Sequence Optimization in CDMA Point-to-point Transmission with Multipath

In this paper, we consider the problem of spreading sequence optimization in a CDMA point-to-point transmission over a multipath fading channel. The aim of the sequence optimization is to construct a set of spreading sequences to support users in the system with the minimum total transmission power when the MMSE receiver is used for signal reception. We consider the sequence optimization for two difference cases: when the number of users is smaller than or equal to the spreading gain, and when the number of users is larger than the spreading gain. Eigenvectors of the multipath channel matrix describe the channel space spanned by the CDMA system. The optimal solution distributes users’ spreading sequences into the channel space in an optimal manner. Keywords— DS-CDMA, multipath, MMSE receiver, sequence optimization