Joint Spatial and Reflecting Modulation for Active IRS Assisted MIMO Communications

This paper proposes an active-intelligent reflecting surface (IRS) assisted joint spatial and reflecting modulation (A-IRS-JSRM). The proposed A-IRS-JSRM engages an active IRS with sub-connected architecture in which several reflecting elements are grouped into panels, and the elements within a panel have the same amplification factor but different reflection angles. Transmit and receive spatial modulation are employed at the base station (BS) and user equipment (UE) by activating a set of transmit antennas and selecting a receiver antenna. Further, only a subset of panels is switched to the ON state in the active IRS, which is determined by the information bits and thus invokes reflecting modulation. The active IRS panels in the ON state also aid in maximizing the received energy in the chosen receiver antenna at the UE. We present the theoretical analysis of the performance of the proposed A-IRS-JSRM system and validate them with simulation results. Further, we have discussed a low-complexity approach for receiver processing in the compressive sensing framework. We compare the proposed A-IRS-JSRM with closely related IRS-assisted spatial modulation schemes in the literature and demonstrate the outperformance of our proposed approach in terms of achievable rate, bit error rate, and outage probability.