[PATCH] wireless-regdb: restore channel 12 & 13 limitation in the US

[PATCH] wireless-regdb: restore channel 12 & 13 limitation in the US

[bkil]

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Existing documents that discuss this are vague and pretty much out of date: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@gmail.com>
---
 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

Re: [PATCH] wireless-regdb: restore channel 12 & 13 limitation in the US

[Seth Forshee]

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@gmail.com>

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

[PATCH] wireless-regdb: restore channel 12 & 13 limitation in the US

[bkil]

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@gmail.com>
---
 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