Advanced Correlation‐Based Techniques for CFO and Channel Estimation in Multiuser OFDMA Systems With RIS Deployment

We present a simple estimation technique for carrier frequency offset (CFO) and uplink channel in multiuser orthogonal frequency division multiplexing access (OFDMA) systems with reconfigurable intelligent surface (RIS) assistance. Based on the block‐impulsive pilot feature, our approach considers a correlation‐based method for conducting CFO estimation on the received signal derived from cyclic prefix data, providing robustness against multiuser interference and channel variation. Channel estimation is formulated utilizing all the CFO‐compensated signals, which requires only a few number of complex multiplication operations. Compared to the existing approach of the reference, the proposed ameliorated technique offers enhanced estimation performance for our scheme, which is validated through a theoretical analysis of the mean squared error of the proposed estimation. Computer simulations have been conducted to confirm its superior performance and reliability.