If you change the FFT size, the allocated carriers do not change. Hence, you'll be using a much smaller fraction of your bandwidth. This is by design. As you point out, if you want to occupy more carriers, you have to modify 'Occupied Carriers'.
Cheers, M On 11/30/2016 09:49 AM, maiconkis...@gmail.com wrote: > Hi list, > > I’m messing around with the OFDM Transmitter/Receiver provided by > GNURadio to test different configurations (basically I want to increase > the throughput, buts thats not the topic of this mail). > > So, I used the basic ofdm/ofdm_loopback.grc example. > > First, I run the example with a FFT size of 64 points (parameter fft_len > in the .grc file). What I have notice is that with this configuration > almost the entire bandwidth of the signal is used by the FFT carriers > (see the file fft_64_spectrum.png for a screenshot) > Afterwards, I changed the FFT size to 256. For my surprise, the > bandwidth used by the FFT reduced significantly (see > fft_256_spectrum.png for a screeshot)? > > > Do anyone know how to solve this? I think that there may have to > perform some additional configuration in the “Occupied Carriers” of the > OFDM Transmitter/Receiver block. > > Best Regards > > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
