How to burst Data?

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.

In telecommunication, a burst transmission or data burst is the
broadcast of a relatively high-bandwidth transmission over a short
period.Burst transmission can be intentional, broadcasting a compressed
message at a very high data signaling rate within a very short
transmission time. This technique is popular with the military and
spies, who both wish to minimize the chance of their radio transmissions
being detected, a low probability of intercept (LPI) and low probability
of recognition.

Data bursts can occur naturally, such as when the download of data from
the internet briefly experiences higher speeds. It can also occur in a
computer network where data transmission is interrupted at intervals.
Burst transmission enables communications between data terminal
equipment and a data network operating at dissimilar data signaling