Integration of the Krylov Subspace Method in an Iterative Multi-User Detector for Time-Variant Channels

Iterative multi-user detection and time-variant channel estimation in a multi-carrier (MC) code division multiple access (CDMA) uplink requires high computational complexity. This is mainly due to the linear minimum mean square error (LMMSE) filters that are used for multi-user detection and time-variant channel estimation. Krylov subspace methods allow for an efficient implementation of the LMMSE filter. We show that a suitable chosen starting value, exploiting the iterative receiver structure, allows for a further speedup of the Krylov method. We achieve a complexity reduction by more than one order of magnitude. The Krylov subspace method allows a parallelization of the computations of the multi-user detector, while keeping the receiver performance constant. Numerical simulation results for a fully loaded system with K = 64 users are presented