I. Introduction
Nowadays, federated learning has been envisioned as a distributed learning framework in which devices cooperate to build and update a globally shared learning model by supporting training the global model over distributed datasets [1], [2]. Federated learning enables each device as a data owner to locally train the global model with individually collected data. This approach exchanges model parameters instead of the actual training data and preserves data privacy of the devices. Due to the significant privacy-friendly characteristic, federated learning is applied to diverse domains, e.g., mobile keyboard prediction [3], wearable activity recognition [4] and content caching placement [5]. The promising approach is also integrated into vehicular networks to forecast traffic information such as traffic flow [6] and traffic speed [7] while guaranteeing reliable data privacy preservation during the forecast. Motivated by the current works, we extend the application of federated learning to parking management in smart cities, and develop a federated learning based parking space estimation scheme named by FedParking.