[Discuss-gnuradio] BER measurement for GMSK transmission with USRP wirelessly

[Sun Wenbin]

Good day everyone,

My sincere apology in advance if this question has been asked before, but i tried search thru the archives but to no avail.


Currently, I am trying to calculate the BER for GMSK, But first I started off on a perfect channel without USRP.


My current block diagram is as follows:

"Random Source"
0s and 1s, 10^6 windows -> "Throttle" -> "GMSK Mod (default settings)" -> "GMSK Demod (default settings)" -> "Error Rate Block"

I am feeding in "Error Rate block" with the random source and the "GMSK Demod" Output.

I am getting BER of 50%... Anyone knows what is wrong?

In fact, I saved the input and output as binary files. I found out that they are not very identical especially in terms of binary length. I tried input 9 bits of binary and I obtained 63 bits from the GMSK Demod Output.

Is there something that is missing? 

Hope someone can advise me. Thank you :)

Best Regards,

Sun