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Signal Processing Challenges in Satellite Communication Networks

Tyrrhenian International Workshop on

Digital Communications

13 September 2016, Livorno, Italy

Björn Ottersten Interdisciplinary Centre for Security, Reliability and Trust (SnT)

University of Luxembourg

Acknowledgements:

Dr. Symeon CHATZINOTAS

Dr. Bhavani SHANKAR

Dr. Shree Krishna SHARMA

Dr. Sina MALEKI

Dr. Maha ALODEH

Dr. Eva LAGUNAS

1. Introduction and Motivation 2. New Satellite Systems for New Services 3. Interference Monitoring and Localization 4. High Throughput Satellites (HTS)

• Precoding at the Gateway • Non-exclusive bands: Cognitive SatComs

5. On-board Processing 6. Conclusions

Outline

Satellite Communications – Business View

• Satellite DTH (Direct-to-Home) TV broadcast is still the core business but meeting increased competition

• New services and applications must be developed

• Internet access growing business – targets rural areas and developing countries

• 5G backhauling, broadcast/multicast services

• 5G Ubiquitous coverage: Mobile/Maritime/Aeronautical satellite services is potentially a growing market

Emerging Market Internet Access via Multibeam Satellites

• ViaSat formerly “Wildblue” first satellite internet service provider 2005

• US and Canadian coverage

• 45 identical spot beams

• Frequency reuse: 5

• Forward link capacity: 4 Gbps

• Return link capacity: 2Gbps

• Small businesses and homes

New Satellite Services and Applications

• O3b – Other 3 Billion (SES, Google, etc.)

• First Medium Earth Orbit satellite constellation – lower latency

• Emerging markets around equator

• Backhaul via satellite for internet service providers and mobile operators

• First GW installed in Greece, first 4 satellites launched in June 2013, 8 launched in 2015

• First commercial service 2014 with 8 satellites, 35 costumers

• 20 satellites by mid-2018

• Ka band (25-40 GHz)

• Several examples of failed ventures (Globalstar, Iridium, Orbcomm, ...) targetting voice services

New Satellite Services and Applications

• Meet competition from terrestrial networks

• Broadcast services: Multimedia delivery, traffic information, fleet management, software downloads, and public safety communications

• Mobile/Maritime/Aeronautical satellite services is potentially a growing market

• Reliable and secure delivery to a wide range of users

• M2M communication applications

Aeronautical Mobile Satellite Services

Emerging Market for Broadband & Telemetry • Services

• Commercial airlines • Passenger internet access, e-mail etc. • Operational services • L- /Ka-band services

• Safety and maintenance • ADS-B • Telemetry data, ACARS, FANS, ATN,

• Bands • L (Inmarsat), Ku (Intelsat Epic) • Ka band : Global Express

• Planned Bands for higher capacity

• Q/ V (40/ 50 GHz) • W (70/ 80 GHz)

• Shift to delivering services and not bandwidth

Large LEO Constellations

• Several initiatives announced: Iridium NEXT, OneWeb, SpaceX, LeoSat

• OneWeb:

– Astrium (Manufacturing), Arianne (Launch), Target 2018

• LeoSat:

– Thales Alenia Space

• Objectives:

– Hundreds of Ka micro-satellites (150Kg) in LEO orbit

– Streamlined production (1 per day) and launch process

– Service variety: Broadband, DTH, Backhauling, Aeronautical

Courtesy of BetaNews Courtesy of SpaceNews

Large LEO Constellations

• Advantages: – Low latency, Global coverage, Redundancy, Interconnected satellites

– Paradigm shift in satellite design

• Challenges: – Interference mitigation/avoidance vs GEO Ka systems

– Large network management (handovers, intra-system interference)

– Regulatory issues

Courtesy of OneWeb.world

Innovative Launch Technologies

SpaceX is disrupting the launch business

- Reuse of launch system (Falcon 9)

- Ion thruster (electric propulsion) for GEO deployment

- Drastic cost reduction

- First commercial launcher to deliver to ISS

- Several successful commercial satellite launches

Satellite Broadband Services EU Digital Agenda

Former Commissioner Kroes blesses satellite broadband

“Every EU household can now have a basic broadband connection, thanks to pan-EU availability of satellite broadband.”

• broadbandforall.eu

• Basic packages start from €10 per month, with 20Mbps packages from €25 per month

• ASTRA2Connect or Eutelsat

Satellite networks integrated in 5G vision!

