QPSK = Quadrature Phase Shift Keying In QPSK amplitude are not much.so the carrier is constant. transmission rate is higher when compared with PSK

bit error is same for QPSK and BPSK.

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QPSK require less bandwidth compare to psk

the phase shift allowed in OQPSK is 900 whereas in QPSK it is 1800 .

QPSK is used in uplink whereas OQPSK is used in downlink.

See the question "What is QPSK".

If you want the difference between QPSK and some other modulation system, you'll need to name the other one.