Forum: GNU Radio GNUradio DQPSK bit error rate

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Kael T. (Guest)
on 2015-12-04 21:04
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

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
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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