5G SatComs in Networld2020

• Networld2020 : European Technology Platform for communications networks and services

• Multimedia distribution – Broadband-broadcast convergence

• Service continuity – Seamless service provisioning

• Machine to Machine – Energy efficiency and security

• Network control signaling offload – Non-Geo satellites

Satellite Networks – Technical Challenges

• Design of a Communication Network rather than broadcast link capable of delivering multiple services

• Satellite Communications (SatCom) striving to increase offered capacity (analogous to terrestrial developments LTE, 5G)

• Reduce the cost per bit via satellite

• Broadband Internet penetration still low in rural areas

• Cope with changes in traffic evolution via satellite

– Traditional broadcasting of audio & video is changing: HDTV, 3DTV

– New services: P2P, Video-on-Demand, non-linearTV, growing Internet traffic

– Traffic imbalance between uplink/downlink is reducing

• Different challenges to increase capacity and deliver reliable services for:

– Fixed satellite terminals (Fixed SatCom)

– Mobile satellite terminal (Mobile SatCom)

Satellite Communications

• Sky Television – was one of the first (1989) Direct Broadcast Satellite (DBS) services in the world to become operational

• Astra 1A satellite owned by SES, based in Betzdorf, Luxembourg

• Not subject to IBA regulation!

• Today some 60 geostationary satellites covering 99% of world’s population

• No 1 global satellite operator

• New launches HTS IBA - Independent Broadcasting Authority in UK

Satellite Communication System: Terminology

Satellite

Feeder Link User Link

Forward Link

Return Link

User Beams

Segments

Ground

Space

User

Ground Segment

• Communications and control systems • Earth Station/ Gateway • Critical Infrastructure • Typically Fixed

• Ground Station Network • Connections to earth stations,

terrestrial network

• Typically “well endowed” • Power, Antenna Size,

Redundancy • Processing complexity and

power not primary constraints

Typical Dish size

25.9m, 18 m C-band (Goonhilly, UK)

19 m, 8 m Ku-band (Goonhilly, UK)

13.5m, 9.1m Ka-band (ViaSat)

Space Segment : Orbits • Space Assets

• Orbital Classification • GEO, MEO, LEO • Van-Allen radiation belts

• GEO Stationary • Satellite visible 24hrs • Fixed Elevation

• LEO, MEO, HEO …… • Satellite in relative motion • Limited visibility per satellite

Orbit Altitude range

(km) Period/ hrs Delay

ms Global Coverage*

LEO (Low Earth) 500-2000 1.5-1.8 ~7.5 78 (LEOSAT)

MEO (Medium Earth) 8,000-20,000 3.8-6 ~75 12 (O3b)

GEO 36,000 24 270 3 (I4/ alphasat)

User Segment

• Different classes of equipment • Mobility Classification

• Mobile Terminal (satellite phone) • Nomadic Terminal (News

Gathering) • Fixed Terminal (VSAT)

• Functionality based classification • Terminal or Access provision

• Service Level based classification • Consumer grade • Professional grade

SatCom vis-à-vis Terrestrial

• After satellite launch, no possibility of making big modifications – Manufacturers & operators very conservative wrt novel approaches

– Effort to add extra processing to the Gateway instead of on-board → vast majority of commercial satellites are transparent (bent-pipe) – this is changing!

• Long propagation delay, especially for GEO (~0.5s for round-trip)

• SatCom extremely power limited (GEO is ~36,000km away) – Necessary to operate close to saturation in non-linear HPA → intermodulation

& non-linear impairments

– In mobile SatCom deep urban reception not feasible → low coding rates and long time interleaving are needed

• Large differences in terms of wave propagation & channel characteristics – SatCom > 10GHz: rain & cloud attenuation, gaseous absorption, scintillations

– Mobile SatCom: Fading depends on elevation – line-of-sight component often necessary

– Longer coherence time for channel

Interference Monitoring and Localization

Satellite Communication Networks

Evolution

1. Interference monitoring and localization

2. Interference mitigation and rejection

3. Multi-user systems

4. Multi-user (co-channel) network design

Interference Monitoring and Localization

Interference detection Three folds increase in the number of

intentional jamming accidents compared to the total of last three years. Source: Safety Space Magazine

Increasing number of VSAT terminals: inter and intra system interference (amount to 90% of interference incidence)

Application in cognitive radios and spectrum cartography Producing a database for dynamic SatCom

access scenarios in Ka band. Tracking the activity of the incumbent

users. Useful ESInterfering

ES

17.3-18.1 GHz

f1

f1

Jammer

f1InterferingTerrestrial

station

Satellite Terminal

f1

f2

2oGEO 2 satellite

GEO 1 satellite

Need to localize interference

• Malicious jammers (can be mobile)

• Localizing misaligned satellite antennas

• Unauthorized transmission (piracy)

Interference Localization

Role of Satellite in Spectrum Monitoring

Satellite as a sensor or relay

• On-board spectrum monitoring • On-board interference detection • On-board interference localization • Relaying remote areas data to the centre

