Quadrature phase shift keying direct sequence-spread spectrum code division multiple access with disparate quadrature chip and data rates

This research examines the performance of a QPSK DS-CDMA system with disparate chip and data rates (thus different processing gains) on the two quadrature channels for synchronous and asynchronous transmission using both orthogonal and random codes. In a CDMA setting, we investigate the effect on performance of unequal user signal energies and a variable number of interfering system users, in both AWGN and Rayleigh fading channels. With this disparate scheme we also obtain a moderate amount of shaping of the transmitted signal power spectrum. Our results show excellent agreement between analysis and simulations, and illustrate the additional degree of flexibility our disparate chip/data rate system provides.