Trellis encoder and OFDM modulator

GNU Radio
1

Hi,

I tried to use trellis_encoder from trellis package to perform
convolution coding before sending the message to the OFDM modulator.
However, ofdm_mod has zero input signature, and relies on send_pkt()
which calls ofdm_packet_utils.make_packet() and then puts the message
in the queue at gr.ofdm_mapper_bcv. Since the chain basically starts
with ofdm_mod I don’t see the way to connect the trellis_encoder
before the signal is already modulated. In ftw80211 project they
modify ofdm_packet_utils and write their own convolution coding
method, I could do the same, but then I would miss all the benefits of
this nice trellis package.

Interestingly, the other modulation blocks such as dbpsk or d8psk have
different input signatures, and I would put the trellis_encoder
between the gr.message_source and modulator in pkt.py. Is there a way
to seamlessly introduce trellis_encoder in the flow graph with an OFDM
modulator? Am I missing something here?

Thanks,

Veljko

2

Did you solve it?

I am trying to add FEC in the OFDM chain but I didn’t figure out how to
do
this, yet.

Any advice or do you know if someone did it and the code is public?

Thanks

Veljko P. wrote:

modify ofdm_packet_utils and write their own convolution coding
Thanks,

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3

Hi

I was also looking around the OFDM Modulation recently. Found this nice
project here: How to build and run RawOFDM?
where ofdm mod and channel est are done separately. I didn’t had the
time to follow ths more…perhaps it helps.

best, friederike

4

thanks

Vanessa

On Tue, Jan 31, 2012 at 12:21 PM, Friederike Maier
[email protected] wrote:

method, I could do the same, but then I would miss all the benefits of

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