Sustainable Vertical Heterogeneous Networks: A Cell Switching Approach with High Altitude Platform Station

TL;DR

This paper introduces a cell-switching algorithm for vertical heterogeneous networks with high-altitude platforms, significantly reducing energy consumption while maintaining quality of service for sustainable 6G networks.

Contribution

It proposes a novel HAPS-enhanced cell-switching method that optimizes energy use in vHetNets with high-altitude platforms, outperforming existing benchmarks.

Findings

Up to 77% energy savings at low loads

Up to 90% energy savings with NoQoS variant

Maintains high traffic service levels

Abstract

The rapid growth of radio access networks (RANs) is increasing energy consumption and challenging the sustainability of future systems. We consider a dense-urban vertical heterogeneous network (vHetNet) comprising a high-altitude platform station (HAPS) acting as a super macro base station, a terrestrial macro base station (MBS), and multiple small base stations (SBSs). We propose a HAPS-enhanced cell-switching algorithm that selectively deactivates SBSs based on their traffic load and the capacity and channel conditions of both the MBS and HAPS. The resulting energy-minimization problem, subject to an outage-based quality-of-service (QoS) constraint, is formulated as a mixed-integer nonlinear program and reformulated into a mixed-integer program for efficient solution. Using realistic 3GPP channel models, simulations show substantial energy savings versus All-ON, terrestrial cell switching, and sorting benchmarks. Relative to All-ON, the proposed method reduces power consumption by up to 77% at low loads and about 40% at high loads; a NoQoS variant achieves up to 90% and 47%, respectively. The approach maintains high served-traffic levels and provides a tunable trade-off between power efficiency and outage-based QoS, supporting scalable and sustainable 6G deployments.