GSM complex waveform

[madd]

Hello

I have found this GSM demodulator. but how to aquire the complex waveform from aqusition(i have RFSA,modulation and spectral measurement tool kits, 5600 and 5142) i have no idea . any one who can guide me i have encircle the point on the figure i have attached.or some who can ammend this given demodulator so that i can demodulate single short or continous aquired signal.

Regards

Madd

[Andy_Hinde]

Hello Madd,
The demodulator code in the image you attached actually includes the acquisition code already.

It is the NI-RFSA IQ Acquisitio0n Express VI block at the top left corner of the block diagram in your image. It is circled in the Acquisition section.

the Express VI allows the settings to be configured interactively and stored internally, which is why there are no controls or wires flowing into it. If you double click on it, it will pop up the settings, which I assume are already set for acquiring a GSM signal with the PXI-5661.

Regards,
Andy Hinde
National Instruments

[madd]

Hello

Tnx 4 ur kind reply but the vi u have mentioned i have it. Nither it has output terminal nor input on the other hand while watching in the help of this vi both inputs and outputs are there i have attached the vi picture.

Regards

Madd

[Andy_Hinde]

Hi Madd,
Trying deleting the NI-RFSA Express VI and dropping a new one from the LabVIEW functions pallette, in the NI-RFSA subpallette.

It should pop of a config window and then create an output containing IQ data.

Use the Modulation Toolkit example MT niRFSA MSK Trellis Diagram.vi located at:

C:\Program Files\National Instruments\LabVIEW 8.6\examples\Modulation\niRFSA examples

to provide you with the GSM symbol rate and filter/filter parameter values. The block diagram of this VI also shows how to calculate the PXI_5661 IQ Rate from these values.

You could also cut the NI-RFSA code from this example and use it in place of the RFSA Express VI.

Regards,
Andy Hinde
National Instruments

[madd]

Hello

 i have a question regarding GSM demodulation as a continuty of above posts when i demodulate the the GSM signal constillation plot is not correct which means demodulator is not demodulating the signal correctly i am here attaching my constillation plot ,my vi snap and signal spectrum that i have acquired any thing u can suggest to get it demodulated correctly.

 Also could u plz tell me is there any requirement of carrier and timing recovery in GSM demodulation

Regards

[The_Red_Barron]

Hi Madd,

What are the configuration settings for the NI-RFSA Express (IQ) Vi?

Regards,

[madd]

Hello

Here are the setting. Also i would like to state that i have demodulated the same frequency by using RFSA Record and playback VI's abvilable on NI support.where i have recorded the same signal and then using the Playback vi of RFSA Record and playback i have just put my GMSK demod where i am playingback it in time domain which means the input is IQ Complex waveform.So except the RFSA Express Vi rest of the code is same

Regards

[The_Red_Barron]

Have you tried using a larger filter parameter for the Generate Filter Coefficients VI?  Try using something like 0.8 rather than 0.3 to make the filter tighter.

Also, since you are working with GSM modulation, you might consider the GSM/EDGE Measurement Suite.

Regards,