Multiple Random Beams Selection Exploiting Chordal Distances

Lan TANG  Pengcheng ZHU  Xiaohu YOU  Yan WANG  

IEICE TRANSACTIONS on Communications   Vol.E91-B    No.11    pp.3722-3726
Publication Date: 2008/11/01
Online ISSN: 1745-1345
DOI: 10.1093/ietcom/e91-b.11.3722
Print ISSN: 0916-8516
Type of Manuscript: LETTER
Category: Wireless Communication Technologies
opportunistic scheduling,  chordal distance,  quantized feedback,  

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We consider a time-division multiple access (TDMA) transmission scheme in MIMO broadcast channels. To cope with the fairness issue in heterogeneous networks with slow fading, an opportunistic scheduling algorithm based on the channel eigen-direction is investigated. In the system with sparse users, the mismatch between a random beamforming vector and the principle eigenvector of the channel incurs a throughput penalty. To reduce such a throughput loss, a multiple random beams selection (MRBS) scheme exploiting chordal distances is proposed. Two feedback schemes (unquantized or quantized chordal distances) are considered. The closed-form throughput expressions of the proposed schemes are derived.