Pilot Spoofing Attack Detection and Downlink Precoding in Massive MIMO Systems

Abstract

In this paper, we investigate the pilot spoofing attack (PSA) detection and downlink precoding schemes in massive MIMO systems with spatially correlated channels. During the uplink channel training phase, we conduct channel estimation by using two different expected covariance matrices with a minimum mean square error (MMSE) based estimator, and the PSA is detected by comparing the power of the channel estimations' difference with a predetermined threshold. Once the PSA is detected, the BS transmits some confidential parameters with beamforming aided physical layer security to the legitimate users for the second channel training. In this case, the subspace of the eavesdropping channel can be estimated by combining the estimations of the two training phases. We then propose a MMSE based precoding scheme to improve the downlink secrecy performance, which can achieve unbounded secrecy rate as long as the channel covariance matrices are linearly independent.