2x2 MIMO Instructions

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DrizztVD
Posts: 2
Joined: Fri Jul 18, 2014 8:28 am

2x2 MIMO Instructions

Post by DrizztVD »

I have two BladeRF boards that I need to implement an interferometry test platform on. I've been looking around the web and can't seem to find a latest update on the MIMO functionality. I just know I have to connect the boards with an SMB cable, but more than that I don't know. What's the detail on the implementation and how do I test that it's working properly? Phase accuracy is rather important for interferometry.
robert.ghilduta
Posts: 156
Joined: Thu Feb 28, 2013 11:14 pm

Re: 2x2 MIMO Instructions

Post by robert.ghilduta »

The SMB cable will give you the ability to synchronize sampling times. `bladeRF-cli -i` can be used to set
mimo clk master - run this to make the radio drive the SMB port
mimo clk slave - run this to make the SMB turn into a clock reference

As for phase alignment, each of the RX and TX chains have their own PLLs which adds an unknown phase component to each. To figure out the unknown phase you can turn one of the TX chains into a pseuderandom noise generator within the bandwidth of your RX chains. You will then be able to compute the phase difference between the transmitter's PLL and each RX chain, which in turn can be used to calculate the RX PLLs's phase to one another.
DrizztVD
Posts: 2
Joined: Fri Jul 18, 2014 8:28 am

Re: 2x2 MIMO Instructions

Post by DrizztVD »

I've attempted to receive two simultaneous streams from the bladeRF, there are some issues :/ The mimo command seems to be doing something. The biggest problem is that the time streams between the two bladeRFs are very far out of alignment. There's about a 0.2 second difference in the output streams. Is there any way to get the bladeRFs to output their streams from the same sampling instant at the same time? I've tried the code at GitHub :Synchronized Tx/Rx of multiple bladeRFs for MIMO using Mini Expansion Header #221 but that also isn't working for me.
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