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

On Thu, Nov 7, 2013 at 7:57 AM, Martin Braun (CEL) <martin.braun@kit.edu> wrote:

On Wed, Nov 06, 2013 at 06:27:40PM -0500, Aditya Dhananjay wrote:
> I created an OFDM TX/RX flowgraph (mostly copying stuff out from the GNU Radio
> reference GRC implementation), where the TX goes out to a USRP UHD sink, and
> the RX reads from a USRP UHD source.
>
> As long as the receive SNR is high enough, the problem does not show up.
> However, as I gradually reduce the RX gain, at some point, the entire thing
> crashes with the "Buffer too small for min_noutput_items" error.

Are you using a current version? This problem was caused by bit errors
creating incorrect, but validated headers. In the current header, we
have an 8 Bit CRC check, which is pretty unlikely to cause this.

Hi Martin,

Thanks for your response.

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.

Best,

Aditya