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Re: Peaks when increasing the FFT lenght ofdm example
From: |
pv |
Subject: |
Re: Peaks when increasing the FFT lenght ofdm example |
Date: |
Tue, 21 Dec 2021 15:08:00 +0000 |
User-agent: |
Horde Application Framework 5 |
Hi Johannes,
First of all thanks for the quick response and time with my problem.
I've made a text file with all specifications of my OFDM example that
can be found in the attachments of this mail.
Thanks again with your help and anything more just let me know.
Best regards,
Pedro Viegas
Citando Johannes Demel <demel@ant.uni-bremen.de>:
Hi Pedro,
we'd need more info to tell why you observe these peaks. How large
are your input packets? Do they span multiple OFDM symbols? How many
subcarriers are active?
Your peaks hint at some kind of repetition or lot's of zeros.
Cheers
Johannes
On 14.12.21 13:07, Pedro Viegas wrote:
Hi everyone,
I'm having a problem when I increase the number of carriers from 64
to 512 in the gnuradio OFDM example. When the number of carriers is
512, the complex envelope of the signal in the time domain has some
peaks, which I can not have for the test I'm trying to make. Can
anyone tell why there are those peaks and how I get rid of them?
A possible cause for the peaks, in my opinion, can be the fixed
frame len of the header, that is filled with zeros when the FFT
size increases, resulting in a peak in the beginning of each frame
because of the ifft block. If this is the problem, how can I change
that frame len?
To better show what I'm saying, there is an image on the
attachments of the complex envelope with the peaks.
Thanks in advance,
Pedro Viegas
--
Pedro Viegas
DSP Engineer
Koala Tech
phone: +351 917 354 070
e-mail: pv@koalatech.pt
512 carriers GRC
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