Secure communication for massive MIMO uplink in the presence of co-located and distributed eavesdroppers

In this paper, we investigate the secure communication in the massive MIMO uplink, where a legitimate single antenna transmitter (Alice) communicates with a legitimate receiver implemented with massive antenna array, in the presence of multiple eavesdroppers (Eves). Considering co-located or distributed antenna (CA or DA) placement of the eavesdropping nodes, we first respectively derive analytical expressions or approximations of the average eavesdropping rate. Based on that, the most harmful eavesdropping antenna configuration is investigated by comparing the CA and DA cases. After determining the worst case, artificial noise-aided jamming is performed at Alice to degrade Eve´s receive SNR and maximize the average secrecy rate. Simulation results show that the worst-case design can be efficient even when Alice does not know the exact number of eavesdropping antennas.