osmo-trx: GSM signal generator

[Tom Tsou]

Hi All,

I wrote a GSM signal generator application based on osmo-trx. The new
osmo-siggen allows random GSM or EDGE burst generation without using
special configurations of osmo-trx or the socket control interface.
Frame trigger output through GPIO is also available.

I use the application for testing modulation parameters and other PHY
level testing. Hopefully it's useful to other developers beyond
myself.

$ ./osmo-siggen -h

Options:
  -h, --help   This text
  -a, --args   UHD device args
  -l  --log    Logging level ('err', 'warn', 'notice', 'info', 'debug')
  -b, --burst  Burst type ('normal', 'access', 'freq', 'sync', 'edge')
  -r, --ref    Frequency reference ('internal', 'external', 'gps')
  -f, --freq   Tx RF frequency
  -g, --gain   Tx RF gain
  -s, --sps    Tx samples-per-symbol (only 4 supported)
  -m, --mod    GSMK modulator type ('laurent4', 'laurent2', 'laurent1', 'nco')
  -p, --ampl   Tx amplitude (0.0 - 1.0)
  -o, --offset Baseband frequency offset
  -t, --tsc    Normal and EDGE burst training sequence (0-7)
  -S, --swap   Swap channels

Currently osmo-siggen is located in the below branch. I've tested
solely with B210. C++14 availability is also required for now.

    git://git.osmocom.org/osmo-trx    ttsou/siggen

   -TT