Download - BROADBAND SATELLITE COMMUNICATIONS : …

1

ESA / ESTEC, Noordwijk, The Netherlands, 20 September 2004

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Laurent CASTANET (ONERA/TéSA)

BROADBAND SATELLITE COMMUNICATIONS :PROPAGATION INFLUENCE

& SYSTEM ADAPTIVITY

ASMS / EMPS Conference

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BBSatCom ESTEC, Noordwijk, The Netherland, 20 September 2004

CONTEXT RELATED TO BROADBAND SATCOM SYSTEMS

❐ TREND TO HIGH FREQUENCY BANDS➢ Conventional bands (L, S, C) overcrowded & Ku-band almost saturated ➢ Increasing use of data rate-hungry multimedia applications

➢ Competition with terrestrial networks : need for larger bandwidths➢ Military satcom systems : need for high discretion

❐ HIGH FREQUENCY BAND ADVANTAGESJ Wide bandwidths : 1 GHz at Ka-band, 3 GHz at Q/V-band, 2 GHz at EHF bandJ Technology : reduced antenna and RF component size,

J Narrow spot beams and high EIRP

❐ HIGH FREQUENCY BAND LIMITATIONSL Current technology not mature enough � high development costs

L Pointing accuracy more critical at equivalent antenna diameterL Propagation issue : influence of tropospheric effects

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✈ NEXT GENERATION OF SATCOM SYSTEMSFOR MULTIMEDIA APPLICATIONS

➢ Access to mass market with Ku/Ka-band transparent p ayloads & star networks ➢ Access to corporate market with Ku/Ka-band OBP payl oads & mesh networks➢ Backbone satcom systems with Ka/Q/V-band payloads

✈ CRITICAL ISSUES FOR MULTIMEDIA SATCOM SYSTEMSRELATED TO THE PROPAGATION CHANNEL

➢ Severe propagation effects for frequencies ≥≥≥≥ 20 GHz to be assessed� Design of system margins and link availability assessment

➢ Design & implementation of Fade Mitigation Techniqu es� Objective : compensate propagation impairments in real time

➢ Need for adaptive resource management protocols � Dynamic resource allocation to optimise system capacity with FMTs

CONTEXT RELATED TO BROADBAND SATCOM SYSTEMS

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OUTLINE OF THE PRESENTATION

❒ INTRODUCTION

❒ PROPAGATION EFFECTS

■ Attenuation■ Scintillation■ Total impairment

❒ FADE MITIGATION TECHNIQUES (FMTs)

■ Review of FMT concepts■ Impact of FMTs on interference■ FMT implementation issues

❒ CONCLUSION

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STRUCTURE OFTHE ATMOSPHERE

❒ IONOSPHERE

➢ High altitude layers➢ Ionised particles

due to sun influence➢ Sporadic medium

❒ TROPOSPHERE

➢ Ground to 10 km altitude

➢ Meteorological phenomena

� Clouds and Rain� Wind and Turbulence

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POWER BUDGET : PROPAGATION LOSS

❒ PROPAGATION ISSUES

➢ Ionospheric effects : important for frequencies lowe r than 5 GHz

➢ Tropospheric effects : dominant for frequencies highe r than 10 GHz

❒ ATTENUATION EFFECTS

➢ Gas attenuation : dry air (oxygen) and water vapour

➢ Hydrometeor attenuation : clouds, rain and melting l ayer

➢ Scintillation : clear sky conditions, with clouds, d uring rain

❒ INFLUENCE ON SATELLITE COMMUNICATIONS

➢ Strong impairments : A tot = Agaz . Arain

➢ Lower availability when frequency increasestotFS

RR AL

GEIRPP

⋅⋅=

3

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❒ INTRODUCTION





❒ CONCLUSION

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➢ Total oxygen attenuation : AO2 [dB]

� Equivalent height of Oxygen :

➢ More precise expressions in Recommendation ITU-R P. 676

222OA OO h×= γkmhO 6

2=

PROPAGATION LOSS : OXYGEN ATTENUATION - 1/5

( )32

223 10

5.157

81.4

227.0

09.61019.7

2

−− ⋅×

+−+

++⋅= f

ffOγ

❒ OXYGEN ABSORPTION MODELLING

➢ Specific oxygen attenuation : γΟ2 [dB/km]

