On Performance of MIMO Link Adaptation in the Presence of Channel Uncertainty

In this paper, link level adaptation algorithms in a system applying spatial multiplexing in the presence of channel uncertainty are considered. The first part of this paper deals with the impact of accuracy of the channel knowledge on the post-processing signal-to-noise ratio (SNR) of transmitted multiple streams. This is evaluated by means of correlation coefficient between post-processing SNR values corresponding to the estimated and used channel matrix.In the second part of this paper, two link adaptation algorithms are introduced: the first algorithm adapts the modulation and coding scheme to the post-processing SNR level, whereas the second one searches for the optimum MIMO scheme (antenna selection) and does afterwards the adaptation of modulation and coding as well. Algorithmspsila performance is evaluated assuming perfect channel knowledge and in the presence of channel uncertainty. The two algorithms show different gains when the channel knowledge is accurate, but also different sensitivity to channel knowledge imperfections.