System Configuration
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6
Configuring Wi-Fi Multimedia
Wireless networks offer an equal opportunity for all devices to transmit data from
any type of application. Although this is acceptable for most applications, multimedia
applications (with audio and video) are particularly sensitive to the delay and
throughput variations that result from this “equal opportunity” wireless access
method. For multimedia applications to run well over a wireless network, a Quality of
Service (QoS) mechanism is required to prioritize traffic types and provide an
“enhanced opportunity” wireless access method.
The access point implements QoS using the Wi-Fi Multimedia (WMM) standard.
Using WMM, the access point is able to prioritize traffic and optimize performance
when multiple applications compete for wireless network bandwidth at the same
time. WMM employs techniques that are a subset of the developing IEEE 802.11e
QoS standard and it enables the access point to inter operate with both WMM-
enabled clients and other devices that may lack any WMM functionality.
Access Categories
— WMM defines four access categories (ACs): voice, video,
best effort, and background. These categories correspond to traffic priority levels
and are mapped to IEEE 802.1D priority tags (see Table 6-1). The direct mapping of
the four ACs to 802.1D priorities is specifically intended to facilitate inter operability
with other wired network QoS policies. While the four ACs are specified for specific
