Simplifying the beamforming optimality region for practical MIMO scenarios

The optimality region for beamforming is redefined in terms of two parameters, the signal to noise ratio and the product of the antenna separation and the angular spread in the transmitter. This is possible by finding an interesting univocal relationship between the two main eigenvalues of the transmitter correlation in terms of this product. This relationship holds for many realistic scenarios, particularly in those where beamforming is a transmission alternative.