Reconfigurable intelligent surface (RIS) is a new paradigm that has great
potential to achieve cost-effective, energy-efficient information modulation
for wireless transmission, by the ability to change the reflection coefficients
of the unit cells of a programmable metasurface. Nevertheless, the
electromagnetic responses of the RISs are usually only phase-adjustable, which
considerably limits the achievable rate of RIS-based transmitters. In this
paper, we propose an RIS architecture to achieve amplitude-and-phase-varying
modulation, which facilitates the design of multiple-input multiple-output
(MIMO) quadrature amplitude modulation (QAM) transmission. The hardware
constraints of the RIS and their impacts on the system design are discussed and
analyzed. Furthermore, the proposed approach is evaluated using our prototype
which implements the RIS-based MIMO-QAM transmission over the air in real time.

本文提出了一种可重构智能表面 (RIS) 架构，以实现幅度和相位变化调制，从而方便多输入多输出（MIMO）正交振幅调制（QAM）传输。