RIS-Assisted Received Adaptive Spatial Modulation for Wireless Communications

TL;DR

The paper addresses the need for higher spectral efficiency in index-modulation-based wireless systems by leveraging RIS-enabled passive beamforming at the receiver to boost SNR on selected antennas and by encoding additional bits via receive-antenna indices in a scheme called RIS-assisted received adaptive spatial modulation (RASM). It combines random antenna-combination (AC) selection with a maximum-likelihood detector and provides a closed-form ABER framework using a moment generating function (MGF) based PEP analysis, with $b=b_1+b_2$, $b_1=ig floor ig( frac{}{}igr) ig floor}$, $b_2=ig floor frac{}{}igr) ig floor$, and $J=2^{N_r}-1$; ACs selected are of size $D= ext{log}_2 b_1$. Through simulations (1×$10^6$ trials) the authors demonstrate that RASM achieves lower BER than several RIS-aided and non-RIS schemes at comparable spectral efficiency and can significantly increase SE with higher $N_d$ (selected antennas). The work indicates RIS-assisted receive-side IM as a practical path to high-rate wireless links with reduced transmitter RF-chain complexity and improved robustness against ICI and IAS issues in ASM schemes.

Abstract

A novel wireless transmission scheme, as named the reconfigurable intelligent surface (RIS)-assisted received adaptive spatial modulation (RASM) scheme, is proposed in this paper. In this scheme, the adaptive spatial modulation (ASM)-based antennas selection works at the receiver by employing the characteristics of the RIS in each time slot, where the signal-to-noise ratio at specific selected antennas can be further enhanced with near few powers. Besides for the bits from constellation symbols, the extra bits can be mapped into the indices of receive antenna combinations and conveyed to the receiver through the ASM-based antenna-combination selection, thus providing higher spectral efficiency. To explicitly present the RASM scheme, the analytical performance of bit error rate of it is discussed in this paper. As a trade-off selection, the proposed scheme shows higher spectral efficiency and remains the satisfactory error performance. Simulation and analytical results demonstrate the better performance and exhibit more potential to apply in practical wireless communication.

Figures (3)

• Figure 1: System model for the RASM scheme.
• Figure 2: Analytical results and simulation ones in BER performance of the RASM scheme.
• Figure 3: Comparison of BER performance and bpcu in the RASM, RSM, RGSM, and RGSSK schemes with $N=8$, $N_r=16$, and $M=2$.