# Stage-Diff: Stage-wise Long-Term Time Series Generation Based on Diffusion Models

## TL;DR

Stage-Diff introduces a staged diffusion-based generative model that effectively captures long-term dependencies and distribution shifts in complex long-term time series data.

## Contribution

It proposes a novel staged approach with sequence decomposition and multi-channel fusion to improve long-term time series generation.

## Key findings

- Outperforms existing models on real-world datasets
- Successfully models long-range dependencies and distribution shifts
- Balances intra- and inter-sequence dependencies effectively

## Abstract

Generative models have been successfully used in the field of time series generation. However, when dealing with long-term time series, which span over extended periods and exhibit more complex long-term temporal patterns, the task of generation becomes significantly more challenging. Long-term time series exhibit long-range temporal dependencies, but their data distribution also undergoes gradual changes over time. Finding a balance between these long-term dependencies and the drift in data distribution is a key challenge. On the other hand, long-term time series contain more complex interrelationships between different feature sequences, making the task of effectively capturing both intra-sequence and inter-sequence dependencies another important challenge. To address these issues, we propose Stage-Diff, a staged generative model for long-term time series based on diffusion models. First, through stage-wise sequence generation and inter-stage information transfer, the model preserves long-term sequence dependencies while enabling the modeling of data distribution shifts. Second, within each stage, progressive sequence decomposition is applied to perform channel-independent modeling at different time scales, while inter-stage information transfer utilizes multi-channel fusion modeling. This approach combines the robustness of channel-independent modeling with the information fusion advantages of multi-channel modeling, effectively balancing the intra-sequence and inter-sequence dependencies of long-term time series. Extensive experiments on multiple real-world datasets validate the effectiveness of Stage-Diff in long-term time series generation tasks.