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Detection of active eavesdropper using source enumeration method in massive MIMO

In the time-division-duplex (TDD) system, the channel state information (CSI) is mainly obtained through channel estimation. The active eavesdropper is able to attack the channel estimation phase by sending the same pilot signals as the legitimate users send to the base station without being detected, which can destroy the CSI acquired through channel estimation and greatly decrease the communication quality, so it is very necessary to detect the active eavesdropper before the data transmission. In this paper, we propose to design a mechanism to detect active eavesdropper in the massive MIMO network. Specifically, the sender will intentionally add noise to the pilot sequence so that it becomes harder for the bad guys to learn the pilot sequence. At the same time, if the real sender and the attacker signals arrive at the receiver simultaneously, the received signals will demonstrate special properties in the rank of the matrix. we design a mechanism to estimate the ranks to detect active eavesdropper. Comparison between the approach and MDL-based detector is conducted.