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Full title—A Novel Simplified RIS-Assisted Hybrid Transceiver Scheme for mmWave MIMO Systems
In this paper, we propose a novel simplified RIS-assisted hybrid transceiver (SRIS-HT) scheme that combines a simple RIS matrix with an efficient hybrid transceiver design. Initially, the optimal unconstrained RIS matrix is derived for scenarios where the direct base station–user link is blocked. For practical implementation, this matrix is approximated by extracting and normalizing its diagonal elements, exploiting its unitary properties. The resulting RIS matrix is then employed to design the hybrid transceiver using momentum and Newton's methods. The SRIS-HT scheme is further extended to cases where a direct base station–user link exists.
Simulation results demonstrate that the proposed SRIS-HT scheme achieves spectral efficiency close to that of fully digital designs, significantly outperforming existing hybrid schemes. Additionally, the results highlight the robustness of SRIS-HT against imperfect channel estimation and weak direct links, while maintaining lower computational complexity compared to conventional optimization methods, especially when the number of transmit antennas is comparable to or smaller than the number of RIS elements.
Full Article: IEEE Transactions on Vehicular Technology, Volume 75, Number 5, May 2026
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