Link adaptation for MIMO systems using reliability values

Link adaptation is used to dynamically adjust the modulation and coding in a wireless system to reflect the characteristics of the wireless link and maximise throughput. Usually the SNR is used as a channel quality indicator but in MIMO systems, the interference between subchannels must be taken into account for efficient link adaptation. In this paper we propose a simple, low complexity technique which uses the soft output from the space-time decoder to perform link adaptation. A lookup table is created off-line and by estimating the channel quality, the most appropriate transmission mode can be selected. A comparison between this new technique and using SNR and capacity as channel quality indicators is presented. Numerical results are given for an OFDM system