802.11 Protocol Architecture
FIGURE 2.22
Data + CF-Poll frame (DATA)
Data + CF-Poll + CF-Ack frame: Identical to the Simple Data
frame, with the following exceptions. The Data+CF-Ack+CF-Poll
frame may be sent only by the point coordinator during a CFP. This
frame is never sent by a station. The Data+CF-Ack+CF-Poll frame is
never used in an IBSS. This frame combines the functions of both the
Data+CF-Ack and Data+CF-Poll frames into a single frame.
FIGURE 2.23
Data + CF-Poll + CF-Ack frame (DATA)
CF-Ack frame: this frame is used by the point coordinator to
acknowledge receipt of a frame from a CF-Pollable station. This frame
also means that the point coordinator does not have any data to send to
the station and does not wish to give the station the right to transmit a
frame (by polling).
