Re: [Discuss-gnuradio] OFDM with fft lenght 2048 and 4096 doesn't work

[An He]

could you try a smaller number of fft sub carriers (e.g., fft=128, occupied=80, cp=32, i/d=32)? usually this works better than an ofdm with a large number of carriers. this might be because the frequency offset of the radio becomes comparable to the bin size when the number of sub carriers is large.

On Mon, Jun 21, 2010 at 10:29 PM, Tom Rondeau <address@hidden> wrote:

On Mon, Jun 21, 2010 at 9:05 AM, Chris_Spain <address@hidden> wrote:
>
> Hello I'm trying to send with benchmark_ofdm_tx and receive with
> benchmark_ofdm_rx a OFDM modulation with next paremeters:
>
> FFT lenght = 2048
> Chanel occupied = 1512
> Size of package = 1024
> CP_adder = 128
>
> and
>
> FFT lenght = 4096
> Chanel occupied = 3024
> Size of package = 1024
> CP_adder = 128
>
> I'm using RFX 900 with F = 900 M, and doesn't work, the RX don't display
> anything and de TX transmitter

If you run the transmitter and use usrp_fft.py on the other one, do
you see any energy coming through?

I'm not sure I've ever tried that many subcarriers. Not sure why it
wouldn't work, though.

Tom

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