Re: [Discuss-gnuradio] gr-lte Receiver Framework

[Johannes Demel]

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Hi Ali


> 1) it always detects the correct cell_id? Yes
That's a good sign.

> 
> 2) the OFDM symbols with RS symbols should be recognizable. Is this
> the case? After the decoding of the cell id the LTE estimator
> generates a RS map with # tags followed by ones and minus ones.
> After this I get a message from pcfich_lte_descrambler and
> lte_channel_estimator that PILOT MAP RESETTED and received message
> vector and the decoding stops.
PCFICH does only work for one specific bandwidth because it calculates
PCFICH positions inaccurately. I suggest you deactivate it for now
because it also needs information from MIB to work correctly.

A Qt time sink should be able to show you all the tags. If you trigger
with tags it should show you a pattern with some energy on symbols
with RS symbols and no energy on most others. That's what I would
expect. Tags should mark the start of a slot.

> 
> I am testing the other flowgraphs apparently they dont have this
> issue. How long does the flowgraph takes to give the final MIB
> output?
Once everything is set correctly, it should only take a moment. I can
just assume that the decoder gets confused by the fact that no payload
is present and thus most OFDM symbols are zero. This is really hard to
investigate from a distance.
I'm confident that the PBCH, BCH, MIB chain works. Also, it has quite
extensive tests. The synchronization part and partially OFDM demod are
more fragile.

> 
> Another quesion would be do you see an error in compilation of the
> program or with my test file? I also have a USRP N210 with me can I
> record an LTE signal with it without a daughterboard?
A daughterboard will be necessary.

- From the given output I can't see any issues.

Cheers
Johannes
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