Reconfigurable Intelligent Surface Aided Loopback Interference Suppression

Interference has become a key impediment to improving the performance of communication systems. In traditional interference management (IM) methods design, acquiring information about interference is critical but can be expensive. Reconfigurable Intelligent Surface (RIS) is a novel equipment in the field of wireless communications. It offers the advantages of low cost and flexible signal adjusting capability, making it ideal for use in IM. In this paper, we propose an IM method called RIS-Aided Loopback Interference Suppression (RIS-LIS), which leverages RIS to achieve low-cost IM. In RIS-LIS, the desired transmitter (Tx) uses the RIS to detect the phase difference between the interference directly sent from the interfering Tx and that forwarded by the desired Rx to the RIS. This information is exploited to deduce the interference phase difference at the desired Rx. The desired Tx then adjusts the reflection coefficient of the RIS based on the measured phase difference so that the reflected interference can counteract the direct interfering component at the desired Rx. The proposed RIS-LIS doesn't require the desired Tx to accurately estimate the channel state information (CSI) with respect to (w.r.t.) the interfering Tx or share its desired data with others to achieve IM. This not only reduces the signaling overhead but also protects the privacy of the interfering communication-pair's data transmission. Our theoretical analysis and simulation results have demonstrated that the proposed RIS-LIS can fully leverage interference to achieve interference suppression and significantly improve the spectral efficiency (SE) of the desired communication-pair.