Rapidly converging polynomial expansion multiuser detector with low complexity for CDMA systems

A polynomial expansion (PE)-based multiuser detector (MUD) with low complexity O(N²) is presented. It approximates the computational intense (O(N³)) matrix inversion necessary for the decorrelating and minimum mean-squared error (MMSE) MUDs. Optimal convergence speed is obtained by normalising the PE detector´s matrix with respect to its smallest and largest eigenvalues. An efficient method to accurately estimate these eigenvalues is shown. Simulations in a CDMA-based system demonstrate that the presented PE MUD converges rapidly to the MMSE MUD