Spatial-polarization diversity HAP-MIMO transmission system for emergency high-capacity mobile communications

The deployment of high-altitude platforms (HAPs) as an emergency communication system is a cost-effective method to deal with the decrease in channel capacity caused by shadows or multipath fading at low elevation angles. This study proposes a 4 x 4 multiple-input multiple-output (MIMO) scheme that employs spatial and polarization diversity to improve the channel capacity for HAP communication systems. This scheme utilizes the advantages of HAP size to install two pairs of dual-polarized antennas between HAP and mobile terminals to form a 4 x 4 spatial-polarized diversity MIMO system to counteract shadows and multipath fading. The polarization and spatial correlation matrices are obtained through the reasonable expansion of a 2 x 2 polarized parametric or spatial geometry MIMO channel model. Simulation results show that the proposed 4 x 4 MIMO transmission scheme can effectively improve the channel capacity by 1.5 times compared with the existing satellite 2 x 2 dual-polarization MIMO system at low elevation angles under typical scenarios. (C) 2019 Published by Elsevier GmbH.