I

Data Centre

S

S

S

S

S

S

S

S

I

S

Gateway Gateway

Uplink Station (I)

Uplink Station (I)

In-Orbit Satellite

I: Incumbent UserS: Sensor

+ Reliable processing due to much higher carrier to noise ratio on-board + Avoid the change in the signal information due to multiplexing + Ability to react faster to interference + Multiple interference tracking with spatial signal processing + Simpler ground based monitoring particularly in multi-beam satellite networks – Bandwidth constraint to share the samples with the ground for complex processing. – Lack of inter satellite communications

Interference Localization

• Examples of existing techniques:

– FDOA (Single/two Satellites)

– TDOA/FDOA (two Satellites)

– Relatively low estimation accuracy

– Highly susceptible to reference signal inaccuracies

– Single emitter localization (per frequency bin)

• Future techniques also using array processing:

– Multiple emitter tracking

– Multiple-antenna moving satellite

– Single-antenna moving satellite (SAR like)

– Cooperative localization techniques

Courtesy: Patent US8462044 B1s

Return link

Forward link

User

linkFeeder

link

GateWay (GW) Users

Point-to-Point Multiuser

MIMO

High Throughput Satellites (HTS)

• Multiple antennas (feeds) at the satellite – Single antenna receivers

• User downlink : Multiuser-MIMO – Similar to cellular?

Multibeam Processing Satellite Systems

• Increasing the frequency re-use via multiple beams: – 82 narrow spot beams are flying in KA-SAT (Eutelsat),

launched in Dec. 2010 covering Europe – System throughput ~90Gbps

• Challenges as no. of beams increases – Interference increases with tighter

frequency reuse

– Resource optimization (freq, time, power)

– Not always possible to avoid beam handover (similar to cellular)

– Efficient routing & synchronization algorithms are needed

• ViaSat 1 launched October 2011

• 72 narrow spot beams in Ka band

• Coverage according to revenue

• Total capacity of 140 Gbps

Advances in Multibeam Satellite

• Shannon formula: 𝐶 = 𝑓 ⋅ log(1 + 𝑆𝐼𝑁𝑅)

• Aggressive frequency reuse: ↑ 𝑓 per user, but ↓ 𝑆𝐼𝑁𝑅

Spectrally efficient, next gen satcoms: “Terabit Satellite: A myth or reality?” Today: Viasat1, 140Gbps

Aggressive Frequency Reuse

Transmission and Reception Technologies

• Improve reliability, efficiency, coverage and reduce costs

• Interference rejection and multi-user detection

• Increased spectral efficiency, higher throughput, new diversity techniques

• Multi-input, multi-output systems

• Ground based beamforming

• Precoding + Predistortion

Intrasystem Interference Management

High no. of beams & aggressive freq. reuse → Intrasystem (interbeam) interference

similar to co-channel interference in terrestrial

Solution: Interference Management Techniques

Precoding in the forward link

MUD in the return link

Both signal processing functions are performed at the Gateway

No complexity increase at the user terminal side

Interference management techniques may be designed jointly with BF and over flexible payloads

Challenges for interference management techniques:

Multiple gateways → Distributed CSIT

Precoding further excites the non-linear behavior of the satellite amplifier (TWTAs)

Interference Mitigation at Gateway Two examples

1. Multibeam Processing 2. Symbol Level Precoding

Precoding for the Forward Link • Joint encoding of all (co-frequency) signals

transmitted by a given gateway to the

subset of beams it is serving – Minimize the mutual interference between

co-channel beams

• Linear Precoding options:

Zero-Forcing (ZF), Regularized Channel Inversion

(MMSE)

• Non-Liner Precoding options: Tomlinshon-Harashima, Dirty Paper Coding

• Precoding @ beam space vs. Precoding @ feed space

Optimized FEC framing structure of legacy communication standards (DVB-S2X):

• Long propagation delay – Long length of frame

• Historically noise limited communications

• Scheduling efficiency

Difficult to design one precoder per frame with satellite adopted constraints

Frame-based Precoding

RF Chain Nt

RF Chain 1

Nt

1

s1w1

s2w2

s1w1

G1

G3 G2

In SatComs, each antenna is driven by a dedicated RF Chain

Multigroup Multicasting

Related Problem

• PHY multicasting to multiple groups

• 𝐺 groups, each group receives same info

• Formation of such groups user scheduling

Non-convex QCQP Approach

• Optimization problem

𝑚𝑖𝑛 | 𝑤𝑚 |2𝐺𝑚=1

𝑠. 𝑡. 𝛾𝑖 ≥ Γ𝑖

• NP-hard • Recast as non-convex Quadratically Constrained Quadratic

Program

• Sub-optimal solution obtained after penalized reformulation [REF 13]

– Faster and efficient than SDR

Symbol-level Precoding for Multibeam Satellite Communications

37

The spatial dimension can be utilized to serve simultaneous users at the same time and frequencyinterference

A new dimension can be added DATA

Exploiting the availability of data dimension and channel state information at the Gateway to perform symbol-level precoding

Conventional Multiuser MISO Precoding

Uses the channel state information only to design the precoding to manage the multiuser spatial interference.

