Secrecy of Massive MIMO Systems Under Antenna Failure

In this paper, we study the secrecy performance of massive multiple-input multiple-output (MIMO) system for a scenario in which a number of BS antennas fail to send/receive any signals rendering them to be a source of additive distortion noise. The secrecy model studied here is based on multiple-input single-output single-eavesdropper (MISOSE) wiretap channel in which a single-antenna eavesdropper performs pilot contamination attack on a target user in order to increase the decodability of the confidential message intended to the target user. A lower bound of the achievable ergodic secrecy rate and a closed form expression for the maximum ratio (MR) precoder are derived. Results show that for the given MISOSE wiretap channel a positive secrecy rate is achievable even when a large number of antennas fail. The study also shows that massive MIMO systems with spatially correlated channels yield higher secrecy rate than with uncorrelated spatial channels albeit the earlier showed to be more impacted by BS antenna failure.