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

TL;DR

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 is proposed, supporting scalable and sustainable 6G deployments.

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.

Figures (10)

• Figure 1: Illustration of a dynamic vHetNet configuration, highlighting CS opportunities between SBSs, MBS, and HAPS to optimize network performance and power efficiency.
• Figure 2: Snapshots of the network status for HAPS-enhanced CS NoQoS and HAPS-enhanced CS under different $P_\mathrm{min}$ values (Case Study A). Outer dotted circles represent the coverage areas of SBSs, while inner solid circles denote their load ($\lambda$ values). The color of each SBS indicates its status: active, offloaded to the MBS, or offloaded to the HAPS. The large blue circle illustrates the SBSs offloaded to the MBS under the corresponding outage-based QoS condition.
• Figure 3: Total power consumption vs. load intensity for various CS methods, with $P_\mathrm{min}=-70\; \mathrm{dBm}$.
• Figure 4: Impact of the number of SBSs ($s=16,25,36,49$) on power consumption.
• Figure 5: Total served traffic with QoS vs. load intensity for various CS methods, with $P_\mathrm{min}=-70\; \mathrm{dBm}$.