Re: [Discuss-gnuradio] Fwd: Questions on rx_ofdm example in GR 3.7.1

[Martin Braun (CEL)]

On Thu, Nov 07, 2013 at 09:59:15AM -0500, Aditya Dhananjay wrote:
> Yes, I am using the current version pulled from the git sources.
> 
> To clarify, this is not a rare occurrence. With a > 50% probability, when I
> reduce the TX/RX gain, the problem shows up. The header/payload demux is 
> always
> the offending block.
> 
> Also, once this problem shows up, the entire RX path freezes up, and needs to
> be restarted.

Hey guys,

and thanks again for testing this.

I ran some tests today and was able to reproduce this problem.

However, to make it happen, you have to severely screw up the OFDM
signal at the transmit side. The preamble detector (which is pretty
robust) will still detect packets, and then flood the header/payload
demuxer with guaranteed garbage. Eventually, even the 8-Bit CRC fails,
after rejecting lots of packets.

At this point, the HPD *should* catch the problem, but doesn't, which
causes the block_executor to throw a runtime_error. I'm not sure where
the bug is, but there definitely is one.

I've opened http://gnuradio.org/redmine/issues/611 and will try and
figure this out.

MB

-- 
Karlsruhe Institute of Technology (KIT)
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