Impact of Direct Sequence Spreading on the Channel Capacity of Binary Non-Gaussian CDMA

Abstract

Multi-user interference (MUI) severely degrades peiformance in wireless CDMA transmission. Due to the central limit theorem, such interference is usually (near) Gaussian distributed [1,2]. Recently, it has been shown that for frequency/time hopping CDMA with single-user demodulation/decoding at the receiver, one can intentionally create appropriate non-Gaussian multi-user interference that allows increasing the capacity up to five times when compared to CDMA with Gaussian MUI [3,4]. This paper considers the impact of direct sequence (DS) spreading on the capacity increases for CDMA with non-Gaussian MUI. First, appropriate channel models are constructed for non-Gaussian DS CDMA when traditional single-user matched filter demodulator is used as well as when the optimal single-user CDMA receiver is used. The obtained numerical capacity results show that the non-Gaussian CDMA capacity gains can be realized with appropriate CDMA receiver.