Multimode transmission has been studied to improve BER and outage capacity in the point-to-point system. In this paper, we consider the multimode transmission for downlink MIMO based on random beamforming(RBF) with limited feedback. We propose four heuristic mode selection and feedback policies to improve the sum rate and outage performance of downlink RBF system based on two approaches: distributed and centralized. Simulation results show that the centralized mode selection scheme with reasonable feedback amount provides waterfilling effect as well as the multiuser diversity gain, leading to the performance improvement of RBF in terms of sum rate and outage probability.
['Hyukjin Chae', 'Yo-Han Kim', 'Jang Hoon Yang', 'Binchul Ihm', 'Dong Ku Kim']
Multimode Random Beamforming for Multiuser Downlink MIMO System with Limited Feedback