Real time adaptive RF and digital self-interference cancellation for full-duplex transceivers

Abstract

The challenges with full-duplex (FD) transceiver implementation and transmission in small area radio communication systems are considered. The main challenge in the FD transceiver design is the self-interference (SI). Analog and digital SI cancellation is used for SI mitigation. Analog SI isolation is performed at radio frequency (RF) by utilizing an antenna design based on the characteristic modes theory and using active cancellation principle. Phase and attenuation values of the active cancellation signal path are tuned using a variable-step steepest descent algorithm while transmitting a data signal to a distant node in foil-duplex mode. After the tuning, the SI isolation at RF processing is 90 dB. The remaining SI is then cancelled at the baseband processing for which the an estimate of the SI channel is needed. The SI channel estimation is done in full-duplex mode. Because the receiver has full knowledge of the transmitted signal, no extra pilots are used for the SI cancellation.