MIMO 4*2 without external clock and PPS

[Wired_]

I am designing 4*2 MIMO using 3 USRPs (TWO for transmitter and 1 for receiver). I dont have access to external clock and pps trigering. I read about using PPS and REF IN/OUT ports at back pannel of USRP. Can I make connections using SMA cable to connect PPS trigger of one USRP(As TX) to PPS in of 1(another 2952 as TX for 4*4) and connect it's PPS out to that of Recever USRP PPS in? Similalry connect clock reference out with IN of other.  Please share architecture of synchroizing multiple USRPs for MIMO design using SMA cable.

[ericthemantis]

Hi Wired_,

The instructions for connecting USRP's for synchronization are included in the USRP Help - http://zone.ni.com/reference/en-XX/help/373380D-01/usrphelp/synchronization/ (This is for the 294x/295x, which is sounds like what you are using). The type of synchronization you are talking about would be Daisy-chaining the USRP's (connecting them directly to eachother). This is currently not supported. You won't be able to connect one USRP directly to another as the outputs are not strong enough to drive multiple triggers and clocks. You will need a timing card or some type of level shifter, as described in this post. Here is another post that would be a good reference, too. You would also need to modify the example code to export the clock from the Master device.

You're really going to need an OctoClock or some other synchronization device/circuitry to synchronize your 3 USRP's. We can see if someone else chimes in here, though.