Pre-Nulling for Self-Interference Suppression in Full-Duplex Relays

Abstract—We consider a full-duplex relay that simultaneously receives and transmits signals over a shared channel and propose techniques for suppressing self-interference caused by huge difference in the signal power of the transmitted and received signals. In particular, a pre-nulling method for self-interference reduction is introduced. It is shown that self-interferences can be efficiently suppressed by pre-nulling without degrading bit error rate (BER) performance of the destination receiver in the flat channel environment. In addition, a hybrid method combining the proposed pre-nulling method and conventional adaptive interference suppressor is proposed to reduce the self-interference further. It is shown by simulations that the hybrid method can secure more relay gain margin for stable operation of full-duplex relays. I.