Re: [Discuss-gnuradio] header_payload_demux_impl.cc - problem when using random bit stream (variable trigger location)

[David Halls]

Dear Martin,

 

I wondered, if you are working on the HPD, if it’s possible to look into making a change when a header is received incorrectly, e.g. low SNR or sudden shadowing. I find that (although it no longer crashes with the recent update to adjust buffer size) it loses synchronisation and does not recover in later packets. I can’t quite work out why…

Regards,

 

David

 

From: discuss-gnuradio-bounces+address@hidden [mailto:discuss-gnuradio-bounces+address@hidden On Behalf Of Aditya Dhananjay
Sent: 22 January 2014 15:02
To: Martin Braun
Cc: address@hidden
Subject: Re: [Discuss-gnuradio] header_payload_demux_impl.cc - problem when using random bit stream (variable trigger location)

 

 

Dear Martin,

 

Thanks for the ideas.

 

Two ideas:
- You could remove the sync block and sync your rx/tx paths with other
means (e.g. MIMO connector, it depends on your hardware). This makes the
sync influence independent of the noise.

 

Good idea, I will try it out once I get the cables.

- Reconsider if the phase rotation really makes your measurements
invalid. You'll have a phase rotation in any case (due to channel,
propagation time etc.). The timing-related phase offset is constant,
after all, and the phase difference between sub-carriers depends on the
sub-carrier distance, too. Perhaps it doesn't matter all that much?

 

That makes sense. I want to study the different phenomena that affect phase rotations in the channel. By eliminating the USRP hardware (by connecting the TX and RX blocks to each other through a channel model block), I can control the PDP of the simulated channel, for example.

 

Thank you for your inputs. This is very useful to me.

 

best regards,

aditya

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