1
$\begingroup$

I am trying to simulate 8QAM with (4,4) amplitude levels. I want to get a constellation like this:

enter image description here

What are the amplitude levels should I select for I and Q?

$\endgroup$
  • $\begingroup$ notice the 001, 010, 110, and 101 all form a square and notice 001, 101, and 011 form an equilateral triangle. that should give you an idea what the relative amplitudes are. the angles for all of the points in the constellation are multiples of 45°. $\endgroup$ – robert bristow-johnson Oct 24 '17 at 2:23
  • $\begingroup$ Also note that there are good reasons why this constellation is NOT commonly used. And the complicated decision boundaries are among those. So if you ask me, you "should" use amplitude levels that distort this constellation to look like a psk. $\endgroup$ – Marcus Müller Oct 24 '17 at 5:57
  • 1
    $\begingroup$ You can simply write a look-up table that maps tuples of 3 bits to in-phase and quadrature amplitudes. $\endgroup$ – MBaz Oct 24 '17 at 13:01
  • $\begingroup$ @MBaz I tried, but I eneded up getting error in Simulinik. Can you give me the exact lookup table that I can map the values? $\endgroup$ – banu reddy Oct 24 '17 at 15:38
  • $\begingroup$ @banureddy That's a different question -- you don't mention simulink at all in your question. I don't use simulink. $\endgroup$ – MBaz Oct 24 '17 at 18:02

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.