Federated learning (FL) is a machine learning paradigm where a shared central model is learned across multiple distributed client devices while the training data remains on edge devices or local clients. Most prior work on federated learning uses Federated Averaging (FedAvg) as an optimization method for training in a synchronized fashion. This involves independent training at multiple edge devices with synchronous aggregation steps. However, the assumptions made by FedAvg are not realistic given the heterogeneity of devices. In particular, the volume and distribution of collected data vary in the training process due to different sampling rates of edge devices. The edge devices themselves also vary in their available communication bandwidth and system configurations, such as memory, processor speed, and power requirements. This leads to vastly different training times as well as model/data transfer times. Furthermore, availability issues at edge devices can lead to a lack of contribution from specific edge devices to the federated model. In this paper, we present an Asynchronous Online Federated Learning (ASO- fed) framework, where the edge devices perform online learning with continuous streaming local data and a central server aggregates model parameters from local clients. Our framework updates the central model in an asynchronous manner to tackle the challenges associated with both varying computational loads at heterogeneous edge devices and edge devices that lag behind or dropout. Experiments on three real-world datasets show the effectiveness of ASO-fed on lowering the overall training cost and maintaining good prediction performance.

本文提出了一种异步在线联邦学习（ASO-Fed）框架，在其中，边缘设备使用连续的流本地数据进行在线学习，而中央服务器从客户端聚合模型参数，我们的框架以异步方式更新中央模型，以应对异构边缘设备的计算负载变化、滞后或丢失的挑战，我们在模拟基准图像数据集和三个真实的非独立同分布数据集上进行了大量实验，结果展示了该模型的快速收敛和良好的预测性能。

非独立同分布数据边缘设备异步在线联邦学习