Adaptive multi-user equalizer using multi-dimensional lattice filters for DS-CDMA

This paper proposes and investigates the adaptive multi-user equalizer based on the multi-dimensional IIR adaptive lattice filter in order to suppress the co-channel interference (CCI) in asynchronous DS/CDMA system. An asynchronous DS/CDMA system with multi-user receiver is modeled as a multi-dimensional or multi-input/out system with cross-coupling that is co-channel interference. From the system model it is shown that the multi-user detection is reduced into a problem of multi-dimensional equalization for multiaccess interference as well as intersymbol interference. The proposed multi-user equalizer can improve the equalizing error of the filter, comparing with that of the multi-dimensional FIR transversal filter of which number of tap is finite. The multi-dimensional lattice filter can adaptively achieve fast and stable convergence with less taps. Since the filter can resolve correlative multiple input into orthogonal output stage by stage, CCI can be removed. Computer simulations show performance of the proposed scheme.