802.11n --modulation--> OFDM
802.11B --modulation--> DSSS
Why CWNA book and many of the other documents saying 802.11n(support only OFDM modulation) is backward compatible with 802.11b(support only DSSS modulation)???

IEEE 802.11N SALIENT FEATURES
PARAMETER IEEE 802.11N STANDARD
Maximum data rate (Mbps) 600
RF Band (GHz) 2.4 or 5
Modulation CCK, DSSS, or OFDM
Number of spatial streams 1, 2, 3, or 4
Channel width (MHz) 20, or 40

https://www.electronics-notes.com/artic ... 02-11n.php

https://community.cisco.com/t5/other-wi ... -p/2677143

IEEE 802.11N SALIENT FEATURES
PARAMETER IEEE 802.11N STANDARD
Maximum data rate (Mbps) 600
RF Band (GHz) 2.4 or 5
Modulation CCK, DSSS, or OFDM
Number of spatial streams 1, 2, 3, or 4
Channel width (MHz) 20, or 40

https://www.electronics-notes.com/artic ... 02-11n.php

https://community.cisco.com/t5/other-wi ... -p/2677143

Thanks a lot...thank you very much

IEEE 802.11N SALIENT FEATURES
PARAMETER IEEE 802.11N STANDARD
Maximum data rate (Mbps) 600
RF Band (GHz) 2.4 or 5
Modulation CCK, DSSS, or OFDM
Number of spatial streams 1, 2, 3, or 4
Channel width (MHz) 20, or 40

https://www.electronics-notes.com/artic ... 02-11n.php

https://community.cisco.com/t5/other-wi ... -p/2677143

So, can 802.11n support DSSS modulation?

When you think you are in control of the wifi parameters. And can avoid the 1Mbps beacon sending of the 802.11b, because every SSID on every AP will consume 3% of the total airtime if 1Mbps beacons are used, you want to avoid them. The 6Mbps beacons only take 0.5% of the airtime per SSID per AP. (See overhead calculator, 35 SSID around at 1Mbps would take all the airtime.

So one chooses 802.11g/n or even 802.11-only-N, not 802.11b/g/n, to avoid the 1Mbps beacons.
To be certain the basic rates at 1,2,5.5, 11 Mbps are de-selected in data-rates, and only 6Mbps is set for basic rate. The b rates are even removed from the supported rates.

Then there is something around in the channel that supports 802.11b, not connected, just detectable. And guess what you get !?
Wow what is predictable here? New since 7.3? Different since 7.3? Supported b-rates not removed for Mikrotik-hAP.

This URL explains why the 1 Mbps DSSS beacon appears.: https://www.excentis.com/blog/disabling ... -ap-or-not

I recently saw an installation with 8 AP's, all with the same SSID set on the same channel, and each AP with 3 hidden SSID. This brings 32 SSID instances on one channel, while the user only sees just one.
If this goes into 1 Mbps backward compatibility mode, because just some 802.11b client passes by using the same channel .... is then all airtime gone??? or not ???? As we see that even mode "802.11-only N", with b-rates as basic rates disabled, and b-rates removed from the supported rates is still sending 1 Mbps beacons. (b-rates are removed as beacon data, but that beacon is sent at the 1Mbps b-rate.) The link above states that the AP then asks anyone else to do the same.