Achieving Positive Covert Capacity over MIMO AWGN Channels

TL;DR

This paper investigates the limits of covert communication over MIMO AWGN channels, demonstrating conditions under which positive covert capacity is achievable and analyzing the impact of system scaling on covert rates.

Contribution

It characterizes the maximum covert coding rate for MIMO AWGN channels across various regimes, including massive MIMO, and derives the scaling laws for covert bits.

Findings

Positive covert capacity achievable in massive MIMO under specific conditions

Covert capacity converges to MIMO channel capacity in certain regimes

Order-optimal scaling laws for covert bits when capacity is zero

Abstract

We consider covert communication, i.e., hiding the presence of communication from an adversary for multiple-input multiple-output (MIMO) additive white Gaussian noise (AWGN) channels. We characterize the maximum covert coding rate under a variety of settings, including different regimes where either the number of transmit antennas or the blocklength is scaled up. We show that a non-zero covert capacity can be achieved in the massive MIMO regime in which the number of transmit antennas scales up but under specific conditions. Under such conditions, we show that the covert capacity of MIMO AWGN channels converges the capacity of MIMO AWGN channels. Furthermore, we derive the order-optimal scaling of the number of covert bits in the regime where the covert capacity is zero. We provide an insightful comparative analysis of different cases in which secrecy and energy-undetectability constraints are imposed separately or jointly.