User-Selection Algorithms for Multiuser Precoding

A general framework for user selection in the broadcast channel with multiuser linear and nonlinear precoding techniques is investigated. Assuming full knowledge of channel-state information at the transmitter and using a minimum-mean-square-error (MMSE) criterion, we propose several user-selection algorithms based on the conventional incremental and decremental search approaches. Furthermore, a novel iterative user selection approach is introduced, offering a flexible performance-complexity tradeoff. New user grouping algorithms are also developed for orthogonal frequency-division multiple-access systems. Simulation results show that the proposed methods outperform well-known algorithms, which select users based on the users´ orthogonality or sum rate bound.