Forum: GNU Radio GNUradio DQPSK bit error rate

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389231c675944f2faf9c6d9ad40a8a5c?d=identicon&s=25 Kael Thas (kael_thas)
on 2015-12-04 20:04
Hello all
Almost a month ago i started working on a digital communications project
which involves GNUradio.
I am now severely struggling to get past some errors or mismatches I am
encountering in GNUradio.
I am desperately in need of some expert help.
I made a DQPSK modulator and demodulator using GRC. ( screenshots
provided )
Gave a vector source with bits 0,1,0,1 and repeat on, on the input of
psk modulator.
I also used an error rate block to calculate bit error rate.
Now almost everything that is appearing on the scopes is completely
wrong.

The bit error rate is 0.5, provided that i have added no noise.(which is
max considering that we will recover 50 percent bits correctly just by
chance).
The scope at the psk modulator output shows four constellation points
even though i am transmitting only one symbol i.e (0,1).

What am i doing wrong?
Can someone please be kind enough to go through the screenshots and tell
me the mistake(s).
Any help will be greatly appreciated.
Thanks in advance.
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