Massive MIMO-NOMA Systems Secrecy in the Presence of Active Eavesdroppers

TL;DR

This paper investigates the vulnerability of massive MIMO-NOMA systems to active eavesdroppers during channel estimation, proposing physical layer security measures to improve secrecy performance and comparing NOMA with OMA.

Contribution

It analyzes active eavesdropper attacks in massive MIMO-NOMA systems and derives secrecy metrics, demonstrating how power allocation enhances security and performance over OMA.

Findings

NOMA outperforms OMA in secrecy rate and SOP with proper power allocation.

Active eavesdroppers can mislead channel estimation, compromising security.

Physical layer security techniques can mitigate active attack vulnerabilities.

Abstract

Non-orthogonal multiple access (NOMA) and massive multiple-input multiple-output (MIMO) systems are highly efficient. Massive MIMO systems are inherently resistant to passive attackers (eavesdroppers), thanks to transmissions directed to the desired users. However, active attackers can transmit a combination of legitimate user pilot signals during the channel estimation phase. This way they can mislead the base station (BS) to rotate the transmission in their direction, and allow them to eavesdrop during the downlink data transmission phase. In this paper, we analyse this vulnerability in an improved system model and stronger adversary assumptions, and investigate how physical layer security can mitigate such attacks and ensure secure (confidential) communication. We derive the secrecy outage probability (SOP) and a lower bound on the ergodic secrecy capacity, using stochastic geometry tools when the number of antennas in the BSs tends to infinity. We adapt the result to evaluate the secrecy performance in massive orthogonal multiple access (OMA). We find that appropriate power allocation allows NOMA to outperform OMA in terms of ergodic secrecy rate and SOP.