Fairwaves UmTRX and UmSITE

Fairwaves UmSITE is a fully fledged GSM BTS which runs Osmocom stack.

Fairwaves UmTRX is an SDR used in Fairwaves UmSITE BTS. It can also be purchased separately and is frequently used by commercial companies and enthusiasts to run OsmoTRX. UmTRX was created at the early days of OsmoTRX (even predating the official osmo-trx) and evolved together with osmo-trx providing excellent compatibility.

Following GSM recommendations UmTRX has a much more precise reference clock and built-in GPSDO function to keep the frequency accuracy within 50ppb required by the GSM standard. This resolves issues often faced by users of other SDRs where phones can't detect a network due to excessive frequency error.


  1. Install UHD and an UmTRX UHD module as described in the UmTRX documentation
  2. Install osmo-trx as usual. If you're compiling from sources, just compile with default parameters.


A typical command line to run osmo-trx with UmTRX:

chrt 20 osmo-trx-uhd -c 2 -a "fifo_ctrl_window=0,status_port=12345" 
  1. -c 2 enables dual-TRX mode,
  2. fifo_ctrl_window=0 works around a frequent issue when UHD can't connect to a UmTRX on the first try.
  3. status_port=12345 enables a special JSON API which exports the whole UHD property tree to allow runtime fine tuning and status query by external applications. See for an example library to access this API and for an example use of this API to query UmTRX VSWR, voltage and temperature sensors while osmo-trx is running.
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UmTRX231.jpg View UmTRX231.jpg 84.9 KB laforge, 04/28/2018 01:14 PM

Updated by roh almost 5 years ago · 4 revisions

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