Spectral Efficiency Maximization for Mixed-Structure Cognitive Radio Hybrid Wideband Millimeter-Wave Transceivers in Relay-Assisted Multi-User Multiple-Input Multiple-Output Systems. - Hafiz Muhammad Tahir Mustafa; Jung-In Baik; Hyoung-Kyu Song 001; Muhammad Adnan; Waqar Majeed Awan (Sensors, 2024)