MMSE space-domain interference suppression for multi-rate DS-CDMA

We consider space-domain interference suppression for reverse-link IS-95 and wideband DS-CDMA (W-CDMA) based on the minimum mean square error (MMSE) cost criterion. An adaptive algorithm for estimating the MMSE combining coefficients for each path is presented which is compatible with IS-95 orthogonal modulation and long spreading codes. The relative performance of noncoherent, maximal ratio (max-ratio), and MMSE combining are compared with mixed (high and low) data rates, where received power is proportional to data rate. Our results show that MMSE combining can offer a significant increase in capacity relative to max-ratio combining. Analytical performance results for W-CDMA based on a large system limit are also presented, and are shown to be accurate even with relatively few combining coefficients