Polarization mismatch based self-interference cancellation against power amplifier nonlinear distortion in full duplex systems

Full duplex systems are more spectrally efficient than conventional half duplex systems if the self-interference (SI) can be significantly mitigated. Digital cancellation is one of the lowest complexity SI cancellation techniques in full duplex systems. However, its mitigation capability is mainly limited by the power amplifier (PA) nonlinear distortion. In this paper, to cancel the SI induced by the PA nonlinear distortion, a SI cancellation scheme based on polarization mismatch (PMC) is proposed. The proposed scheme takes advantage of the characteristic that the polarization state of the SI is immune to the PA nonlinearity. And it cancels the SI in the digital baseband by a polarization mismatch matrix which has an orthogonal polarization state to that of the SI. Analysis and numerical results demonstrate that the proposed scheme can cancel the nonlinear SI induced by the PA efficiently. Besides, the desired signal to interfere and noise (SINR) gain will not deteriorate even if the power of the SI is high compared with the existing cancellation scheme. Further, the achievable rate of it can reach more than two times compared with the half duplex when the similarity coefficient of the polarization states is greater than 0.5.