802.11e, QBSS and Wi-Fi Multimedia (WMM)

802.11e defines Quality of Service (QoS) for the wireless LAN and The WMM standard is a subset of IEEE 802.11e.


The 802.11e standard includes a method that allows an AP to advertise its load to wireless clients. Specifically, the QBSS element is used to advertise load via beacons. The WMM standard is a subset of IEEE 802.11e. 

The QBSS (QOS enhanced basic service set) information element is an 802.11e construct that enables an access point to communicate its channel usage to wireless phones. It is intended to solve the problem of candidate access point selection, or intelligent roaming. It is located in the beacon frames of access points.

Station Count : Indicates the total number STAs currently associated with the QBSS (2 octets, unsigned integer value)
 Channel Utilization: A percentage of time (normalized to 255) that the QAP sensed the medium was busy, Medium busy measured as physical or virtual carrier sense (CS) mechanism
 Available Admission Capacity: Signals the remaining amount of medium time available via explicit admission control, Values from 0-31250 (2 octets long), Units of 32 µs/s