Re: [Discuss-gnuradio] a question to make sure Tx and Rx start times w.r.t. each other

[Josh Blum]

On 09/21/2012 10:06 AM, abdullah unutmaz wrote:
> Hi everybody,
>  
> I have been trying to design a ionosonde with USRPs in my final year project.
> I am responsible for the signal processing part of the project. I will have 
> been
> using USRP1 untill hardware part, that is amplifier and antennas, is set up.
> I have been using another USRP1 & a PC to model an HF channel, and processing
> the delayed signal in my own PC. As far as I see in web site of Ettus 
> Research,
> http://files.ettus.com/uhd_docs/manual/html/usrp1.html , and several similar
> projects completed USRP2s are better to use for such a purpose.
>  
> In processing of the received signal, the peak of the result of the 
> x-correlation
> must not even be different from the its actual instant as three micro seconds.
> That is why, I need to make sure if Tx and Rx starts working at the same 
> instant
> and perfectly synchronized, in other words , if they perform parallelly at 
> all?
>  

In this link you can find an explanation of the stream tags used by the
USRP source and sink block and a demo application.

http://code.ettus.com/redmine/ettus/projects/uhd/wiki/GNU_Radio_UHD#Using-UHD-with-GNU-Radio

You can use stream tags to precisely time the transmission of samples
and to know precisely the time of received samples. The timing of
streams will require something more recent than USRP1

-josh