Partial Parallel Interference Cancellation Techniques with Adaptive RAKE Combining for DS-CDMA Ultra-Wideband Wireless Communications

Two kinds of RAKE receiver combining schemes are investigated for a partial parallel interference cancellation (PPIC) technique, including maximal ratio combining (MRC) and minimum mean-squared error (MMSE) combining, in directsequence code-division multiple access (DS-CDMA) ultrawideband (UWB) systems. We use the normalized least meansquared algorithm to approach the MMSE solution for the RAKE combining weights. Simulation results show that multiple access interference can be effectively reduced by the proposed methods and whether channel information is given to the MRC scheme or not, the MMSE combining scheme outperforms the MRC scheme. This implies that complicated channel estimation of accurate fading gains may not be needed in a PPIC detector for DS-CDMA UWB systems. Keywords-Direct-sequence code-division multiple access (DSCDMA); ultra-wideband (UWB); multiple access interference (MAI); partial parallel interference cancellation (PPIC); normalized least mean-squared (NLMS) algorithm