Augmented Pattern Index Modulation Empowered by RIS

Reconfigurable intelligent surface (RIS) assisted spatial-domain pattern index modulations (PIMs) are recently emerged as promising transmission candidates for the next generation wireless. In this research, we are motivated to investigate a novel augmented PIM (APIM) framework empowered by RIS, such that the potentials of PIM and RIS can be merged for realizing energy efficient high data rate transmissions. In contrast to the spatial-domain PIM, the proposed APIM is implemented by utilizing the indices of activated patterns of the transmitter, receiver and the RIS to modulate information. To maximize the signal power observed with the desired receive pattern, the element-wise and subset-wise phase alignment based reflection designs are provided for the RIS, which may be imposed with different requirements regarding the reflection implementation complexity. Based on the principle of maximum-likelihood estimation, we introduce the optimal joint detection (OJD) to accomplish detecting of APIM signals. Furthermore, we analyze the error and capacity performance of the APIM systems employing the OJD, so as to evaluate the performance limits achievable by the proposed APIM. Finally, simulation results demonstrate the efficiency of our APIM scheme and verify the accuracy of the performance evaluation.