PAGE CONTENTS
Objectives
Current terrestrial mobile technology is not able to cover demand in some use cases. This is why operators and industry are making analysis and trials for these services using HAPS.
The candidate communication protocols to be used (DVB, 4G/5G, CCSDS) suffer from some drawbacks and cannot be directly deployed. DVB was designed for a use case where both base station and the satellite are at fixed locations (no mobility). 4G/5G will suffer from latency and channel impairments which have not been tested until now. Furthermore, there are regulatory issues which are new in this situation (a HAPS cell may be much larger than a conventional 4G cell), due to the distance of the remote antenna, and which will need to be addressed in the future.
5G is a standard which still needs consolidation. Testing will also be required to assess if it works under the proposed conditions. So, an analysis seems as the optimal choice, before economic resources are committed to trials with physical equipment.
The work is focused on analysing the use cases and possible architecture solutions, selecting those most promising. Then to determine which concrete analysis and simulations are performed taking into account the maturity level of the 5G standard definition. At the end of the project, a diagnostic is provided indicating what are the necessary modifications, for the selected use cases.
Challenges
Main challenge is placed in determining the suitability of 5G standard considering HAPS platform and the related interface with satellite.
From an 5G user terminal perspective, HAPS platform is as an antenna but far away compared with terrestrial. From satellite point of view, HAPS platform is as a user terminal.
Channel model, waveform analysis, hardware impairments, synchronization, handover management are some topics to be analysed.
System Architecture
Architecture system definition is analysed in this project. As starting point have been defined several scenarios
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Satellite as simple backhaul of 5G base station
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Satellite as support of aggregated non-3GPP access
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Satellite interconnecting 5GC located on board HAPS
Additionally, other variants could be proposed, by implementing some technology enablers previously described within the Satellite Backhauled HAPS architecture. Firstly, a transparent satellite payload is assumed, New Radio is used over the satellite backhaul link.
Then the most advanced technology is assumed, with regenerative payloads (more suitable for implementation with LEO constellation). A complete 5G integration level is achieved.
Plan
The project is developed in one phase with the following milestones:
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MS1: System Requirements Review (SRR)
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MS2: System Analysis Review (SAR)
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MS3: Final Review (FR) including conclusions, roadmap and recommendations.
Current Status
The project has been completed and all activities achieved:
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WP1000: Case Selection & Scenario Definition, including the selected scenarios, the justification of the selection and relevance of the selected scenarios for the satcom sector.
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WP2000: Suitability Analysis, Adaptations and Development Plan assesses the suitability of the current technology required for each scenario at least at physical, link and network layers, and identify necessary adaptations accordingly.
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WP3000: Implementation and adaptation includes the simulations and emulations carried out to evaluate the performance of the proposed system and to verify the previously identified issues.
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WP4000: Contributions to 3GPP summarizes the findings of the activity and presents a development roadmap leading to the realization of each of the scenarios studied in the activity.
