Beam Hopping in DVB –S2X

DVB Webinar – 30 March 2020• Nader Alagha – ESA ESTEC (European Space Research and Technology Centre)• Avi Freedman – SatixFy• Peter Nayler – EASii IC

1. Context and requirements for beam hopping2. Beam Hopping Definitions 3. Beam Hopping System Scenarios4. General description of new Formats for Beam hopping5. Simulation and Analysis 6. Maintenance, further work and closing remarks

Content

1. Context and requirements for Beam-Hopping

• DVB-S2: March 2005, EN302307 • DVB-S2X : October 2014, EN… part 2• Main improvements were

• More MODCODs -> Higher dynamic range (VLSNR, 256APSK), smaller gaps between MODCODs

• Time slicing (new header) -> manageable complexity

• Lower roll off -> more efficient BW use • Scrambling -> Tighter beams (spot

beams)• Channel bonding -> statistical mux

DVB-S2 to S2X

• The S2X standard was all very well but:• The standard did not easily allow for

dynamic reallocation of resources.• Satellite capacity tended to be fixed at

launch• Satellite throughput limited by

amplifiers and TWTs• Some areas (cells) required much more

capacity than others.• More flexibility in throughput allocation

was required.

New requirements

Some cells require more capacity

• Satellite technology moved on. Ferrite switches, regenerative payloads, electronically steerable

antennas… Bandwidth could now be allocated to each cell as a function of time.

• -> BEAM-HOPPING Studies showed that 20% improvement in unmet demand1

• In order to exploit the potential the DVB-S2 standard had to be upgraded again.

New Technologies

1/ ETSI TR 102 376-2 V1.1.1 (2015-11): Implementation Guidelines DVB-S2X

• In October 2017 the CM agreed that CM-S should work on commercial requirements• amending the DVB-S2X specification to include optimisations for beam-hopping. • chairmanship of Thomas Wrede.

• In October 2018, the DVB-S-CM published a set of commercial requirements for Beam-Hopping (DVB-S CM-S0050).

DVB-CM-S and Beam-Hopping

• The main requirements were:• Enable a wider range of applications

• IOT, flight connectivity, Consumer broadband, maritime, IP trunking..

• Evolution, not revolution• Technical requirements:

• high illumination ratios (period on vs off), single or multiple carriers per beam, low power, low latency, GEO, MEO, LEO…

• Interoperability between equipment providers and service providers• Holistic approach

• updating linked standards where appropriate: SI, GSE, RCS

• In June 2018 DVB-TM-S, under the chairmanship of Alberto Morello, was mandated to work on the new standard

• Over to Nader…

DVB-TM-S and Beam-Hopping

2. Beam Hopping Definitions

Basic Definitions• A Beam is a directional Radio Signal

Transmitted from a Satellite Transmission Channel towards a Cell

• At any given time only one Cell within a Cluster is illuminated.

• A Transmission Channel is serving one Cluster

• The Beam Hopping Time Plan determines cell dwell times and the BH Cycle within a cluster.

Tx

Tx

Tx

Tx

Transmission Channels

Beam

Cell

Cluster

Satellite Payload

• Satellite Gateway to User Terminal Forward Link: Time-multiplexing data traffic of multiple

cells within each Cluster Typically a Wideband Transmission A satellite beam switching (hopping) to

different Cells

• Reconfigure according to changing traffic demands and user locations

• Applicable also to the Return Link

Beam Hopping Concept

Cell 1

Cell 2

Cell 3

R&D Activities

System Studies:• Beam Hopping Techniques in Multi-Beam Satellite Systems

https://artes.esa.int/projects/beam-hopping-techniques-multi-beam-satellite-systems-eads-astriumhttps://artes.esa.int/projects/beam-hopping-techniques-multibeam-satellite-systems-indra-espacio

Proof of Concept :• Beam Hopping Emulator for

Satellite Systems: https://artes.esa.int/projects/behop

Expected Benefits• Capacity increase by up to +15%• Reduction of the unmet and excess capacity

by 20%• Better flexibility in allocating capacity to the

beams with variable traffic demand• Lower DC power consumption

0 5 10 15 20 25 30 35 40 45 50 55 60 65 700

200

400

600

800

1000

1200

Beam #

Capa

city

[Mbp

s]

