Point Coordination Function (Pcf); Ad-Hoc Networks - Alvarion BreezeNET PRO.11 Series User Manual

the Duration field of the previous frame, minus the time, in microseconds, required
to transmit the ACK frame and its SIFS interval.

9.5.11 Point Coordination Function (PCF)

Beyond the basic Distributed Coordination Function, there is an optional Point
Coordination Function, which may be used to implement time-bounded services,
like voice or video transmission. This Point Coordination Function makes use of the
higher priority that the Access Point may gain by the use of a smaller Inter Frame
Space (PIFS).
By using this higher priority access, the Access Point issues polling requests to the
stations for data transmission, hence controlling medium access. To still enable
regular stations to access the medium, there is a provision that the Access Point
must leave enough time for Distributed Access in between the PCF.

9.5.12 Ad-Hoc Networks

In certain circumstances, users may wish to build up wireless LAN networks
without an infrastructure (more specifically without an Access Point). This may
include file transfer between two notebook users, co-workers meeting outside the
office, etc.
The 802.11 standard addresses this need by the definition of an "ad-hoc" mode of
operation. In this case, there is no Access Point and part of its functionality is
performed by the end-user stations (such as Beacon Generation, synchronization,
etc.). Other AP functions are not supported (such as frame-relaying between two
stations not in range, or Power Saving).
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Appendix
User's
Guide