Block acknowledgement

Block acknowledgement (BA) was initially defined in IEEE 802.11e as an optional scheme to improve the MAC efficiency.

Block acknowledgement consist of a setup and tear-down of the session phases.

In the setup phase, capability information such as buffer size and BA policy are negotiated with the receiver.

Finally the BA session is torn down with a so-called DELBA frame.

The confirmation from the recipient station, stating which frames have been received, this is explicitly mentioned in a matrix (part of the BAR) call the "bit map".