Symbol-aided channel estimation and multiuser detection for synchronous CDMA systems using a decorrelating decision-feedback detector

A decorrelating decision-feedback detector is considered for multiuser detection for frequency-selective synchronous CDMA channels. This detector operates on the outputs of matched filters which are matched to the original code waveforms of the system. A maximum likelihood estimation to estimate the parameters of the decorrelating decision-feedback filters is proposed and derived. The estimation method is based on inserting known training sequences into the information data by all users simultaneously. To achieve minimum mean-square-error (MMSE) in estimation, a criterion for how to select the training sequences is suggested. The estimation method requires a matrix inversion at the end of each training period. The simulation results show some degradations in system performance compared to the case where perfect knowledge of the channel is assumed. This degradation is clearly due to errors in the channel estimation.