Calculating transmitter power from spectral density
You're right, to convert from a power density to a power, you integrate over frequency!
However:
Well, if neither of your transmitter nor receiver are calibrated, then you simply can't find the &quot;real&quot; transmitted or received power. The plots you have are &quot;amplitude relative to maximum ADC input&quot;. You don't know what power &quot;maximum ADC input&quot; corresponds to without calibration.
End of story - there's not a single absolute power in your system that you can use as reference!
The solution here is to calibrate; i.e. send a signal, measure it with a calibrated spectrum analyzer, measure the same signal with your USRP, and then calculate the factor between these two powers. Due to linearity, that factor (==corrective additive term in dB) stays the same for all powers.