Advantages of QPSK | Disadvantages of QPSK

This page covers advantages and disadvantages of QPSK modulation technique. It mentions QPSK advantages or benefits and QPSK disadvantages or drawbacks. It provides links on various topics on QPSK (Quadrature Phase Shift Keying) modulation basics.

What is QPSK?

The term QPSK stands for Quadrature Phase Shift Keying. It is digital modulation technique where in two binary bits are represented by change in carrier phase by 90 degrees with respect to the other nearby constellation. The phase transition of maximum of 180 degrees can occur between the two constellations. This is shown in the constellation diagram in the figure-1.


In QPSK modulation, each carrier carries two bits hence symbol rate is half of the bit rate. QPSK is considered to be bandwidth efficient and not power efficient.
Refer QPSK modulation>> , OQPSK & π/4QPSK>>, DQPSK>> , SQPSK>> and BPSK vs QPSK>> for more information.

Benefits or advantages of QPSK

Following are the benefits or advantages of QPSK:
➨In QPSK modulation, two bit are carried by one single analog carrier. Hence bandwidth is twice efficient in comparison to BPSK modulation. Here symbol rate is half of the raw bit rate.
➨BPSK is bandwidth efficient modulation technique as two bits are carried by single carrier.

Drawbacks or disadvantages of QPSK

Following are the disadvantages of QPSK:
➨In QPSK modulation technique, one complex symbol represents two binary bits. Due to this, QPSK receiver is more complex compare to BPSK receiver due to four states needed to recover binary data information.
➨Due to above reason, QPSK is not power efficient modulation technique compare to other modulation types as more power is required to transmit two bits.

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