Treats the interference as a harmful factor.

Tackle the interference at average.

Examples: Closed form solutions: Zero forcing and

maximum ratio transmissions.

Objective based solutions: power minimization (Bengtsson[00], Yu[05])

38

Symbol-level Processing

Symbol-level processing was firstly proposed as Directional modulation [Baghdady 90]

It can be used to exploit the multiuser interference in a constructive fashion.

It uses the channel state information and data information to design the appropriate precoding based on a certain objective

39

Exploring the Data Dimension in Multiuser

In phase (Real)

Ou

t o

f p

ha

se (

imag

ina

ry)

Destructive interference

Interfering signal

In phase (Real)

Ou

t o

f p

ha

se (

imag

ina

ry)

Constructive interference

40

Interference using symbol-level precoding can be classified into Destructive and Constructive

Symbol-level Precoding

Aims at keeping the interference when it is constructive and remove or rotate it when it is destructive.

Applied to finite alphabets

Disadvantage: Complexity change when the set of symbols changes

41

In phase (Real)

Ou

t o

f p

ha

se (

ima

gin

ary

)

Interfering signals

Mathematical Formulation

42

The optimization that aims at minimizing total power with

respect to quality of service constraint as:

Application to Multibeam Satellite Communications

Satellite multibeam systems suffer from the nonhomogeneous and the non-linear amplification step at each antenna feed.

This affects both the amplitude and the phase of each feed output can jeopardize the feasibility of employing precoding

43

Application to Multibeam Satellite Communications

Using symbol-level precoding, it is possible to constrain the instantaneous transmitted power of each feed within limited range.

SLP ensures that the power of each feed does not reach saturation.

SLP guarantees that phase distortion is limited which reduces the differential phase among the different feeds

44

Results and Simulation

45

• CIPM (proposed)

• OB(conventional [Bengtsson00])

• 16 QAM

Impact on SatCom Ecosystem

• At least two European Space Agency projects

• Study Phase projects: SatNEx III, Next Generation Waveforms for improved spectral efficiency – Partners : Multiple universities from

– Beamforming and precoding

– Conclusions • Modelling, Identification and Estimation of parameters

• Significant gain from simulations

• Software Demonstrator project: Precoding Demonstrator for broadband system forward links – Partners : DLR (German Aerospace Agency), Fraunhofer, Uni Lu, SES

(Luxembourg)

– Software demonstration of gains from precoding in a system wide environment

– Ongoing, planned completion: December 2016

Cognitive SatComs for HTS

One of the main bottlenecks: spectrum scarcity

Future Solutions

Exploration of higher bands (Q/V bands, optical for feeder links)

Cognitive Satellite Communications (SatComs)

Hybrid and Dual Cognitive Scenarios

Non-exclusive Ka-band

Important recent attention from EC, ESA, CEPT, academic institutions as well

as from satellite operators/manufacturers

Cognitive SatComs: Scenarios

Hybrid Satellite-Terrestrial Scenario

Dual Satellite Coexistence Scenario

S. K. Sharma, S. Chatzinotas, B. Ottersten, “Cognitive Radio Techniques for Satellite Communication Systems”, in proc. IEEE VTC-fall, Las Vegas, Nevada, Sept. 2013.

S. K. Sharma, S. Chatzinotas, and B. Ottersten, “Satellite cognitive communications: Interference modeling and techniques selection,” in Proc. 6th ASMS and 12th SPSC, Baiona, Spain, 2012, pp. 111-118.

Spectrum Awareness Techniques Database and interference modeling

Spectrum Sensing

Spectrum Exploitation Techniques Beamforming

Resource Allocation

Dynamic carrier allocation

Adaptive power control

Enabling Techniques

Interference Modeling

Propagation Model (ITU) System Parameters Cognitive Zone

Area Analysis Database

Interference threshold adopted by regulatory bodies

Interference Matrix

Spectrum Sensing

Spectrum Utilization Unit: Beamforming & Carrier Allocation

Spectrum

Awareness Optimal resource

allocation

Coexistence Dual Satellite Scenarios

Ku-band downlink and uplink Coexistence (10.7-12.75 GHz and 13.75-14.5GHz)

Both satellite links operating in normal forward mode

Both satellite links operating in normal return mode

Examples: Coexistence of two multibeam systems/coexistence of

multibeam and monobeam systems

Primary

Satellite

Secondary

Satellite

Gateway 1Gateway 2

Cognition

Interference Alignment

Shree K. Sharma, Symeon Chatzinotas, and B. Ottersten, Shree K. Sharma, Symeon Chatzinotas, and B. Ottersten, “Interference Alignment for Spectral Coexistence of Heterogeneous Networks”, EURASIP Journal on Wireless Communications and Networking, vol. 2013:46, 2013.

