Re: [Discuss-gnuradio] Default value of fft_length

[Eric Blossom]

On Sat, May 17, 2008 at 01:07:29AM +0800, Chin-Ya Huang wrote:
> Hi,
> 
> I want to double check that if the default value of fft_length for the ofdm 
> is 512 ?
> 
> Thanks
> Chin-Ya


If you care, you should specify it.  Don't count on the default never changing.

Investing two minutes looking at code reveals that ofdm.py defaults it to 512.  


    def add_options(normal, expert):
        """
        Adds OFDM-specific options to the Options Parser
        """
        normal.add_option("-m", "--modulation", type="string", default="bpsk",
                          help="set modulation type (bpsk or qpsk) 
[default=%default]")
        expert.add_option("", "--fft-length", type="intx", default=512,
                          help="set the number of FFT bins [default=%default]")
        expert.add_option("", "--occupied-tones", type="intx", default=200,
                          help="set the number of occupied FFT bins 
[default=%default]")
        expert.add_option("", "--cp-length", type="intx", default=128,
                          help="set the number of bits in the cyclic prefix 
[default=%default]")


I used a very special tool to figure this out: grep
It's probably installed on your system too...

Eric