A multi-stage MCI cancellation receiver for multicode CDMA systems

Multicode CDMA is a new transmission scheme for flexible and high-speed data communications. In a multipath environment, these intra-user multicode signals from different delay paths no longer maintain their orthogonality, thus causing significant interference, i.e. multicode interference (MCI), to each other. A multicode CDMA receiver with RAKE structure and multi-stage MCI cancellation is proposed. By pilot aided channel estimation, the MCI associated with the reference user is regenerated and subtracted from the received signal. The detailed receiver structure is presented and theoretical analysis is given to show that the system performance is significantly improved by the MCI cancellation. It is shown that the optimal cancellation factor in the k-th stage can be approximated by λ_opt^(k) ⩽1-2P_e^(k-1), where P_e^(k-1) is the error probability of the (k-1)th stage