Multicarrier Division Duplex Aided Millimeter Wave Communications

The existing time-division duplex (TDD) and frequency-division duplex (FDD) techniques rely on a guard time and/or a guard band to avoid self-interference (SI) between the uplink and downlink channels, which results in the wastage of precious spectral resources. The full-duplex (FD) schemes of in-band FD (IBFD), as well as multicarrier division duplex (MDD), may overcome this drawback while retaining the key benefits of both TDD and FDD. Moreover, the MDD exhibits the exclusive benefits of the reduced peak-to-average-power ratio (PAPR) for signal transmission as well as the SI-free signal detection. Against this background, in this paper, we propose a novel FD scheme conceived for frequency-selective millimeter-wave (mmWave) channels, which have not been investigated in the open literature. Furthermore, we propose a novel projection-aided iterative eigenvalue decomposition (P-IEVD) algorithm, which performs null-space SI cancellation in the inherent beamforming structure of mmWave communication. Our simulation results confirm that the MDD is capable of outperforming its half-duplex (HD) counterparts of the TDD/FDD, even the IBFD can only achieve a better bandwidth efficiency than the MDD when a sufficiently high SNR is provided.