BACKHAULED HAPS

Status

Completed
Status date

2024-06-14
Activity Code

1B.114

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.

Benefits

This is an opportunity for the telecommunications industry: to provide services with the help of High-Altitude Pseudo-Satellites (HAPS).

The HAPS by themselves allows to provide services of the highest quality, if a series of requirements are met. One of the main handicaps is the need to obtain a high-capacity terrestrial backbone Internet access line within the scope of HAPS coverage. This may be possible in a large number of occasions, but many others may not be trivial. On those occasions, having the trunk link through geostationary satellites can solve the problem.

This hybrid solution would allow to provide services globally, regardless of whether or not there are terrestrial trunk links and, in addition, to simplify the user terminal equipment, allowing for example the provision of 5G services, since in case of not using geostationary satellites, it would not be possible to provide this "global" service.

This activity contribute to the development of society and improving the quality of life by allowing provision by the satellite industry of services to a larger extent of the population.

Features

The fact of including HAPS infrastructure between satellite and user terminal has an impact in the networks system architecture.

Thanks to that, 20 km HAPS location has an improvement in the link budget capabilities by the fact of reducing link budget losses (compared with satellite) reaching higher bit rates.

On the other hand, regarding the terrestrial network, the fact of having HAPS placed 20 km over users increases the interest in medium density population areas by the sense of infrastructure and service development.

System Architecture

Architecture system definition is analysed in this project. As starting point have been defined several scenarios

Satellite as simple backhaul of 5G base station
Satellite as support of aggregated non-3GPP access
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:

MS1: System Requirements Review (SRR)
MS2: System Analysis Review (SAR)
MS3: Final Review (FR) including conclusions, roadmap and recommendations.

Current status

The project has been completed and all activities achieved:

WP1000: Case Selection & Scenario Definition, including the selected scenarios, the justification of the selection and relevance of the selected scenarios for the satcom sector.
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.
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.
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.