Physical Layer Security in Distributed Antenna Systems Using One-Bit Feedback Information

Abstract

This article concerns the physical layer security (PLS) problem in distributed antenna systems (DASs), where eavesdroppers are equipped with multiple antennas. If both legitimate transmitter (Alice) and receiver (Bob) broadcast wireless signals via a DAS, the channel state information (CSI) between Alice and Bob may be exposed to an eavesdropper (Eve) due to the broadcast nature of wireless signals. Based on the exposed CSI, Eve can use multiple antennas to improve the eavesdropping capability on the confidential message transmitted from Alice. The prior PLS approaches to defend against the eavesdropping attack have two limitations. The first limitation is to assume that the CSI of Bob is available to Alice. The second limitation is to assume that there is no error in the feedback CSIs. In this article, we propose a new PLS scheme of a DAS by using one-bit feedback information. The basic idea of our approach is to generate a null transmission vector from the distributed transmitters of Alice to Bob while using different artificial noise components to protect the exposure problem of CSI between Alice and Bob. The proposed scheme has the following advantages: improved secrecy rate, rapid convergence, and good performance under a time-varying channel. We implemented our scheme and conducted extensive performance comparisons through simulations. Our experimental results show that the proposed scheme improves the secrecy rate with 1.20 b/s/Hz as compared to prior approaches. At last, we present some interesting future works for the PLS problem in a DAS.