Timing synchronization function
Timing Synchronization Function (TSF) is specified in IEEE 802.11 WLAN standard to fulfill timing synchronization among users. A Timing Synchronization Function (TSF) keeps the timers for all stations in the same BSS synchronized. All stations shall maintain a local TSF timer. Each mobile host maintains a TSF timer with modulus 264 counting in increments of microseconds. The TSF is based on a 1-MHz clock and "ticks" in microseconds. On a commercial level, industry vendor assume the 802.11 TSF's synchronization to be within 25 microseconds.
Timing synchronization is achieved by stations periodically exchanging timing information through beacon frames. Each station in an IBSS shall adopt a received timing if it is later than the station’s own TSF timer. All stations in the IBSS adopt a common value, aBeaconPeriod, that defines the length of beacon intervals or periods. This value, established by the station that initiates the IBSS, defines a series of Target Beacon Transmission Times (TBTTs) exactly aBeaconPeriod time units apart. Time zero is defined to be a TBTT.
References
- IEEE Std 802.11. Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specification, 1999 edition.
See also
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