Re: [Discuss-gnuradio] DVB-T/T2

[Ron Economos]

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.

 

From: address@hidden [mailto:address@hidden] On Behalf Of Ralph A. Schmid, dk5ras
Sent: Tuesday, April 7, 2015 07:04
To: address@hidden
Subject: Re: [Discuss-gnuradio] DVB-T/T2

 

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.

 

From: address@hidden [mailto:address@hidden] On Behalf Of Ralph A. Schmid, dk5ras
Sent: Tuesday, April 7, 2015 06:39
To: address@hidden
Subject: [Discuss-gnuradio] DVB-T/T2

 

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.