Interference diversity gains via adaptive block-diagonalisation for multiuser MIMO downlinks

Proposed is an adaptive fully transmitter-based block-diagonalisation scheme for multiple input multiple output (MIMO) multiuser downlink systems. A relaxation to the beamforming optimisation constraints is proposed, which introduces interference diversity and attains a more efficient performance optimisation. The trade-off to the performance improvement is an increase in the precoding complexity imposed by the adaptive nature of the proposed beamforming. A sub-optimal adaptive-decomposition beamforming scheme is also proposed with a reduced complexity overhead. Comparative analytical and simulation results to conventional beamforming demonstrate the significant diversity gains offered by the proposed scheme.