SAT 1SAT 2

Gateway 1

Gateway 2

ST2

ST2

ST2ST1

Coordination

1 2 3 4 5 6 7 8 9 100

0.2

0.4

0.6

0.8

1

Number of beams N

Prim

ary

Pro

tection R

atio

Primary OnlyNo mit igation

Resource DivisionInterference Alignment Static

Interference Alignment CoordInterference Alignment Uncoord

Cognitive Beamhopping

Shree K. Sharma, S. Chatzinotas, and B. Ottersten, “Cognitive Beamhopping for Spectral Coexistence of Multibeam Satellites”, to appear in proc. Future Network Mobile Summit 2013, July 2013.

Primary

SatelliteSecondary

Satellite

Gateway 1Gateway 2

Cognition Link-5 0 5 10 15 20 25

0

10

20

30

40

50

60

70

80

Primary SNR in dB

Spectr

al E

ffic

iency (

bits/s

ec/H

z)

Multibeam system, Freq. reuse factor = 3

Beamhopping system, slot reuse factor = 3

Primary throughput in presence of secondary

Secondary Throughput in presence of Primary

Total throughput, cognitive beamhopping

Coexistence Multiple Satellite Scenarios

Ka band downlink/uplink GEO/NGEO scenario (17.8-20.2 GHz and 27.5-30 GHz)

Coexistence of LEO/ MEO uplink with GEO uplinks

Coexistence of LEO/MEO downlink with GEO downlinks

Mitigation of Inline interference is an open research challenge.

GEO satelltie

MEO

satellite

MEO

satellite

Hybrid Satellite-Terrestrial Scenario Fixed Satellite Service (FSS) and Microwave Links (FS) in Ka-band Status

Only 500 MHz Ka band exclusive spectrum available for both downlink (19.7-20.2 GHz) and uplink (29.5-30 GHz) of FSS systems

Non-exclusive spectrum allocation

400 MHz (17.3-17.7 GHz) primarily allocated to BSS feeder links

2 GHz (17.7-19.7 GHz) primarily allocated to terrestrial Fixed Service (FS) links

2 GHz (27.5-29.5 GHz) primarily allocated to terrestrial FS links

Research Problem: How to utilize the non-exclusive band by satellite systems effectively

without interfering the existing licensed systems ?

Cognitive SatCom Scenario

Example: Ka band downlink Scenario (17.3-19.7 GHz)

Coexistence of terrestrial FS links (incumbent) with GEO FSS downlink

(cognitive) in 17.7-19.7 GHz

Incumbent

FS link

Cognitive FSS

downlink

Interference link

Terminal-Side 3D Beamforming

Sample Result with a feed array having 7 LNBs

Hexagonal feed configuration with 7 LNBs can

effectively mitigate interference from/towards the

interference sector with more than 5 degrees

azimuthal span.

S. K. Sharma, S. Chatzinotas, J. Grotz, and B. Ottersten, “3D Beamforming for Spectral Coexistence of Satellite and Terrestrial Networks,” to

appear in IEEE VTC-Fall, 2015.

Challenges (Contd.) Low number of feeds due to cost and

implementation issues

DoA Acquisition (solutions: database, Sector based

blind approach)

Example Feed Configurations

FSS Downlink-FS Coexistence Resource Allocation and Beamforming

Beam pattern of FSS satellite and FS link distribution over Marseille, France

Exploitation Techniques: Carrier Allocation (CA) and Beamforming (BF)

SINR distribution significantly degrades

in the presence of FS interference

S. K. Sharma, E. Lagunas, S. Maleki, S. Chatzinotas, J. Grotz, J. Krause, and B. Ottersten, “Resource Allocation for Cognitive Satellite Communications in Ka-band (17.7-19.7 GHz)’’, to appear in proc. IEEE ICC, London, June 2015.

Parameters about FS links are obtained via ITU-R BR IFIC database.

Population density database from NASA SEDAC.

