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Re: [Discuss-gnuradio] tx_ofdm.grc & rx_ofdm.grc output data


From: eontool
Subject: Re: [Discuss-gnuradio] tx_ofdm.grc & rx_ofdm.grc output data
Date: Thu, 24 Oct 2013 18:00:23 -0700 (PDT)

Hello again.

OK, so now after changing a few things it finally works, I get the expected
data correctly at the output.

Apparently it works automatically for BPSK Modulation on both header and
payload because the arguments on these variables are equal to "1". But, in
order to work for QPSK o QAM you need to add the variables to the
"header_formatter" and to the project itself.

Issues I found:

Change the "header_formatter" to:
digital.packet_header_ofdm(occupied_carriers, 1, "packet_len", "frame_len",
"", bps_header, bps_payload)
 
Add the corresponding variables:
bps_header = header_mod.bits_per_symbol()
bps_payload = payload_mod.bits_per_symbol()

Change the argument on the OFDM Frame Equalizer to:
digital.ofdm_equalizer_simpledfe(fft_len, *payload_mod.base()*,
occupied_carriers, pilot_carriers, pilot_symbols, 2).base()

Add "1" skip symbol to the Payload Serializer block.

Add a Repack block just before de CRC on the tx part.
Bits per input byte: payload_mod.bits_per_symbol()
Bits per output byte: 8

Change the GRG Block on the rx side from "generate" to "check".
 
If you want QPSK for the header or QAM on the payload, try changing the "80"
delay to "72" or "84".

That should do it, it works for BPSK, QPSK and 16QAM. I'm uploading the grc
file anyway.

ofdm_txrx_full.grc
<http://gnuradio.4.n7.nabble.com/file/n44374/ofdm_txrx_full.grc>  

Thanks for the help.



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