User's Manual

Appendix
BreezeNET PRO.11 Series 8-31 User’s Guide
stations wake up in order to receive the Beacon Frame. If there is an
indication that there is a frame stored at the AP waiting for delivery, then
the station stays awake and sends a Polling message to the AP to get these
frames.
Multicasts and Broadcasts are stored by the AP, and transmitted at a pre-
known time (each DTIM), when all Power Saving stations who wish to
receive this kind of frames are awake.
8.5.9. Frame Types
There are three main types of frames:
• Data Frames: which are used for data transmission
• Control Frames: which are used to control access to the medium (e.g.
RTS, CTS, and ACK), and
• Management Frames: which are frames that are transmitted in the same
manner as data frames to exchange management information, but are not
forwarded to upper layers (e.g. beacon frames).
Each frame type is subdivided into different Subtypes, according to its
specific function.
8.5.10. Frame Formats
All 802.11 frames are composed of the following components:
Preamble
PLCP Header MAC Data CRC
8.5.10.1 Preamble
This is PHY dependent, and includes:
• Synch: An 80-bit sequence of alternating zeros and ones, which is used
by the PHY circuitry to select the appropriate antenna (if diversity is
used), and to reach steady-state frequency offset correction and
synchronization with the received packet timing.
• SFD: A Start Frame delimiter which consists of the 16-bit binary pattern
0000 1100 1011 1101, which is used to define frame timing.