Re: [Discuss-gnuradio] Introducing noise/ considerable BER

[Martin Braun]

On Sun, Aug 07, 2011 at 02:47:10PM -0400, Daniel Zeleznikar wrote:
> As Marcus pointed out, there will always be packet loss associated with
> higher BER in real systems that employ packet switching. The only thing I
> could suggest is that you somehow move further upstream in your receive
> system to make the BER measurement happen at the bit/symbol level if you
> really want it to be accurate. Otherwise you can just collect data for both
> packet loss rate, and the BER of obtained packets, since that is the best
> thing you have to work with. The packet loss statistic may be important
> anyhow.
> Suggestions from anyone for moving the BER measurement closer to symbol
> level?

It's not quite clear what exactly you're trying to do. Here's some more
suggestions:
- Don't use benchmark_{tx,rx} scripts, but write something that doesn't
  do CRC checks on packets. However, you still  have to synchronize,
  that'll eventually conk out at very low SNR.
- Don't use USRP's at all. If you're running simulations (e.g. to test a
  channel coding scheme), do it all in GRC. You can either use the
  channel model that comes with GNU Radio to increase SNR, or, of you
  want to stick to bits, try the Channel Coding Toolbox from
  https://www.cgran.org/wiki/chancoding which includes some elaborate
  bit error models.

MB



 
> 
> On Sat, Aug 6, 2011 at 6:54 PM, Marcus D. Leech <address@hidden> wrote:
> 
> > **
> > On 08/06/2011 06:27 PM, shantharam balasubramanian wrote:
> >
> > Hi
> > I have been working in usrp2 testbed, and I have been modifying the
> > benchmark_tx and rx programs for my project. There have been situations
> > where I was supposed to introduce noise to find out BER. I did that by
> > giving lower  transmitter amplitude values. But very low values cause packet
> > loss along with higher BER values. I just want to know if there Is there
> > anyway to just cause high BER values, without causing packet loss? Is there
> > any way I can do that inside the program or should I do it by any other way
> > e.g.by using some noise producing source?
> >
> >  Well, in real-world radio communications systems, low-SNR *does* cause
> > packet loss.  That's entirely expected.  Nature doesn't discriminate
> >   between packet-synchronization data, and the actual payload data.
> >
> >
> > --
> > Marcus Leech
> > Principal Investigator
> > Shirleys Bay Radio Astronomy Consortiumhttp://www.sbrac.org
> >
> >
> > _______________________________________________
> > Discuss-gnuradio mailing list
> > address@hidden
> > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
> >
> >
> 
> 
> -- 
> Dan Zeleznikar
> address@hidden
> address@hidden
> (216) 233-6232

> _______________________________________________
> Discuss-gnuradio mailing list
> address@hidden
> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio


-- 
Karlsruhe Institute of Technology (KIT)
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