Beacon frame is one of the management frames in IEEE 802.11 based WLANs. It contains all the information about the network. Beacon frames are transmitted periodically to announce the presence of a wireless LAN. Beacon frames are transmitted by the Access Point (AP) in an infrastructure Basic service set (BSS). In IBSS network beacon generation is distributed among the stations.
Components of a Beacon frame
- After receiving the beacon frame all the stations change their local clocks to this time. This helps with synchronization.
- Beacon interval
- This is the time interval between beacon transmissions. The time at which a node (AP, station when in ad hoc or P2P GO mode) must send a beacon is known as Target Beacon Transmission Time (TBTT). Beacon interval expressed in Time Unit (TU). It is a configurable parameter in the AP and typically configured as 100 TU.
- Capability information
- Supported rates
- Frequency-hopping (FH) Parameter Set
- Direct-Sequence (DS) Parameter Set
- Contention-Free (CF) Parameter Set
- IBSS Parameter Set
- Traffic indication map (TIM)