Linear space-time multiuser receivers for wireless CDMA systems

We derive and evaluate the performance of two minimum mean-squared error (MMSE) multiuser multi-antenna detectors for multipath channels. We consider the case of synchronous BPSK data signals for which the two detectors differ in the order of the “real” operation (r) and the linear transformation (T) for mitigating multi-access interference. In the adaptive implementations of these detectors, the Tr detector does not require prior channel estimates whereas the rT does. We show that as the noise floor vanishes, these MMSE detectors are equivalent to respective rT and Tr decorrelating (zero-forcing) detectors. If the channel parameters are known exactly, we show that the performance of the rT decorrelating detector uniformly outperforms the Tr decorrelator. Semi-analytic results demonstrate the capacity gains achieved using these multiantenna detectors