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
