Artificial-noise strategy for single-antenna systems over multi-path fading channels

In this paper, a novel artificial-noise strategy is proposed for single-antenna point-to-point systems over multi-path fading channels. Unlike existing artificial-noise schemes that are used in multi-antenna systems for the only purpose of confusing eavesdroppers, the main objectives of the artificial noise generated in the proposed strategy are not only to guarantee secure communications, but also to compensate inter-symbol interference induced by multi-path propagation while achieving full multi-path diversity in the desired link between source and legitimate destination. Based on maximal-ratio combining at the destination, the artificial noise herein is specified by the channel state information (CSI) of the desired link. Specifically for the time-division duplex mode, thanks to channel reciprocity, the CSI is available at the source to generate the artificial noise. However, third-party eavesdroppers that are blind to the CSI are not able to decode the source information injected with the artificial noise. Illustrative discussions on the performance not only substantiate the validity of the proposed strategy both in overcoming multi-path effects and for physical layer security, but also provide a useful tool for the frame design with the proposed strategy.