Robustness of Low-Complexity Massive MIMO Architectures Against Passive Eavesdropping

TL;DR

This paper demonstrates that low-complexity massive MIMO architectures, such as antenna selection and hybrid precoding, maintain near-perfect secrecy against passive eavesdroppers as the array size increases, with leakage diminishing at specific rates.

Contribution

It extends the understanding of massive MIMO secrecy by analyzing the robustness of reduced-complexity architectures against passive eavesdropping, showing their effectiveness as array size grows.

Findings

Normalized information leakage vanishes with increasing array size.

Leakage decay rates are double-logarithmic for antenna selection and logarithmic for hybrid precoding.

Numerical results confirm the analytical decay rates across various architectures.

Abstract

Invoking large transmit antenna arrays, massive MIMO wiretap settings are capable of suppressing passive eavesdroppers via narrow beamforming towards legitimate terminals. This implies that secrecy is obtained almost for free in these settings. We show that this property holds not only for fully digital MIMO architectures, but also in massive MIMO settings whose transmitters employ architectures with reduced complexity. The investigations consider two dominant approaches for complexity reduction, namely antenna selection and hybrid analog-digital precoding. We show that using either approach, the information leakage normalized by the achievable sum-rate vanishes as the transmit array size grows large. For both approaches, the decaying speed is determined. The results demonstrate that, as the transmit array size grows large, the normalized leakages obtained by antenna selection and hybrid analog-digital precoding converge to zero double-logarithmically and logarithmically, respectively. These analytic derivations are confirmed for various benchmark architectures through numerical investigations.