I'm trying to configure OpenWRT on a Netgear WN3000RPv3 as an access point with minimal RF output.
I've increased the Beacon Interval to 10000. However, an RF meter detects a pulse every 2 seconds (which disappears when the AP is turned off).
Would this 2 second pulse be the beacon? (which should be 10s?). Is there a way to disable the beacon entirely? I've tried disabling the ESSID but that doesn't make a difference.
Beacon interval values higher than 10000 (10001 and higher) result in the wireless not working at all.
Also AP works for a few minutes and then is not contactable at all either via Wi-Fi or ethernet without restarting.
Wireshark on a monitor interface will tell you what it is.
Considering you're way outside the range of expected operation of beacon frames (100 ms is typical), it's possible you're running into number-representation problems or have violated some other assumption of rationality in the code.
See https://mrncciew.com/2014/10/08/802-11-mgmt-beacon-frame/ for some more information on beacon frames and their timing and contents.
Of particular interest
- Beacon Interval (2 byte)
Beacon Interval field represent the number of time units (TU) between target beacon transmission times (TBTT). Default value is 100TU (102.4 milliseconds)
2 bytes = 65536 * 1024 µs seems to be the longest beacon that can be represented.
what happens if you lower them under 1024ms?
Running Wireshark shows that it is sending a Beacon Frame every 2 seconds, although interestingly in the frame itself it indicates that the beacon interval is 10.24 seconds.
Lowering the beacon Interval to 1000 sends it every second.
hostapd has a configuration option start_disabled=1 to disable the beacon, however this option is not available in /etc/config/wireless. Is there any way to pass through hostapd options using the /etc/config/wireless file?
I tried to find the script which generates the /var/run/hostapd-phy0.conf file but couldn't find it.
Small update, it turns out start_disabled can be put into /etc/config/wireless, it needs to go into the 'config wifi-iface' section. However, this turns the radio off altogether, which means that it is not possible to connect to wifi.
Looking into this further I don't think it is possible to disable the beacon without using a vendor-specific command, if the chipset supports it.