Authors: Mark Briers Arnaud Doucet Simon Maskell
Publish Date: 2009/06/09
Volume: 62, Issue: 1, Pages: 61-
Abstract
Twofilter smoothing is a principled approach for performing optimal smoothing in nonlinear nonGaussian state–space models where the smoothing distributions are computed through the combination of ‘forward’ and ‘backward’ time filters The ‘forward’ filter is the standard Bayesian filter but the ‘backward’ filter generally referred to as the backward information filter is not a probability measure on the space of the hidden Markov process In cases where the backward information filter can be computed in closed form this technical point is not important However for general state–space models where there is no closed form expression this prohibits the use of flexible numerical techniques such as Sequential Monte Carlo SMC to approximate the twofilter smoothing formula We propose here a generalised twofilter smoothing formula which only requires approximating probability distributions and applies to any state–space model removing the need to make restrictive assumptions used in previous approaches to this problem SMC algorithms are developed to implement this generalised recursion and we illustrate their performance on various problems
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