Deep neural networks have shown the ability to extract universal feature representations from data such as images and text that have been useful for a variety of learning tasks. However, the fruits of representation learning have yet to be fully-realized in federated settings. Although data in federated settings is often non-i.i.d. across clients, the success of centralized deep learning suggests that data often shares a global feature representation, while the statistical heterogeneity across clients or tasks is concentrated in the labels. Based on this intuition, we propose a novel federated learning framework and algorithm for learning a shared data representation across clients and unique local heads for each client. Our algorithm harnesses the distributed computational power across clients to perform many local-updates with respect to the low-dimensional local parameters for every update of the representation. We prove that this method obtains linear convergence to the ground-truth representation with near-optimal sample complexity in a linear setting, demonstrating that it can efficiently reduce the problem dimension for each client. Further, we provide extensive experimental results demonstrating the improvement of our method over alternative personalized federated learning approaches in heterogeneous settings.

本文提出了一个新的联邦学习框架和算法，用于在客户之间学习共享的数据表示和每个客户的独特的本地头。我们的算法利用了跨客户的分布式计算能力，以便每次更新表示时进行许多针对低维本地参数的局部更新。我们证明该方法在线性设置中获得与地面实况表示的线性收敛，并获得接近最优样本复杂度，从而在每个客户端高效地降低问题维度。这个结果超出了联合学习，是一类希望在数据分布中学习共享的低维表示的问题的广泛兴趣，例如在元学习和多任务学习中。此外，广泛的实验结果显示了我们的方法在异构数据的联邦环境中相对于可选的个性化联邦学习方法的经验改进。

利用共享表示进行个性化联邦学习