It’s just the built in basic FDE. Its not awesome, but works well enough
at high SNR.
Yes, when I send multiple packets, its only the last OFDM symbol of the
last packet that is affected.
I have tried suffixing FFT_len/4 (i.e. 16 = CP) lots of 0’s in the TD at
the transmitter, and this fixes the problem (low power noise instead of
0’s also works).
Could it be an analogue issue? It is always the last symbol, i.e. the
end of the transmission, and it looks like the power might trail off
from the attached picture? But it seems strange that it’s exactly the
Could the pulse shaping performed in the cyclic prefixer have any
From: Martin B. [[email protected]]
Sent: 30 April 2014 14:56
To: David Halls; [email protected]in.invalid
Subject: Re: OFDM Example, ‘Noisy’ final symbol
On 30.04.2014 13:14, David Halls wrote:
This is OTA or over a cable, 2.48GHz using the N210 with XCVR2450. The
results I sent are over a cable, and the results I sent are post equalizer.
Which equalizer are you using? A custom one? Those in GNU Radio aren’t
fantastic, and they don’t output soft info.
It is only the final symbol of a burst, not the final symbol of each packet.
So what you’re saying is that when you send several packets directly one
after another, only the last one gets this?
I agree they should all be equally noisy, and I am certain it’s not
‘noise’ as such.
I thought if the timing window is too late, then some TD samples for the
final symbol will be included in the FFT that are just noise. I have
stored the TD samples and manually performed FFT and eq’n and shifting
the window of samples to pass to the FFT (either forwards or backwards)
by up 16 samples does not help.
If the timing window’s late, something’s seriously wrong. It should
always be early.
I currently don’t have a good idea, though.
On 30.04.2014 11:51, David Halls wrote:
Is it to do with sample alignment/timing error? I have tried sliding the
NOTE: The information in this email and any attachments may be
confidential and/or legally privileged. This message may be read, copied
and used only by the intended recipient. If you are not the intended
recipient, please destroy this message, delete any copies held on your
system and notify the sender immediately.
Toshiba Research Europe Limited, registered in England and Wales
(2519556). Registered Office 208 Cambridge Science Park, Milton Road,
Cambridge CB4 0GZ, England. Web: www.toshiba.eu/research/trl