Re: [Discuss-gnuradio] Measure BER

[George Nychis]

Hi,

BER is defined as the % of bits that have errors to the total number of 
bits.  Therefore, you need to calculate the number of incorrect bits. 
To do this you would need to know the correct bits to compare your 
received bits to.  You can then easily compute the number of incorrect bits.

Therefore, if the input to gr.vector_source_b() is your input data, you 
would compare it to the output of gr.vector_sink_b() and calculate the 
bit difference.  If 1 bit out of 10^3 bits are different, your BER is 
1/10^3.  The more input, the more accurate your BER estimate is.

I don't think a BER calculator exists in GR, but it shouldn't be that 
difficult.  The block would take two input streams, one being the 
correct data and the other being the decoded data.  It could then 
compare the two.

Or you could compare the two outside of GNU Radio pretty easily.

It's not clear to me if you're performing the modulation and 
demodulation on the same machine.  If so you have easy access to both 
data sets.  Otherwise, transfer the known data to the receiver in a 100% 
accurate method and then compare.

- George


irene159 wrote:
> Hi all,
> I'm currently working on a GSMK modem, and I would like to calculate the BER
> of the link. I send data using gr.vector_source_b( ) connected to a GMSK
> modulator/demodulator and receive the signal in gr.vector_sink_b( ).
> 1) How can I measure BER from the vector_source and vector_sink ?
> 2) Does a BER calculator recovering from clock shifting (bit lost by clock
> sliding) exist ?
> Thanks !