Re: B2xx round trip delay

[Marcus D. Leech]

On 13/08/2023 00:36, Ali G. Dezfuli wrote:
> Hi all,
> I'd like to measure the round-trip delay (RTD) between two B200 USRPs. 
> For that, I send a raised-cosined-filtered, BPSK modulated 
> PN-sequence, and as soon as
> I get this signal at the receiver, send back the same sequence from 
> the Rx to the Tx, and by correlation, I find the RTD.
> The question is that the measured RTD is not fixed. I wonder how can I 
> make it fixed when the distance between the two USRPs is fixed.
> After that (A -> B -> A) I want to do that in reverse order (B -> A -> 
> B) and expect to have the same RTD.
> Thanks
In your scenario, the latency will necessarily be variable--after all 
your samples are entering a computer program where those
  samples are processed and then sent back in the other direction. 
Since computer software on a general-purpose operating
  system cannot have fixed latency at fine-grained levels, this is 
completely expected.

This document may help:

https://kb.ettus.com/Synchronizing_USRP_Events_Using_Timed_Commands_in_UHD