Federated learning (FL) is a machine learning paradigm where multiple clients collaborate to optimize a single global model using their private data. The global model is maintained by a central server that orchestrates the FL training process through a series of training rounds. In each round, the server samples clients from a client pool before sending them its latest global model parameters for further optimization. Naive sampling strategies implement random client sampling and fail to factor client data distributions for privacy reasons. Hence we proposes an alternative sampling strategy by performing a one-time clustering of clients based on their model's learned high-level features while respecting data privacy. This enables the server to perform stratified client sampling across clusters in every round. We show datasets of sampled clients selected with this approach yield a low relative entropy with respect to the global data distribution. Consequently, the FL training becomes less noisy and significantly improves the convergence of the global model by as much as 7.4% in some experiments. Furthermore, it also significantly reduces the communication rounds required to achieve a target accuracy.

联邦学习是一种机器学习范式，其中多个客户端通过利用私有数据来优化单一全局模型。本研究提出了一种基于高级特征进行一次聚类的客户端抽样策略，以在每一轮中实现分层的客户端抽样，以减少噪音并显著提高全局模型的收敛率，并显著减少了达到目标准确性所需的通信轮次。

LEFL：联邦学习中的低熵客户样本选择