OFDM with fft lenght 2048 and 4096 doesn't work

GNU Radio
1

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

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2

On Mon, Jun 21, 2010 at 9:05 AM, Chris_Spain [email protected]
wrote:

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

3

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.