Equitable 6G Access Service via Cloud-Enabled HAPS for Optimizing Hybrid Air-Ground Networks (2212.02052v1)

Abstract: The evolvement of wireless communication services concurs with significant growth in data traffic, thereby inflicting stringent requirements on terrestrial networks. This work invigorates a novel connectivity solution that integrates aerial and terrestrial communications with a cloud-enabled high-altitude platform station (HAPS) to promote an equitable connectivity landscape. Consider a cloud-enabled HAPS connected to both terrestrial base-stations and hot-air balloons via a data-sharing fronthauling strategy. The paper then assumes that both the terrestrial base-stations and the hot-air balloons are grouped into disjoint clusters to serve the aerial and terrestrial users in a coordinated fashion. The work then focuses on finding the user-to-transmitter scheduling and the associated beamforming policies in the downlink direction of cloud-enabled HAPS systems by maximizing two different objectives, namely, the sum-rate and sum-of-log of the long-term average rate, both subject to limited transmit power and finite fronthaul capacity. The paper proposes solving the two non-convex discrete and continuous optimization problems using numerical iterative optimization algorithms. The proposed algorithms rely on well-chosen convexification and approximation steps, namely, fractional programming and sparse beamforming via re-weighted $\ell_0$-norm approximation. The numerical results outline the yielded gain illustrated through equitable access service in crowded and unserved areas, and showcase the numerical benefits stemming from the proposed cloud-enabled HAPS coordination of hot-air balloons and terrestrial base-stations for democratizing connectivity and empowering the digital inclusion framework.

• The paper introduces a cloud-enabled High-Altitude Platform Station (HAPS) system that integrates terrestrial and aerial networks to provide equitable 6G access.
• It employs numerical iterative algorithms like fractional programming and sparse beamforming to jointly optimize user association and beamforming for sum-rate and fairness.
• Simulation results demonstrate that the cloud-enabled HAPS system significantly enhances broadband access and user coverage, especially in rural and underserved areas.

Overview of Equitable 6G Access via Cloud-Enabled HAPS

The paper "Equitable 6G Access Service via Cloud-Enabled HAPS for Optimizing Hybrid Air-Ground Networks" introduces a novel connectivity solution that integrates non-terrestrial communication systems with terrestrial networks. This approach is designed to augment the capabilities of forthcoming 6G networks, addressing the issues of digital inequity and connectivity in underserved and rural areas. By employing high-altitude platform stations (HAPS) equipped with cloud capabilities, the research aims to provide seamless connectivity, complementing terrestrial base stations (TBS) and integrating hot-air balloons (HBS) in a combined framework.

System Architecture and Objectives

The paper proposes a cloud-enabled HAPS system architecture that uses a fronthauling strategy to connect terrestrial and aerial networks, establishing a coordinated air-ground network. Different clusters consisting of TBS and HBS are formed to serve both terrestrial and aerial users. The major objectives of the proposed system are twofold: maximizing the sum-rate and promoting fairness to democratize access.

1. Sum-Rate Maximization: By focusing on maximizing the network throughput, the paper adopts advanced numerical optimization strategies that iteratively refine user-to-transmitter associations and beamforming policies. The methodology relies heavily on numerical iterative algorithms like fractional programming (FP) and re-weighted sparse beamforming approximations.
2. Fairness Optimization: The research advances a fairness-driven approach by optimizing the sum-of-log of average rates. This creates a resource allocation framework based on proportional fairness scheduling, particularly important for 6G networks intended to span users of varied service conditions.

Numerical Techniques and Algorithmic Solutions

To tackle the proposed non-convex optimization problems, the research devises specific algorithmic solutions. By applying techniques such as FP and sparse beamforming, the paper addresses intricacies of joint optimization problems involving discrete and continuous variables. Key highlights include:

• Iterative numerical solutions: Sequentially optimizing association parameters and beamforming vectors to maximize throughput and fairness.
• Quadratic transformations in FP: Employed to manage the objective functions' complexity, transforming them into treatable forms, ensuring computational feasibility and efficiency.

Numerical and Simulation Results

The simulations presented affirm the cloud-enabled HAPS's effectiveness in enhancing broadband access in diverse geographic areas. Comparisons with standalone terrestrial infrastructure demonstrate significant improvements in sum-rate and user coverage, particularly in rural and underserved locations. Importantly, the adaptive clustering and beamforming solutions show notable performance improvements over fixed strategies, evidencing the utility of dynamic resource allocation paradigms in addressing emergent network demands.

Implications and Future Developments

The research on cloud-enabled HAPS within non-terrestrial networks substantially informs the development of inclusive connectivity frameworks for 6G. The proposed methodologies not only offer high data rates but also effectively address equity issues across different user demographics:

• Practical: Offers a scalable solution for bridging connectivity gaps in remote areas, vital for global 6G deployment strategies.
• Theoretical: Expands our understanding of integrated air-ground network optimizations, influencing future multi-layer network design research.

Conclusion

This paper makes a significant contribution by providing a methodical approach to integrating cloud-enabled HAPS with terrestrial and aerial networks for the 6G era. It highlights the potential of non-terrestrial components to play a pivotal role in equitable and efficient network management, setting a precedent for future studies and system deployments aimed at democratizing digital access via robust technical frameworks.