Concepts, Key Challenges and Open Problems of Federated Learning

With the modern invention of high-quality sensors and smart chips with high computational power, smart devices like smartphones and smart wearable devices are becoming primary computing sources for routine life. These devices, collectively, might possess an enormous amount of valuable data but due to privacy concerns and privacy laws like General Data Protection Regulation (GDPR), this enormous amount of very valuable data is not available to train models for more accurate and efficient AI applications. Federated Learning (FL) has emerged as a very prominent collaborative learning technique to learn from such decentralized private data while reasonably satisfying the privacy constraints. To learn from such decentralized and massively distributed data, federated learning needs to overcome some unique challenges like system heterogeneity, statistical heterogeneity, communication, model heterogeneity, privacy, and security. In this article, to begin with, we explain some fundamentals of federated learning along with the definition and applications of FL. Subsequently, we further explain the unique challenges of FL while critically covering recently proposed approaches to handle them. Furthermore, this paper also discusses some relatively novel challenges for federated learning. To conclude, we discuss some future research directions in the domain of federated learning.