BEHOP-GC

Status

Ongoing
Status date

2021-09-29
Activity Code

6B.070

Objectives

In a beam-hopping system as illustrated below, a beam-hopping time plan (BHTP) is executed repeatedly to serve different service areas. The dwell times correspond to the current traffic demands by the remote terminals. This cyclic execution runs until a new BHTP is provided, which defines a new time plan and possibly new beam coverages (new cluster) matching changed traffic demands. Therefore, beam-hopping provides the required flexibility and variability to match non-uniform and time-varying traffic demands to the satellite system resources.
A key features of beam hopping systems is to support seamless updates of the BHTP (no interruption and no loss of synchronization between gateway, satellite and user terminals) in order to assure a given quality of service (QoS).
DVB-S2X specifies three new Super-Frame Formats (5, 6, 7) for beam-hopping and two application modes of beam-hopping: pre-scheduled (using Format 5) and traffic-driven (using Format 6, 7). This project focuses on the first mode, which relies on repetitive cycles of the BHTP until a new BHTP is applicable. This allows for extra features compared to Format 6 and 7:

PLFrame fragmentation among dwells for increased efficiency
Validation of the start of dwell detection
Close tracking of carrier frequency or timing drifts due to e.g. Doppler

The project objectives are the following:

Implementation and validation of a complete DVB-standard compliant signal transmission chain for forward link beam hopping
Enhancement of a wideband modulator (capable of DVB-S2X Annex E, Super-Framing Format 4) to support now Format 5, NCR distribution and signalling of BHTP updates
Enhancement of a wideband user terminal device (capable of DVB-S2X Annex E, Super-Framing Format 4) to support now Format 5, NCR synchronization, exploiting the signalling of BHTP updates for seamless data reception
Integration of all devices in an automated testbed for analysis, testing, demonstration, and evaluation of different system configurations and transmission scenarios

Challenges

Variable Super-Frame length
Correct insertion of the new signalling elements of Format 5
Implementation of individual queues for all service areas (coverages)
Accurate and standard compliant NCR implementation
Standard compliant lower layer signalling for BHTPs
Seamless BHTP update procedure
Coping with channel impairments, e.g. Doppler induced drifts

Benefits

Based on the previous ESA project on beam-hopping (cf. link below), large and proven heritage can be re-used and extended for these developments.

Benefits on modulator side:

Accurate NCR insertion for different cells
Scheduling and planning of BHTP updates as well as NCR time tagged execution
Cell-specific data queueing

Benefits on user terminal side:

Initial learning of BHTP and seamless BHTP update handling based on information from lower layer signalling and NCR
Adjacent cell interference awareness
Design is also suitable for continuous reception mode.

Features

Implementation and test of DVB standard compliant ground components
- Modulator with beam-hopping-specific flexibility
- User terminal with beam-hopping-specific synchronization and data decoding
- Automated lab testing employing a beam-hopping payload emulator and a satellite channel emulator
Wideband transmission up to 500 Mbaud over L-band
End-to-end data transmission in a beam-hopping system
DVB-S2X compliant implementation of beam-hopping using Super-Frame Format 5
- All roll-offs: 5%, 10%, 15%, 20%, 25%, 35%
- All MODCODs: VLSNR-MODCODs, QPSK … 256 APSK

System Architecture

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

Wideband modulator with IP encapsulator configurable to the actual BHTP
Satellite payload emulator implementing the beam-hopping characteristic
Satellite channel emulator for the transmission scenario related impairments (e.g. Doppler and Doppler drift)
User terminal for data reception, decoding and IP decapsulation

Plan

Milestones & Meetings

Planned Schedule

Kick-Off

11/2020

SDSR

System Definition and Specification Review

02/2021

PDR

Preliminary Design Review

06/2021

CDR