Optimal Secure GDoF of Symmetric Gaussian Wiretap Channel with a Helper

TL;DR

This paper characterizes the optimal secure generalized degrees-of-freedom (GDoF) for a symmetric Gaussian wiretap channel with a helper, showing how a helper can significantly enhance secrecy capacity through cooperative jamming.

Contribution

It provides the first characterization of the optimal secure GDoF for this channel, introducing a new scheme with cooperative jamming and a novel converse proof.

Findings

Adding a helper increases secure GDoF significantly.

The proposed scheme effectively minimizes GDoF penalty via cooperative jamming.

The analysis employs noise removal and signal separation techniques.

Abstract

We study a symmetric Gaussian wiretap channel with a helper, where a confidential message is sent from a transmitter to a legitimate receiver, in the presence of a helper and an eavesdropper, under a weak notion of secrecy constraint. For this setting, we characterize the optimal secure generalized degrees-of-freedom (GDoF). The result reveals that, adding a helper can significantly increase the secure GDoF of the wiretap channel. The result is supported by a new converse and a new scheme. In the proposed scheme, the helper sends a cooperative jamming signal at a specific power level and direction. In this way, it minimizes the penalty in GDoF incurred by the secrecy constraint. In the secure rate analysis, the techniques of noise removal and signal separation are used.