� Simplified expression for frequencies f [GHz] lower than 57 GHz :

➢ Dependency with respect to temperature

➢ Example of oxygen attenuation prediction

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➢ Total oxygen attenuation : AO2 [dB]

� Equivalent height of Oxygen :

➢ More precise expressions in Recommendation ITU-R P. 676

222OA OO h×= γkmhO 6

2=


( )32

223 10

5.157

81.4

227.0

09.61019.7

2

−− ⋅×

+−+

++⋅= f

ffOγ

❒ OXYGEN ABSORPTION MODELLING

➢ Specific oxygen attenuation : γΟ2 [dB/km]


➢ Dependency with respect to temperature

➢ Example of oxygen attenuation prediction

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➢ Total water vapour attenuation : AH2O [dB]

sat

OHtOH E

VA

sin2

2 ⋅⋅

=ρ

γ

❒ WATER VAPOUR ABSORPTION MODELLING

➢ Specific water vapour attenuation : γΗ2Ο [dB/km]


� More precise expression in Recommendation ITU-R P.6 76

( ) ( ) ( )42

222 103.264.325

9.8

0.93.183

6.10

5.82.22

6.30021.005.0

2

−⋅⋅×

+−+

+−+

+−+⋅+= ρργ f

fffOH

PROPAGATION LOSS : WATER VAPOUR ATTENUATION - 2/5

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➢ Total water vapour attenuation : AH2O [dB]

sat

OHtOH E

VA

sin2

2 ⋅⋅

=ρ

γ

❒ WATER VAPOUR ABSORPTION MODELLING

➢ Specific water vapour attenuation : γΗ2Ο [dB/km]


� More precise expression in Recommendation ITU-R P.6 76

( ) ( ) ( )42

222 103.264.325

9.8

0.93.183

6.10

5.82.22

6.30021.005.0

2

−⋅⋅×

+−+

+−+

+−+⋅+= ρργ f

fffOH


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PROPAG. LOSS : CLOUD ATT. - 3/5

sat

ltN E

KWA

sin=

❒ CLOUD ATTENUATION MODELLINGTotal cloud attenuation : Acl [dB]

� Wt : ILWC [kg/m2]

( ) GHzl fK ⋅+

=21"

819.0

ηε

� K l : Specific attenuation coefficient[(dB/km)/(g/m3)] @ 0°C

� Esat : Elevation angle [°]

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More precise expression of Kl

in Rec. ITU-R P.840

Double-Debye modelbased on Rayleigh scattering

0840-01

5 10 20 50 100 200

0° C

20° C

10° C

– 8° C

Frequency (GHz)

FIGURE 1

Specific attenuation by water droplets at varioustemperatures as function of frequency

Sp

eci

fic a

tte

nua

tion

coef

ficie

nt, K

l ((d

B/k

m)

/ (g/

m³)

)

0.01

0.02

0.05

0.1

0.2

0.5

1

2

5

10

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More precise expression of Kl in Rec. ITU-R P.840Double-Debye model based on Rayleigh scattering

0840-01

5 10 20 50 100 200

0° C

20° C

10° C

– 8° C

Frequency (GHz)

FIGURE 1

Specific attenuation by water droplets at varioustemperatures as function of frequency

Sp

eci

fic a

tte

nua

tion

coef

ficie

nt, K

l ((d

B/k

m)

/ (g/

m³)

)

0.01

0.02

0.05

0.1

0.2

0.5

1

2

5

10

sat

ltN E

KWA

sin=

❒ CLOUD ATTENUATION MODELLINGTotal cloud attenuation : Acl [dB]

� Wt : ILWC [kg/m2]

( ) GHzl fK ⋅+

=21"

819.0

ηε

� K l : Specific attenuation coefficient[(dB/km)/(g/m3)] @ 0°C

� Esat : Elevation angle [°]

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PROPAGATION LOSS : RAIN ATTENUATION - 4/5

❒ TOTAL SLANT PATH ATTENUATION :

through N rain cells, with R not constant

in most of the statistical models : L001 = f(LES, Esat,hr,R001,F,γγγγ001)see Rec. ITU-R P.618

