Reliable network simulators are important tools for research and development in the field of wireless communication. Although the ns-2 simulator is quite popular for testing wireless network protocols in industry and academia, it is more than clear that it needs numerous improvements in order to produce results fitting to realistic scenarios. There are many PHY/MAC modelling parameters that contribute to the overall accuracy but are not taken into account in the current ns-2 versions. In this paper we stress out the importance of adaptive error models, propagation and mobility models and better interference calculation. We propose a SNIR-based error model in order to reliably simulate the behaviour of the wireless channel and facilitate more realistic results of WLAN simulations. The results proove that our extensions are suitable and allow precise simulations of static WLAN scenarios.