Implementation of linear multiuser detectors for asynchronous CDMA systems by linear interference cancellation algorithms

The decorrelating and the linear, minimum mean-squared error (MMSE) detectors for asynchronous code-division multiple-access communications are ideally infinite memory-length detectors. Finite memory approximations of these detectors require the inversion of a correlation matrix whose dimension is given by the product of the number of active users and the length of the processing window. With increasing number of active users or increasing length of the processing window, the calculation of the inverse may soon become numerically very expensive. In this paper, we show that by applying iterative algorithms for the inversion of the correlation matrix in the frequency domain, linear multiuser detectors can be implemented with low complexity, low memory consumption and small detection delay.