A Residual Scheme for Digital Self-Interference Cancellation in Full Duplex Communication

Full duplex (FD) communication is one of the candidate technologies for future wireless systems due to its potential to double link data rates using the same bandwidth. Since FD radios transmit and receive at the same time in the same frequency band, the transmitted signal is obtained at the receiver end as an interference. Therefore, the self-interference (SI) signal should be canceled to enable FD communication. At high transmit power levels, nonlinear behavior of the hardware affects the SI cancellation and hence nonlinear digital cancellation is necessary to eliminate this nonlinearity. In this paper, we propose to employ linear and nonlinear digital cancellation successively. First, linear SI cancellation is completed, then nonlinear SI cancellation is utilized over the residual SI signal. The employed nonlinear cancellation algorithm is memory polynomial based. The solution is tested on a setup which includes only a real software defined radio and a single antenna as an RF equipment. In the laboratory environment tests, the proposed nonlinear cancellation provides up to 7 dB enhancement in total SI cancellation with respect to only linear digital cancellation. Moreover, the utilized FD radio set-up does not require any hardware change or circuitry modification, thus it can be adapted to any hardware which supports the same modulation scheme.