Finite-SNR Regime Analysis of The Gaussian Wiretap Multiple-Access Channel

TL;DR

This paper introduces a novel scheme for the Gaussian wiretap multiple-access channel that improves secure communication rates at finite SNR levels by combining lattice alignment, cooperative jamming, and advanced decoding strategies.

Contribution

It proposes a new achievable scheme that outperforms existing methods at moderate and high SNR by scaling with log(SNR) and achieves optimal degrees of freedom at infinite SNR.

Findings

Achieves sum secure rate that scales with log(SNR)

Outperforms i.i.d. Gaussian codes at finite SNR

Reaches optimal secure degrees of freedom at infinite SNR

Abstract

In this work, we consider a K-user Gaussian wiretap multiple-access channel (GW-MAC) in which each transmitter has an independent confidential message for the receiver. There is also an external eavesdropper who intercepts the communications. The goal is to transmit the messages reliably while keeping them confidential from the eavesdropper. To accomplish this goal, two different approaches have been proposed in prior works, namely, i.i.d. Gaussian random coding and real alignment. However, the former approach fails at moderate and high SNR regimes as its achievable result does not grow with SNR. On the other hand, while the latter approach gives a promising result at the infinite SNR regime, its extension to the finite-SNR regime is a challenging task. To fill the gap between the performance of the existing approaches, in this work, we establish a new scheme in which, at the receiver's side, it utilizes an extension of the compute-and-forward decoding strategy and at the transmitters' side it exploits lattice alignment, cooperative jamming, and i.i.d. random codes. For the proposed scheme, we derive a new achievable bound on sum secure rate which scales with log(SNR) and hence it outperforms the i.i.d. Gaussian codes in moderate and high SNR regimes. We evaluate the performance of our scheme, both theoretically and numerically. Furthermore, we show that our sum secure rate achieves the optimal sum secure degrees of freedom in the infinite-SNR regime.