How to transmit data using GFSK modulation?

Question

I am new to this domain. I want to transmit data using GFSK modulation using GNU Radio which response to the following specifications :

• Deviation : +/-2,4 kHz +0,2%
• Modulation index : 2
• Filter index : 0.5 BT
• Bitrate : 2400 bit/s

I want to transmit this data (data is in HEXA): Preamble : 55 55

• Synchro : F6 72
• L-field ( data + CRC) : 20

Answer 1

I have based on this example of FSK transmitter, https://nccgroup.github.io/RFTM/fsk_transmitter.html so you need juste to put the value of BT equal to 0.5 to make a GFSK transmitter. And everthing works correctely.

Answer 2

Please start with the gr-digital (part of GNU Radio dist) GFSK Mod block. Take a peek at the source python, and then you'll want to look at the gr-analog frequency_modulation.h source for details about FM, specifically frequency deviation. For some reason, the doxygen output does not generate the embedded formula, which is why looking at the header file is suggested.

Then I suggest you do some simple experiments in GNU Radio Companion to better understand the GFSK Mod block.

Hope this helps.