[Paper Review] Facilitating Satellite-Airborne-Terrestrial Integration for Dynamic and Infrastructure-less Networks

Ahmad Alsharoa, Mohamed‐Slim Alouini|arXiv (Cornell University)|Dec 9, 2019

Satellite Communication Systems18 references4 citations

TL;DR

This paper proposes an integrated satellite-airborne-terrestrial network using high-altitude platforms (HAPs) with free-space optical (FSO) backhaul to enhance data rates in infrastructure-less and dynamic environments. By jointly optimizing user association, HAP placement, and power allocation—especially via FSO-enabled backhaul—it achieves up to 88% higher average user throughput compared to benchmarks, significantly mitigating backhaul bottlenecks.

ABSTRACT

This paper studies the potential improvement in the achievable data rate available to ground users by integrating satellite, airborne, and terrestrial networks. The goal is to establish dynamic wireless services in remote or infrastructure-less areas. This integration uses high-altitude platforms in the exosphere, stratosphere, and troposphere for better altitude reuse coupled with emerging optical or other high-frequency directional transceivers. Hence they offer a significant increases in the scarce spectrum aggregate efficiency. However, managing resource allocation with deployment in this integrated system still has some difficulties. This paper aims to tackle resource management challenges by (i) providing wireless services to ground users in remote areas and connecting them with metropolitan and rural areas, (ii) employing high-altitude platforms (HAPs) equipped with free-space-optical communication modules for back-hauling backbone. Finally, we show how our results illustrate the advantages of using the proposed scheme.

Motivation & Objective

• Address the challenge of providing reliable, high-throughput wireless connectivity in remote, disaster-affected, or infrastructure-less areas.
• Overcome the limitations of traditional satellite and terrestrial networks, including high path-loss, high latency, and backhaul bottlenecks.
• Enhance network capacity and coverage by integrating HAPs as aerial relays between satellites and ground users.
• Mitigate backhaul constraints through hybrid RF/FSO communication links on HAPs and terrestrial stations.
• Optimize resource allocation—including user association, HAP positioning, and power control—to maximize end-to-end user throughput.

Proposed method

• Integrate satellite, airborne (HAPs), and terrestrial networks to enable dynamic, infrastructure-less connectivity.
• Deploy HAPs in the stratosphere (17–20 km altitude) as high-capacity aerial base stations with solar power and FSO transceivers for backhaul.
• Use free-space optical (FSO) communication for high-bandwidth, low-latency backhaul between HAPs and core networks, reducing RF spectrum limitations.
• Formulate a joint optimization problem for user association, HAP deployment, and power allocation to maximize sum rate under backhaul and power constraints.
• Propose two low-complexity solutions: an approximate solution and a low-complexity heuristic that reduces computational load while maintaining performance.
• Model the system in a 180 km × 180 km area with three user subareas of varying density and HAP/terrestrial station coverage, evaluating performance under different backhaul bandwidths.

Experimental results

Research questions

• RQ1 How does integrating HAPs with FSO backhaul improve end-to-end user throughput in infrastructure-less and dynamic networks compared to traditional RF-only or non-optimized systems?
• RQ2 What is the impact of backhaul capacity on the achievable data rate, and how does hybrid RF/FSO backhaul mitigate the backhaul bottleneck?
• RQ3 How do different user association and HAP placement strategies affect system performance under increasing user load?
• RQ4 To what extent does joint optimization of access and backhaul links, along with power control, enhance spectral efficiency and coverage?
• RQ5 How does the performance gap between optimal and low-complexity solutions evolve with increasing user count and HAP deployment constraints?

Key findings

• The proposed joint optimization of user association, HAP placement, and power allocation increases average user data rate by at least 39% compared to optimizing only associations with uniform power.
• The proposed scheme achieves up to 88% higher average data rate than the benchmark using random associations with uniform power, especially under high user loads.
• As the number of users increases, the performance gap between the approximate and low-complexity solutions widens due to limited HAPs covering dense areas, though the gap remains acceptable due to HAPs’ large coverage footprint.
• The average data rate of HAP users increases with HAP peak power up to a saturation point, indicating that backhaul capacity becomes the limiting factor beyond that threshold.
• Increasing the backhaul bandwidth $ B_0 $ improves system performance, confirming that backhaul is a critical bottleneck in the network.
• Hybrid RF/FSO backhaul significantly enhances data rates by overcoming RF spectrum limitations, though it introduces additional complexity due to line-of-sight alignment optimization.