Interpreting QPSK Modulation Angles

[fran1942]

Hello, I have attached a diagram of QPSK modulation angles. I was wondering how would the red and yellow dots be interpreted.
Those dots are not exactly on either of the 4 different phase angles. But I understand QPSK has a discrimination of 90 degrees so would the red equate to 45 degrees and the yellow to -45 degrees ? Is that how it works or would the red equate to 135 degrees and the yellow to 45 degrees ?

Thanks for confirmation.

 

[marcusl]

Points at these locations only occur when the SNR is abnormally low or there is some kind of corruption, indicating that they are probably not valid. A simple decoder would assign them to the closest location, but it is likely that they will give symbol errors.