An Access Control Method Of Channel Capacity And Channel Reserved In Wireless LANs

WLAN(Wireless Local Area Network) becomes more and more popular recently. In contrast to LAN, WLAN has a series of advantages such as mobility, flexibility and expansibility. As a result, WLAN develops rapidly and widely, and people begin to expect QoS support for multimedia applications. To achieve the goal, IEEE Std. 802.11eTM is published on Nov.2005, and provides guidance to implement QoS guarantees.The main QoS facility of IEEE 802.11e is Hybrid Coordination Function (HCF) mechanism. The HCF uses both a contention-based channel access method, called the Enhanced Distributed Channel Access (EDCA) mechanism for Prioritized QoS Services, and a controlled channel access method, referred to as the HCF Channel Access (HCCA) mechanism for Parameterized QoS Services. HCCA is a central controlled method, hard to realize and does not fit market request. EDCA is more popular, but it just provides Prioritized QoS, and cannot provide QoS guarantees based on traffic streams. Several Access control schemas are proposed to provide further QoS control, but the existing schemas still have many problems, such as have no link with upper layer, cannot adjust dynamically to make full use of bandwidth, the bandwidth is dithering and so on.The article provides a overall QoS mechanism based on IEEE 802.11e call access control. A new method by improving on call access control in IEEE 802.11e guarantees QoS under EDCA method. This method considers the current channel utilization and the future channel load. And it can admit in term of real condition. The method is considerate, easy to realize, and it can be implemented in distributed environment such as Ad-hoc network.