European Space Agency

BACKHAULED HAPS - INTEGRATION OF SATELLITE BACKHAULED HAPS IN FUTURE SATCOM NETWORKS

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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 selecting those most promising. Then to determine which concrete analysis and simulations are performed. At the end of the project, a diagnostic is provided indicating what are the necessary modifications, for which protocols selected for the use cases.

Challenges

On the original proposal was planned to study also DVB communications between HAPS and Satellite and 4G. After SRR DVB and 4G have been discarded focusing the activity on 5G.

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, 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 will 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.

Finally, ground UEs are not 3GPP managed UEs but are instead any generic device equipped with a wireless connection (could be some WIFI access, WIMAX (802.16), other communication standard, or possibly a dedicated future waveform operating in its authorized frequency band, shared or not) allowing the connection to the HAPS. Ground UEs and HAPS are logically under a pseudo LAN model, as studied in 3GPP TR 22.821 considering a home (residential) LAN case

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 System Requirements Review has been successful, on this work package has been analysed several use cases and scenarios considering the best way to provide services by looking at the technical and economic constraints.

Finally, on this WP, a scenario has been selected taking into account the point of view of service manufacturer, service provider and final user.

Status date

Monday, March 16, 2020 - 11:18