PP Presentation
The foundation protocol is at the medium Access Control
(MAC) level of the Data Link Layer.
Remember, this specifies which nodes will have access to the
medium of transmission.
The MAC-part of the 802.11 standard is named Distributed
Foundation Wireless Medium Access Protocol (DFWMAC),
and is based on a CSMA/CA type access protocol with a
rotating back-off window.
In order to understand this scheme lets review Ethernet’s
CSMA/CD operation.
Nodes will listen to the medium (wired) for a free slot to
transmit their packets. When two or more nodes begin to
transmit simultaneously, a collision occurs and the packets
are backlogged. The packets are then re-transmitted with the
probability of q=1/2^i; i=no. of collisions for that packet