Hi all, I'm pretty confused about how to select the "primary" channel when using wide channels with 802.11ac (and also 802.11n, really). My hostapd contains a section like this: hw_mode=a channel=149 country_code=US ieee80211d=1 ieee80211h=1 ieee80211n=1 ieee80211ac=1 ht_capab=[HT20][HT40+][RX-STBC1] vht_capab=[MAX-A-MPDU-LEN-EXP4] vht_oper_chwidth=1 vht_oper_centr_freq_seg0_idx=155 If I understand correctly, this will have the following results: - at 20 MHz, it will use channel 149 - at 40 MHz, it will use channels 149+153 (HT40+) - at 80 MHz, it will use channels 149+153+157+161 (centr_freq_seg0_idx) This is fine when I'm the only AP around. But let's imagine I'm in a crowded apartment building with lots of APs, and various clients support only 20 MHz channel width (increasingly rare), or 20/40, or 20/40/80. In such a situation, we'd like to spread around the APs so that clients that can only do 20 or 40 don't always fall back to channel 149 or 149+153; otherwise we're just wasting tons of empty space on channels 157 and 161. The obvious way to do this would be to try a configuration like this (HT40-): channel=153 ht_capab=[HT20][HT40-][RX-STBC1] vht_capab=[MAX-A-MPDU-LEN-EXP4] vht_oper_chwidth=1 vht_oper_centr_freq_seg0_idx=155 or perhaps this (40 Mhz uses upper half instead of lower half): channel=157 ht_capab=[HT20][HT40+][RX-STBC1] vht_capab=[MAX-A-MPDU-LEN-EXP4] vht_oper_chwidth=1 vht_oper_centr_freq_seg0_idx=155 But when I try to do this, hostapd seems to abort and claim it can't register to use the channels. Am I doing something wrong? Is it hostapd version related? Also, hostapd contains code to swap the primary/secondary 20 MHz channels in the 40 MHz channel, based on what other APs are around. If I read correctly, it seems to want to use the same primary channel as everyone else. Wouldn't it be better to equailze things to try to get about half the APs using each sub channel? Any advice on this topic is very welcome. Thanks! Have fun, Avery -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
