Performance Analysis of Time-Indexed Reconfigurable Intelligent Surface Assisted Media-Based Modulation

In this paper, we propose a cyclic-prefixed single-carrier (CPSC) transmission scheme with time-indexing assisted by two eminent physical layer technologies (i) reconfigurable in-telligent surface (RIS), and (ii) media-based modulation (MBM). MBM can be viewed as an index modulation (IM) technique where the channel fades from the transmitter to the receiver are used to convey additional information bits along with the bits conveyed by the complex modulation symbols. Considering a frame of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</tex> time-slots, the time-indexed MBM (TI-MBM) is a block transmission scheme, where only <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K</tex> time-slots are used for data transmission (active slots) and the remaining <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$N-K$</tex> time-slots are left vacant (inactive slots). With the aid of time-indexing, extra bits of information can be conveyed for indicating the time-slot activation pattern (TAP). It has been shown that TI-MBM can extract the multipath diversity of the channel for suitable choice of system parameters. Our proposed TI-RIS-MBM system is designed such that it can gain additional multipath channel diversity by the simultaneous transmissions across the RIS elements in a CPSC manner. It also demonstrates better bit error rate (BER) performance than the conventional TI-MBM and other CPSC transmission schemes.