Re: wireless-regdb: Wrong ETSI tranmit power without TPC

[Alexander Wilhelm <alexander.wilhelm@westermo.com>]

Am Fri, May 16, 2025 at 10:38:04AM +0200 schrieb Johannes Berg:
> On Fri, 2025-05-16 at 16:15 +0800, Chen-Yu Tsai wrote:
> > > The frequencies 5470 - 5725 have a power of 500 mW. It results in 26 dBm. But I
> > > believe 27 dBm are allowed.
> 
> Seems like. But units are hard...
> 
> The link in the db went stale, but the current versions
> 
> https://urldefense.com/v3/__https://www.bundesnetzagentur.de/SharedDocs/Downloads/DE/Sachgebiete/Telekommunikation/Unternehmen_Institutionen/Frequenzen/Allgemeinzuteilungen/MobilfunkDectWlanCBFunk/WLAN_5GHz_pdf.pdf?__blob=publicationFile&v=1__;!!I9LPvj3b!Hih48oBC7IPvu59VI1FRTqSb45uwWEnAELFqlK_ubfJdtkTnODDPuyA5gG6olCgbiPxC6m0zQdcuNJ3nzRJ1RJ_PT6ux0w$ 
> 
> states (page 5):
> 
> --------------------
> Frequenzband 5470–5725 MHz
> ...
> Maximale mittlere EIRP für
> bandinterne Aussendungen
> 
> 1 W
> Ausnahmen:
> für Anlagen in Straßenfahrzeugen gilt eine maximale
> mittlere EIRP von 200 mW.
> 
> ...
> 
> Maximale mittlere EIRP-Dichte für
> bandinterne Aussendungen
> 
> 50 mW/MHz in jedem 1 MHz-Band
> 
> ...
> 
> Sendeleistungsregelung (TPC)
> 
> TPC muss durchschnittlich einen Abschwächungsfaktor von
> mindestens 3 dB gegenüber der höchstzulässigen
> Sendeleistung der Systeme erbringen; oder ohne TPC muss die
> höchstzulässige mittlere EIRP und die Obergrenze für die
> entsprechende mittlere EIRP-Dichte um 3 dB verringert
> werden.
> --------------------
> 
> 
> So to be _really_ precise you'd end up with 1W reduced by 3dB which of
> course _is_ precisely 27dBm since 1W is 10^30 or precisely 30 dBm.
> 
> (Except in "street vehicles", apparently. Rail has its own things, so I
> guess that really does mean cars/trams/etc.)
> 
> But given the unit conversions are hard, we should probably just do this
> in the db in dBm?
> 
> johannes

I referred to the following EU Rules:

* ETSI EN 300 328 V2.2.2 (2.4 GHz)
* ETSI EN 301 893 V2.1.1 (5 GHz)
* ETSI EN 300 440 V2.2.1 (5.8 GHz)

The problem with them is that almost always the unit _mW_ is used. And the
reduction without TPC then is given in _dBm_. However, for 5.8 GHz (SRD devices)
the transmission power is stated as 25 mW. Does the EU Rules means 14 dBm or
only 13 dBm are allowed?


Best regards
Alexander Wilhelm