Last Post: March 4, 2005:
I quess I am not sure if I understand the use of this and how it would work.
DSSS-OFDM is optional for 802.11g and If I understand correctly it could be used instead of ERP-OFDM so 802.11b stations can understand the transmission from a "g" AP or STA and thereby alleviating the need for the 802.11g APs and STAs to set the Use_Protection bit.
If this is true, would this be used only at the MAC header portion and not the frame body? Would the supported rates be 1, 2, 5.5 and 11Mbps? Is this actually used?
Am I off in left field on this?????
Thanks for any help !
DSSS, HR/DSSS, and ERP chipsets can read the preamble and PLCP header
(DSSS is restricted to long preamble) and defer for the balance of
the ERP DSSS-OFDM frame based on the length field in the PLCP header,
but they can not demodulate the MAC header and its duration field in
order to get the full benefit of frame exchange sequence protection
based on the duration field.
This is a significant improvement over popular ERP OFDM using ERP
protection mechanisms to contend with nearby HR/DSSS stations, but
ERP protection mechanisms may still be called for with the mysterious
ERP DSSS-OFDM. We may never know for sure since no one seems
interested in deploying this optional ERP modulation.
I hope this helps. Thanks. /criss