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Re: [Discuss-gnuradio] [ USRP configuration with/without MIMO in unshare


From: Josh Blum
Subject: Re: [Discuss-gnuradio] [ USRP configuration with/without MIMO in unshared Ethernet mode ]
Date: Wed, 10 Oct 2012 21:17:52 -0700
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120912 Thunderbird/15.0.1


On 10/10/2012 08:53 PM, Ashish Raste wrote:
> *Hi all,
> 
> Recently, I tried testing how the data flows from one USRP to another in a
> 2x2 setup. My configurations went as follows:
> 
> 2 USRPs were connected via a MIMO. Each USRP was connected to an Ethernet
> cable and so both of them were in two different subnets. Now when I set one
> of the USRPs clock source and time source to MIMO, I observed that both of
> them were synchronized and believe that its acting as a slave for the
> Master's clock and time source.
> What I'm not able to understand is whether the slave is receiving its data
> via the MIMO (from the Master) or via its own RF input i.e whether . I
> thought that modulating the RF input to both the USRPs would show some
> difference on the FFT plot but both were identical. Could any one please
> tell me how the data flow occurs by suggesting a good test case?

If both usrps are attached to an ethernet cable, the data does not
travel over the mimo cable.

If only one usrp is attached to an ethernet cable, the mimo cable acts
like a network switch.

> 
> My second question is:
> In a 4X4 USRP setup, how can we synchronize all the 4 USRPs without a MIMO
> connection (between 2 USRPs within a pair), using a 10MHz reference given
> to each of the USRP and a PPS source?

You will want to share a 10MHz ref and PPS signal to the two master
devices. The other two devices in the configuration can get reference
and time, each from a mimo cable.

http://files.ettus.com/uhd_docs/manual/html/sync.html

CHeers,

-josh

> Please not that I'm using USRP N210 for my experiments.
> 
> Looking forward to your reply.
> *
> 
> 
> 
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