Unable 40MHz bandwidth in the 2.4GHz band?

Nicolas Boullis nboullis at debian.org
Tue Apr 16 12:45:51 PDT 2019


Hi,

I’ve been using hostapd for ~15 years, but my use has always been very 
basic.

I’m using hostapd with a USB Ralink-RT5370-based adapter.
As I understand it, my adapter is a 802.11b/g/n adapter which should 
support a 40MHz bandwidth. Running "iw phy" reports:

…
        Band 1:
                Capabilities: 0x17e
                        HT20/HT40
                        SM Power Save disabled
                        RX Greenfield
                        RX HT20 SGI
                        RX HT40 SGI
                        RX STBC 1-stream
                        Max AMSDU length: 3839 bytes
                        No DSSS/CCK HT40
…


Hostapd is configured with:

interface=wlan0
driver=nl80211
…
ssid=…
country_code=FR
ieee80211d=1
hw_mode=g
channel=1
…
ieee80211n=1
ht_capab=[HT40+][SHORT-GI-20][SHORT-GI-40]
…


But as far as I can see, only 20MHz connections are proposed to the 
stations that connect to the SSID. On a station, running "iw dev wlp2s0 
scan" reports:

…
	HT operation:
		 * primary channel: 1
		 * secondary channel offset: no secondary
		 * STA channel width: 20 MHz
		 * RIFS: 0
		 * HT protection: no
		 * non-GF present: 0
		 * OBSS non-GF present: 0
		 * dual beacon: 0
		 * dual CTS protection: 0
		 * STBC beacon: 0
		 * L-SIG TXOP Prot: 0
		 * PCO active: 0
		 * PCO phase: 0
…

Moreover, on the AP, running "iw dev wlan0 info" reports:

Interface wlan0
…
        channel 1 (2412 MHz), width: 20 MHz, center1: 2412 MHz


Any hint how I can understand why 40MHz is not enabled?


Cheers,

-- 
Nicolas



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