[Discuss-gnuradio] Usage of header/Payload demux in OFDM transceiver

[Simran Kaur]

Hello all,

I am trying to simulate OFDM transceiver. I am not using any synchronize as I am not using an channel model to simulate the effects of a channel. After connecting OFDM cyclic prefixer to Header/Payload Demux, it is not giving me any output in Tag_debug. Attached is the .grc file which I am using. 

I have a number of queries regarding the blocks that I used.

1) How to determine the header length(in symbols) which we provide in Header/Payload Demux?

2) I have added Tag_debug after modulation and after CP addition given number of samples = 100 and packet_len = 10. According to the code,

     symbols_to_read = 4 (this is the output of OFDM carrier allocator)

     d_output_size = 80

     therefore, output of the CP block = 3 * 80 = 320

   My query is, how is the symbols_to_read is calculated? (pictures attached)

3) Why don't we use OFDM channel estimation with the payload data before OFDM frame equalizer because that's what we do with header data.

Can anyone help with this?

Best,

Simran Kaur

After_OFDM_CA.png
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After_mod.png
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Sample.grc
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