• Hi All,

    I need to look on a DATA frame and check whether Data is transmitted using STBC or not. (From the AP, To the STA)
    So it's ping request and I am using Wireshark - Will this information be we under the 'Radio tap header' (PLCP) header ?

    I have a Atheros AP (Tx,Rx STBC enabled) and Ralink STA (Forced to 1x1, STBC Tx,Rx enabled), I confirmed it by sniffing the beacons and probe resp (HT capabilities info).

    How to confirm whether the DATA frame is sent using STBC or not ?


  • By (Deleted User)

    The radio tap header, to my knowledge, does not yet report the STBC field in the PLCP header.

    If you just want to see an STBC frame, find an STBC beacon. In the HT Operation element, there is a field called "STBC Beacon," which is set to 1 in an STBC beacon.

  • Yeah I would be able to see it on a beacon but

    How will you be able to identify whether a DATA frame is sent using STBC or not, so that the Rx can know

  • Hi Ravi,
                    Quite late for a reply although not sure if you have had any luck on this. Happened to revisit the standard, after coming across your query and so am putting across my thoughts on this:
    * First of all, from your query I presume the mode of operation(protocol wise) is either in HT-Mixed or HT-GreenField mode, as these are the only 2 modes where one can enable STBC. So with this assumption in mind, let's look at the standard(802.11n-2009).

    * Going through the HT-SIG definition (HT Preamble > HT portion of HT Mixed format preamble > HT-SIG Definition > HT-SIG fields table), the standard says use of STBC field parameter "to indicate the difference between the number of spacetime
    streams (Nsts) and the number of spatial streams (Nss) indicated by the
    MCS. Set to 00 to indicate no STBC (Nsts = Nss )."

    * So to sum up: Look in the PLCP Header part of the said data frame & locate the STBC sub-field under HT-SIG. In a proper implementation(AP/STA firmware made with religious reference to standard), the STBC sub-field should be present for one and for two should be a 2 bit value as described above.
        Hope this helps.

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