Resource-Efficient HAPS-RIS Enabled Beyond-Cell Communications

TL;DR

This paper proposes a resource-efficient beyond-cell communication system using RIS-mounted HAPS to connect unsupported UEs, optimizing power consumption and maximizing connected devices in urban environments.

Contribution

It introduces a novel optimization framework and a low-complexity algorithm for resource-efficient HAPS-RIS systems supporting beyond-cell communications.

Findings

The proposed algorithm outperforms benchmarks in connected UEs and resource efficiency.

Connected UEs are more sensitive to CS transmit power than HAPS size.

Numerical results validate the effectiveness of the approach.

Abstract

In the future, urban regions will encounter a massive number of capacity-hungry devices. Relying solely on terrestrial networks for serving all UEs will be a cost-ineffective approach. Consequently, with the anticipated supply and demand mismatch, several UEs will be unsupported. To offer service to the left-out UEs, we employ an energy-efficient and cost-effective beyond-cell communications approach, which uses reconfigurable intelligent surfaces (RIS) on a high-altitude platform station (HAPS). Particularly, unsupported UEs will be connected to a dedicated control station (CS) through RIS-mounted HAPS. A novel resource-efficient optimization problem is formulated that maximizes the number of connected UEs, while minimizing the total power consumed by the CS and RIS. Since the resulting problem is a mixed-integer nonlinear program (MINLP), a low-complexity two-stage algorithm is developed. Numerical results demonstrate that the proposed algorithm outperforms the benchmark approach in terms of the percentage of connected UEs and the resource-efficiency (RE). Also, the results show that the number of connected UEs is more sensitive to transmit power at the CS than the HAPS size.