OpenWRT Boot Times Affected by WiFi

OpenWRT Wireless Regulatory Flags

OpenWRT uses the Linux wireless regulatory database to decide which channels, channel widths, and transmit powers are allowed for a selected country code.

A regulatory rule has this general form:

(frequency_start - frequency_end @ maximum_channel_width), (maximum_power), optional_flags

Example:

(5250 - 5350 @ 80), (24), DFS, AUTO-BW

In that example:

• 5250 - 5350 is the allowed frequency range in MHz.
• @ 80 means the maximum allowed channel width is 80 MHz.
• (24) means the maximum transmit power is 24 dBm.
• DFS means Dynamic Frequency Selection is required.
• AUTO-BW affects how the regulatory code handles bandwidth across adjacent ranges.

Flag Meanings

DFS means Dynamic Frequency Selection. The radio must check for radar before using that channel as an access point. This can delay wireless startup.

AUTO-BW means automatic bandwidth handling inside the regulatory code. It helps determine whether wider channels are allowed across compatible frequency ranges. It does not mean automatic channel selection.

NO-OUTDOOR means outdoor use is not allowed for that frequency range.

NO-IR means No Initiating Radiation. The device is not allowed to initiate transmissions on that range. In practice, this can prevent access point mode or active scanning.

NO-OFDM means Orthogonal Frequency-Division Multiplexing is not allowed. This is mostly relevant to special legacy restrictions.

wmmrule=ETSI applies ETSI Wireless Multimedia parameters. This affects Quality of Service / contention behavior, not DFS startup delay.

Practical Effect

These flags do affect final wireless behavior. They can determine whether OpenWRT, the kernel, the wireless driver, and hostapd allow a radio to start on a given channel.

For DFS startup testing, the important item is the DFS flag. If the same frequency range starts faster after removing DFS, then DFS/radar handling was part of the delay.

Changing transmit power alone is not a direct DFS test.

US Regulatory Block

country US: DFS-FCC
	# S1G Channel 1-3
	(902 - 904 @ 2), (30)
	# S1G Channel 5-35
	(904 - 920 @ 16), (30)
	# S1G Channel 37-51
	(920 - 928 @ 8), (30)
	(2400 - 2472 @ 40), (30)
	# 5.15 ~ 5.25 GHz: 30 dBm for master mode, 23 dBm for clients
	(5150 - 5250 @ 80), (23), AUTO-BW
	(5250 - 5350 @ 80), (24), DFS, AUTO-BW
	# This range ends at 5725 MHz, but channel 144 extends to 5730 MHz.
	# Since 5725 ~ 5730 MHz belongs to the next range which has looser
	# requirements, we can extend the range by 5 MHz to make the kernel
	# happy and be able to use channel 144.
	(5470 - 5730 @ 160), (24), DFS
	(5730 - 5850 @ 80), (31), AUTO-BW
	# https://www.federalregister.gov/documents/2021/05/03/2021-08802/use-of-the-5850-5925-ghz-band
	# max. 33 dBm AP @ 20MHz, 36 dBm AP @ 40Mhz+, 6 dB less for clients
	(5850 - 5895 @ 40), (27), NO-OUTDOOR, AUTO-BW, NO-IR
	# 6g band
	# https://www.federalregister.gov/documents/2020/05/26/2020-11236/unlicensed-use-of-the-6ghz-band
	(5925 - 7125 @ 320), (12), NO-OUTDOOR, NO-IR
	# 60g band
	# reference: section IV-D https://docs.fcc.gov/public/attachments/FCC-16-89A1.pdf
	# channels 1-6 EIRP=40dBm(43dBm peak)
	(57240 - 71000 @ 2160), (40)