I. Introduction
Federated learning mechanism offers training sensitive data (more often, healthcare data) securely as it decentralizes local data model. Local models contain sensitive data and predictive score are shared accordingly with global model. As the large number devices/clients participate in this process, the global model is responsible for collecting the data from all the clients/local models. denotes the data distribution associated with each client c, then the number of samples from each client is , and therefore, we have total sample collection, . Considering medical data, the data collected by the local hospital needs to be preprocessed and then trained by the local model. In brief, the following are the steps followed by the local hospital: a) data preprocessing, b) model broadcasting, c) local model training, d) model aggregating, and e) parameter broadcasting. The patient’s data may contain sensitive information and they need to be preprocessed, and it also includes feature extraction/selection [1].