Re: [Discuss-gnuradio] continuous data collection?

[Eric Blossom]

On Sun, Feb 26, 2006 at 11:23:08AM -0500, Clark Pope wrote:
> I've been collecting snapshots through my DBS and USRP to do DBPSK and 
> DQPSK bit error rate testing. I'm not able to get the BER below about 1e-5. 
> It seems that slips are occuring spontaneously in the data even though no 
> over/underflow is reported during the collection.

What are you using as your input signal?  How's the level/gain?  What
is the avg peak signal level you are seeing from the USRP?  What
decimation rate are you using?  Are you running some kind of symbol
tracking algorithm?

> Questions:
> 1. Has anyone successfully done long term collections without any slips?

Yes.   I've run the gsmk2 code at 500k bit/sec with no FEC and no
errors for many (10's ?) seconds at a time.

> 2. Are the O/U flags sticky?, i.e. if I don't see an under or overflow
> reported then I can be sure the fifos were okay?

You're building from CVS, right?  There was a xrun reporting
problem that was fixed a couple of months ago.

Yes, they are sticky.  They are checked and cleared at about 10 Hz.

> I've done BERs from 1 Mbaud to 11 Mbaud all with the same frequency of 
> slips so it does not appear to be speed related.

Eric