N210 MIMO

[Tarang]

Hello Xavier G.

I am referring to the TX Waveforms input to the subAsyncMulti-ChannelTransceiver(NIUSRP) function. When I try to probe the input/output of that array it gives me a message, stating 'not executed'.

I am thinking that maybe my SubVI files that I downloaded may not be correct. Is it possible to run the examples without the correct SubVI files?

And if you can please provide me the SubVI files as an attachment to your message.

Regards

Tarang

[xavvvv]

Hi Tarang,

I obtained this example from the community example (I believe the same as you), which means all the subVIs are included (here's the link just in case: https://decibel.ni.com/content/docs/DOC-21751)

If your probe says "not executed", this means you haven't reached that function yet. Are you seeing this when you are running the VI? Effectively, we want to check when the waveforms array is "becoming" empty. I would suggest probing that double array from function to function and (when running the VI) looking at what the data looks like (ie. symbols, baseband streams, output transmit packets and transmit packets and Rx waveforms, the output of the function you mentioned). If you do get to that point, perhaps sending in a screenshot of the probe window (along with your block diagram to see where probes are) would be helpful.

[Tarang]

Hello Xavier G.

Thanks for replying. In this message, I have attached a screen shot of the error that I get every time. You can find the probe display as well. The error code is 1074118625. I have also attached the screen shot of the complete block diagram. Along with that I have encircled the blocks where I am getting the errors.

Please tell me what is the problem.

Regards

Tarang Singal

[xavvvv]

Hi Tarang,

he error sounds like the timing of the synchronization (the Rx not being able to lock onto the Tx's symbols) is off. Full disclosure, I've looked around and seen other mentions of this example not working right-away so there might be some amount of tweaking you need to do. For example, changing the "Next Timebase Edge" constant input to "Now" for the second VI in the "Tx and Rx with NI-USRP" box, or modifying the timing of the Tx and Rx (making fractionnal seconds the same, or changing "whole seconds" to zero).

I have also seen this mention on another thread of some Link parameter settings to change (http://forums.ni.com/t5/USRP-Software-Radio/2X2-MIMO-Example-Alamouti-Coding-is-executable-using-two...). I think increasing the symbols per packet would help for locking onto the signal, so you might want to try that as well. Good luck!

[Tarang]

Hello Xavier G.

Thank you for replying. I have tried both the changes that you have mentioned. Changing the timestamp to 'now' and 

changing whole seconds to zero and fractional seconds to same values. Also I looked at the other thread and changed everything like youngmin did in the link parameters block. But like him, I am still getting the same error.

Actually, I am really confused as I am not able to figure out why does the trigger get lost at the receivers.

Thank you.

Regards

Tarang Singal

[xavvvv]

Hi Tarang,

Could you expand the "Per Device" clusters for Rx and Tx and post a screenshot of your front panel settings? From what I can understand, it appears previous versions of this Alamouti example were working (without having the BER measurements however). Could you try that and see if you're able to make this work? For example, here is Version 5: https://decibel.ni.com/content/docs/DOC-21751/version/5

If you are looking for a simple 2x2 MIMO, you might want to also try downsizing a 6x6 (https://decibel.ni.com/content/docs/DOC-23285) or 8x8 (http://www.ni.com/white-paper/14311/en/) example and seeing if you are getting the same type of error. Hope this helps!

[cochenob]

The two error messages "Invalid input symbol array; Input symbol array is empty", and "PLL did not lock in time", might be unrelated.

The first one sounds like you don't have one of the fields set correctly when synthesizing your symbols.  I know sometimes if I try to send the USRP Tx vi's a bogus array of data, I've seen similar error messages.  Usually because I didn't format the array correctly, or it was null.  Make sure you're actually generating the data you think you're generating.

As for the other error...I always find it good practice to set the acquisition trigger to 1 or 2 seconds after whatever you set the system time to (usually 0).

[memooo]

Dear all,

I want to connect two usrp n210 with mimo cable, one usrp for TX and another usrp for RX so how i can do that to get a coherent transceiver with mimo cable

I appreciate your help

Thanks,