Re: [Discuss-gnuradio] question on sample rate and ethernet rate

[Marcus D. Leech]

On 04/24/2019 10:05 PM, Achilleas Anastasopoulos wrote:
> Hi all,
>
> I am trying to figure out what I am doing/thinking wrong in the 
> following example:
>
> I have a simple flowgraph with a complex source sending samples to USRP.
> The sample rate is fs=200e6/32=6.25 Msps which is the parameter that I 
> set in the USRP.
>
> I assume that this parameter will result in fs x 8 =  50 MBytes/sec 
> transmission
> over the ethernet (2 complex samples and float32 (4 bytes) each. This 
> is the format that I have set in USRP).
>
> However, when I observe the transmission rate on the system monitor 
> (Ubuntu Linux) it reports a sustained rate of exactly half of it, ie, 
> 25 MBytes/sec.
>
> I cannot figure out what I am doing wrong and I get this factor of 2 
> mismatch.
> All the above is run in an ubuntu box with gnuradio maint-3.7 
> installed and uhd 3.14.0
>
> thanks in advance for any explanation,
> Achilleas
The over-the-wire format is 16-bits I, 16-bits Q.  There is no 
floating-point over-the-wire.