A method and an apparatus for self-interference cancellation in a communication device. The communication device includes an antenna configured to transmit a transmit signal and receive a receive signal through a duplexer in FDD communications, a first analog to digital converter (ADC) configured to convert the receive signal from analog to digital, a coupler configured to couple a sample of the transmit signal to a second ADC, which is configured to convert the sample of the transmit signal from analog to digital, and self-interference cancellation circuitry configured to process the digital sample of the transmit signal to generate a self-interference cancellation signal and apply the self-interference cancellation signal to the digital receive signal to cancel an amount of interference induced in the receive signal by the transmit signal. The SIC process provides additional isolation between TX signal and RX signal. The additional isolation could be utilized to relief the isolation requirement for the duplexer, reducing the cost and form factor of the duplexer.