1

I am working on a project to transmit and receive the binary data by using QPSK modulation and demodulation technique on GNURadio via SDR (BladeRFx40). Here is the sketch of the task to be implemented.

The flow graph is simple and workable when the intent is not to use bladeRF or is solely to modulate and demodulate binary data as the image shows But problem arises when using osmocom source and sink (i.e. QPSK transceiver via BladeRFx40).

Few Important Questions and Problems Regarding the Working:

  1. On the receiver side, the osmocom source(or the received signal) when tested directly using FFT plot gives no signal. How can this be made to work successfully?

  2. Theoretically, QPSK modulation is mapping plus up-conversion, but in GNURadio, QPSK Mod block only shows mapping but no up-conversion, does the purpose of up-conversion is fulfilled itself when osmocom sink block is used(since it shows frequency at which signal is to be transmitted)? Or the up-conversion is done separately by multiplying QPSK Mod Block output with sinosoid along with osmocom sink block? Precisely how is up-conversion done on GNURadio for such a task?

  3. If only i do modulation and demodulation without transmitting and receiving on SDR platform, then i must up-convert and down-convert it separately according to my understanding. Even then, i am unable to get the binary data: here is the attachment for it too, Kindly rectify me for any misplacement or misuse of the blocks and recommend for any changes needed in the flow graph of image.

Andronicus
  • 25,419
  • 17
  • 47
  • 88
Khan
  • 23
  • 1
  • 7

1 Answers1

0

I recommend that you visit the following link (if you have not seen it yet). When we talk about digital modulations, and these are transmitted / received by a USRP, HackRF, etc., the recovery of the signal is not as easy as in FM or AM. I do not fully understand your question because I just entered the world of SDR, but in the sdr sinks (UHD or OSMOCON) is where the RF frequency is configured (M / GHz).

If you want to simulate the TX / RX process, you do not need to configure the RF frequency because it will not transmit this signal to the air. You will be working in Baseband

Alvaro Segura
  • 1
  • 1
  • This should probably be a comment as it does not seem to answer the questions, even though it may contain useful information. – ophychius Apr 12 '19 at 08:26