Backward Smoothing versus Fixed-Lag Smoothing in Particle Filters

Fuente: arXiv
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Autor principal: Kitagawa, Genshiro
Formato: Preprint
Publicado: 2026
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author Kitagawa, Genshiro
author_facet Kitagawa, Genshiro
contents Particle smoothing enables state estimation in nonlinear and non-Gaussian state-space models, but its practical use is often limited by high computational cost. Backward smoothing methods such as the Forward Filter Backward Smoother (FFBS) and its marginal form (FFBSm) can achieve high accuracy, yet typically require quadratic computational complexity in the number of particles. This paper examines the accuracy--computational cost trade-offs of particle smoothing methods through a trend-estimation example. Fixed-lag smoothing, FFBS, and FFBSm are compared under Gaussian and heavy-tailed (Cauchy-type) system noise, with particular attention to O(m) approximations of FFBSm based on subsampling and local neighborhood restrictions. The results show that FFBS and FFBSm outperform fixed-lag smoothing at a fixed particle number, while fixed-lag smoothing often achieves higher accuracy under equal computational time. Moreover, efficient FFBSm approximations are effective for Gaussian transitions but become less advantageous for heavy-tailed dynamics.
format Preprint
id arxiv_https___arxiv_org_abs_2602_13635
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Backward Smoothing versus Fixed-Lag Smoothing in Particle Filters
Kitagawa, Genshiro
Methodology
62M20(Primary), 62M05(Secondary)
Particle smoothing enables state estimation in nonlinear and non-Gaussian state-space models, but its practical use is often limited by high computational cost. Backward smoothing methods such as the Forward Filter Backward Smoother (FFBS) and its marginal form (FFBSm) can achieve high accuracy, yet typically require quadratic computational complexity in the number of particles. This paper examines the accuracy--computational cost trade-offs of particle smoothing methods through a trend-estimation example. Fixed-lag smoothing, FFBS, and FFBSm are compared under Gaussian and heavy-tailed (Cauchy-type) system noise, with particular attention to O(m) approximations of FFBSm based on subsampling and local neighborhood restrictions. The results show that FFBS and FFBSm outperform fixed-lag smoothing at a fixed particle number, while fixed-lag smoothing often achieves higher accuracy under equal computational time. Moreover, efficient FFBSm approximations are effective for Gaussian transitions but become less advantageous for heavy-tailed dynamics.
title Backward Smoothing versus Fixed-Lag Smoothing in Particle Filters
topic Methodology
62M20(Primary), 62M05(Secondary)
url https://arxiv.org/abs/2602.13635