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Thread: 2,4 GHz channels width...

  1. Default 2,4 GHz channels width...

    Hi Metageek,
    I'am a brand new user of InSSIDer, just discovered two days ago. Good product!!!

    A question arises to me: as far as I know, b/g channels are 22 MHz wide (i.e. Ch.1
    is from 2401 to 2423 MHz), while the graphic of inSSIDer seems to show a 20 MHz
    width. 20 MHz is indeed the standard width of "g" channels (UNII-1 from 36 to 48,
    UNII-2 from 52 to 64, UNII-3 from 147 to 163 for outdoor applications).

    I'm I correct or wrong?
    Best! Marco.

  2. #2

    Default

    You are correct in that the 802.11b channel width is 22 MHz, while G and A are 20 MHz. (G is in 2.4 GHz, and A in in 5 GHz).
    In the 2.4 GHz band, there 3 modes:
    802.11B - 11 Mbps, 22 MHz wide
    802.11G - 54 Mbps, 20 MHz wide
    802.11N - 65-260/150-600 Mbps, 20/40 MHz wide

    inSSIDer will show a 20 MHz channel width for access points that support G/A mode, while it should show a 22 MHz width for B-only mode.

  3. Default Again on channel width

    Thanks Tyler for your precise answer.

    I see on the web that the matter of 802.11g channel width is quite a discussed one.

    I.E. the attachment from Wikipedia (?) clearly shows that they are 22 MHz wide (for
    backward compatibility with the 802.11b standard in the 2,4 GHz band, I suppose).

    Other say that DSSS modulation in the g standard uses 22 MHz channels (for 5.5 and
    11 Mbps speed only; 1 & 2 Mbps are not supported, then), while OFDM modulations
    (for the "native" 8 speeds from 6 to 54 Mbps) use 20 MHz wide channels.

    Anyway, since clearly the 20 MHz channels fit into the 22 MHz ones, 802.11g can use
    both width, as needed.

    Have you perhaps access to the original IEEE 802.11g-2003 standard, to check what
    the most authoritative source say? Can you please quote out the relevant paragraph?

    Tnx in adv. & best!
    Marco
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