Re: [Discuss-gnuradio] have a question about ofdm subcarriers and transferring data in benchmark_ofdm_tx.py

[Tom Rondeau]

James Park wrote:
> Hi,
>  
> In benchmark_ofdm_tx.py, I heard that the middle number of subcarriers 
> among the occupied_tones is alloacted to carry actual data, and the 
> frequency band of each subcarrier depends on the interpolation rate.
> does it mean that if I change the occupied tones, I can control the 
> number of subcarriers that carry actual data while having same the 
> total number of subcarriers?
> and if that's true, how can I distinguish and 
> analyze the subcarriers which carry data and which doesn't carry data?
> Thanks.
>  
> James,

It seems like you've answered your own question. There are fft_length 
number of subcarriers; the occupied_tones number of subcarriers in the 
middle are used to carry data. When you set the interpolation rate, you 
set the bandwidth of the output signal, but that is completely 
independent of the subcarrier parameters.

Look at gnuradio-examples/python/ofdm/gr_plot_ofdm.py to visualize the 
signal. Use '-h' to see how to set the right parameters.

Tom