Downlink RIS-NOMA with Constellation Adjustment for 6G Wireless Communication Systems.

We consider a downlink reconfigurable intelligent surfaces-based non-orthogonal multiple access technique with constellation adjustment (RIS-NOMA-CA) for 6G wireless communication systems. We mathematically analyze the bit-error-rate (BER) performance of the RIS-NOMA-CA technique assuming the optimal joint maximum likelihood (JML) detector at receivers. To the best of our knowledge, theoretical analysis of the downlink RIS-NOMA-CA technique has not been reported in the literature. We show that the RIS-NOMA-CA technique yields a better BER performance than the conventional RIS-NOMA technique without CA through computer simulations, and our analytical result matches well with simulation results.