2X2 MIMO Example(Alamouti Coding) is executable using two 2920's?

[youngmin]

Hi,

I'm trying to execute 2X2 MIMO example with two NI 2920's.

H/W configuration is two 2920's with IP of 192.168.10.2 and 192.168.10.3. Those are connected with MIMO cable. And 192.168.10.2 is connected to a Host PC(192.168.10.1).

Firewall is unset, OS is Win7.

Using 4 2920 accessory antenna and separated RX antennas from Tx antennas using SMA cables.

The parameters are set as below.

But I'm getting errors such as "stream command was issued in the past." and "Packet had timestamp that was late (or too early)." in Write/Fetch APIs.

I also tried to change trigger time and channel list option of Write/Fetch APIs, but still getting same errors.

Is it possible executing 2X2 MIMO example(Alamouti coding) using two 2920's?

Thanks.

Regards,

YoungMin 

[ErikL]

Please set the first usrp to use the internal clock and second to use the mimo cable for both 10Mhz and Timebase.

Secondly on the string input at the top of the VI that resets the Timebase to zero, it should have a 0 in it. This will reset the time only on the device using the internal clock reference.

[youngmin]

Hi Erik,

Checked first USRP is using internal reference and Timebase clock as well as second USRP is using mimo option.

But what do you mean by "Secondly on the string input at the top of the VI that resets the Timebase to zero, it should have a 0 in it"?

Can you describe or capture an image for your comment?

Thanks.

Regards,

YoungMin

[sshearman]

He means the two string fields in the Start Trigger Time cluster. The Transmitter needs to start just after the receiver and you may need to tune the time a bit to get the capture window to acquire the whole frame.

[ggnii]

Hi. 

I try that on the string input at the top of the VI that resets the Timebase to zero.

but I cannot execute.

Can you give me comment about this problem?

Best regards

MinKeun

[pixus]

Hi,

You cannot set MIMO 2x2 with only 2 USPRs. Whit that configuration you can set SISO and SIMO systems, but not MIMO and MISO.

Best regards

 Pixus

[youngmin]

Hi pixus,

As NI USRP 2920 is able to generate and receive data simultaneously, 2X2 configuration is OK with just 2 2920's.

But NI USRP 2921 can't.

And I already made it work! 🙂

Thanks for your comment.

Regards,

YoungMin

[pixus]

Hi,

What did you do to made it work? I just connect 2 NI USRPs 2920 in MIMO 2x2 with alamouti coding and it doesn't work.

error: A stream command was issued in the past...

What can i do to solve it?

Thanks

Pixus 

[pixus]

Hi youngmin,

Do you want to share with us what did you do to solve the problem? 🙂

Thanks,

[youngmin]

Hi pixus,

Sure.

Refer to the below picture about what I did.

First, I set USRP parameters like this. Hardware connection was made through MIMO Cable and 192.168.10.2 USRP was connected to TCP/IP Hub.

Next, I changed timing parameter to "Now" on Main VI.

Finally, also changed channel list option of Fetch API to "0,0" and "1,1"

Hope this works for your trial.

Regards,

YoungMin