Phase versus time graph of QPSK In wikipedia, there was an example on QPSK modulation where the main signal was 11000110 and I contained 1001 and Q contained 1010, now their output was shown by the Signal in the figure. 



Now according to constellation diagram Signal can be represented as 

11 -&gt; pi/4                           
00 -&gt; -(3*pi)/4                           
01 -&gt; (3*pi)/4                            
10 -&gt; -pi/4                               




But my confusion was in the phase vs time diagram shown in another figure given below  



For 11 it starts from phase pi/4, but for 00 shouldn't the phase start from -(3*pi)/4 = -135 ?
You're right that the phase plot doesn't match the signal plot. Note that it also shows more symbols than the signal plot. Those two plots do not refer to the same bit sequence, and the phase plot is only meant to illustrate the difference between QPSK and OQPSK (the original figure consists of two plots, one for QPSK and one for OQPSK).