Abstract: In MIMO systems, the throughput of system is increased by always scheduling the subscribers with good channel conditions to transmit. This is the multi user diversity. The fairness over all subscribers is the weak point. In this paper, the fairness of the MIMO systems was concerned and an adaptive proportional fair scheduling schemes based on opportunistic beamforming were proposed to increase the throughput of the subscribers in the bad channel conditions and guarantee the fairness allover the systems. In each timeslot, the adaptive parameters monitor the requested data rate and the mean of the rectuested data rate in the past period. And the adaptive parameters are updated per-user basis. The proposed schemes find a tradeoff between the throughput and the fairness. And the simulation results show the validity.

Key words: MIMO system,Multi-user diversity,Opportunistic beamforming,Proportional fair scheduling