[Discuss-gnuradio] BER AWGN example - question

[bieniu]

Dear GNU Radio users,

I have just read the tutorial about simulations in GNU Radio 
(http://gnuradio.org/redmine/projects/gnuradio/wiki/Simulations) and I 
would be grateful if you could help me with understanding part of it.

Could you explain how the converting the EbNo value to the noise 
voltage in the following example is done?
http://gnuradio.org/redmine/projects/gnuradio/repository/entry/gr-digital/examples/berawgn.py

I can see that there is a function (EbNo_to_noise_voltage) responsible 
for that but I have problem with understanding where this equation came 
from. Could you possibly explain it to me or at least recommend some 
book where I can find the solution?

Best Regards,
Piotr Bieńkowski