Analysis of combined MMSE/PIC multi-user detection for CDMA spread spectrum systems

This paper analyses combinations of the linear MMSE detector and a non-linear parallel interference canceller (PIC) for multi-user CDMA detection. Approximate formulas and upper and lower bounds for the error probability are derived and verified through simulation. It is shown that the combined MMSE/PIC detector almost always is better than the MMSE, and a partial MMSE/PIC is derived that has superior performance in all cases. It is also shown that although the MMSE detector is near-far resistant, it is sensitive to the code cross-correlation matrix, while the combined MMSE/PIC detector is both near-far resistant and insensitive to the cross-correlation matrix.