[Discuss-gnuradio] Problem with output of inverse FFT

[Hans-Christian]

Hi @all,

on my long way to send multiple  802.11g frames i found another problem…

During the process the data is converted from frequency domain to time
domain by inverse fft.  
The fft length is 64, and the input is the OFDM symbol with carrier tones
(vector of 64 * gr_complex) 
The frame consists of 3 ofdm symbols and i want to convert two identical
frames.
So there are 6 elements with a size of  64* gr_complex.  (6*64 *8Byte = 3072
Byte)

When I compare the result of the first frame (Bytes 0 – 0x5FF) with the
result of the second frame (0x600 – 0xBFF) in a hex editor the frames are
NOT the same. 

They differ from each other, starting at Byte 0x800 to 0x200 in the fist
frame. (0x800 = 2048dec!?)

I’m able to reproduce the problem in GRC, using a file source
–>throttle->inverse fft(size 64) -> file sink  flowgraph., my input file is
attached.

Is there a problem with the precession of the ifft? (gnuradio 3.2.2, ubuntu
10.04)

Has anybody an idea how to fix this?

http://old.nabble.com/file/p31056403/input.dat input.dat  
http://old.nabble.com/file/p31056403/output.dat output.dat 

-Hans
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