In-band full-duplex (IFD) system has been considered as an attractive solution for increasing the spectral efficiency of wireless networks. Compared to the conventional half-duplex (HD) node, an IFD node suffers not only selfinterference (SI) from its own transmitted signal, but also more severe co-channel interference (CCI), which affect the system performance significantly. To investigate the performance gain of IFD system with both interferences over the conventional HD system, this paper considers two different IFD systems, pairwise IFD (P-IFD) and 3 node form IFD (3n-IFD) under IEEE 802.11ax outdoor large BSS scenario. Also, this paper adopts an intuitive space scheduling (SSC) algorithm to reduce additional CCI of IFD nodes. Numerical results reveal that the self-interference cancellation (SIC) requirement can be reduced with help of the SSC and the implementation burden of IFD devices can be loosened. In addition, numerical results show that the performance of 3n-IFD is similar to that of P-IFD. 3n-IFD has backward compatibility with conventional HD station as well as sufficient performance gain of IFD mode.