Spatial Multiplexing using 2 USRP pairs

[Dor_Afriat]

Hello,

I have two pairs of USRP 2920, 2 MIMO cables and 4 antennas. I want to create a simulation of Spatial Multiplexing. Is it possible to transmit from two USRPs connected by a MIMO cable to a third USRP, without using external PPS in signal or REF clock of any kind? All 3 USRPs will be connected to my PC with a switch. From my previous work of Alamouti scheme, I figured that it is not always possible to synchronize two USRPs to a third one without extra hardware.

Was there any example posted about SM? couldn't find any.

In another topic, is there any working example to a simulation of LTE system or WIFI to the USRP 2920?

Thank you in advance,

Dor

[ErikL]

Sure, but typically you need to sync the two transmitters in a MIMO system sync the frequencies (prevent frequency offset) and sync the sample clocks.  

http://www.ni.com/white-paper/14311/en/

[Dor_Afriat]

Thank you for the fast replay.

Does it mean I need to buy external hardware to connect to the USRPs?