What is QPSK?

49. What is QPSK?

The Quadrature Phase Shift Keying (QPSK) is a 4-ary PSK signal. The phase of the carrier in the QPSK takes 1 of 4 equally spaced shifts.
Two successive bits in the data sequence are grouped together.
1 symbol = 2 bits
This reduces bit rate and bandwidth of the channel.
Coherent QPSK = 2 x coherent BPSK system
The phase of the carrier takes on one of four equally spaced values such as π/4, 3π/4, 5π/4 and 7π/4.