When Wireless Hierarchical Federated Learning Meets Physical Layer Security: A Finite Blocklength Approach for MIMO Channel

In the authors' previous work, a framework for the wireless hierarchical federated learning (HFL) in the presence of physical layer security (PLS) is established, and a finite blocklength (FBL) approach for the wireless SISO channel is proposed. In this paper, we further propose an FBL approach for the MIMO channel, and show that the proposed scheme almost achieves perfect secrecy without affecting the learning performance of wireless HFL, and the transmission latency of our proposed scheme is significantly shorter than that of classical LDPC code.