• I did a search and didn't see any mention of this in the errata for the CWAP. I didn't even catch it until subsequent readings...

    On page 48 of the CWAP book it mentions:

    "... ERP stations must transmit the protection mechanism frames using a modulation understandable by all stations in the BSS, typically either BPSK or QPSK. The duration field value in the MAC frame header must be set to an appropriate value..."

    BPSK and QPSK are more advanced modulation techniques versus DBPSK/DQPSK because they are modulated/demodulated against a reference signal and hence are less error prone versus DBPSK/DQPSK (only measuring relative differences in phase i.e. 'differential') as I understand it. Therefore, if a modulation must be used in an 802.11g cell for backwards compatibility to 802.11b and even 802.11, wouldn't this mean DBPSK and DQPSK at the lower datarates? Therefore a frame using those rates with a duration value long enough for the full ERP transmision sequence would be heard by everyone and not transmitted on top of each other?

    This error is used throughout this same chapter (at least 2 other times that I noticed) until you get to the Physical Layer chapter where it's corrected.

    Hope I'm not repeating a previous post, but I didn't see any mention.


  • Hey, how come I get no love from this post??? :)

    I know the CWAP is in the past, but I still hold it as a valuable resource and would certainly recommend it for someone studying for the CWNE.

  • Hi Shawn:

    You are correct. Sorry I missed your 04Dec2006 post.

    What other pages do you see this error on?

    I hope this helps. Thanks. /criss

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