Investigation on the FFT-Based Antenna Selection for Compact Uniform Circular Arrays in Correlated MIMO Channels

Using the beamspace preprocessing in RF chains, the fast Fourier transform (FFT)-based antenna selection scheme can reduce the performance degradation of traditional antenna selection schemes in correlated multiple-input multiple-output (MIMO) channels. Based on this technique, an antenna selection method in beamspace is developed for MIMO systems using compact uniform circular arrays (UCAs) at the receiver. To take advantages of the FFT-based antenna selection scheme for application in practical scenarios, a parametric physical model that considers the geometrical properties of the scattering environment is introduced to include realistic fading conditions into the channel matrix. Furthermore, due to the limited spatial phase modes of UCAs, the channel matrix resulting from the beamspace preprocessing only possesses a limited and small number of nonzero rows. This substantially reduces the computational load in the following beam selection procedure. More importantly, the optimal beam selection can be realized even without channel state information (CSI) at the receiver. This characteristic is especially useful for compact UCAs with a large number of elements. Besides, it is also found that the severe mutual coupling effect resulting from compact UCAs does not affect these favorable characteristics of the FFT-based preprocessing technique. Numerical examples considering strong mutual coupling in compact UCAs are provided to verify and validate the proposed method.