I. Introduction
INDUSTRIAL Internet of Things (IIoT is a shifting paradigm that is foreseen to reform the production of factories. Given the distributed nature of IIoT devices, it is hard for an IIoT device alone to train a model that could be widely applicable. Therefore, we need federated learning to enable the intelligence of IIoT [1]. A large number of IIoT devices can collect and train their own models and then share those models with a central service for model aggregation. However, the implementation of federated learning is difficult as IIoT devices are often battery-limited and face heterogeneity.