BEHOP

Status

Completed
Status date

2018-10-15
Activity Code

3A.072

Objectives

Beam hopping is an emerging technique to enhance flexibility, agility, and throughput of satellite systems. Due to adaptive activation/deactivation of beams according to the actual traffic demands, congestion problems are mitigated and the power efficiency is improved, compared to conventional systems with quasi-static illumination.

The project objectives are the following:

Demonstration of a complete signal transmission chain providing beam hopping network emulation
Enhancement of a wideband modulator (capable of DVB-S2X Annex E, Super-Framing Format 4) to provide beam aligned data streams
Establishment of a beam hopping emulator hardware to emulate the satellite
Evolvement of a terminal device (capable of DVB-S2X Annex E, Super-Framing Format 4) to operate with bursty receive signals
Development, optimization, and showcasing of network synchronization techniques between gateway and satellite based on feedback from a reference terminal implementation
Analysis, testing and evaluation of different system configurations (cf. example in figure) using the developed testbed
Performing an over-the-air test to demonstrate the maturity of the developed concept and its implementation in hardware

Challenges

One of the key challenges of the project is the alignment between user data traffic, addressed beam and signalling the beam switching to the satellite in a synchronized manner. Next to that the provision of a DVB-S2X conform terminal coping with burst-wise data reception is of key importance, where special signal processing and synchronization techniques are required. More specifically, a reference terminal provides means for alignment of the modulator transmission and the beam switching window with an accuracy of only a few symbols.

Benefits

The entire testbed finally serves as proof-of-concept for the ground segment technologies required to enable beam hopping in future missions like Eutelsat’s Quantum project. The close cooperation between the technology providers Fraunhofer IIS and WORK Microwave with technical support from Eutelsat allows for a most realistic emulation of the Quantum payload and the optimization of the ground segment to enable a successful deployment after system launch.

On the other hand, the testbed will also be capable to host other payload characteristics or payload emulations by means of usage of standard L-Band interfaces for the signal transmission path as well as standard IP interfaces for the interaction between modulator and reference terminal.

Consequently, the testbed devices are used in the final phase of the project also for over-the-air tests. Due to usage of a conventional bent-pipe satellite, the payload emulator is placed in the uplink transmission chain. So all developed beam hopping techniques are verified over-the-air as well.

The chosen waveform, DVB-S2X Annex-E Super-Frame Format 4, is considered the best candidate in order to show a comprehensive proof-of-concept since it supports:

Operation under low SNR ensuring proper signal detection
Wideband processing by means of time slicing for throughput maximization and efficient user data multiplexing
Dynamic Super-Frame padding for termination of transmission minimizing overhead and being adjustable to padding demands

Other waveforms (no Super-Framing) or even other Super-Frame Formats have not shown any advantage against the selected waveform.

Features

Implementation and test of special beam hopping network synchronization schemes
- Reference terminal for network monitoring
- Modulator with beam hopping-specific flexibility
- Automated procedures for network acquisition and configuration verified in lab and over-the-air
Wideband transmission over L-band
End-to-end data transmission in a beam-hopping system
DVB-S2X conform implementation of beam-hopping
- All roll-offs: 5%, 10%, 15%, 20%, 25%, 35%
- All MODCODs: QPSK … 256 APSK

System Architecture

The hardware testbed (as visualized in the figure) consists of four key components:

Wideband modulator that runs network synchronization algorithms
Payload emulator that handles switching to different outputs according to a reconfigurable beam switching time plan (BSTP) relative to its internal clock
Reference terminal that estimates various offsets from the bursty input signal and provides feedback to the modulator-side synchronization algorithms
User terminal for demodulation and decoding of the bursty input signal

Plan

Milestones & Meetings		Planned Schedule
KO	Kick-Off Meeting	February 2016
SDR	System Design Review	July 2016
BDR	Baseline Design Review	December 2016
TRR	Test Readiness Review	December 2017
OTR	Over-The-Air Test Readiness	May 2018
VR	Validation Review	October 2018
FR	Final Review	January 2019
FP	Final Presentation	January 2019