Question about 4 x 4 MIMO transmitting and receiving

GNU Radio
1

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. And more disappointing, there isn’t any docs and codes about
transmitting with multiple USRPs.

What should be done to make a 4 X 4 MIMO possible with 2 USRPs and 4
rfx2400s?

Thanks :sunglasses:

2

hanwen wrote:

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