SINR Distribution

Per beam throughput comparison

445.45 % throughput improvement with

shared+exclusive (CA) w.r.t. the exclusive only case

580.5% throughput improvement with

shared+exclusive (CA+BF) w.r.t. the exclusive only

case

On-Board Signal Processing

On-Ground Techniques

• Work horse for enhancing performance

• Allows use of well established bent-pipe design

– Saves on-board power, mass

– Payload design can be agnostic to • Service and traffic

• Waveform

• Techniques used

• Incorporates Flexibility

– Use of new techniques

– Upgrade algorithm/ parameters

– Implementation platform

• Poses Academic Challenges

– Differentiates with terrestrial communication design

Courtesy: DLR

Traditional bent-pipe satellite payload: Functionality

Component Functionality

LNA Front end Low Noise Amplifier

LO Local Oscillator : Frequency conversion

IMUX Input Multiplexing Filter : Rejects out of band noise

HPA High Power Amplifier

OMUX Output Multiplexing Filter : Rejects out of band emissions

Pic Courtesy: Thales, L-3

On-Ground Processing Limitations

• High throughput New techniques

• New techniques bring new challenges – Can overload the workhorse

• Complex on-ground processing cannot be implemented at UT

• Stronger impairments and poorer efficiency – Propagation effects

• Inefficient Feeder Link Utilization – E.g., on-ground beamforming

• Higher Latency – Large round trip delays affect applications

(typically 250 ms)

On-Ground Processing Limitations

• Inadequacy of information – Loss of useful information after multiplexing (e.g., angles of arrivals)

• Inadequacy of support – Full-duplex relaying

– Network coding

– Anti-jamming

– Multiple interference tracking over one carrier

– Inter-satellite communications

Courtesy: DLR Institute for Communication and Navigation

Benefits of OBP

• Increasesd flexibility creating more networking capability in the sky – Routing, mesh connectivity – Lower latency – Resource management

• Relieving the burden of on-ground processing

• Less complex ground equipment – Spectrum monitoring units – Uplink gateways – User equipment – Uplink Energy-efficiency

• Feeder link BW reduction, fewer GWs

Courtesy: Thales Alenia Space

Benefits of OBP

• Higher user and system throughput, link spectral efficiency – Predistortion and interference mitigation improve SINR

– Newer Waveforms

– Full Duplexing

• System Robustness – Anti-jamming

– Higher resilience to the interference

On-board processing is an important component in the next generation of satellites

to keep SatCom competitive in the market.

TAS designed Digital Transparent Processor

Evolution of On-Board Processing

Traditional Bent-pipe On-board Digital Processing (DTP)

Wideband On-board Digital Processing

(Regenerative)

Digitize to IF for switching, beamforming,

bandwidth allocation, frequency shifting, etc.

Demod/remod, decode/uncode

ultimately a fully activie network element

Analog processing, frequency shift, amplification,

multiplexing, switching, digital control

Current On-Board Processing Technology

SATELLITE, BAND PROCESSOR FUNCTIONALITIES APPLICATIONS & BENEFITS

Hotbird6 (Ka, K-band)

Regenerative Skyplex

Multiplexing streams with audio, video and data content, Turbo decoding. Flexibility in (i) channel gains, (ii) uplink-downlink channel mapping, (iii) BW allocation on uplink.

Internet and TV Reduced latency

SPACEWAY 3 (Ka band)

Regenerative

Switching, Routing, user-user connectivity, Dynamic Beamforming. Flexibility in (i) channel to beam assignment, (ii) Bandwidth and power allocation, (iii) uplink-downlink channel mapping.

Broadband IP services Reduced latency

Amazonas 1, 2 (Ku-band) HISPASAT-AG1 (Ku-band)

Regenerative AmerHis REDSAT

Routing (DVB-S/S2/RCS support), Multiplexing, Mesh networking, Digital filtering, turbo decoding. user-user connectivity, Flexibility in (i) channel to beam assignment, (ii) Bandwidth allocation, (iii) uplink-downlink channel mapping.

Multibeam broadband multimedia services Reduced latency

Thuraya (L band)

DTP (Processing in IF)

Digital Beam forming; Flexibility in (i) channel to beam assignment, (ii) Bandwidth allocation, (iii) channel gains, (iv) uplink-downlink mapping.

Interactive services, GSM Real-time adaptation

Inmarsat-4 (L band)

DTP (Processing in IF)

Digital Beam forming; Flexibility in (i) channel to beam assignment, (ii) Bandwidth allocation, (iii) channel gains, (iv) uplink-downlink mapping.

Global 3G Mobile Communications Enhanced rate,

flexibility, capacity

Challenges with OBP

• Additional payload/hardware is required

– Higher mass and power consumption

– Manage processor heating

• Reliability

– Backup DSP chains is required in case of component failure

• Adaptivity

– Reconfiguring HW chains

• Limited sampling capability (ADC dynamics and power requirements)

• A key question to be answered: How much OBP?

