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Point coordination function (pcf) – Siemens IEEE802.11 User Manual

Page 37

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WLAN-IEEE802.11 Tutorial (Maximilian Riegel), 021018-wlan-tutorial.ppt

Page 37

© Siemens, 2002

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Contention Free Period

Contention Period

CFP repetition interval

D1+Poll

U1+ACK

D2+Poll

Stations

Access

Point

U2+ACK

CF end

Point Coordination Function (PCF)

n

Optional PCF mode provides alternating contention free and
contention operation under the control of the access point

n

The access point polls stations for data during
contention free period

n

Network Allocation Vector (NAV) defers the contention traffic until
reset by the last PCF transfer

n

PCF and DCF networks will defer to each other

n

PCF improves the quality of service for time bounded data