Uplink Transmission of Local RIS Data Using Orthogonal Polarizations

We propose several uplink transmission schemes of local RIS data using two orthogonal polarizations for the array elements. The first scheme transmits 1 bit of local data per user symbol period using two simple polarization patterns. The second is a multilevel scheme that transmits 2 bits of local data per user symbol period using 4 polarization patterns. Finally, the third is a multi-dimensional scheme that transmits 3 bits of local data every two user symbol periods. Compared to the earlier local RIS data transmission schemes based on the concept of spatial modulation (RIS-SM), the proposed schemes have two fundamental advantages: First, by activating all of the RIS array elements, they do not involve any degradation in user signal performance, and second, they overcome the strong performance degradation caused by spatial correlation in RIS-SM system.