Re: [Discuss-gnuradio] Question about 4 x 4 MIMO transmitting and receiving

[Martin Dvh]

hanwen wrote:
> Hi, my friends.
> 
> Our 2 x 2 MIMO-OFDM system is nearly acomplished. I'm glad to share some
> details about it later.
> Now I'm starting to working on a 4 x 4 one. Of course it'll needs two clock
> locked USRP , 4 tx db and 4 rx db. We're using rfx2400.
> 
>> From the wiki (http://gnuradio.org/trac/wiki/MultiUsrp) I saw how to
>> archive
> 
> clock sync and phase coherent between multiple USRPs and dbs. However,
> according to the instruction, I found there isn't something called J25 on
> rfx2400.
The required pins are somewhere on the one of the two headers on the RFX2400 
(J24 or J101).
You could check in the schematics or documentation which pins on these headers 
correspond to the right pins on J25 of basicRX.

> And more disappointing, there isn't any docs and codes about
> transmitting with multiple USRPs.
This is because it is not implemented yet.

> 
> What should be done to make a 4 X 4 MIMO possible with 2 USRPs and 4
> rfx2400s?
Implementing this becomes much easier when the new inband signaling is 
completed.
As soon as the in-band signaling is working for the usrp, work will probably 
start on MIMO transmit.

A complete synchronisation chain should be build for gr-usrp, usrp driver, fx2 
firmware, fpga firmware verilog code.

Greetings,
Martin
> 
> Thanks 8-)
> 
> 
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