MIMO-NOMA Enabled Sectorized Cylindrical Massive Antenna Array for HAPS with Spatially Correlated Channels

TL;DR

This paper introduces a cylindrical antenna array with NOMA clustering for HAPS, addressing high spatial correlation issues to improve spectral and energy efficiency in high-altitude communication systems.

Contribution

It proposes a novel cylindrical antenna architecture with sectorized ULA and a NOMA-based clustering method to mitigate spatial correlation effects in HAPS systems.

Findings

Spatial correlation significantly impacts spectral efficiency.

The proposed NOMA clustering improves energy efficiency.

Simulation confirms effectiveness of the antenna design.

Abstract

The high altitude platform station (HAPS) technology is garnering significant interest as a viable technology for serving as base stations in communication networks. However, HAPS faces the challenge of high spatial correlation among adjacent users' channel gains which is due to the dominant line-of-sight (LoS) path between HAPS and terrestrial users. Furthermore, there is a spatial correlation among antenna elements of HAPS that depends on the propagation environment and the distance between elements of the antenna array. This paper presents an antenna architecture for HAPS and considers the mentioned issues by characterizing the channel gain and the spatial correlation matrix of the HAPS. We propose a cylindrical antenna for HAPS that utilizes vertical uniform linear array (ULA) sectors. Moreover, to address the issue of high spatial correlation among users, the non-orthogonal multiple access (NOMA) clustering method is proposed. An algorithm is also developed to allocate power among users to maximize both spectral efficiency and energy efficiency while meeting quality of service (QoS) and successive interference cancellation (SIC) conditions. Finally, simulation results indicate that the spatial correlation has a significant impact on spectral efficiency and energy efficiency in multiple antenna HAPS systems.