Capacity enhancement of DS-CDMA synchronous channels by frequency-shift filtering

We present a technique based on the cyclostationary properties of data signals that allows direct sequence spread-spectrum (DS-SS) code division multiple access (CDMA) system. The doubling is achieved with a moderate increase in bandwidth relatively to the original system or equivalently with a reduction when compared to the conventional approach of doubling the code length to duplicate the number of channels. The proposal makes use of two sets of DS-SS signals modulated by two carriers separated by a fraction of the the chip rate. The synchronous condition ensures cyclostationarity of the received signals, allowing the design of a receiver that explores the correlation between nonoverlapping frequency bands to cancel the inter-set interference