Spatial-Correlation-Based Antenna Grouping for MIMO Systems

We investigate antenna-grouping algorithms, which are hybrids of beamforming and spatial multiplexing. We partition transmit antennas into several groups and use beamforming in a group and spatial multiplexing between groups. With antenna grouping, we can achieve diversity gain through beamforming and spectral efficiency through spatial multiplexing. In this paper, we review existing criteria and present several new criteria in multiple-input-multiple-output (MIMO) antenna-grouping systems where the number of transmit antennas is larger than that of receive antennas. We then propose a novel low-complexity antenna-grouping algorithm, which reduces the computational complexity with little degradation of the bit error rate (BER). Comparing the BER and complexity with existing criteria, we demonstrate the benefits of the proposed algorithm. We also derive the BER lower bound of the proposed algorithm in independent and identically distributed (i.i.d.) channels by using the probability density function of the largest eigenvalue of a Wishart matrix.