ROMAN: A Multiscale Routing Operator for Convolutional Time Series Models

원문 초록

We introduce ROMAN (ROuting Multiscale representAtioN), a deterministic operator for time series that maps temporal scale and coarse temporal position into an explicit channel structure while reducing sequence length. ROMAN builds an anti-aliased multiscale pyramid, extracts fixed-length windows from each scale, and stacks them as pseudochannels. ROMAN provides a training-free mechanism to control the inductive bias of downstream models: it can reduce temporal invariance, make temporal pooling implicitly coarse-position-aware, and expose multiscale interactions through channel mixing, while often improving computational efficiency by shortening the processed time axis. We formally analyze the operator and evaluate it as preprocessing for four convolutional classifiers: MiniRocket, MultiRocket, a standard CNN-based classifier, and a fully convolutional network (FCN) classifier. Synthetic mechanism studies that isolate coarse position, long-range correlation, multiscale interaction, and full positional invariance show that ROMAN behaves as intended, and comparisons with coordinate augmentation and single-scale routing distinguish the benefits of positional routing from those of the multiscale cascade across the evaluated backbones. On long-sequence subsets of the UCR and UEA archives, ROMAN's effect on accuracy varies across datasets while its effect on efficiency is often favorable. At \(S=4\) on UCR, accuracy changes are positively correlated across the pooled backbones, consistent with the proposed role of task structure. We give practical guidance for choosing the operator's two hyperparameters and illustrate its use on very long sequences, where it is both more accurate and several times cheaper, and as a source of representation diversity for ensembles. The ROMAN operator library is available at \href{https://github.com/gon-uri/ROMAN}{github.com/gon-uri/ROMAN