Forum

long -short preamble (again)

2 posts by 2 authors in: Forums > Wi-Fi Alliance Certifications & the 802.11 Standard
Last Post: August 21, 2007:
  • By bizoo
    Reply

    HI all

    i am currently using netgear 802.11g compatible card and am try to decode the signal received at the base band and for tat reason looking at the preamble every now and then
    Now i know that it is upto the AP vendor which preamble to allow and whthere look for greater compatibility or increased throughput for the clients.

    But whatever the case is, AP only uses either long or short, not both,

    now in my case, at times my card(i am monitoring the data delivered by my card to AP) sends long premble and sometimes short(though apparently short preamble appears more often than long preamble)

    i am pretty bamboozled by this, has any one else experienced such a thing, ne one with any clues

    ?
    br

  • By Devinator
    Reply

    Hi bizoo,

    There are now five (5) preambles we have to consider:

    1. non-ERP Long (DSSS, HR/DSSS) - 802.11 DS, 802.11b (or 802.11g sending frames using DSSS or HR/DSSS data rates)

    2. non-ERP Short (HR/DSSS) - 802.11b (or 802.11g sending frames using HR/DSSS data rates)

    3. OFDM (ERP, OFDM) - 802.11a, 802.11g

    4. HT Mixed (HT Mixed Mode) - 802.11n

    5. HT Greenfield (HT Greenfield Mode) - 802.11n

    More info:

    http://www.cwnp.com/phpBB2/viewtopic.php?t=1999&highlight=preamble

    Hope this helps.

    Devinator

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