Medium access control protocol data units are a package of data (group of data bits) that contain header, connection address and data protocol information that is used to control and transfer information across a type of medium (such as a radio channel). The WiMAX system MAC PDUs contain a header, which holds the connection identifier along with control information. MAC PDUs may also have payload of data and error checking bits (CRC) bits after the header (e.g. user data). A MAC PDU header contains a header type, encryption control field, payload type and error checking (CRC) code.

A header type is a data field within the packet header that indicates the type of the header. The header type typically indicates the field format of the header and/or sub-headers that are part of the data packet.

Encryption control is the transferring parameters or sending of signaling messages in a data field within the header of a data packet that indicates encryption is used and possibly the type of encryption that is used. An encryption control field in a header typically indicates the payload of the data packet is encrypted.

Payload type is a data field within a packet header that indicates the format of the payload of data including any sub-headers

A cyclic redundancy check indicator is a data field within a packet header that indicates if and how a CRC error check code is used for the packet of data.

Encryption key...