Performance Analysis of RIS-SSK in the Presence of Hardware Impairments

Reconfigurable Intelligent Surface-based Space Shift Keying (RIS-SSK) was recently proposed as a promising transmission technique. In order to design strategic radio environments, this system takes advantage of RIS-based communication and adjusts the propagation channels. Furthermore, using SSK as a special case of the Spatial Modulation (SM) reduces the detection complexity by using only the index of the active antenna to transmit the data. However, when considering an effective RIS-SSK system, the transmit antenna is modeled by spatial constellation points with different weights. This requires the knowledge of Channel State Information (CSI), including the index of the activated antenna at each transmission which is impractical. In contrast, blind RIS-SSK does not require this information, decreasing its complexity and increasing its practicality. In this paper, a blind RIS-SSK system without phase-adjusting is studied in the presence of hardware impairments and compared to the standard SSK. Additionally, analytically error probability expressions based on the Maximum Likelihood (ML) detector are developed and proven with simulations. The results illustrate the negative effects of modeling the hardware impairments for robust RIS-SSK system implementation.