Joint analog and digital self-interference cancellation and full-duplex system performance

The challenges with full-duplex transceiver (FD) implementation and transmission in small area radio communication systems are introduced. The main challenge in the FD transceiver design is the self-interference (SI). A three-stage 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 while transmitting a data signal to a distant node. After the tuning the SI isolation at RF is 90 dB. The remaining SI is then cancelled at baseband. For the baseband SI cancellation an estimate of the SI channel is needed. SI channel estimation is done in full-duplex mode and since the receiver has full knowledge of the transmitted signal no extra pilots are used for the SI cancellation.