NS-2, as an open-source network simulator, is widely used in wireless communication studies and VANET safety applications. In [1], Chen et al. implemented a completely modified architecture about IEEE 802.11 MAC and physical layer modules which depicted the signal transmission and reception process in IEEE 802.11, as well as the method of handling collision. However, in the process of using the latest version of NS2, we found some problems. First, its approach of deciding whether to receive the signal by comparing the SINR and threshold is not flexible in actual simulation. Second, the capture thresholds for collision do not work well. Third, as for the RXThreshold_ property, class WirelessPhyExt doesn't achieve relevant functions. In this paper, we put forward a viable scheme to solve these problems by deeply understanding the signal reception process based on SINR.