802.11 Protocol Architecture
FIGURE 2.6
Timestamp field in the beacon
With an IBSS, the first active Ad Hoc station establishes the RF
channel and starts sending beacons. Other Ad Hoc stations can join the
network after receiving a beacon and accepting the IBSS parameters
(e.g., beacon interval) found in the beacon frame. All stations that join
the IBSS participate in the sending of beacons. Each station schedules
itself to send a beacon a very short random delay interval after each
Target Beacon Transmission Time (TBTT). TBTTs are the exact
points in time that each access point has scheduled a beacon to be sent
onto the wireless medium. TBTTs are based on a zero reference time
and spaced according to the beacon interval. Each station that receives
a beacon during its delay cancels sending its beacon this time and
schedules one for a new random delay interval after the next TBTT.
