Abstract
In multiuser multipleโinput multipleโoutput/orthogonal frequencyโdivision multiplexing (MIMO/OFDM) systems, the EigenValue Decomposition (EVD) method was proposed to construct a number of parallel spatial channels. The beamforming technique which only exploits the spatial subchannel related to the largest eigenvalue is usually adopted in many papers to deal with adaptive resource allocation. Although these previous studies could maximise the received signalโtoโnoise ratio (SNR), they could not get the maximum system throughput. In this paper, all the spatial subchannel are investigated. With the goal of maximising the overall system throughput, we derive a simple effective criterion of subcarrier allocation and introduce an adaptive resource allocation algorithm. The proposed algorithm could get higher system throughput especially at high SNR, that is the spectral efficiency is improved about 3 bit/s/Hz at 14 dB. At the same time, in order to decrease the computational complexity, a timeโfrequency blockwise loading design is suggested. In practical channel with partial channel state information (CSI), a modified algorithm based on mean feedback model is proposed. The simulation results show that under imperfect CSI, the modified algorithm could achieve optimum system throughput while guaranteeing prescribed error performance. On the other hand, in comparison to perfect CSI, the system throughput decreases. Copyright ยฉ 2008 John Wiley & Sons, Ltd.