Offered vs Required Beam Capacities

RequiredOffered

0 5 10 15 20 25 30 35 40 45 50 55 60 65 700

200

400

600

800

1000

1200

Beam #

Capa

city

[Mbp

s]

Offered vs Required Beam Capacities

RequiredOffered

Air Interface Technical OverviewA sketch of the Physical Layer Changes:1. Before each burst, introduce a TRAINING SEQUENCE (Preamble) to allow receiver

synchronization: 2. Between bursts, introduce a IDLE-SEQUENCE to allow satellite beam switching: Post-

amble

A Generic Beam Hopping Model

• the carrier frequency,• carrier bandwidth and• number of carriers (per cell)

DT(1)SF 0

Beam Hopping Cycle

DT(2) DT(3)DT(1) DT(N-1) DT(N)

Frequency

Time

A beam hopping transmission channel may switch:

3. Beam Hopping System Scenarios

Satellite systems: Multi-beam GEO satellites (HTS, VHTS) Medium Earth Orbit Satellites Low Earth Orbit constellations

Potential applications: Broadband bi-directional traffic (B2B, B2C) Maritime, Airborne In-Flight Communications VoIP (low delay and jitter), IoT (low power consumption of user

terminal)

Beam Hopping System Scenarios

Prescheduled BH cycles: Regular and periodic illumination pattern

Traffic Driven BH: Non-periodic illumination pattern (Beam Hopping Time Plan), driven by traffic profile.

Beam Hopping Operation Strategies

GW

Cluster 1

Cluster 2

Cluster 3

Traffic Driven Beam Hopping

Point and ShootEvery packet to a user is directly transmitted

Quality of ServiceMore Flexibility to minimize Scheduling Delay (higher QoS)

Fixed Container StrategyFixed size transmission packet. Transmitted when filled up. 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

Time (sec )

1

2

3

4

Cel

l N

o.

Non-Periodic Beam Hopping

Beam Hopping Channel Model

Performance Evaluation:• Acquisition Mode• Tracking Mode

Performance Metrics:

Acquisition Modes• Mean Acquisition Time• Estimation Statistics of Sync. Parameters

Tracking Mode• Frame Error Ratio • Header Decoding Ratio

Parameters Acquisition TrackingCarrier Frequency Offset

340 kHz [ 1 kHz +1kHz]

Carrier Symbol Rates

57.526 MBaud 57.526 MBaud

Symbol Rate Offset 15 ppm 1 ppm – 1 ppm

Timing Offset Uniformly distributed in [-Ts/4 +Ts/4]

Uniformly distributed in [-Ts/4 +Ts/4]

Initial Phase Offset

Uniformly distributed in [-π +π] interval

Uniformly distributed in [-π +π] interval

SNIR -9.5 dB -9.5 dB0 dB10 dB

4. General description of new Formats for Beam hopping

• Based on Annex E superframes Supports multibeam operation and future waveforms Variable superframe length to provide required granularity for beam-hopping operation

• Format 5: Periodic BH and VLSNR Strong preamble and header protection for cold acquisition and operation at SNR>-10dB Enable fragmentation of frames

• Format 6: Traffic Driven BH and VLSNR Long preamble to strengthen acquisition Protection Level Indicator (PLI) to enable VLSNR support No Fragmentation

• Format 7: Traffic driven, SNR>-3dB Reduced overhead for higher SNR scenarios

DVB-S2X Waveforms for Beam Hopping Support

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Annex E Superframe - Concept

WH coded SOSF and Pilots – Ref Scrambler– Identify and estimate adjacent cell interference

Fragmentation enabled by SFH pointer VLSNR Support by

– VLSNR modcods– variable header Protection Level by an Indicator (PLI)

SOSF SFFI

Scrambler RESET

Superframe Length = 612540 symbols

SFH P PLH

PLH

Annex E

Annex E Format 4

P PLH P

Joint Reference ScramblerCell Specific Scrambler

Pointer

WHcell WHcell WHcell WHcell

PLI

SOSF: Start of Super-FrameSFFI: Super-Frame Format IndicationSFH: Superframe HeaderPLH- Physical Layer frame Header

P

Payload (90 symbols)

Pilot group (36 symbols)

