On Mon, Oct 05, 2020 at 03:01:22PM +0200, bkil wrote: > The precisely allowed transmission power on channel 12 & 13 is not clear. > > I did some fact checking and document reviews in the past, but still > failed to come up with an exact reference or calculation regarding what TX > power should be allowed in general to reduce interference in the > neighboring restricted band 2483.5-2500 MHz and whether indoor vs. outdoor > and b/g/n modulation would make a difference (probably yes). > > Existing documents that discuss this are vague and pretty much out of date: > https://en.wikipedia.org/wiki/List_of_WLAN_channels#endnote_B > > Following these guidelines, I failed to come up with an approximate > formula that would prohibit usage of channel 12 & 13, but still allow > usage of channel 11 with full power, hence at least part of the argument > for prohibiting channel 12 & 13 needs to be refined. > > Until further research, just to stay safe, I propose that we restore the > previous limitation of disabling channel 12 & 13 as before. We should > work towards finding a safe transmission power to use on both and specify > that (like 50mW on channel 13 and 100mW on channel 12?). > > I've also started a discussion for investigation on Wikipedia: > https://en.wikipedia.org/wiki/Talk:List_of_WLAN_channels#Should_the_2.4GHz_channel_12_and_13_in_the_USA_need_updating? > > Signed-off-by: bkil <b.K.il.h.u+tigbuh@xxxxxxxxx> I tried doing a little research, and it does appear that use of channels 12 and 13 is more complicated than it might seem on the surface. I cannot find any clear guidance on power limits and lack the background to determine appropriate limits from the information I did find, so it does seem prudent to restore the previous limitation. Applied, thanks! > --- > db.txt | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/db.txt b/db.txt > index ac32483..68613cf 100644 > --- a/db.txt > +++ b/db.txt > @@ -1568,8 +1568,12 @@ country UG: DFS-FCC > > # https://www.ecfr.gov/cgi-bin/text-idx?SID=eed706a2c49fd9271106c3228b0615f3&mc=true&node=pt47.1.15&rgn=div5 > # Title 47 Part 15 - Radio Frequency Devices, April 2, 2020 > +# Channels 12 and 13 are not forbidden, but are not normally used with full > +# power in order to avoid any potential interference in the adjacent restricted > +# frequency band, 2,483.5–2,500 MHz which is subject to strict emission limits > +# set out in 47 CFR § 15.205. TODO: reenable and specify a safe TX power here. > country US: DFS-FCC > - (2400 - 2483.5 @ 40), (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), (23), DFS, AUTO-BW
