IEEE 802.11e is a wireless local area networking standard introducing quality of service. It defines new MAC protocols, mainly HCF and EDCF. EDCF is a contention-based channel access scheme and is part of HCF for infrastructure networks and may be used as a separate coordination function for wireless ad-hoc networks. The aim of this paper is to propose a set of methods in order to enhance the QoS performances in the wireless local area network WLAN 802.11 in the congested environments under high traffic load. A Slow Decrease scheme is adopted as static method and dynamic tuning of CWmin. Simulations are used to show their performances to the legacy standard IEEE 802.11e, and then the two approaches are compared in high congested environments.