Blind Self-Interference Canceller with Adaptive Differential Delay for IBFD in the Presence of Fractional Delay Path

This paper proposes a novel blind self-interference (SI) canceller with adaptive differential delay for in-band full duplex (IBFD) communications, even in the presence of a fractional delay path. As an SI cancellation method, active SI canceller (ASIC) that generates and subtracts a replica of the SI signal from the received signal has been proposed. However, the replica generation requires accurate and periodic channel state information (CSI) acquisition, causing system performance degradation due to increased communication overhead. To avoid this inconvenience, differential active SI canceller (DASIC) without prior channel estimation of SI has been proposed. However, due to the effects of a fractional delay path, DASIC cannot completely cancel SI, resulting in residual SI. The proposed method adaptively controls the differential delay to eliminate the residual SI, according to the occurrence pattern of its own transmission signal. In addition, an appropriate maximum a-posteriori probability (MAP) detector is designed based on the DASIC outputs. Finally, computer simulations confirm the efficacy of the proposed method with and without error correction code (ECC) in terms of bit error rate (BER) performance.