Enhanced efficiency and flexibility while supporting QoS concepts: an adaptive MAC framework for 802.11 WLANs

This paper proposes enhancements to the current IEEE 802.11 medium access control (MAC) distributed coordination function (DCF) through the coordinated adaptation of several MAC configuration parameters and the introduction of a traffic management function. MAC parameter adaptation is based upon the many novel methods that exist in literature. The proposed framework, referred to in this paper as the network efficiency enhancement device (NEED), aims to integrate several proposed adaptive methods into a coordinated framework along with an additional traffic management function to provide traffic conditioning and enable quality of service (QoS) both at the traffic class and platform levels. The adaptively controlled parameters include minimum and maximum contention window (CW) sizes; interframe spacing (IFS); maximum number of retries; fragmentation; and request to send/clear to send (RTS/CTS). Each of these individual methods has been shown in literature to provide, often significantly, enhanced MAC performance. However, these individual methods are typically scenario-specific, and can degrade performance if improperly applied. The goal of the NEED is to integrate these and other methods. These adaptations are based upon the statistics of the offered traffic, the wireless channel conditions, and the perceived network topology