∑=

⋅=N

iii

satEsat RL

E

kA

1sinα

satE

LA

sin

⋅= γ

❒ SPECIFIC ATTENUATION : γ = k R α see Rec. ITU-R P.838

where k and αααα : coefficients, frequency and polarisation dependen t

( )∫ ⋅=L

dxxA0

γ❒ ATTENUATION THROUGH A PRECIPITATION OF LENGTH L :

where γγγγ(x) : specific attenuation [dB/km]

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❒ TOTAL SLANT PATH ATTENUATION :

through N rain cells, with R not constant

in most of the statistical models : L001 = f(LES, Esat,hr,R001,F,γγγγ001)see Rec. ITU-R P.618

∑=

⋅=N

iii

satEsat RL

E

kA

1sinα

satE

LA

sin

⋅= γ

❒ SPECIFIC ATTENUATION : γ = k R α see Rec. ITU-R P.838

where k and αααα : coefficients, frequency and polarisation dependen t

( )∫ ⋅=L

dxxA0

γ❒ ATTENUATION THROUGH A PRECIPITATION OF LENGTH L :

where γγγγ(x) : specific attenuation [dB/km]

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❒ INTRODUCTION





❒ CONCLUSION

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❒ QUIET ATMOSPHERE

� Stratified atmosphere : pressure, temperature & humidity profiles

� Slow variation of n(P,T,H) with altitude (as in the horizontal plane)� Low elevation : curved rays and multipaths� REFRACTION effect

❒ VERTICAL ATMOSPHERIC AIR CURRENTS (CLEAR SKY, CLOUD S)

� Turbulent atmosphere instead of stratified atmosphere

� Small scale inhomogeneities of refractive index� Atmospheric multipaths : with incident ray predominant w.r.t. diffracted ones

� Fast fluctuations of amplitude, phase & angle-of-arrival of received signals� SCINTILLATION effect

PROPAGATION LOSS : SCINTILLATION - 5/5

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❒ METEOROLOGICAL DEPENDENCY

➢ Normalized scintillation STD : σσσσref = fct (N wet) see Rec. ITU-R P.618

➢ Meteorological parameters : Nwet, T, H, Whc

❒ LONG-TERM STATISTICAL DISTRIBUTION

➢ where a & b = polynomial (Log10p, d°3)

•=•=

χ

χ

σσ

%)(

%)(

pbx

pax

ev

renf

❒ DEPENDENCY W.R.T. LINK CHARACTERISTICS

➢ Scintillation STD on the considered period(T >> stationarity period)

➢ where αααα = 7/12 & ββββ = 1.20➢ and g(D) : antenna aperture factor

( )β

α

χ θσσ

sin)(

FDgref ••=


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❒ QUIET ATMOSPHERE

� Stratified atmosphere : pressure, temperature & humidity profiles

� Slow variation of n(P,T,H) with altitude (as in the horizontal plane)� Low elevation : curved rays and multipaths� REFRACTION effect

❒ VERTICAL ATMOSPHERIC AIR CURRENTS (CLEAR SKY, CLOUD S)

� Turbulent atmosphere instead of stratified atmosphere

� Small scale inhomogeneities of refractive index� Atmospheric multipaths : with incident ray predominant w.r.t. diffracted ones

� Fast fluctuations of amplitude, phase & angle-of-arrival of received signals� SCINTILLATION effect

❒ METEOROLOGICAL DEPENDENCY

➢ Normalized scintillation STD : σσσσref = fct (N wet) see Rec. ITU-R P.618

➢ Meteorological parameters : Nwet, T, H, Whc

❒ LONG-TERM STATISTICAL DISTRIBUTION

➢ where a & b = polynomial (Log10p, d°3)

•=•=

χ

χ

σσ

%)(

%)(

pbx

pax

ev

renf

❒ DEPENDENCY W.R.T. LINK CHARACTERISTICS

➢ Scintillation STD on the considered period(T >> stationarity period)

➢ where αααα = 7/12 & ββββ = 1.20➢ and g(D) : antenna aperture factor

( )β

α

χ θσσ

sin)(

FDgref ••=


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❒ INTRODUCTION





❒ CONCLUSION

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%

At

%

Ar

%

Aml

RR(0.01 %) Rain height

&

Ac

%ILWC (0.1 %) ILWC (0.3 %) ILWC (1 %) ILWC (3 %) ILWC (10 %)

Awv

%IWVC (0.3 %) IWVC (1 %) IWVC (3 %) IWVC (10 %) IWVC (30 %)

Model

%

As

Nwet

AO

2

%Temperature

TOTAL IMPAIRMENT : METHODOLOGY - 1

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Total impairment @ 30 GHz Propagation loss @ 20 GHz

Predictions performed with Recommendation ITU-R P.6 18

TOTAL IMPAIRMENT : SINGLE LINK - 2

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Prediction performed for 0.5 % of an average year

Total impairment @ 30 GHz Propagation loss @ 20 GHz

TOTAL IMPAIRMENT : COVERAGE AREA - 3

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❒ INTRODUCTION





❒ CONCLUSION

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FMT :POSITION OF THE PROBLEM

❒ SEVERE PROPAGATION EFFECTS !

