• I appreciate that this topic is slightly irrelevant, but can someone explain how FHSS technology achieves synchrnisation please? more out of interest than need.



  • Hi Beridor:

    IEEE 802.11 section 11.1.5 Timing synchronization for frequency-hopping (FH) PHYs

    "NOTE?¡é?€?¡±This subclause pertains only to STAs using an FH PHY.

    "The TSF described here provides a mechanism for STAs in an FH system to synchronize their transitions from one channel to another (their ?¡é?€??hops?¡é?€??). Every STA shall maintain a table of all of the hopping sequences that are used in the system. All of the STAs in a BSS shall use the same hopping sequence. Each beacon and probe response includes the channel synchronization information necessary to determine the hop pattern and timing for the BSS.

    "STAs shall use their TSF timer to time the aCurrentDwellTime. The aCurrentDwellTime is the length of time that STAs shall stay on each frequency in their hopping sequence. Once STAs are synchronized, they have the same TSF timer value.

    "STAs in the BSS shall issue an appropriate PLME service primitive for the PHY in use to tune to the next frequency in the hopping sequence whenever

    "TSF timer MOD aCurrentDwellTime = 0"

    FHSS clients tune to one channel and listen for beacons as the BSS's dwell and hop by. DSSS, HR/DSSS, ERP, and OFDM clients tune to each successive channel and listen for beacons of BSS's each centered on one channel.

    I hope this helps. Can you add your location to your forum profile. Thanks. /criss

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