A Subspace Multiuser Beamforming Algorithm for the Downlink in Mobile Communications

A new algorithm for downlink multiuser beamforming in mobile communications is described. The optimization problem is reformulated by modifying the constraints so that weight vectors of different mobile stations are optimized in a reduced feasible region which is a subset of that of the multiuser beamforming problem. The downlink beamforming weight vectors of different mobile stations are then jointly optimized in a subspace instead of searching in the entire parameter space. Simulation results show that the modified optimization problem leads to solutions that satisfy the signal-to-noise-plus-interference ratio specification at each mobile station and that the total power transmitted from the base station is very close to the optimal one. The solution of the modified optimization problem requires significantly less computation than the optimal multiuser beamforming algorithms