Quadri-Phase Shift Keying (QPSK)

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lokesh anand

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tell me about what is Quadri-Phase Shift Keying (QPSK) modulation scheme for digital transmission all about?
 

hi,
in dqpsk modulation, we transmit two bits of digital data on a phase which is pi/4 or odd multiple of it like 3*pi/4, 5*pi/4..........
Since in this modulationwe transmit two bits on a single carrier, this technique is relatively more efficient in data transmission.
 

from Proakis ch 4 p 171
in Mpsk signals' formula is
sm(t)=g(t) cos[2πfct+2π(m-1)/M]
for m=1 ,2,...,M ,fc is central freq and g(t) is pulse shape say rect pulse
it means that you have M diffrent signal that differ in phase as is clear in second term of bracket
in qpsk we have M=4 and phases will be 0 ,π/2,π,3π/2

viva Persia
 

thanks a lot for your help. those infomation will be very useful for me.thanks
 

These files are for QPSK modulator and soft-output demodulator.
 

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