Optimal Number of Transmit Antennas for Secrecy Enhancement in Massive MIMOME Channels

Abstract

This paper studies the impact of transmit antenna selection on the secrecy performance of massive MIMO wiretap channels. We consider a scenario in which a multi-antenna transmitter selects a subset of transmit antennas with the strongest channel gains. Confidential messages are then transmitted to a multi-antenna legitimate receiver while the channel is being overheard by a multi-antenna eavesdropper. For this setup, we approximate the distribution of the instantaneous secrecy rate in the large-system limit. The approximation enables us to investigate the optimal number of selected antennas which maximizes the asymptotic secrecy throughput of the system. We show that increasing the number of selected antennas enhances the secrecy performance of the system up to some optimal value, and that further growth in the number of selected antennas has a destructive effect. Using the large-system approximation, we obtain the optimal number of selected antennas analytically for various scenarios. Our numerical investigations show an accurate match between simulations and the analytic results even for not so large dimensions.

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

“…In [12] and [13], it was demonstrated that in several MIMO settings, energy efficiency is not an increasing function of the number of transmit antennas, and thus, it can be improved by switching off some of them. The authors in [14], moreover, showed that in MIMO wiretap settings, the secrecy performance, when no precoding is utilized at the Base Station (BS), is optimized when only a few transmit antennas are set active. The security benefits of optimal single antenna selection was further discussed in [15].…”

Optimal Transmit Antenna Selection Algorithm in Massive MIMOME Channels

“…(10) and Equ. (13),C m,n+1 ≤C m,n holds, which indicates thatC m,n is monotonically decreasing with the increase of the number of the selected antennas. As Z n is the maximal value in each level, they are constants once the search tree is fixed.…”

Optimal Transmit Antenna Selection for Massive MIMO Wiretap Channels

“…with a ǫ := −3q 0 ψ/ √ 2, the outage secrecy rate is a decreasing function of L, and therefore, L ⋆ = 1. Nevertheless, when (38) does not hold, the optimal number of active transmit antennas antennas is given by 1…”

“…This work has been presented in part at GLOBECOM 2017 [1]. Saba Asaad and Amir Masoud Rabiei are with the School of Electrical and Computer Engineering (ECE), University of Tehran (UT), Tehran, Iran (e-mail: saba_asaad@ut.ac.ir).…”