System information

 Wi-Fi Multimedia
Working Principles of Basic Functions
WMM Operating
 For legacy 802.11 network, CSMA/CA-based Distributed Coordination
Function (DCF) is used for transmit data which avoids the collision condition.
Each client has to wait for a random backoff time. If there is no other clients
transmittin
g,
the client will
g
et the
p
ermission and start to deliver the data
g, g p
 With DCF, all the clients get the same priority
 WMM defines 4 Access Categories, Voice, Video, Best Effort, and
Background. The categories are mapped to different priories which are
defined in IEEE 802 1p
defined in IEEE 802
.
1p
.
 The default priority is Best Effort
Access Cate
g
or
y
Descri
p
tion
IEEE 802.1p
priority
gy
p
priority
Voice Highest priority 7, 6
Video Prioritize video traffic above other data traffic 5, 4
Bt Efft
Traffic from legacy devices, or traffic from applications
0 3
94
B
es
t Eff
or
t
Traffic from legacy devices, or traffic from applications
or devices that lack QoS capabilities
0
,
3
Background
Low priority traffic (file downloads, print jobs) that does
not have strict latency and throughput requirements
2, 1