Spectrally Shaped DS–CDMA with Dual Sideband Combining for Increased Diversity on Dispersive Fading Channels

Abstract

A new modulation scheme is proposed in this paper. This scheme uses sinusoidal chip waveforms to shape the spectrum of a direct sequence spread spectrum (DS-SS) signal such that the transmitted signal has two distinct spectral lobes, one from a lower sideband (LSB) and the other from an upper sideband (USB). By properly selecting the frequency of the sinusoidal chip waveforms, the two sideband signals can be made to undergo independent fading in a dispersive fading channel. These two independent sideband signals, when combined at the receiver, provide diversity gain. Our analysis and simulation results show that the bit error ratio (BER) performance of the proposed scheme is superior to that of the equivalent DS-SS system that uses conventional rectangular chip waveforms for severely faded channels.