➢ Total impairment > 10 dB for p = 0.5 % of an average year @ 30 GHz

➢ VSAT networks : low margin � low availability

➢ Not acceptable for all kinds of services, especially interactive services

❒ HOW TO PROVIDE SUFFICIENT AVAILABILITY ?

➢ Large static margins not applicable (due to current technology)� Fade Mitigation Techniques (FMT)

❒ OBJECTIVE OF THIS PRESENTATION

➢ State of the art of FMT concepts➢ Review of Interference contributions

➢ Impact of FMTs on interference

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❒ INTRODUCTION





❒ CONCLUSION

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FMT : MAIN OBJECTIVES

❒ POWER CONTROL : aims at keeping constant C/N 0

➣ Up-Link Power Control, End-to-End PC, Down-Link PC, On-Board Beam Shaping

❒ ADAPTIVE WAVEFORM : aims at reducing the required C /N0 at constant BER

➣ Adaptive Coding or Modulation : allows the required Eb/N0 to be decreased ➣ Data Rate Reduction : aims at decreasing the information data rate (Rb)

❒ DIVERSITY : aims at adopting a re-route strategy of the network

➣ Site Diversity, Satellite Diversity, Frequency Diversity

❒ LAYER 2 : aims at retransmiting

➣ Automatic Repeat reQuest, Time Diversity

Link performance equation :b

0

b

0

RNE

NC ×=

User 1

User 2

User N

Coding Modulation

Ru1

Ru2

RuNRb Rc Rs

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❒ UPLINK (ULPC)

➢ compensates for uplinkpropagation impairments

➢ allows operating at low powerin clear sky cond. to limit interference

➢ constant carrier power level at the transponder input(satellite antenna gain roll-off & mispointing, RF chains degradations)

➢ avoids satellite EIRP reduction due to uplink impairment

❒ EEPC (transparent repeater operated far from satura tion)

➢ maintains a constant margin on the overall link budget

➢ mitigates downlink impairments if sufficient repeater marginkeeping reasonable non-linear effects (intermodulation noise & capture effects)

POWER CONTROL - 1

OBBS

DLPC

ex : ULPC

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❒ ON-BOARD BEAM SHAPPING

➢ Objective : maintaining up - down and overall link budget s ➢ Action : adapting the size of spot beams to the propag ation conditions

through active antennas➟ Concerns all stations in the same beam

➟ Detection from short-term weather predictions (Meteorological Nowcasting of propagation conditions)

➢ Limitation : ground power flux density specification t o be respected

❒ DOWN-LINK POWER CONTROL

➢ Objective : maintaining the downlink budget➢ Action : adapting TWTA output power (weak extra powe r allocation)➢ Limitations :

➟ no channel interference or intermodulation products➟ ground power flux density specification

to be respected

POWER CONTROL - 2

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Adaptive PSK Modulation

ADAPTIVE WAVEFORM

AC, AM : Adaptive Coding or Modulation

OPERATION MODE :

Perf. objective : BER = Cte

� Constant bandwidth& variable info data rate (Rb)(Additional mitigation dueto DR adjustment)

� Variable bandwidth& constant info data rate (Rb)

Eb/N0 (dB)

Threshold

ρρρρ0000

ρρρρ1111

ρρρρ2222

M1 M0M2

10-3

10-9

10-6

BER

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❒ SITE DIVERSITY (SD)

➢ Principle :2 ES inter-connectedby a terrestrial link

➢ Limitations :uncorrelated fades=> convective cells

� Low percentages of time - Control ES or gateways

❒ FREQUENCY DIVERSITY (FD)

➢ Objective : in presence of fading, re-routing a com.through a lower frequency band payload

