Van:
"Ron Economos"
<address@hidden>
Aan: address@hidden
Verzonden: Dinsdag 7 april 2015 08:14:22
Onderwerp: Re: [Discuss-gnuradio] DVB-T/T2
Yes, rotated constellations are a new feature of DVB-T2. More
reading here.
http://www.etsi.org/deliver/etsi_ts/102800_102899/102831/01.02.01_60/ts_102831v010201p.pdf
See section 9.2.3. In addition to the rotation, the I and Q
components of a QAM/QPSK symbol are cyclically delayed. Since
there's a time and a frequency interleaver after the
modulator, the I and Q components of a symbol get sent at a
different time and a different frequency (OFDM carrier).
Almost all DVB-T2 broadcasters turn this feature on, even with
256QAM. All DVB-T2 receivers must support rotated
constellations.
Be sure to change the "Constellation rotation" parameter in
both
the Modulator block and the Frame Mapper block, or the
receiver will get confused.
BTW, both the DVB-T2 and DVB-S2 transmitters will be included
in GNU Radio in the next release (3.7.7) as part of gr-dtv.
If you place a Scope Sink after the modulator, you can see the
"virtual" constellation mentioned in the link above.
Ron
On 04/06/2015 10:14 PM, Ralph A.
Schmid, dk5ras wrote:
It _is_ intended:
http://dcis2009.unizar.es/FILES/CR2/p41.pdf
So forget about my
question :)
Ralph.
Hmm, now I see, there
is an option "constellation rotation" in the modulator
block. Maybe this is not an accident, but wanted
behavior?! I will check this evening...
Ralph.
Hi,
With Rons help I got the DVB-T/T2
flowgraphs up and running.
DVB-T works great, no issues at all,
while DVB-T2 is somehow flaky in reception.
When using a cheap DVB-x tester, the
DVB-T2 constellation is phase shifted. I have no real
world T2 signals to compare, but at least the tester
shows normal constellation views when looking at S and T
signals off the air.
This is how things look:
http://dk5ras.dyndns.org/tmp/DVB/
The flowgraphs are almost original,
just adopted to the USRP B210, and I added channel
slider...
Any ideas what I could tweak?
Ralph.
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