A Method to Compute All Fixed Points for the Iterative MUD of CDMA Systems with Chip-Level Interleavers

This paper proposes a simple method to compute all fixed points for the iterative MUD of CDMA systems with chip-level interleavers. The task of finding all fixed points is difficult because a set of nonlinear equations with multiple variables has to be solved. It is shown that this set of equations can be reduced to an equivalent equation with just one variable. As a result, all fixed points can be obtained by simply locating the roots of this univariate equation. An application of the proposed method in optimal power allocation with a numerical example is presented as well.