Define offset QPSK and p/4 differential QPSK.

50. Define offset QPSK and p/4 differential QPSK.

In offset QPSK the amplitude of data pulses are kept constant. The time alignment of the even and odd bit streams are offset by one bit period in offset QPSK. In p/4 QPSK, signaling points of the modulated signal are selected from two QPSK constellations which are shifted by p/4 with respect to each other. It is differentially encoded and detected so called p/4 differential QPSK.