Optimal antenna spacings for uncoded space-time labelling diversity systems with linear and non-linear antenna configurations

Abstract

—Uncoded Space-Time Labelling Diversity (USTLD) is a recent technique that has been applied to multiple-input, multiple-output (MIMO) systems to improve their error performance. However, the presence of multiple antennas leads to correlation, resulting in a performance degradation. Given that 5G systems aim to operate with large-scale antenna arrays and in the millimetre-wave frequency spectrum, antenna correlation is highly likely in next-generation MIMO systems. It is thus insightful to predict the optimal antenna spacing required to balance robustness to correlation with small form factor in USTLD systems. This paper investigates the cases of densely arranged, linearly arranged and equispaced antenna configurations to propose an optimal antenna spacing for each configuration. The results presented indicate that the optimal spacings are 0.3λ for dense antenna arrays, 0.4λ for linearly arranged antenna arrays and 0.3λ for equispaced antennas, where λ is the transmission carrier wavelength.