On the Performance of Spatially Correlated Large Antenna Arrays for Millimeter-Wave Frequencies

A spatially correlated large antenna array operating at millimeter-wave (mmWave) frequencies is considered. Based on a Saleh-Valenzuela channel model, closed-form expressions of the 3-D spatial correlation (SC) for wide, narrow, and Von Mises power elevation spectra (PESs) are analytically derived. The effects of the PES on the convergence to massive multiple-input-multiple-output properties are then illustrated by defining and deriving a diagonal dominance metric. Numerically, the effects of antenna element mutual coupling (MC) are shown on the effective SC, eigenvalue structure, and mmWave user rate for different antenna topologies. It is concluded that although MC can significantly reduce SC for side-by-side dipole antenna elements, the change in antenna effective gain (and, therefore, signal-to-noise ratio) caused by MC becomes a dominating effect and ultimately determines the antenna array performance. The user rate of an mmWave system with hybrid beamforming, using an orthogonal matching pursuit (OMP) algorithm, is then shown for different antenna topologies with dipole and cross-polarized (x-pol) antenna elements. It is seen that even for small numbers of radio frequency chains, the OMP algorithm works well relative to the fully digital case for channels with high SC, such as the x-pol antenna array.