Setting up a simple packet radio in 3.7.7.2

GNU Radio
1

Hello,

I am trying to get a simple packet radio GRC working but so far have had
no luck with the following scheme:

tcp-source (port 9000) -> packet encoder -> gmsk mod -> gmsk demod ->
packet decoder -> tcp-sink (port 9001)

If I remove the encoder/decoder and the gmsk mod/demod and go directly
between the ports, then I am able to clearly see everything (I am using
two terminals, one for tcp source and one for tcp sink). If I add back
in the gmsk mod/demod I see stuff in my other terminal window (although
it is garbled). Once I add the packet encoder nothing gets through
again.

I’ve been trying to follow some examples of this done in the past, but
they were with much older versions of GNU radio and some of them used
GR-extras which is no longer supported in GnuRadio 3.7.

Any help would be greatly appreciated.

Thanks!

Priyank Patel

2

Hi Priyank,

The packet decoder is checking for a preamble sequence in the data
stream.
If there is no output coming from the decoder the preamble is probably
not being detected.
How does the output of the gmsk demod look like?
Also, are you transmitting the signal or are you just simulating
locally?

Cheers,
Julian

3

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[email protected]
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio

4

Hi Julian,

Thanks for responding so quickly! I’ve attached a picture of the
current setup (if it gets through). I’ve tried looking at the output of
the encoder and am seeing nothing come out of it and so there is no
signal from that point on (through the gmsk mod->gmsk
demod->decoder->tcp-sink). Is there something I need to do for the
terminal messages I am sending through the tcp-source in order for the
encoder block to properly process it?

I am currently just simulating it locally by going directly between the
gmsk-mod->gmsk-demod as I wanted to make sure everything goes through
before I add in the USRPs.

Thanks,

Priyank

From: [email protected] [email protected]
Sent: Monday, August 24, 2015 3:16 PM
To: Patel, Priyank
Cc: [email protected]
Subject: Re: [Discuss-gnuradio] Setting up a simple packet radio in
3.7.7.2

Hi Priyank,

The packet decoder is checking for a preamble sequence in the data
stream.
If there is no output coming from the decoder the preamble is probably
not being detected.
How does the output of the gmsk demod look like?
Also, are you transmitting the signal or are you just simulating
locally?

Cheers,
Julian

Am 24.08.2015 um 21:05 schrieb Patel, Priyank
<[email protected]mailto:[email protected]>:

Hello,

I am trying to get a simple packet radio GRC working but so far have had
no luck with the following scheme:

tcp-source (port 9000) → packet encoder → gmsk mod → gmsk demod →
packet decoder → tcp-sink (port 9001)

If I remove the encoder/decoder and the gmsk mod/demod and go directly
between the ports, then I am able to clearly see everything (I am using
two terminals, one for tcp source and one for tcp sink). If I add back
in the gmsk mod/demod I see stuff in my other terminal window (although
it is garbled). Once I add the packet encoder nothing gets through
again.

I’ve been trying to follow some examples of this done in the past, but
they were with much older versions of GNU radio and some of them used
GR-extras which is no longer supported in GnuRadio 3.7.

Any help would be greatly appreciated.

Thanks!

Priyank Patel

5

Discuss-gnuradio mailing list
[email protected]
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio

6

Discuss-gnuradio mailing list
[email protected]
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio