Channel in HT40 and VHT80

Vu Hai NGUYEN vh.nguyen at actiasodielec.fr
Fri Jun 13 04:00:48 EDT 2014


Hello every one,
I'm newbie and I just had a dumb question :D
Can someone explain to me that why hostapd use 802.11n Annex J to set up channel like this way:
	HT40-		                                           HT40+
	40,48,56,64,104,112,..                               36,44,52,60,100,108,...
It is not the same information as debugfs file "ht40allow_map". For example, If I set channel for a monitor 
interface using "iw", I can have:
channel 44 (5220 MHz), width: 40 MHz, center1: 5210 MHz 
channel 44 (5220 MHz), width: 40 MHz, center1: 5230 MHz
But if I set up an AP using hostapd I can only have the 2nd one as channel 44 allowed only in HT40+.

I also have another questions: I can set up channel from 36 to 128 for 802.11ac mode using ath10k and
hostapd. But both channels 132 and 136 is automatically converted to another channel (100,116 or whatever..)
Is this normal???. And channel 140 is only enabled in HT20 (not HT40 and VHT80) for Atheros card?

Thanks,
NGUYEN Vu Hai
Acita-Sodielec
Route de Mayres - B.P. 9
12100 St GEORGES DE LUZENCON
FRANCE



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