Secure Degrees of Freedom of Wireless X Networks Using Artificial Noise Alignment

TL;DR

This paper investigates the secure degrees of freedom in wireless X networks using artificial noise alignment, deriving bounds and proposing schemes that enhance confidentiality and performance even with limited channel information.

Contribution

It introduces a novel artificial noise alignment approach for secure communication in wireless X networks, achieving tight bounds and new SDOF results with blind schemes.

Findings

SDOF upper bound derived for M×K X networks with confidential messages.

Achieved SDOF of K(M-1)/(K+M-1) for K≥3, even with eavesdroppers.

Proposed blind ANA scheme attains SDOF with reconfigurable antennas at receivers.

Abstract

The problem of transmitting confidential messages in $M \times K$ wireless X networks is considered, in which each transmitter intends to send one confidential message to every receiver. In particular, the secure degrees of freedom (SDOF) of the considered network are studied based on an artificial noise alignment (ANA) approach, which integrates interference alignment and artificial noise transmission. At first, an SDOF upper bound is derived for the $M \times K$ X network with confidential messages (XNCM) to be $\frac{K(M-1)}{K+M-2}$. By proposing an ANA approach, it is shown that the SDOF upper bound is tight when $K=2$ for the considered XNCM with time/frequency varying channels. For $K \geq 3$, it is shown that SDOF of $\frac{K(M-1)}{K+M-1}$ can be achieved, even when an external eavesdropper is present. The key idea of the proposed scheme is to inject artificial noise into the network, which can be aligned in the interference space at receivers for confidentiality. Moreover, for the network with no channel state information at transmitters, a blind ANA scheme is proposed to achieve SDOF of $\frac{K(M-1)}{K+M-1}$ for $K,M \geq 2$, with reconfigurable antennas at receivers. The proposed method provides a linear approach to secrecy coding and interference alignment.