MIMO-assisted HAPS as IMT Base Station for Uplink Spectrum Efficiency Enhancement

The High Altitude Platform Station (HAPS), as a as an NTN (Non-Terrestrial Network) network node, has evolved as an important component of the 6G wireless network. Acting as an IMT base station (HIBS) in mobile services, HAPS is a promising way to achieve vertical heterogeneous coverage enhancement. HIBS can operate in the stratosphere up to 20 km high to provide more coverage, however, it is limited by the ability to accommodate more users in scarce spectrum resources. To improve the SE of the uplink, we propose a MIMO-assisted HIBS technique in this study. A Monte Carlo method is used to calculate the CDF curves of the system SE for each configuration, which makes the simulation results closer to the actual deployment. HIBS is configured with three different combinations of MIMO antenna arrays, including single antenna, 2x2MIMO+ 2x4MIMO, and 4x4MIMO+ 4x8MIMO. The simulation results show that appropriately sized MIMO antenna panels can significantly improve the HIBS uplink link SE.