  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.
