Re: [Discuss-gnuradio] Ettus E310 & MIMO -- data rate?

[CEL]

Hi Johannes, Hi Rob,
On Tue, 2019-02-26 at 15:00 +0000, Johannes Demel wrote:
> Hi Rob,
> 
> > (1) I cannot set an arbitrary sampling rate (for instance 9.1428M), but 
> > I am required to set e.g. 4M.
> 
> USRPs, like every hardware, is constraint in terms of available sampling 
> rates. You should stick with power of 2 divides of the master clock 
> rate. Otherwise, the CIC filters on the USRP will corrupt your signal.
> 

While that's true, it's omitting the important point, maybe: The E310
has a very flexible master clock rate. So, from the top of my head,
9.1428 MHz could be possible, but only if you set the MCR to a multiple
of that first.

> > (2) even with small sampling rates (like 2M), and despite a 10MB buffer 
> > in between the USRP source and the ZMQ sink, the system keeps overflowin
> > 
That's not very surprising. The Zynq's architecture makes it very hard
to keep both the USRP sample interface and the network interface afloat
at the same time.

All in all, the E310 has not a great CPU, and what needs to be done
should be done on the E310 until the data rate is really low.

This might imply that multi-MHz bandwidth applications need FPGA
design.

Best regards,
Marcus

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