Forum: How to burst Data?

786952aca0dddea980adc7729805216f?d=identicon&s=25 Maay Daniel (maaay)
on 2017-01-12 15:36
Attachment: gfsk.PNG (50 KB)
Hi all,
I am new to gnu radio, I did look around at different places at the
internet but did not really find an answer.  I am trying to send data
using a GFSK transmitter in a bursted mode (ie :I need to send the
“Premable +Synchro + L-field + data +CRC” N times per second).
Eventually, my task is to develop a GFSK transmitter based on the
following requirements:

• Preamble : 55 55
• Synchro : F6 72
• L-field ( data + CRC) : 20
• Modulation : GFSK
• Deviation : +/-2,4KHz +0,2%
• Modulation index : 2
• Filter index : 0.5 BT
• Bitrate : 2400 bit/s
• Carrier Frequency : 169.41 Mhz
I have designed a transmitter based on gnu radio as follow

The main blocs are :
•             File source block which contain the data to be
•             GFSK Mod block :I choose the number of samples per symbol
(sps)= 100, I used the following equation to calculate the sensitivity
sensitivity = Pi * modulation Index / sample par symbol and filter index
BT= 0.5
•             Rotational resampler block: the interpolation = samp_rate
* (sps -1) and decimation is equal to my sample_rate
•             And finally a multiply const block that feeds the USRP
sink and Gui FFT and time sinks

I am using gnuradio, USRP X310 with UBX daughterboard and UHD
I have visualized my signal with a spectrum analyzer and It looks good (
I hope that what I did was correct  ).

Now, I am trying to burst my data. In fact, I would like to transmit the
“Premable +Synchro + L-field + data +CRC” N times per second.
I have tried to use the “PDU to stream” bloc and the unpacked to packed
bloc but I was always getting a continuous transmission.
Any hint please on how to make data contained in my file bursted ?

Best regards.
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