Pilotless Self-Interference Canceller of IBFD for BLE in the Presence of Fractional Delay Paths

In this paper, considering its application in Bluetooth low energy (BLE), we propose a novel self-interference (SI) cancellation method for in-band full-duplex (IBFD) communications in the presence of fractional delay paths. Traditional SI cancellation methods, such as the active SI canceller (ASIC), generate and subtract a replica of the SI signal from the received signal. However, generating this replica requires accurate channel state information (CSI), which increases communication overhead and reduces spectral efficiency. Therefore, the differential active SI canceller (DASIC) has been proposed, which does not require prior CSI information. Nonetheless, the presence of fractional delay paths results in residual SI, making cancellation insufficient. In this paper, we propose a method to generate a replica of the residual SI from DASIC outputs, resolving the residual SI issue. The efficacy of the proposed method is confirmed through computer simulations by comparing its bit error rate (BER) performance with that of ASIC.