Colocated antenna arrays: design desiderata for wireless communications

We report on in this paper is motivated by the drive towards antenna array miniaturization: going from an array of identical antennas that get spread out in space towards an array of colocalized antennas with differing responses. We address the problem of designing the colocated antenna array response for two applications: diversity reception using maximum ratio combining and MIMO communication capacity. The design criteria are derived under specific models regarding the distribution of the parameters of the frequency flat channel. We are particularly interested in evaluating the performance of two opposite extremes in terms of design: very selective beamspace type of operation versus spatially allpass antennas. We also show that the pathwise channel model converges for large number of paths to the stochastic channel model with separable correlation between TX and RX sides.