Throughput optimization in multi-user MIMO-OFDM systems

MIMO and OFDM are two PHY layer techniques in present day broadband wireless communication systems providing increased data rates and multiple access capability. As applied to cellular communication systems, these techniques should be adopted to a Multi-User environment where the performance depends on sophisticated algorithms to allocate antennas (eigen channels), subcarriers, and power to users such that to minimize mutual interference. This can be achieved with precoding where either capacity optimization solution (waterfilling) or Sum Mean Square Error (SMSE) minimization is used. This paper presents hierarchical precoding algorithms where the two approaches are used simultaneously. Criteria for selecting one of the two processes for each eigen channel and OFDM subcarriers are formulated. The performance is evaluated by simulation using system and propagation models as per IEEE802.16 Evaluation Methodology Document.