|Subject:||Re: [Discuss-gnuradio] DVB-T/T2|
|Date:||Mon, 06 Apr 2015 23:14:22 -0700|
|User-agent:||Mozilla/5.0 (X11; Linux i686; rv:24.0) Gecko/20100101 Thunderbird/24.6.0|
Yes, rotated constellations are a new feature of DVB-T2. More
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.
On 04/06/2015 10:14 PM, Ralph A. Schmid, dk5ras wrote:
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