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Re: [Discuss-gnuradio] trellis encoder and OFDM modulator

From: Vanessa Gardellin
Subject: Re: [Discuss-gnuradio] trellis encoder and OFDM modulator
Date: Thu, 2 Feb 2012 09:34:13 +0100



On Tue, Jan 31, 2012 at 12:21 PM, Friederike Maier
<address@hidden> wrote:
> Hi
> I was also looking around the OFDM Modulation recently. Found this nice
> project here: http://people.csail.mit.edu/szym/rawofdm/README.html
> where ofdm mod and channel est are done separately. I didn't had the
> time to follow ths more...perhaps it helps.
> best, friederike
> On 01/20/2012 02:38 PM, vanITA1082 wrote:
>> 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 Pejovic wrote:
>>> 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
>>> _______________________________________________
>>> Discuss-gnuradio mailing list
>>> address@hidden
>>> http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
> _______________________________________________
> Discuss-gnuradio mailing list
> address@hidden
> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio

Vanessa GARDELLIN, Ph.D.
Institute for Informatics and Telematics (IIT),
Italian National Research Council (CNR)
Via G. Moruzzi 1
56124 Pisa - ITALY
Phone: +390503158297
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E-mail: address@hidden
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