Re: [Discuss-gnuradio] Re: Discuss-gnuradio Digest, Vol 65, Issue 45
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 ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[Discuss-gnuradio] Re: Discuss-gnuradio Digest, Vol 65, Issue 45
> 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? 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? Regards. Yaya ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio