Secure Massive MIMO Systems with Limited RF Chains

TL;DR

This paper introduces a joint data and artificial noise precoding framework for secure massive MIMO systems with limited RF chains, balancing security performance and hardware complexity.

Contribution

It proposes a novel hybrid precoding scheme with analytical bounds for secrecy rate under imperfect CSI, reducing computational complexity and hardware costs.

Findings

Hybrid precoding improves security with lower complexity.

Analytical lower bounds guide optimal power allocation.

Reduced hardware costs compared to full-dimensional precoding.

Abstract

In future practical deployments of massive multi-input multi-output (MIMO) systems, the number of radio frequency (RF) chains at the base stations (BSs) may be much smaller than the number of BS antennas to reduce the overall expenditure. In this paper, we propose a novel design framework for joint data and artificial noise (AN) precoding in a multiuser massive MIMO system with limited number of RF chains, which improves the wireless security performance. With imperfect channel state information (CSI), we analytically derive an achievable lower bound on the ergodic secrecy rate of any mobile terminal (MT), for both analog and hybrid precoding schemes. The closed-form lower bound is used to determine optimal power splitting between data and AN that maximizes the secrecy rate through simple one-dimensional search. Analytical and numerical results together reveal that the proposed hybrid precoder, although suffers from reduced secrecy rate compared with theoretical full-dimensional precoder, is free of the high computational complexity of large-scale matrix inversion and null-space calculations, and largely reduces the hardware cost.