Which is the major advantage of QPSK in terms of bandwidth and noise immunities ?

Which is the major advantage of QPSK in terms of bandwidth and noise immunities ?

a. Requirement of Bandwidth is half than PSK with similar noise immunities
b. Requirement of Bandwidth is twice than PSK with similar noise immunities
c. Requirement of Bandwidth is one -third than PSK with different noise immunities
d. Requirement of Bandwidth is double than PSK with either same or different noise immunities depending on the transmission rate

Correct Answer : a. Requirement of Bandwidth is half than PSK with similar noise immunities

Explanation :

Phase angle in QPSK is supposed to change by 90 degree & hence ultimately results in the generation of phase angles of 0, 90, 180 & 270 degrees. Therefore, QPSK bandwidth necessity is half the bandwidth of PSK & hence noise immunities are semantic as they do not depend on the subjectivity of phase shift angles.