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OFDM reference design v11 does not seem to work in MIMO mode. We have made the changes from SISO to MIMO and synthesized, and it does not seem able to ping. We have also simulated MIMO mode in simulink for this reference design and in the BER calculator it reports 39% errors. With the changes made to OFDM reference design 11, do we need to do more things to switch from SISO to MIMO mode that we did not have to do with reference design 9?
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I haven't tried MIMO mode in v11. It's probably (hopefully) some small configuration detail I missed. I'll dig into it this weekend and post what I find.
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A quick update- I see the same bug in simulation, and have traced it back to some changes I made in the PHY for reference design 11. It definitely breaks MIMO mode. I'm still trying to find the exact source. I'll post again when it's fixed.
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Hi.
Just wondering what is the DATA packet size when you measured this -->DATA-ACK turnaround now 19.8µsec. Also SIFS and DIFS time are much appreciated.
Any news about fixing the MIMO ?
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the 19µsec measurement was for a 1450 byte (nearly full-size) data packet. The turnaround will be longer for short data packets, as the ACK-generation won't be as efficiently pipelined with the payload processing in the PHY.
I'm still (slowly) searching for the MIMO bug. We were preparing for a big demo the last few weeks (we gave it yesterday), so I'll have more time to direct at this now. I'm almost sure it's a mistake I made restructuring the Rx FFT control & timing; I just haven't found exactly where yet.
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I finally found the MIMO bug. It was a control signal in the receiver's post-FFT memory address generator that dropped 1 cycle early. It caused the receiver to ignore the last subcarrier of full-rate symbols from antenna B, which is why it only broke MIMO mode. I'll build a new reference design project and post the URL here soon.
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OFDM reference design v11.1 is posted. I tested MIMO mode over-the-air successfully. See the changelog for more details.
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