Robust hybrid beamforming in full-duplex broadband mmWave relay systems

In this paper, the robust hybrid beamforming scheme in full-duplex (FD) millimeter-wave (mmWave) relay systems is designed under imperfect channel estimates. The inherent characteristic of mmWave signals, i.e., the large available bandwidth, is considered in the design, and the orthogonal frequency division multiplexing (OFDM) technique is utilized to overcome the multipath fading. A self-interference cancellation module is inserted at the relay to attenuate the self-interference, which is the main challenge of the FD mode. A decomposition algorithm for mmWave OFDM relay systems is proposed to obtain the hybrid processors with analog-digital-analog structures and closed-form least-squared-based solutions. Numerical results show that the proposed design provides significant improvements by comparing with existing designs. (C) 2022 Elsevier Inc. All rights reserved.