2-Step Maximum Likelihood Channel Estimation for Multicode DS-CDMA With Frequency-Domain Equalization

Frequency-Domain Equalization (FDE) based on the Minimum Mean Square Error (MMSE) criterion can provide better downlink Bit Error Rate (BER) performance of Direct Sequence Code Division Multiple Access (DS-CDMA) than the conventional rake combining in a frequency-selective fading channel. FDE requires accurate channel estimation. In this paper, the authors propose a new 2-step Maximum Likelihood Channel Estimation (MLCE) for DS-CDMA with FDE. The 1st step uses the conventional MMSE-CE and the 2nd step carries out the MLCE using decision feedback from the 1st step. The BER performance improvement achieved by 2-step MLCE over conventional MMSE-CE is confirmed by computer simulation.