lms: User correct scale factor for transmit samples
Due to (I believe) a copy+paste mistake from the USRP1 code,
we were using only a scale range of up to 9830 when transmitting
samples, rather than the full 16 bit signed integer range up to
32767.
As a result, we were loosing almost two bits (MSBs) of resolution
as well as a lot of transmit power.
This changes the scale factor to 0.707 (1/sqrt(2)).
Please note that the much higher DAC output level means that the analog
gain should be reduced. The theoretic range of up to 73dB should not
be used, but Lime Microsystems suggest a value of 61..67 dB. This can
be achieved by using a "osmotrx tx-attenuation" value of 6..12 inside
the osmo-bts-trx configuration file.
Related: OS#3341
Related: OS#3342
Change-Id: I71702feaa11f53e7614a6938a984dd748405474a
1 file changed