Re: [Discuss-gnuradio] [ USRP configuration with/without MIMO in unshared Ethernet mode ]

[Ashish Raste]

I made some refinement to my previous question, as follows, for you to get a better view of my problem:

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 (This is the commonly 
known unshared Ethernet Mode) . I have a host PC which runs the GRC design.
 Now when I set one of the USRPs clock source and time source to MIMO, 
and the other USRP’s clock source and time source to default, I observed
 that both of them were synchronized and believe that one is acting as a
 slave for the Master's clock and time source.. What I'm not able to understand is the baseband data path  between the USRPs and the host PC. That is,
 whether the slave’s baseband date within the GRC design  is 
received/transmitted via its own Ethernet interface  and the master’s 
basedband data within the GRC design is received/transmitted  via its 
own Ethernet interface? So, this means that the MIMO cable is only used 
for  sending the clock and time signals from the Master to the Slave ?

 

Next, I retained the MIMO cable, set the Master USRP’s clock source to external  and have a 10MHz source connected to the Reference input. The slave USRP’s clock source and time source remained as MIMO mode.  So my question is would the Slave USRP received the 10MHz Reference via the MIMO cable  ?

 

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 split to each of the USRP and a PPS source? 

Please not that I'm using USRP N210 for my experiments.

Best Regards,

On Thu, Oct 11, 2012 at 11:53 AM, Ashish Raste <address@hidden> 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?

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? 
Please not that I'm using USRP N210 for my experiments.

Looking forward to your reply.

--
Ashish

-- 
Ashish