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

摘要

We consider a broadcast channel, in which a multi-antenna transmitter (Alice)sends $K$ confidential information signals to $K$ legitimate users (Bobs) inthe presence of $L$ eavesdroppers (Eves). Alice uses MIMO precoding to generatethe information signals along with her own (Tx-based) friendly jamming.Interference at each Bob is removed by MIMO zero-forcing. This, however, leavesa "vulnerability region" around each Bob, which can be exploited by a nearbyEve. 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 friendlyjamming signal while simultaneously receiving an information signal over thesame channel. We minimize the powers allocated to the information, TxFJ, andRxFJ signals under given guarantees on the individual secrecy rate for eachBob. The problem is solved for the cases when the eavesdropper's channel stateinformation is known/unknown. Simulations show the effectiveness of theproposed solution. Furthermore, we discuss how to schedule transmissions whenthe rate requirements need to be satisfied on average rather thaninstantaneously. Under special cases, a scheduling algorithm that serves onlythe strongest receivers is shown to outperform the one that schedules allreceivers.