[USRP-users] revc and missing samples

Martin Braun martin.braun at ettus.com
Wed Jul 15 15:01:41 EDT 2015


On 15.07.2015 08:50, Crozzoli Maurizio via USRP-users wrote:
> One more question (sorry, but I (almost) am new in the world of SDR).
> 
> With reference to B210 and E310, when I use the recv function to acquire
> received data for LTE signals, can I physically receive all the date in
> time window or I might run the risk to lose some samples because the HW
> RF FE is too fast with respect to the capabilities of the HW devoted to
> handling received data and at least save them to memory (first, then to
> file).
> 
> If the generic answer were yes, in which time window (under a reasonable
> set of assumptions in terms of sampling frequency, bit per sample, …).

recv() may fail if your process is too slow. What happens is that the
buffers on the device fill up, and the device will tell you it had an
overrun (or sometimes we call it overflow). You can easily reproduce
this behaviour by simply not calling recv() after issuing a stream
command, and you will see lots of "O"s on your console -- that's UHD's
way of telling you there was an overrun.

The buffers are not very large on the device. So say you're running at 1
Msps, and you want to receive 1000 samples, that's 1 ms worth of data.
So when you receive 1000 samples, you have to re-call recv() within
about 1 ms.

M




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