This paper is the study of the QPSK (Quadrature Phase Shift keying) modulation technique using AWGN (Additive White Gaussian Noise) and Multipath Rayleigh fading channel. In QPSK scheme the authors can transmit one of the 4 possible signals during each interval of signaling. WCDMA systems are based on higher modulations which provide transmission at higher data rates. In this they studied the scatter plot, eye diagram and signal trajectory of QPSK system over different communication channels. All modulation techniques have different performance characteristics over various signals which are affected by noise and interference.