On Robustness of Massive MIMO Systems Against Passive Eavesdropping under Antenna Selection

TL;DR

This paper demonstrates that massive MIMO systems inherently provide strong security against passive eavesdropping through beamforming, even with minimal active antennas, due to the system's ability to focus signals and diminish leakage.

Contribution

It shows that massive MIMO's secrecy benefits persist even with limited active antennas, highlighting a 'secrecy for free' property against passive eavesdroppers.

Findings

Secrecy is maintained with minimal active antennas.

Passive eavesdropping impact is negligible as antenna count grows.

Linear precoding effectively reduces information leakage.

Abstract

In massive MIMO wiretap settings, the base station can significantly suppress eavesdroppers by narrow beamforming toward legitimate terminals. Numerical investigations show that by this approach, secrecy is obtained at no significant cost. We call this property of massive MIMO systems `secrecy for free' and show that it not only holds when all the transmit antennas at the base station are employed, but also when only a single antenna is set active. Using linear precoding, the information leakage to the eavesdroppers can be sufficiently diminished, when the total number of available transmit antennas at the base station grows large, even when only a fixed number of them are selected. This result indicates that passive eavesdropping has no significant impact on massive MIMO systems, regardless of the number of active transmit antennas.