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 lattice filter in order to suppress the co-channel interference (CCI) in an asynchronous DS/CDMA system. An asynchronous DS/CDMA system with a 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 to 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, compared with that of the multidimensional FIR transversal filter of which the number of taps is finite. The multi-dimensional lattice filter can adaptively achieve fast and stable convergence with less taps. Since the filter can resolve a correlative multiple input into an orthogonal output stage by stage, the CCI can be removed. Computer simulations show the performance of the proposed scheme