Many existing FL methods assume clients with fully-labeled data, while in realistic settings, clients have limited labels due to the expensive and laborious process of labeling. Limited labeled local data of the clients often leads to their local model having poor generalization abilities to their larger unlabeled local data, such as having class-distribution mismatch with the unlabeled data. As a result, clients may instead look to benefit from the global model trained across clients to leverage their unlabeled data, but this also becomes difficult due to data heterogeneity across clients. In our work, we propose FedLabel where clients selectively choose the local or global model to pseudo-label their unlabeled data depending on which is more of an expert of the data. We further utilize both the local and global models' knowledge via global-local consistency regularization which minimizes the divergence between the two models' outputs when they have identical pseudo-labels for the unlabeled data. Unlike other semi-supervised FL baselines, our method does not require additional experts other than the local or global model, nor require additional parameters to be communicated. We also do not assume any server-labeled data or fully labeled clients. For both cross-device and cross-silo settings, we show that FedLabel outperforms other semi-supervised FL baselines by $8$-$24\%$, and even outperforms standard fully supervised FL baselines ($100\%$ labeled data) with only $5$-$20\%$ of labeled data.

在本研究中，我们提出了FedLabel方法，该方法可以在标签有限的本地数据情况下，通过全局模型或本地模型对未标记数据进行伪标记，进而利用全局模型和本地模型的知识，通过全局-本地一致性正则化提高模型的泛化能力，它不需要额外的专家、通信参数，也不需要服务器标记数据或完全标记的客户端数据，并在跨设备和跨网络隔离设置中表现优于其他半监督联邦学习方法和完全监督方法。

本地或全局：有限标签下的选择性知识综合联邦学习