Exploiting Full-duplex Receivers for Achieving Secret Communications in Multiuser MISO Networks

TL;DR

This paper proposes a novel multi-antenna broadcast scheme combining transmitter and receiver friendly jamming, with self-interference suppression, to enhance secrecy in multiuser MISO networks against eavesdroppers.

Contribution

It introduces a combined Tx-based and Rx-based friendly jamming approach with self-interference suppression for improved physical layer security.

Findings

The proposed scheme effectively enhances secrecy rates.

Power minimization is achieved under secrecy constraints.

Scheduling strategies improve performance under rate requirements.

Abstract

We consider a broadcast channel, in which a multi-antenna transmitter (Alice) sends $K$ confidential information signals to $K$ legitimate users (Bobs) in the presence of $L$ eavesdroppers (Eves). Alice uses MIMO precoding to generate the information signals along with her own (Tx-based) friendly jamming. Interference at each Bob is removed by MIMO zero-forcing. This, however, leaves a "vulnerability region" around each Bob, which can be exploited by a nearby Eve. We address this problem by augmenting Tx-based friendly jamming (TxFJ) with Rx-based friendly jamming (RxFJ), generated by each Bob. Specifically, each Bob uses self-interference suppression (SIS) to transmit a friendly jamming signal while simultaneously receiving an information signal over the same channel. We minimize the powers allocated to the information, TxFJ, and RxFJ signals under given guarantees on the individual secrecy rate for each Bob. The problem is solved for the cases when the eavesdropper's channel state information is known/unknown. Simulations show the effectiveness of the proposed solution. Furthermore, we discuss how to schedule transmissions when the rate requirements need to be satisfied on average rather than instantaneously. Under special cases, a scheduling algorithm that serves only the strongest receivers is shown to outperform the one that schedules all receivers.