Generalized Self-Interference Model for Full-Duplex Multicarrier Transceivers

In the modeling of full duplex (FD) transceivers using multicarrier modulations, it is usually assumed that the intercarrier interference of the coupling path is negligible. Therefore, the system can be analyzed on a subcarrier basis, because the model reduces to a set of orthogonal flat channels. However, for more general FD transceivers, or when hardware components introduce nonlinear distortion, the orthogonality is lost and a more rigorous model is needed. In this paper, we introduce a model for the coupling interference of FD systems, which allows the uplink and the downlink to have different time and frequency offsets, and different parameters such as the number of subcarriers and symbol length. In addition, we present a linear approximation for the nonlinear coupling based on a generalization of the Bussgang's theorem, for the case of transmitters with nonuniform power allocation. We validate the proposed model with measurements and show numerically that it improves the accuracy of the signal to interference plus noise ratio expression, and the formulation of optimization problems. Therefore, the proposed model paves the way for a more realistic performance analysis and the derivation of more accurate power allocation strategies than is possible with the classic model.