Target Beacon Transmission Time Time (TBTT) and beacon interval
Target Beacon Transmission Time Time (TBTT) is the time at which a node (AP or station when in Ad-hoc) must send a beacon. The time difference between two TBTTs is known as the beacon interval. The beacon interval is given in Time Units (TU), each TU represents 1024 microseconds. The beacon interval is typically set to 100 TUs (102400 microseconds, or 102.4 ms) and its length is two bytes.