Low cost but reliable processing techniques are required

Conclusions

Driving applications for SatCom are changing: Absolute need to take advantage of new & advanced DSP solutions

overcoming conservative approach of the satellite industry New paradigms are emerging, large-LEO networks, small/cheap/redundant

satellites

From link to communication network design Applicability of different transceiver solutions

Important differences between Sat/Terr: Not straightforward extension of terrestrial solutions

Long channel coherence time favors many advance DSP solutions

High Throughput Satellites Interference mitigation required – MUD, pre-coding, interference

cancellation, resource management, etc. Cognitive radio techniques have great potential to exploit spectrum more

efficiently

On-board Processing Networking functionality on-board Increased flexibility adapting to traffic demand Numerous challenges remain

Contact Info

SnT – Interdisciplinary Centre for Security,Reliability and Trust

University of Luxembourg

Luxembourg

http://www.securityandtrust.lu

KTH – Royal Institute of Technology

References

[Moh2000] M. Moher, “Multiuser Decoding for Multibeam Systems”, IEEE Trans. Vehicular Technol., vol.49, no.4, Jul. 2000.

[Bei2002] B. F. Beidas, H. E. Gamal, S. Kay, “Iterative Interference Cancellation for High Spectral Efficiency Satellite Communications”, IEEE Trans. Commun., vol. 50, no. 1, Jan. 2002.

[Cot2006] L. Cottatellucci, M. Debbah, E. Casini, R. Rinaldo, R. Mueller, M. Neri, and G. Gallinaro, “Interference mitigation techniques for broadband satellite system,” in 24th AIAA International Communications Satellite Systems Conference (ICSSC 2006), San Diego, USA, 2006.

[Cas2007] E. Casini, R. De Gaudenzi, O.d.R. Herrero, “Contention Resolution Diversity Slotted ALOHA (CRDSA): An Enhanced Random Access Schemefor Satellite Access Packet Networks,” IEEE Trans. Wireless Commun., vol. 6, no. 4, pp. 1408-1419, 2007.

[Dia2007] M. Diaz, N. Courville, C. Mosquera, G. Liva, and G. Corazza, “Nonlinear interference mitigation for broadband multimedia satellite systems,” in International Workshop on Satellite and Space Communications (IWSSC 2007), pp. 61 –65, 2007.

[Mil2007] J. P. Millerioux, M. L. Boucheret, C. Bazile, and A. Ducasse., “Iterative interference cancellation and channel estimation in multibeam satellite systems”, Int. J. Satell. Commun. Network., vol. 25, pp. 263 – 283, 2007.

[Zor2008] N. Zorba, M. Realp, A.I. Pérez-Neira, “An improved partial CSIT random beamforming for multibeam satellite systems,” in 10th Int. Work. Signal. Process. Space Commun., SPSC 2008, Oct. 2008.

[Ang2009] P. Angeletti and N. Alagha, “Space/Ground Beamforming Techniques for Emerging Hybrid Satellite Terrestrial Networks”, in Proc. 27th AIAA, Edinburgh, UK, pp. 1-6, Jun. 2009.

[Pog2009] M. Poggioni, M. Berioli, P. Banelli, “BER Performance of Multibeam Satellite Systems with Tomlinson-Harashima Precoding,” in Proceedings of ICC'2009. pp.1-6, 2009.

[Gro2010] J. Grotz, B. Ottersten, J. Krause, “Signal Detection and Synchronization for Interference Overloaded Satellite Broadcast Reception “ IEEE Trans. Wireless Commun. , vol. 9, no. 10, pp. 3052-3063, 2010.

References (cont’d)

[Mar2004] Martin, C.; Geurtz, A.; Ottersten, J.; , "Spectrally efficient mobile satellite real-time broadcast with transmit diversity," Vehicular Technology Conference, 2004. VTC2004-Fall. 2004 IEEE 60th , vol.6, no., pp. 4079- 4083 Vol. 6, 26-29 Sept. 2004

[Ara2011a] P.-D.M. Arapoglou, K.P. Liolis, M. Bertinelli, A.D. Panagopoulos, P.G. Cottis, R. De Gaudenzi, “MIMO over satellite: A review,” IEEE Communications Surveys & Tutorials, vol. 13, no. 1, pp. 27-51, 2011.

[Sat2011] SatNEX III, COO 1 Task 2, Final Report: “Hybrid Space-ground Processing”, Jun. 2011.

[Van2011] A. Vanelli-Coralli , “Trends in Satellite Communication Technologies”, IEEE Benelux Workshop , European Space Agency, Noordwijk, The Netherlands, Wednesday, May 4, 2011.

