Performance Enhancement of IRS-Aided Coded Index Modulation for D2D Communications Systems

Intelligent Reflecting Surface (IRS) is regarded as an innovative solution for enhancing reliability and spectrum efficiency for the future 6G wireless networks. In this paper, we aim to improve the spectrum efficiency and error performance of device-to-device (D2D) systems over Rician fading channels by jointly using IRS and coded index modulation (IM) concept. Specifically, at the transmitter, the system uses the spreading code’s index to transmit extra information, thereby improving transmit diversity without requiring additional power consumption. At the receiver, a maximum likelihood (ML) detection process is formulated. Simulation results demonstrate that the IRS-aided Coded IM solution achieves significantly better error performance and spectral efficiency enhancements compared to conventional D2D systems without IRS and/or without coded IM under different system parameters.