Exploiting the Spatial Information Provided by Channel Statistics and SNR Feedback

A major limiting factor in communication systems utilizing multi-antenna transmission is the amount of spatial channel information available at the transmitter. Since the channel realizations, in most cases, can only be estimated at the receiver, such information must be fed back to the transmitter. In multiuser systems the amount of feedback must be kept minimal, which seriously limits the information that can be fed back. Herein it is shown that the feedback of a scalar signal to noise ratio (SNR), together with knowledge of the statistical properties of the channel, provides substantial spatial information about the current channel realization. The spatial information is particularly good for strong channel realizations, i.e. for users that are candidates for scheduling. Previous results are extended to the Ricean channel model and the impact of the non-zero expected value is shown to further improve the spatial information