[Gal2011] G. Gallinaro, “Improving The Spectral Efficiency of Satellite Communication Systems,” IEEE Benelux Workshop , European Space Agency, Noordwijk, The Netherlands, Wednesday, May 4, 2011.

[Cha2011] S. Chatzinotas, G. Zheng, B. Ottersten, “Joint Precoding with Flexible Power Constraints in Multibeam Satellite Systems,” submitted to IEEE Globecom 2011, 2011.

[Sha2011a] B. Shankar M.R., P.-D. Arapoglou, B. Ottersten, “Golden Codes for Dual Polarized MIMO-OFDM Transmissions in Hybrid Satellite/Terrestrial Mobile Systems,” IEEE International Conference on Communications, ICC2011, June 2011.

[Sha2011b] B. Shankar M.R., P.-D. Arapoglou, B. Ottersten, “Space-Frequency Coding for Dual Polarized Hybrid Mobile Satellite Systems,” submitted to IEEE Transactions Wireless Communications, 2011.

[Ara2011b] P.-D. Arapoglou, B. Shankar M.R., A.D. Panagopoulos, B. Ottersten, “Gateway Diversity Strategies in Q/V Band Feeder Links,” 17th Ka and Broadband Communications Conference, Palermo, Italy, 3-5 October, 2011.

[Gau2011] R. De Gaudenzi, “Satcoms 2020 R&D Challenges,” Distinguished Lecture, University of Luxembourg, 10th May 2011.

[Zhe2011] G. Zheng, S. Chatzinotas, B. Ottersten, “Energy-Efficient MMSE Beamforming and Power Optimization in Multibeam Satellite Systems”, Asilomar 2011, submitted.

[Chr2011] D. Christopoulos, S. Chatzinotas, M. Matthaiou, B. Ottersten , “On the Capacity of Multi-beam Joint Decoding over Composite Satellite Channels”, Invited Paper, Asilomar 2011.

References (cont’d)

[Chr2014] D. Christopoulos, S. Chatzinotas, and B. Ottersten, “Weighted fair multicast multigroup beamforming under per-antenna power constraints," IEEE Trans. Signal Process., vol.62, no.19, pp.5132–5142, Oct.2014.

[Chr2015] D. Christopoulos, S. Chatzinotas, and B. Ottersten, “Multicast Multigroup Precoding and User Scheduling for Frame-Based Satellite Communications," IEEE Trans. Wireless Commun., vol.0, pp.1-1, 2015.

[Chr2014pat] P.-D.Arapoglou, A.Ginesi, G.Taricco, D.Christopoulos, S.Chatzinotas, B.Ottersten, M. A. Vazquez, A.-I.Perez-Neira, Andrenacci, Vanelli-Coralli, “Joint Transmitter Signal Processingin MultiBeam Satellite Systems,” in European Space Agency Patent: 641-05628EPTE/BD,2014

Contact Info

Interdisciplinary Centre

for Security, Reliability and Trust – SnT

University of Luxembourg

Luxembourg

http://www.securityandtrust.lu

School of Electrical Engineering

KTH – Royal Institute of Technology

Stockholm

Sweden

http://www.ee.kth.se

• LEO for global comms (Iridium, Globalstar) • GEO for broadband (Inmarsat) • An example:

• Inmarsat Xpresslink • Ku-/L-band service

• L-band for coverage • Ku-band for capacity

Maritime Mobile Satellite Services

• Niche Market • Broadband Services

• Coverage in the Arctic • Provisioning more frequencies for ship-ship, ship-

shore communications • Satellite to enhance coverage

• Challenges • Low SNR • Low Bandwidth Multiple Access Channel

Aeronautical Scenario

Emerging Market for Broadband & Telemetry • Services

• Commercial airlines • Passenger internet access • Operational services

• Safety and maintenance • ADS-B (Automatic Dependent

Surveillance-Broadcast) • Telemetry data….

• Bands • L (Inmarsat), Ku (Intelsat Epic,

Viasat) • Ka band : Global Express

Picture Courtesy: NBAA Satcomdirect

Symbol Level Precoding

• Symbol level precoding – Precoding dependent on channel as well as symbols – [REFS 6, 8, 10, 11, 12]

• Additional degrees of freedom – Exploit interference

– Higher complexity

• Constellation 𝜍 comprising symbols 𝑑𝑘

76

Symbol Level Precoding : Representative Result 2 antennas, 2 users

77

CIPM: Symbol level precoding OB: Optimal unicast channel

Symbol Level Precoding : Representative Result (16 QAM, target SNR 11.76 dB)

78

CIPM: Symbol level precoding OB: Optimal unicast channel