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doesn't Oscilloscope show SFD? RRS feed

  • Question

  • hello-. while trying to do some stuffs with umxdot11 source code, I got some questions.

     

    1.

    as far as I know, there is SFD between preamble and MAC header, in 802.11b scheme.

    But using 'Oscillograph' application, I couln't find any SFD. (standards say it is 1111 0011 1010 0000 (when frame uses long preamble)

    or 0000 0101 1100 1111 (when frame uses short preamble) ). doesn't your Oscilloscope program show SFD on purpose?

    I also dumped commercial AP's beacon and showed it and I couldn't find SFD either.

     

    2.  Analyzing source code, I show some part of generating MAC header. but  I couldn't find MAC header in Oscilloscope

    when SORA machines transmit and receive a sample packet using umxdot11. On the contrast, MAC header of commercial

    AP's beacon could be confirmed. doesn't umxdot11 generate MAC header at all?

    Thursday, December 22, 2011 1:32 PM

Answers

  • yes,  Oscillograph app does not show SFD on purpose.

    umxdot11 get packet from network stack. the packets include MAC header which is generated  by the network stack.


    Danial.F
    • Marked as answer by d_k_fox Monday, January 16, 2012 12:31 PM
    Monday, January 2, 2012 4:30 PM

All replies

  • 1. SFD is part of preamble. Although it's not printed in Oscillograph, you can easily infer that whenever a frame is detected (and may be decoded) by Oscillograph, a SFD must have been detected.

    2. Oscilloscope doesn't parse MAC layer, but all the MAC information is included in the decoded bits.

    -Jiansong

    Monday, December 26, 2011 3:03 AM
  • then again,

     1. you're saying that your Oscillograph application omit SFD on purpose. right?

     2. of course I know  Oscilloscope doesn't parse MAC layer. What i was saying is that whether umxdot11, your sample code,

    generate MAC header or not when it transmits a packet. which one is true?

     



    • Edited by d_k_fox Monday, December 26, 2011 3:33 PM
    Monday, December 26, 2011 3:31 PM
  • yes,  Oscillograph app does not show SFD on purpose.

    umxdot11 get packet from network stack. the packets include MAC header which is generated  by the network stack.


    Danial.F
    • Marked as answer by d_k_fox Monday, January 16, 2012 12:31 PM
    Monday, January 2, 2012 4:30 PM