➢ Config. : Cross-shaping (OBP) or Double-hop (3rd ES)

DIVERSITY FMT

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❒ RETRANSMISSION TECHNIQUES

➢ Objective : waiting for good propagation conditionsinteresting for push services (file transfer, …)

➢ Messages re-sent regularly or randomly (ALOHA-type protocols) = ARQ➢ Use of propagation information to optimise system capacity = Time Diversity

❒ ADAPTIVE RESOURCE MANAGEMENT : not a FMT

➢ Objective : adjust the resource allocation to specific communication services depending on propagation conditions

➢ Need : detection of propagation conditions in the considered areamid-term weather forecast (Meteorological Nowcasting)

➢ Necessary in complement to FMTs,but High system complexity : CAC, DAMA, …

LAYER 2 FMT

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JOINT FMT

5 dB

10 dB

30 dB

40 dB

0.01 % 0.1 % 1 % 10 % % of year

Fade depth (dB)

20 dBSD

ULPC

AM

SatD

DLPC

OBBS

FD

AC

1

2

3

4

5

OBBS

OBBS + ULPC

OBBS + ULPC + AM

OBBS + ULPC + AM + SatD

OBBS + ULPC + AM + SatD + SD

2

3

4

5

1

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❒ INTRODUCTION





❒ CONCLUSION

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❒ INTRA-SYST. INTERF.➢ Adjacent-channel

interference

INTERFERENCE SOURCES ON THE UPLINK

� At the input ofthe satellite transponder

UPLINKIntra-systemInterference

(no polar. re-use)

Orthogonalpolarisation

Samepolarisation≠ frequency

Useful ES

➢ Co-channel interf.Inter / intra beam

➢ Inter-beam cross-channelinterference

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interference





UPLINKIntra-systemInterference

(with polar. re-use)

Useful ESInterfering ES

➢ Intra-beam cross-channelinterference

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interference





❒ INTER-SYST. INTERF.➢ Adjacent satcom

system interference

Interfering ES

3°


UPLINKAdjacentsystem

Interference

Useful ES

➢ Other system interference

InterferingadjacentFWBAsystem

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� At the input ofthe satellite transponder❒ INTRA-SYSTEM INTERFERENCE

➢ Adjacent-channel interference : IES in the same spot beam,≠ frequency, same polarisation

➢ Co-channel interference : IES in a ≠ spot beam, same freq., same polar. (TDMA)IES in the same spot beam, same freq., same polar. (CDMA)

➢ Inter-beam cross-channel interference : IES in a ≠ spot beam,same frequency, orthogonal polarisation

➢ Intra-beam cross-channel interference : IES in the same spot beam,same frequency, orthogonal polarisation

❒ INTER-SYSTEM INTERFERENCE

➢ Adjacent satcom system interference : operating @ the same frequency & polarisation

➢ Other systems : Fixed Broadband Wireless Access systems, radar systems : negligible

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DOWNLINKIntra-systemInterference

(no polar. re-use)

INTERFERENCE SOURCES ON THE DOWNLINK

� At the input ofthe ES receiver❒ INTRA-SYST. INTERF.



➢ Multicarrier interf.

Orthogonalpolarisation

Useful ES

➢ Adjacent channel interf.

≠ frequencySame

polarisation

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❒ INTRA-SYST. INTERF.





DOWNLINKIntra-systemInterference

(with polar. re-use)

� At the input ofthe ES receiver

Useful linkInterfering ES


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❒ INTRA-SYST. INTERF.




❒ INTER-SYST. INTERF.➢ Adjacent satcom

system interference

➢ Other system interference



3°

InterferingadjacentSatComsystem

InterferingadjacentFWBAsystem

DOWNLINKAdjacentsystem

Interference


Useful link


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❒ INTRA-SYSTEM INTERFERENCE

➢ Multi-carrier interference : intermodulation noise,carrier suppression effects

➢ Adjacent channel interference : carrier to the same spot beamsame frequency, same polarisation

➢ Co-channel interference : carrier to a ≠ spot beam, same freq., same polar. (TDMA)carrier to the same spot beam, same freq., same polar. (CDMA)

➢ Inter-beam cross-channel interference : carrier to a ≠ spot beam,same frequency, orthogonal polarisation

➢ Intra-beam cross-channel interference : carrier to the same spot beam,same frequency, orthogonal polarisation

❒ INTER-SYSTEM INTERFERENCE

➢ Adjacent satcom system interference : operating @ the same frequency& @ the same polarisation

➢ Other systems : Fixed Broadband Wireless Access systems,radar systems : coordination

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IMPACT OF POWER CONTROL ON INTERFERENCE LEVEL

❒ DLPC (analysis for unicast) :

➢ Objective : ct power flux density @ ground level ?

