Link adaptation in a multi-antenna system

We investigate a simple link adaptation scheme for a multi-antenna system based on adaptive channel inversion. A step-wise trade-off between spatial multiplexing and diversity is used to keep the power constant after spatial signal processing at the transmitter and to guarantee a pre-defined bit error rate. Therefore, both the number of data streams and the modulation format may be optimized according to the channel state. A rather smooth adaptation of the throughput may be realized in this way which comes close to the achievable capacity when current coding is employed. The technique is suitable in channels with spatial fading correlation as well.