GSM data acquisition using NI USB 6221

[tyr0ne]

Hi Folks

This is my first post at NI and I just acquired LabView for my NI USB 6221. Now my area of research is GSM data modulation, acquisition and analysis. I haven't seen much traction along this area and I was wondering if anyone would have done something similar.

Thanks

[mudson]

Hello Tyr0ne,

Are you using some kind of upconverter and downconverter for this setup?  The 6221 on its own won't likely generate or discriminate signals that would be useful for GSM.

The 6221 is typically seen as a more general Multifunction DAQ device.  

NI does have a GSM\Edge Toolkit, but you would probably need to be working with our RF-specific hardware to make use of it.

Here is a white-paper that covers GSM testing with NI products.  At the bottom of the document you will find links to compatible hardware.

Here is another white-paper, only this one is geared towards more generic RF applications.

Finally, here is a some example code posted up on the NI Developer's Community that generates GSM using RFSG.

Hopefully these links will get you started in the right direction.

Best regards.

[tyr0ne]

Thank you very much Matthew. Your revert is highly appreciated.

Actually I have both upconverter and downconverter for the task. The challenge with this is that the boards aren't detected by the DAQ board. However, I reckon there is a solution to this via Labview and since I'm new to this, It is exciting to know how I can proceed.

Thanks

[mudson]

Hello Tyr0ne,

Tell me more about your setup.  What is the make/model of the upconverter and downconverter you're using?  

Can you describe what you mean by, "the boards aren't detected by the DAQ board"?  What is the expected behavior, and what is it that you are seeing?  Generally, Multifunction DAQ devices don't do anything more complex than generating and receiving signals.

Best regards,

[tyr0ne]

Thanks Matthew.

Here are the boards I have in my setup. (Attached). Ideally the set up is akin to having a USRP with its FPGA board and a WBX board which will perform analog reception and digital processing is carried out by whatever software radio you are running. In my case, I have the DAQ board which came with the 2 converters connecting to it. My hypothesis so far is that the DAQ will recieve the signals, the converters determine if its the up or down conversion. Unfortunately I got the additional boards without much documentation and it has been difficult to get any documentation so Im working blindly. However, every connector to the DAQ fits in properly.

Thanks for your time

[mudson]

Hello Tyr0ne,

It looks like you have the insides of this 6221, so if nothing else, you should be able to breakout your intended signals through the screw terminals.  

Where did you get those other boards?  That would be the first place I'd check for documentation.  Without knowing much more about your Upconverter and Downconverter, we're going to have a difficult time making any progress.  With the USRP (and other RF equipment), we have to do things like setting the Carrier Frequency, Modulation and IQ rate.  I cannot imagine how one would go about guessing their way into programming undocumented RF equipment to make those calls.

Best regards.

[tyr0ne]

Hi Matthew. 

How have you been? Been a while since I visited this thread and you were right. I tried working with the other boards in vain since they had no circuit diagram or documentation and I have finally given up.

Now my question is with the USB 6221 board already in place, and after having successfully done basic calibration and measurement to verify it is working well, how do I proceed with the following?

- Does NI have additional Upconverters and Downconverters for the purposes of building a GSM signal measurement device? Also, the capabilities must be along the lines of having very high signal processing capabilities

- From the pointers you provided, the sample code seems to "generate" sample GSM data as opposed to intercepting simulated GSM signals. 

My objective is as follows. I have a GSM environment in a controlled environment (Faraday cage and all) and I have an ongoing research on GSM security which involves interception, decryption and replay of the data intercepted. I have done this with the USRP but its not scalable in terms of processing capabilities. That's why after doing my research I came across the USB 6221 which fitted my bill. However, as I mention earlier, i needed converters for both upstream and downstream and that's where I got the "unknown" boards.

I will highly appreciate any pointers.

Thanks

-tyrus

[mudson]

Hello Tyrus,

I am not certain if the 6221 will accomplish what you need it to, if you are working with GSM.  A single GSM channel occupies 200kHz of bandwidth, so even once we've got the signal downconverted to baseband, the 250kS/s maximum sampling rate of the 6221 will not be able to accurately capture the signal (Nyquist rears his ugly head here).

We do have the NI Modulation Toolkit (capable of encoding/decoding GMSK), and a GSM/Edge Measurement Suite.  Both of these software suites are compatible with the 5661, 5663E,and 5665 - which are typically the vector signal analyzers used by our customers in mobile/cellular test.  Our customers doing more sigint-related work typically turn to the 5667, 5644R, or 5645R.  The 5667 has a tuneable pre-selector, while the 5644R and 5645R have user programmable FPGAs (allowing for reconfigurable DSP in hardware).

Except for the 44R and 45R, our RF tools are comprised of multiple individual modules - but these modules are not sold individually.  So even though the 5661 has a downconverter (NI-5600), the 5600 is not available for stand-alone purchase.

That's all a long way of saying:  yes, we do have downconverters that will work with GSM signals, but one cannot be had for purchase on its own.

Normally this is where I would recommend the USRP.  It is a flexible, low-cost option for doing RF work, and it can make use of our Modulation Toolkit as well as our Spectral Measurements Toolkit.
What kind of processing were you doing on-board on the USRP?  A typical application would use the USRP to bring the data back to the host PC, and process it in Windows.

Best regards

[tyr0ne]

Hi Matthew

Been a while. Now, so good news, after slaving away with the USB 6221, we finally decided to acquire the PXIe-1082 along with the 

PXIe-8135, PXIe-5663/5663e vector signal analyzer. 

As far as the correct hardware is concerned, I believe we are on the right track. The only thing that was missing was an antennae specifically for receiving GSM signals. So my question was, will any antennae serve the purpose?

Thanks and good day.

[mudson]

Hello tyr0ne,

If your DUT has an SMA interface, a cabled connection will give you the cleanest read on your signal.  Otherwise, I would recommend a half or quarter-wave antenna.  Getting an antenna that will meet your needs should be pretty straightforward (but designing one is generally not, there are entire courses dedicated to antenna design).
GSM operates at about 900MHz, I believe.  So  with lambda = v/f,  we're looking at (3x10^8m/s)/(900(s^-1)) which puts lambda at about 0.333 m.  Appropriate antennae should be around 16.65cm or 8.325cm.  

All of that being said, a more generic product search for GSM Antenna should return products that will work.  Just make sure the antenna has the appropriate SMA connector.

Best regards