Intelligent Time-Varying Metasurface Transceiver for Index Modulation in 6G Wireless Networks

Index modulation (IM) is one of the candidate technologies for the upcoming sixth-generation (6G) wireless communications networks. In this letter, we propose a space-time-modulated reconfigurable intelligent metasurface (RI-MTS) that is configured to implement various frequency-domain IM techniques in a multiple-input-multiple-output (MIMO) array configuration. Unlike prior works that mostly analyze the signal theory of general RI-MTS IM, we present novel electromagnetics-compliant designs of specific IMs such as subcarrier index modulation (SIM) and MIMO orthogonal frequency-domain modulation IM (MIMO-OFDM-IM). Our full-wave electromagnetic simulations and analytical computations establish the programmable ability of these transceivers to vary the reflection phase and generate frequency harmonics for IM. Our experiments for the bit error rate show that RI-MTS-based SIM and MIMO-OFDM-IM are lower than the conventional MIMO-OFDM.