➢ Static compensation ? LdwnES

➢ Dynamic compensation : Adwn� Clear sky conditions ⇒ Limited IM (w.r.t. system operated @ saturation)

� Rain conditions ⇒ Higher interference during activation

❒ ULPC : maximum Tx power fixed from SoA & technology

➢ Objective : ct carrier level @ transponder input

➢ Static compensation : Grsat->ES - LupES

➢ Dynamic compensation : Aup� Clear sky conditions ⇒ Lower nominal power to limit uplink interference� Rain conditions ⇒ Constant uplink interference during activation

inside ULPC dynamic range

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IMPACT OF ADAPTIVE WAVEFORM ON INTERFERENCE LEVEL

❒ ADAPTIVE CODING / MODULATION

➢ Objective : improve spectral efficiency in clear sky conditions� Higher interference level due to more limited range of ULPC (w.r.t. ULPC only)

➢ Constant bandwidth : with appropriate adjustment of information data rate � Different attenuation per UES : ≠ carrier levels @ the transponder input ⇒ variable uplink C/I

➢ Variable bandwidth : constant information data rate� During AC or AM activation ⇒ variable interference (I0)

❒ DATA RATE REDUCTION

➢ Objective : adjust data rate to meet the required Eb/N0

� Constant transmitted data rate : possible if fade spreading

➢ Impact on interference : � Depends if bandwidth is kept constant or not

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IMPACT OF OTHER FMT ON INTERFERENCE LEVEL

❒ DIVERSITY

➢ Site Diversity : interference to be calculated with respect to

� ≠ diversity schemes : Double ground segment, 2 or more smaller Gateways instead of 1,Limited number of spare gateways in different beams, Same number of gateways connected to the terrestrial backbone...

� Switched diversity vs simultaneous operation

➢ Frequency Diversity : interference to be calculated @ each frequency band

� No clear tendency, scenario dependent

❒ LAYER 2

➢ ARQ & Time Diversity :

� No change on the physical layer ⇒ transparent w.r.t. interference

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IMPACT OF FMT ON INTERFERENCE LEVEL

❒ SUMMARY

➢ Impact of FMT on interference if in presence of fad ing :

� Real time adjustment of power : ULPC, EEPC, DLPC, OBBS

� No adjustment of C/N0 : AC, AM, DRR� Real time adjustment of bandwidth : AC, AM, DRR

➢ No clear impact for diversity :

� Impact depends on Earth station relative position for SD� Impact depends on back-up payload configuration for FD

� To be analysed from system configuration and FMT solutions

➢ No impact on interference :

� Only for re-transmission FMTs

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❒ INTRODUCTION





❒ CONCLUSION

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DETECTION & DECISION SCHEMES (D&D)

❒ OBJECTIVES

➢ Estimate of variable parameters impacting the physi cal layer :� Interference contributions internal/external to the system� Atmospheric propagation impairments

� Hardware issues : Satellite antenna gain roll-off & mispointing RF chain degradations ⇒ both supposed to be known

➢ Necessity to separate :� Propagation impairments / interference contributions� Uplink / downlink propagation impairments

❒ POSSIBLE D&D SCHEMES

➢ Open-loop : Retrieval of propagation fades from direct measurements➢ Closed-loop : QoL estimation from physical layer performance monitoring @ Rx

➢ Hybrid-loop : Combination of both open-loop & closed-loop techniques

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DISTRIBUTED D&D SCHEMES

Open-loop Hybrid-loopClosed-loop

Measurement, signalling, com. link

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CENTRALIZED D&D SCHEMES : BENT-PIPE SYSTEM

UES NCC

GES

Open-loop Closed-loop

UES NCC

GES

Measurement, signalling, com. link

Hybrid-loop

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❒ OPEN-LOOP FADE ESTIMATION

➢ Meteorological measurements : bucket rain-gauge, optical rain-gauge, disdrometer� Rain rate measurements� Radiometer measurements

