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

Alexander Wilhelm
2025-05-16T09:23:03Z

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