Generating noise from USRP

[pradha]

Hi,

I am working on USRP packet transmitter and receiver. I would like to add noise generated from another USRP. 

In total, I am using 3 USRP's, one for transmitter, one for receiver and other for noise generator.  

Is it necessary that I manually add the transmitted signal with the noise? or Can USRP itself add the incoming two signals? 

If I send signal and noise independently, the USRP transmitting data stops responding and gets hanged. Also, only the noise 

is received at the receiver, not the transmitted data. 

Can anyone suggest how to incorporate noise in the transmission? 

Thanks!

[Insiderbe]

Hi pradha, 

It helps a lot if you explain what you're trying to do. (You're trying to simulate real life noise? And with that, still receiving your transmitted signal?)

1) try to lower the gain of your noise transmitting USRP.

2)  there are a variety of noise functions (gaussian noise, uniform white noise, .. ) which you can add to your signal before modulating it that distort your signal..

Is that what you mean?

Grtz

Laurent

[pradha]

Hi Laurent,

Thanks for the reply.

I am working on Jammer implementation. I have a working transmitter-receiver (USRP pair) setup. 

When I generated Gaussian white noise from another USRP (acting as Jammer), the receiver receives

distorted data for some time and then gets hanged. Overflow error at niUSRP Fetch Rx data is shown

after some time.  

I tried different sampling rates and number of samples, which are inputs to Gaussian white noise vi.

The time it takes for the overflow error to occur varies with the sampling rate.  I am not sure what is

happening in the time between USRP stops receiving and the error is thrown.

Any suggestions on how to avoid this error?

Thanks!

[Insiderbe]

Pradha,

That's something completely different 🙂

The overflow errors have a lot to do with the hardware you use, i've had a random overflow problem, occurring at different times, using different IQ rates and sample values......just tried with a different computer and it never happened again (for IQ rates lower than 5M and samples lower than 20 000).

Is the time before error varying lineairly with the IQ rate? Or is it happening at different/random timings?

try using switching the computer you use for your Tx USRP with that of your Rx USRP (or do you use only one?)

Hope i can help

Laurent

[pradha]

Laurent,

I have a PXIe 1082 controller with 4 GB RAM. All the 3 USRPs are connected to the controller. 

The error occurs at random times. If I switch on only the 2 transmitters, there is no error.

When the receiver is also on, the buffer related error occurs. 

Could this be memory related? If I upgrade RAM, can this be resolved?

Thanks!

[Insiderbe]

Hi,

Yes i think it's hardware related, I upgraded from 4GB RAM to 8GB RAM (using other computer) and had no more errors.
Also, I tested the USRP with higher IQ rates on a ubuntu-system withouth any errors.... So it could also be a problem with the fetch setting from the usrp...

I asked the question to NI support too and they think it has something to do with empyting the buffer 😕

Begin with upgrading your RAM, or try to use another computer to test it 😉

greets,
Laurent

[charlybskz]

Hi

I'm doing something similar and what I read is transmitted to the same modulation and frequency of the original transmitter but with more power. Correct me if I'm wrong but if I want to block a cellular signal only I have to convey to 16QAM, 8QAM, QPSK with the same ARFCN BTS