Performance characteristics of QPSK and MSK DS/FH hybrid CDMA systems in Rayleigh fading

Hybrid code division multiple access (CDMA) scheme utilizes advantages of both direct sequence spread spectrum (DS/SS) and frequency hopped spread spectrum (FH/SS) systems, while overcoming some of their shortcomings. To enhance performance of this hybrid system, an efficient modulation scheme must be used that can perform favorably in a fading environment. We have compared the bit error rate (BER) performance of two spectrally efficient schemes namely, quadrature phase shift keying (QPSK) and minimum phase shift keying (MSK), when used in a hybrid system, over a Rayleigh fading channel. Simulation results show that hybrid MSK indeed is a better scheme in a multi-user (CDMA) environment in that, it achieves lower BER than hybrid QPSK. The comparison has been extended by including a predetection diversity reception scheme