Wireless Multimedia-Scheduled Access (WMM-SA), a certification
by the Wi-Fi Alliance, was designed to ensure interoperability between devices that support deterministic QoS for wireless LANs. QoS
over wireless is important for delivering voice and video with less jitter, latency
loss, letting businesses develop enterprisewide mobile voice strategies and manufacturers deliver hybrid cell/wireless LAN
handsets with business-grade voice quality.
The Wi-Fi Alliance, an industry group composed of leading WLAN manufacturers, certifies products. The IEEE
creates the standards on which those certifications are based.
In 2006, the Wi-Fi Alliance quietly dropped WMM-SA, which means that deterministic QoS for wireless LANs is not going to be widely implemented in the arena. Vendors can still produce products that are compliant with the IEEE 802.11e standard for deterministic QoS, but without the Wi-Fi Alliance's certification, buyers are on their own to ensure that different vendors' implementations interoperate. An additional component of the 802.11e QoS standard is expected to be implemented in a future certification, which will help the access point
manage its resources.
Some age-old networking arguments never die--they just get rolled into new technologies. Just ask the wireless vendors working on the 802.11e standard for wireless QoS. A battle between random versus predictable access has played out, sounding remarkably similar to the battles between Ethernet and Token Ring.
EDCA (Enhanced Distributed Channel Access), the more Ethernet-like contender, has largely trounced the HCCA (HCF Controlled Channel Access), the predictable, more Token-Ring-like alternative. HCCA was more suitable for high-density, Vo-Fi deployment than EDCA and its loss could set off alarms among IT pros. The Wi-Fi Alliance claims it's addressing the problem by enhancing the EDCA portion of 802.11e to support a high number of voice calls; it expects to complete this work in early 2008. But despite the Wi-Fi Alliance's ongoing efforts surrounding EDCA, that work won't entirely replace HCCA.
Directing Wireless Traffic