectrum access and power
consumption patterns are interdependent, and the power value harvested from
certain environmental sources are spatially correlated, the new power dimension
could provide additional information to enhance the spectrum sensing accuracy.
In this paper, the Markovian behavior of the primary users is considered, based
on which we adopt a hidden input Markov model to specify the primary vs.
secondary dynamics in the system. Accordingly, we propose a 2-D spectrum and
power (harvested) sensing scheme to improve the primary user detection
performance, which is also capable of estimating the primary transmit power
level. Theoretical and simulated results demonstrate the effectiveness of the
proposed scheme, in term of the performance gain achieved by considering the
new power dimension. To the best of our knowledge, this is the first work to
jointly consider the spectrum and power dimensions for the cognitive primary
user detection problem
The iterated auxiliary particle filter
We present an offline, iterated particle filter to facilitate statistical
inference in general state space hidden Markov models. Given a model and a
sequence of observations, the associated marginal likelihood L is central to
likelihood-based inference for unknown statistical parameters. We define a
class of "twisted" models: each member is specified by a sequence of positive
functions psi and has an associated psi-auxiliary particle filter that provides
unbiased estimates of L. We identify a sequence psi* that is optimal in the
sense that the psi*-auxiliary particle filter's estimate of L has zero
variance. In practical applications, psi* is unknown so the psi*-auxiliary
particle filter cannot straightforwardly be implemented. We use an iterative
scheme to approximate psi*, and demonstrate empirically that the resulting
iterated auxiliary particle filter significantly outperforms the bootstrap
particle filter in challenging settings. Applications include parameter
estimation using a particle Markov chain Monte Carlo algorithm
MCMC, likelihood estimation and identifiability problems in DLM models
In this article we deal with the identification problem within the Dynamic Linear Models family and show that using Bayesian estimation procedures we can deal better with these problems in comparison with the traditional Maximum Likelihood estimation approach. Using a Bayesian approach supported by Markov chain Monte Carlo techniques, we obtain the same results as the Maximum likelihood approach in the case of identifiable models, but in the case of non-identifiable models, we were able to estimate the parameters that are identifiable, as well as to pinpoint the troublesome parameters. Assuming a Bayesian approach, we also discuss the computational aspects, namely the ongoing discussion between single- versus multi-move samplers. Our aim is to give a clear example of the benefits of adopting a Bayesian approach to the estimation of high dimensional statistical models.Bayesian Statistics, DLM Models, Markov chain Monte Carlo, Maximum Likelihood, Model Identification.
EM-algorithm in software reliability modeling
International audienceThe purpose of this paper is to give an overview on the use of the Expectation-Maximization (EM) algorithm in software reliability modeling. This algorithm is related to Maximum Likelihood Estimates (MLE) of parameters in a context of missing data. Different ways to implement this algorithm are highlighted for hidden Markov models in software reliability
USLV: Unspanned Stochastic Local Volatility Model
We propose a new framework for modeling stochastic local volatility, with
potential applications to modeling derivatives on interest rates, commodities,
credit, equity, FX etc., as well as hybrid derivatives. Our model extends the
linearity-generating unspanned volatility term structure model by Carr et al.
(2011) by adding a local volatility layer to it. We outline efficient numerical
schemes for pricing derivatives in this framework for a particular four-factor
specification (two "curve" factors plus two "volatility" factors). We show that
the dynamics of such a system can be approximated by a Markov chain on a
two-dimensional space (Z_t,Y_t), where coordinates Z_t and Y_t are given by
direct (Kroneker) products of values of pairs of curve and volatility factors,
respectively. The resulting Markov chain dynamics on such partly "folded" state
space enables fast pricing by the standard backward induction. Using a
nonparametric specification of the Markov chain generator, one can accurately
match arbitrary sets of vanilla option quotes with different strikes and
maturities. Furthermore, we consider an alternative formulation of the model in
terms of an implied time change process. The latter is specified
nonparametrically, again enabling accurate calibration to arbitrary sets of
vanilla option quotes.Comment: Sections 3.2 and 3.3 are re-written, 3 figures adde
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