Hi,

attenuation is controlled in first place by osmo-bts, which gets information about the nominal Tx power from the currently running device from osmo-trx, by using TRXC protocol. BTS sends "NOMTXPOWER" command and osmo-trx answers with "RSP NOMTXPOWER <dBm>". Then osmo-bts tells osmo-trx which attenuation to apply based on the nominal Tx power by means of using "SETPOWER" or "ADJPOWER" TRXC commands.

I don't see any "NOMTXPOWER" "SETPOWER" or "ADJPOWER" TRXC protocol command in the logs of osmo-trx or osmo-bts, so I bet you don't have osmo-bts properly configured to set the attenuation. Maybe you didn't set enough verbosity for the TRXC category in logs, debug would be great.

So have a look around those TRXC command strings in osmo-bts and osmo-trx code, those are the ones in charge of setting attenutation.

In any case, the UmTRX is probably going to provide wrong information to the BTS when it asks for the nominal Tx Power, since it is using the B210 device values as fallback, as warned here:

<0005> UHDDevice.cpp:250 No Power parameters exist for device UmTRX

4/1 Tx/Rx SPS on band GSM900, using B210 ones as fallback

To fix that, have a look in osmo-trx.git, grep for "struct dev_band_desc", and add entries to the table called "dev_band_nom_power_param_map" in UHDDevice.cpp (and submit a patch to gerrit ;).

See also: * osmo-bts User Manual "14.2.3 Configuring power ramping" https://ftp.osmocom.org/docs/latest/osmobts-usermanual.pdf

* osmo-trx User Manual "19.2.1 Power Control" https://ftp.osmocom.org/docs/latest/osmotrx-usermanual.pdf

Hi Pau,

We are now able to achieve the correct value when we are setting tx-attenuation using B210. However, using UmTRX 2.3.1 SDR we are still encountering this error *<0005> UHDDevice.cpp:250 No Power parameters exist for device UmTRX4/1 Tx/Rx SPS on band GSM900, using B210 ones as fallback *even we already add entries to "dev_band_nom_power_param_map" in UHDDevice.cpp.

[image: image.png]

[image: image.png]

Please see attached file for logs. Thank you.

Regards, Justin

On Wed, Sep 21, 2022 at 6:30 PM Pau Espin Pedrol pespin@sysmocom.de wrote:

Hi,

btw you can find more information on the process of filling in the gain tables for each device here: https://osmocom.org/issues/4583

--

• Pau Espin Pedrol pespin@sysmocom.de http://www.sysmocom.de/

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• sysmocom - systems for mobile communications GmbH
• Alt-Moabit 93
• 10559 Berlin, Germany
• Sitz / Registered office: Berlin, HRB 134158 B
• Geschaeftsfuehrer / Managing Director: Harald Welte

Hi Pau,

It seems that the said errors are now gone after rebuilding the osmo-trx. But osmo-bts keeps on restarting. I've attached the logs and UHDDevice.cpp file for your reference.

Regards, Justin

On Tue, Oct 25, 2022 at 4:33 PM Pau Espin Pedrol pespin@sysmocom.de wrote:

Hi Justin,

You could start by sharing the patch with the modifications you mention, in gerrit or here.

Quick look at the log I see: "UHDDevice.cpp:250 No Power parameters exist for device UmTRX 4/1 Tx/Rx SPS on band GSM900, using B210 ones as fallback"

hence line 250, which is the current line in master. So not sure if you are really running the modified version, since I'd expect that line to be higher if you added entries to the dev_band_nom_power_param_map table.

Regards, Pau

--

• Pau Espin Pedrol pespin@sysmocom.de http://www.sysmocom.de/

=======================================================================

• sysmocom - systems for mobile communications GmbH
• Alt-Moabit 93
• 10559 Berlin, Germany
• Sitz / Registered office: Berlin, HRB 134158 B
• Geschaeftsfuehrer / Managing Director: Harald Welte