Towards Collaborative Fairness in Federated Learning Under Imbalanced Covariate Shift

Fuente: arXiv
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Main Authors: Yu, Tianrun, Wang, Jiaqi, Wang, Haoyu, Lin, Mingquan, Liu, Han, Yee, Nelson S., Ma, Fenglong
Format: Preprint
Published: 2025
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_version_ 1866909685213298688
author Yu, Tianrun
Wang, Jiaqi
Wang, Haoyu
Lin, Mingquan
Liu, Han
Yee, Nelson S.
Ma, Fenglong
author_facet Yu, Tianrun
Wang, Jiaqi
Wang, Haoyu
Lin, Mingquan
Liu, Han
Yee, Nelson S.
Ma, Fenglong
contents Collaborative fairness is a crucial challenge in federated learning. However, existing approaches often overlook a practical yet complex form of heterogeneity: imbalanced covariate shift. We provide a theoretical analysis of this setting, which motivates the design of FedAKD (Federated Asynchronous Knowledge Distillation)- simple yet effective approach that balances accurate prediction with collaborative fairness. FedAKD consists of client and server updates. In the client update, we introduce a novel asynchronous knowledge distillation strategy based on our preliminary analysis, which reveals that while correctly predicted samples exhibit similar feature distributions across clients, incorrectly predicted samples show significant variability. This suggests that imbalanced covariate shift primarily arises from misclassified samples. Leveraging this insight, our approach first applies traditional knowledge distillation to update client models while keeping the global model fixed. Next, we select correctly predicted high-confidence samples and update the global model using these samples while keeping client models fixed. The server update simply aggregates all client models. We further provide a theoretical proof of FedAKD's convergence. Experimental results on public datasets (FashionMNIST and CIFAR10) and a real-world Electronic Health Records (EHR) dataset demonstrate that FedAKD significantly improves collaborative fairness, enhances predictive accuracy, and fosters client participation even under highly heterogeneous data distributions.
format Preprint
id arxiv_https___arxiv_org_abs_2507_08617
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Towards Collaborative Fairness in Federated Learning Under Imbalanced Covariate Shift
Yu, Tianrun
Wang, Jiaqi
Wang, Haoyu
Lin, Mingquan
Liu, Han
Yee, Nelson S.
Ma, Fenglong
Machine Learning
Artificial Intelligence
Collaborative fairness is a crucial challenge in federated learning. However, existing approaches often overlook a practical yet complex form of heterogeneity: imbalanced covariate shift. We provide a theoretical analysis of this setting, which motivates the design of FedAKD (Federated Asynchronous Knowledge Distillation)- simple yet effective approach that balances accurate prediction with collaborative fairness. FedAKD consists of client and server updates. In the client update, we introduce a novel asynchronous knowledge distillation strategy based on our preliminary analysis, which reveals that while correctly predicted samples exhibit similar feature distributions across clients, incorrectly predicted samples show significant variability. This suggests that imbalanced covariate shift primarily arises from misclassified samples. Leveraging this insight, our approach first applies traditional knowledge distillation to update client models while keeping the global model fixed. Next, we select correctly predicted high-confidence samples and update the global model using these samples while keeping client models fixed. The server update simply aggregates all client models. We further provide a theoretical proof of FedAKD's convergence. Experimental results on public datasets (FashionMNIST and CIFAR10) and a real-world Electronic Health Records (EHR) dataset demonstrate that FedAKD significantly improves collaborative fairness, enhances predictive accuracy, and fosters client participation even under highly heterogeneous data distributions.
title Towards Collaborative Fairness in Federated Learning Under Imbalanced Covariate Shift
topic Machine Learning
Artificial Intelligence
url https://arxiv.org/abs/2507.08617