HAPS Relay Segments Satellite Feeder Link for MIMO RF and FSO
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Solution Overview
Problem
Conventional ground-to-satellite free-space-optical (FSO) links are hindered by atmospheric impairments such as attenuation, scintillation, beam wandering, and pointing errors, as well as the requirement for an unobstructed line-of-sight, which is often obstructed by clouds, leading to frequent link failures and high deployment costs.
Innovation Solution
A relay-assisted hybrid radio frequency/free-space-optical (RF/FSO) ground-satellite link is implemented using a high-altitude platform station (HAPS) that splits the link into a ground-to-HAPS MIMO RF link and a HAPS-to-satellite FSO link, mitigating atmospheric impairments and reducing bandwidth and propagation disparities between RF and FSO links.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a ground-to-satellite FSO link is implemented, then data rate is improved, but reliability deteriorates due to atmospheric impairments and cloud obstruction
Solution Approach 1:
The ground-to-satellite link is segmented into two separate links: a ground-to-HAPS RF link and a HAPS-to-satellite FSO link. This segmentation allows the FSO link to operate from elevated altitude where atmospheric impairments are reduced, while the RF link handles the ground segment, thereby maintaining high data rates while improving overall link reliability.
Solution Approach 2:
A high-altitude platform station (HAPS) is introduced as an intermediary node between the ground and satellite. The HAPS serves as a relay that receives signals via RF from the ground and transmits via FSO to the satellite, mitigating the effects of atmospheric turbulence and cloud obstruction by operating the FSO link from elevated altitude.
2Reliability
If multiple redundant optical gateways are deployed to overcome cloud attenuation, then reliability is improved, but deployment cost increases
Solution Approach 1:
Instead of adding redundancy in the horizontal dimension (multiple ground-based gateways spread over large geographical regions), the solution moves to the vertical dimension by deploying a single HAPS at high altitude (approximately 18-24 kilometers). This dimensional shift allows a single platform to access clearer atmospheric conditions above most cloud layers, achieving reliability improvement without proportional cost increase.
3Reliability
If an RF link is used as backup when optical link has outage, then reliability is improved, but bandwidth is reduced
Solution Approach 1:
The system dynamically switches between RF and FSO links based on atmospheric conditions and operational requirements. The HAPS can communicate with the ground via RF when needed and with the satellite via FSO when optimal, allowing the system to adapt to changing conditions while maintaining high capacity through the FSO link during normal operation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly improves the reliability of the ground-to-satellite link by reducing the effects of atmospheric impairments and bandwidth disparities, while also lowering the costs associated with deployment and maintenance.
Implementation Method 1
a first sub-link from a ground terminal to the HAPS relay station implemented as a line-of-sight (LoS) multiple-in-multiple-out (MIMO) radio frequency (RF) link, and a second sub-link from the HAPS relay station to a satellite implemented as a free-space-optical (FSO) link
Data Source
AI summary
Techniques are described for providing satellite communications via a relay-assisted hybrid radio frequency/free-space-optical (RF/FSO) ground-satellite link. A high-altitude platform station (HAPS) splits the ground-to-satellite link into a ground-to-HAPS line-of-sight (LoS) multiple-in-multiple-out (MIMO) radio frequency (RF) link, and a HAPS-to-satellite FSO link. The approach mitigates the effects of atmospheric impairments on the FSO link, while also appreciably reducing adverse effects of bandwidth and propagation disparity between the RF and FSO links.