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L-SIG TXOP Support

2 posts by 2 authors in: Forums > CWDP & CWAP - Enterprise Wi-Fi Design & Analysis
Last Post: January 19, 2016:
  • By almotasem
    Reply

    Hi,

    When I do a traffic capture for various devices like iOS, Android and OSX stations and I notice they send the L-SIG TXOP set to 0 in their HT Capability IE. That means they don't support the legacy OFDM header (cant read the Signal field). The same is also noticed by many APs.

    Now I am confused, because mixed mode protection is mandatory in 11n and the legacy header is always in front of the 11n header (PLCP header). What does it  mean the STA does not support L-SIG? Can't it interpret the legacy header and read the signal field (length/data rate), although it should do according the standard? Or do vendors in the real world just use RTS/CTS as a protection mechanism and HT stations use the greenfield header?

    Motasem, 

  • By abaa
    Reply

    Hi Motasem,

    according to the 802.11n book by Matthew Gast, the CTS-to-self protection mechanism is required, but the L-SIG spoofing is optional (page 58).

     -- Anders

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