DVB-S2X Waveforms for Beam Hopping SupportNew Annex E Superframe Formats

BeamSwitching

time

SOSF SFFI SFH P NCU-1 NCU PA-Seq

SOSF SFFI P NCU-1 NCU PA-SeqEHF PLI P

SOSF SFFI P NCU-1 NCU PA-Seq

Postamble

P

Superframe Length = SFL symbols

Format 5Periodic BHVLSNR

Format 6Traffic Driven BHVLSNR

Format 7Traffic Driven

720 Symbols 720 Symbols

504 Symbols 216 Symbols

P

Payload CU (90 symbols)

Pilot group (36 symbols)

SOSF: Start of Super-FrameSFFI: Super-Frame Format IndicationSFH: Superframe HeaderEHF: Extended Header FieldPLI: Protection Level IndicationPA-Seq: Postamble sequence

Superframe Format 5 – Operation CasesFull Flexibility to the System Designer

25

SOSF PASFH PLH PLH PLH

Protection Level

SOSF PASFH PLH PLH SOSF SFH

PLH

Middle SuperframeInteger number of pilot blocks

Last SuperframeAny length as required

Fragmentation Pointer

PASOSF SFH PASOSF SFHPointer=0

PA

PA

PA

Single superframe All terminals on a similar SNR level

Multiple SuperframesTerminals of different SNR levels

Very short dwells Frame carried among hops

Multi Carrier operationVariable superframe length per carrier

Grid Operation• Hops take place only at an integer

multiple of a basic time unit (the grid points)

• Advantages: Ensure alignment of SF among beams Reduces burst acquisition and time

and increases acquisition reliability

• Disadvantages Reduces flexibility in the choice of

dwell time per cell

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5. Simulation and Analysis

• Robust cold acquisition Detection of the signal at SNR> -10dB Short acquisition time Essential estimation of timing, frequency, phase and SNR

• Robust cycle time learning (for the case of periodic beam hopping)

• Correct header decoding at SNR >-10dB• Minimal degradation in performance

FER at tracking mode

Purpose of Analysis and SimulationBurst Reception Performance

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Parameter Estimation:- Time: 0.06 symbol time- Frequency: 10-5 symbol rate- SNR: 0.7 dB

Burst Acquisition- Results

False Alarm and detection rates< 10-6 Acquisition within a single hop time

Cycle learning within 2.5 dwells

Information Detection- Results

SFH Detection (Format 5): WER<10-7

SNR degradation 0.07dB at VLSNRReference to continuous case

-12.5 -12 -11.5 -11 -10.5 -10

Es/No [dB]

10 -7

10 -6

10 -5

10 -4

10 -3

FER

SFH 16bits 720 symbols FER , 100 errors per point

SFH 14/630 hop acquisition

SFH 16/720 hop acquisition

SFH 16/720 AWGN

-16 -15 -14 -13 -12 -11 -10

Es/No [dB]

10 -7

10 -6

10 -5

10 -4

10 -3

10 -2

WER

210 symbols

270 symbols

2bits by SFH 270

216 Symbols-Analytic

270 Symbols-Analytic

PLI Detection (Format 6): WER<10-7

9.4 9.5 9.6 9.7 9.8

Es/No [dB]

10-6

10-5

10-4

10-3

10-2

FER

first hop frame

reference

-10.5 -10.45 -10.4 -10.35 -10.3 -10.25 -10.2

Es/No [dB]

10-6

10-5

10-4

10-3

10-2

FER

first hop frame

reference

SNR degradation 0.02dB at High SNRReference to continuous case

6. Maintenance, further work and closing remarks

• The DVB-TM-S also took the opportunity or solve some problems which had been observed in the DVB-S2X

Maintenance

Co-existence of VLSNR frames with standard S2X frames.

– Problem: Instability in transition zone between VLSNR and S2X MODCODs

– Solution: Dummy Synchronisation Frame Same correlation structure as per new annex-E format 6.

– VLSNR frames can now coexist in the same carrier as S2X frames thanks to DSF.

• Alberto Morello retired from DVB-TM-S in December 2019 • Replaced by Vittoria Mignone (welcome).

The work continues

Continuity

• Further work Updating linked standards.

– RCS, GSE, SI tables– To support Beam-Hopping

V&V: Verification and Validation– Test patterns – Common models– File exchange

– Text based– Human and machine readable

Further work

• The DVB-S standard now includes Beam-Hopping

All of the commercial requirements for Beam-Hopping have been met.

• This has been an excellent cooperation between multiple companies and institutions. We can be confident that we have a standard that is robust, forward looking and well maintained.

Concluding remarks

Questions and Answers

END