Forum: GNU Radio bit error rate

ber_before_tx.png
<http://gnuradio.4.n7.nabble.com/file/n40088/ber_be...
ber_tx.png <http://gnuradio.4.n7.nabble.com/file/n40088/ber_tx.png>

I am trying to find the Bit error rate for a vector signal.I get a error
rate of 0.528(i am assuming it to be 52%) when i don't transmit  and an
error rate of 0.625000 when i transmit.

Am i right on this??i dont understand the logic behind it..

Also,is 52% not too high??!!!

thank you

On Fri, Mar 8, 2013 at 8:47 PM, manjusha <yandamuri.manju@gmail.com> 
wrote:

> ber_before_tx.png
> <http://gnuradio.4.n7.nabble.com/file/n40088/ber_be...
> ber_tx.png <http://gnuradio.4.n7.nabble.com/file/n40088/ber_tx.png>
>
>
It doesn't look like you're doing any carrier recovery?

Before putting USRP blocks in there, maybe you should try a straight
simulation that adds noise and some frequency offset artificially.  Get
that working, and then connect up the USRP source/sink?


> I am trying to find the Bit error rate for a vector signal.I get a error
> rate of 0.528(i am assuming it to be 52%) when i don't transmit  and an
> error rate of 0.625000 when i transmit.
>
> Am i right on this??i dont understand the logic behind it..
>
> Also,is 52% not too high??!!!
>

Around 50% BER is what you would expect from a random signal.  100% BER 
is
very good since you just need to flip all the bits and you get the right
answer!  That is also given the input signal statistics are sufficiently
whitened/random.


>
> thank you
>
>
>
You might want to take a step away from putting blocks in GRC and just 
take
a look at some of the resources on the GNU Radio wiki about suggested
reading:

  http://gnuradio.org/redmine/projects/gnuradio/wiki...
  http://gnuradio.org/redmine/projects/gnuradio/wiki...

Sanity is hard to come by if you're dealing with magic.

Good Luck!

Brian

> very good since you just need to flip all the bits and you get the right
> answer!  That is also given the input signal statistics are sufficiently
> whitened/random.
>
Just tagging on here... The way you have it set up is compare the
incoming bit to 1, next compare the incoming bit to 0. And it will
alternately compare incoming bits between 1 and 0. This BER block will
probably not be useful if you don't have access (within this
flowgraph) to the source generating data.

>   http://gnuradio.org/redmine/projects/gnuradio/wiki...
>   http://gnuradio.org/redmine/projects/gnuradio/wiki...
>
> Sanity is hard to come by if you're dealing with magic.

If you haven't looked at examples yet you should do that too. They are
probably located in /usr/local/share/gnuradio/examples/

There's a BER example at
/usr/local/share/gnuradio/examples/digital/demod/ber_simulation.grc