The optimization of spreading sequences for CDMA systems in presence of frequency-selective fading

In the case of frequency-selective fading channels, the performance of CDMA systems depends on both, the auto- and the cross-correlation properties of the users' spreading sequences. However, there is an inherent trade-off between the auto- and the cross-correlation properties. In this paper, it is shown that the performance of the RAKE receiver in the single user case depends on a new correlation parameter referred to as weighted mean-square auto-correlation parameter. Moreover, it is shown that the best performance in the multiuser case is achieved by optimizing the sequences with respect to an appropriately weighted sum of the mean-square cross- and the weighted mean-square auto-correlation parameter.