On asymptotic performance of iterative channel and data estimation in large DS-CDMA systems

We study the spectral efficiency of large random direct-sequence code-division multiple-access systems utilizing linear minimum mean square error (LMMSE) channel estimation and iterative multiuser detection and decoding (MUDD). Iterative MUDD based on non-linear data estimation and single-user decoding is considered as a benchmark for the more practical iterative LMMSE data estimator with soft parallel interference cancellation. The results showed that the channel parameters and the choice of error correction code have a great impact on the achievable spectral efficiency. It was also found that for the considered setups, the iterative LMMSE based channel estimator is near optimal for slowly time-varying multipath fading channels.