MIMO channel analysis typically includes capacity; a more diverse channel will result in increased channel capacity. Many statistical measures for wireless channels exist but throughput performance ultimately is determined through the orthogonality of the subchannels comprising the MIMO channel. The capacity of MIMO channels is considered in conjunction with the angles between the complex channel impulse response vectors. The angle between complex Euclidean vectors is derived. For simulated complex baseband Rayleigh fading channel impulse responses, a short finite-length response with a constant power delay profile is similar in angle distribution to a longer response with an exponential profile, whose amplitude time constant is the same as the length of the former. The exponential profile limitations on the sub-channel vectors is shown to extend to capacity. The relationship of the variance of the complex sub-channel vector angles to the variance of the channel capacity is shown.
https://www.ece.unb.ca/petersen/pubs/CoPeMeBe20/