Power and Rate Adaptation Based on Imperfect Channel Estimation over MIMO Fading Channels

Alireza KOBRAVI  Mohammad SHIKH-BAHAEI  

IEICE TRANSACTIONS on Communications   Vol.E91-B    No.4    pp.1063-1067
Publication Date: 2008/04/01
Online ISSN: 1745-1345
DOI: 10.1093/ietcom/e91-b.4.1063
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Wireless Communication Technologies
MIMO,  adaptive modulation,  imperfect channel estimation,  PSAM,  

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We derive the optimum power and rate adaptation for maximizing the spectral efficiency of Multilevel Quadrature Amplitude Modulation (MQAM) over Multiple-Input Multiple-Output (MIMO) fading channels based on imperfect channel estimation. We use Pilot Symbol Assisted Modulation (PSAM)-based Minimum Mean Square Error (MMSE) channel estimator, and show that the optimum power adaptation on each sub-channel is a generalization of water-filling. We also show that the conventional water-filling (with bias) strategy for power adaptation is a suboptimum solution of the general optimization problem and it tends to the optimal solution as the correlation coefficients between eigenvalues of the true channel matrix and its estimate tend to one.