� Radar measurements� Satellite imagery

➢ Beacon measurement

❒ CLOSED-LOOP FADE ESTIMATION

➢ Data link layer performance estimation

➢ Link quality estimation from BER measurements

➢ Link quality estimation from Power measurements� Measurement of the average amplitude of the received symbols� Signal to Noise + Interf. Ratio Estimation (SNORE)

FADE ESTIMATION TECHNIQUES

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❒ DETECTION OF THE CHANNEL BEHAVIOUR

� Purpose :real-time estimateof current fade level

� Real-time estimateof overall SNIR

❒ SHORT-TERM PREDICTION

� Purpose : compensation of the system reaction time

� Filtering of fast varying component, frequency scaling, short-term prediction

❒ DECISION FUNCTION

� Purpose : to authorise & trigger a given mitigation� Introduction of local margins to compensate control loop inaccuracies

FMT CONTROL LOOP CONFIGURATION

Monitoredsignal

® State of the art : design of only very simple loop

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EVENT-BASED ANALYSIS WITH FMT

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IMPLEMENTATION OF ULPC

❒ APPLICATION DOMAIN

� Possible whatever the type of service :real time or not, reliable or not, ...

❒ DEFINITION OF ULPC

� Output power : from 600 mW to 2 W� ULPC dynamic range ≈ 6 dB

Frequency 29.75 GHz 29.75 GHzCoding rate 2/3 2/3Uplink information data rate 2272 kbit/s 2272 kbit/sNominal SSPA output power 600 mW 2 WUplink Eb/(N0+I0) 6.35 dB 11.5 dBRequired Eb/ N0 (BER = 1.4*10-9) 4.6 dB 4.6 dBUplink margin 1.75 dB 6.9 dBULPC dynamic range / 5.2 dB

Requiredavailability= 99.8 %

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JOINT FMT IMPLEMENTATION

❒ DEFINITION OF THE JOINT FMT

� ULPC : from 800 mW to 2 W

� AC : Constant Tx DR : Rc = 3019 kbit/s

� DRR : DR / 2 and DR / 4

� FMT dynamic range : 16.0 dB

Frequency 29.75 GHz 29.75 GHz 29.75 GHz 29.75 GHzCoding rate 3/4 1/2 1/3 1/3Uplink info. data rate 2272 kbit/s 1515 kbit/s 1010 kbit/s 505 / 252 kbit/sSSPA output power 0.8 / 2 W 2.0 W 2.0 W 2.0 WUplink Eb/(N0+I0) 7.0/11.0 dB 12.7 dB 14.5 dB 17.5 / 20.5 dBReq. Eb/ N0 (1.4*10-9) 5.4 dB 3.6 dB 2.9 dB 2.9 dBUplink margin 1.6 / 5.6 dB 9.1 dB 11.6 dB 14.6 / 17.6 dBFMT dynamic range - / 4.0 dB 7.5 dB 10.0 dB 13.0 / 16.0 dB

Requiredavailability= 99.8 %

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❒ INTRODUCTION





❒ CONCLUSION

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FMT PRINCIPLE & IMPLEMENTATION : SUMMARY

AvailabilityUser

data rateAffected nb

of usersReaction

time SignallingComplexity

/ cost

ULPC ++ 0 local ++ 0 ++

DLPC + 0 beam + 0 +

OBBS + 0 beam + 0 --

AC + - channel/TDM - -- -

AM + - channel/TDM - -- --

DRR ++ -- local + - +

SD +++ 0 local/global + - --

SatD + 0 global - -- --

FD ++ 0 global - -- --

TD ++ - global -- - ++

Already used

Planned

Not mature

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SYSTEM PERFORMANCE

❒ PERFORMANCE ASSESSMENT

➢ User point of view :� Service availability : function of link outage @ physical layer ⇐ mitigation� Minimum data rate : impact Quality of Service and user perception

➢ Operator point of view :� Spectral efficiency (modulation & coding) : directly impact system capacity� Interference : strong limitation on link budgets (high sporadic traffic)

❒ FMT DESIGN FOR PERFORMANCE IMPROVEMENT

➢ Choice of FMT strongly dependent on systems characteristics

➢ Interest to combine ≠ FMT : better mitigation performances & system efficiency

➢ Trade- off : MITIGATION - CAPACITY - INTERFERENCE