Reconfigurable Intelligent Surface Enabled Joint Backscattering and Communication

Reconfigurable intelligent surface (RIS) as an essential topic in the sixth-generation (6G) communications aims to enhance communication performance or mitigate undesired transmission. However, the controllability of each reflecting element on RIS also enables it to act as a passive backscatter device (BD) and transmit its information to reader devices. In this paper, we propose a RIS-enabled joint backscattering and communication (JBAC) system, where the backscatter communication coexists with the primary communication and occupies no extra spectrum. Specifically, the RIS modifies its reflecting pattern to act as a passive BD and reflect its own information back to the base station (BS) in the backscatter communication, while helping the primary communication from the BS to the users simultaneously. We further present an iterative active beamforming and reflecting pattern design to maximize the user average transmission rate of the primary communication and the goodput of the backscatter communication by solving the formulated multi-objective optimization problem (MOOP). Numerical results fully uncover the impacts of the number of reflecting elements and the reflecting patterns on the system performance, and demonstrate the effectiveness of the proposed scheme. Important practical implementation remarks have also been discussed.