Interference Management Strategies for HAPS-Enabled vHetNets in Urban Deployments
Afsoon Alidadi Shamsabadi, Animesh Yadav, Halim Yanikomeroglu
TL;DR
This paper investigates interference management in HAPS-enabled vHetNets for urban deployments operating in harmonized spectrum. It identifies HAPS-specific constraints—extensive coverage, limited onboard energy, constrained backhaul, LoS-dominated and correlated channels, and jitter—and surveys interference management strategies adapted for these conditions, including coordination, power control, advanced beamforming, versatile user association, joint algorithms, residual processing, UL/DL decoupling, and cell-switching. It also discusses efficient mathematical tools, such as centralized and distributed optimization (RLT/SCA, ADMM, ALM) and AI-driven methods (RL, GenAI, L2O), highlighting the trade-offs between centralization and distribution. A case study demonstrates that distributed beamforming weight design can nearly match centralized performance while reducing complexity and information exchange, supporting scalable interference management in large-scale vHetNets. Overall, the work provides a roadmap for deploying practical, energy-aware, and scalable interference management in HAPS-enabled urban networks and points to fruitful avenues for optimization and AI-driven approaches in future 6G systems.
Abstract
Next-generation wireless networks are evolving towards architectures that integrate terrestrial and non-terrestrial networks (NTN), unitedly known as vertical heterogeneous networks (vHetNets). This integration is vital to address the increasing demand for coverage, capacity, and new services in urban environments. Among NTN platforms, high altitude platform stations (HAPS) play a promising role in future vHetNets due to their strategic positioning in the stratosphere. In HAPS-enabled vHetNets, various tiers can operate within the same frequency band, creating a harmonized-spectrum integrated network. Although this harmonization significantly enhances spectral efficiency, it also introduces challenges, with interference being a primary concern. This paper investigates vHetNets comprising HAPS and terrestrial macro base stations (MBSs) operating in a shared spectrum, where interference becomes a critical issue. The unique constraints of HAPS-enabled vHetNets further complicate the interference management problem. To address these challenges, we explore various strategies to manage interference in HAPS-enabled vHetNets. Accordingly, we discuss centralized and distributed approaches that leverage tools based on mathematical optimization and artificial intelligence (AI) to solve interference management problems. Preliminary numerical evaluations indicate that distributed approaches achieve spectral efficiency comparable to the centralized algorithm, while requiring lower complexity and less reliance on global information.