Achieving Maximum Spectrum Efficiency for Full-Duplex MIMO: The Fractal Array-Element Based Self-Interference Mitigation Approach

Full-duplex (FD), where the terminal transmits and receives signals simultaneously using the same frequency-band and time-slots, has been treated as one of the potential candidate techniques to enhance the spectrum efficiency of wireless communications. To achieve the maximum transmission rate for FD multiple input multiple output (MIMO) terminal, all antennas equipped on the terminal need to not only work in FD mode, but also in multiplexing mode. However, the most challenging problem in wireless FD MIMO communications is how to efficiently mitigate the self-interference (SI). In this paper, we propose the correlation-based digital mitigation scheme, the positive-negative array-element (PNAE) block, and the fractal array-element-based mitigation approach to mitigate the SI within one antenna. Then, we integrate the FD into the multiplexing MIMO. The large SI among the different antennas and array-elements are mitigated using the proposed adaptive diagonal loading (ADL)-based beamforming SI mitigation scheme. The simulation results verify our theoretical analyses and show that our developed SI mitigation schemes can significantly reduce the SI for FD MIMO.