Federated learning (FL) is an important technique for learning models from decentralized data in a privacy-preserving way. Existing FL methods usually uniformly sample clients for local model learning in each round. However, different clients may have significantly different data sizes, and the clients with more data cannot have more opportunities to contribute to model training, which may lead to inferior performance. In this paper, instead of client uniform sampling, we propose a novel data uniform sampling strategy for federated learning (FedSampling), which can effectively improve the performance of federated learning especially when client data size distribution is highly imbalanced across clients. In each federated learning round, local data on each client is randomly sampled for local model learning according to a probability based on the server desired sample size and the total sample size on all available clients. Since the data size on each client is privacy-sensitive, we propose a privacy-preserving way to estimate the total sample size with a differential privacy guarantee. Experiments on four benchmark datasets show that FedSampling can effectively improve the performance of federated learning.

本文提出了一种新颖的数据均匀采样策略用于联邦学习中，通过基于服务器期望的采样大小和所有可用客户端的总采样大小的概率来随机采样每个客户端上的本地数据进行局部模型学习，同时提出了一种基于差分隐私技术的隐私保护方法来评估总采样大小，实验结果表明FedSampling可以有效提高联邦学习的性能。

FedSampling：一种更好的联邦学习采样策略