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.