CHIN-YA HUANG wrote:
Message: 6
The OFDM system uses fft_length number of subcarriers and
occupied_tones
number of used subcarriers. The used subcarriers are mapped to the
middle of the fft_length subcarriers leaving the same number of
guardband subcarriers on either side. The middle two subcarriers are
also nulled to avoid DC affects.
The mapping is done in gr_ofdm_mapper_bcv.cc. If you want to play with
this, I'd make a copy of this one as a different version of the mapping.
Tom
Thanks Tom.
Do you mean mapping to the fft_length?
No, the fft_length is the total number of subcarriers. Only
occupied_tones number of subcarriers carry data.
But, my questions is when received a packet, I saw the code in
gr_ofdm_mapper_bcv.cc that
the bits in the packet is sequentially to the subcarrier in order, and then do
modulation according to desired constellation. Do I misunderstand anything?
Seems like you got it.
Tom
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