Ripple Hell

4 posts by 2 authors in: Forums > CWNA - Enterprise Wi-Fi Admin
Last Post: September 26, 2007:
  • I've been spending every waking moment reading 802.11n for a while now. This is one complicated document. Remember "Protection Ripple"? Get ready for a tidal wave of protection ripple - thanks to a little field called "OBSS Non-HT STAs Present". This is a field in the HT IE of Beacons, Probe Request frames, etc that lets other APs know if there is a need for them to protect greenfield and RIFS sequence transmissions due to a non-HT STA being present. In a nutshell, this is a mechanism where one AP can indicate to another adjacent AP whether or not it should use protection mechanisms - of which there are now MANY in 802.11n.

    One thing to note is that the indication of the need to use protection should not extend beyond 1 adjacent AP; however, as non-HT and non-ERP stations roam and reassociate, this will cause major protection status flipping as they move. It'll still be Ripple Hell.


  • Hi,

    Can you explain me clearly, Under what are the conditions the "OBSS non-HT STA present" sub field is set to 1.


    Section III

  • Thank you very much.

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