Scheduling Algorithm with Power Allocation for Random Unitary Beamforming

Yuki TSUCHIYA  Tomoaki OHTSUKI  Toshinobu KANEKO  

IEICE TRANSACTIONS on Communications   Vol.E91-B   No.1   pp.232-238
Publication Date: 2008/01/01
Online ISSN: 1745-1345
DOI: 10.1093/ietcom/e91-b.1.232
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Wireless Communication Technologies
random beamforming,  MIMO,  power allocation,  AMC,  

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Random unitary beamforming is one of the schemes that can reduce the amount of feedback information in multiuser diversity techniques with multiple-antenna downlink transmission. In Multiple-Input Multiple-Output (MIMO) systems, throughput performance is greatly improved using AMC (Adaptive Modulation and Coding). Throughput performance is also improved by allocating power among streams appropriately. In random unitary beamforming, the transmitter has only partial channel state information (CSI) of each receiver. Thus, it is difficult for random unitary beamforming to use conventional power allocation methods that assumes that all receivers has full CSI. In this paper, we propose a new scheduling algorithm with power allocation for downlink random unitary beamforming that improves throughput performance without full CSI. We provide numerical results of the proposed scheduling algorithm and compare them to those of the conventional random unitary beamforming scheduling algorithm. We show that random unitary beamforming achieves the best system throughput performance with two transmit antennas. We also show that the proposed algorithm attains higher throughput with the small increase of feedback than the random unitary beamforming scheduling algorithm.