In order to maximize the throughput of MIMO-OFDMA downlinks by using delayed channel state information, an adaptive transmission scheme combining Orthogonal Space-Time Block Code and eigen-beamforming was proposed,and subsequently a computationally efficient two-step sub-carrier allocation algorithm was presented. This scheme allocated bandwidth for every user based on their average channel state and data rate requirement. Then each sub-carrier was assigned to users according to the minimum scaled constellation distance criterion, capturing multi-user diversity gain. Finally available power was distributed among sub-carriers to ensure each user’s data rate requirement. Simulation results showed that the scheme could make use of delayed channel state information and multiple transmit antennas to increase throughput.
