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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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BBSatCom ESTEC, Noordwijk, The Netherland, 20 September 2004
✈ 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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BBSatCom ESTEC, Noordwijk, The Netherland, 20 September 2004
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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BBSatCom ESTEC, Noordwijk, The Netherland, 20 September 2004
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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BBSatCom ESTEC, Noordwijk, The Netherland, 20 September 2004
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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BBSatCom ESTEC, Noordwijk, The Netherland, 20 September 2004
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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BBSatCom ESTEC, Noordwijk, The Netherland, 20 September 2004
➢ 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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PROPAGATION LOSS : OXYGEN ATTENUATION - 1/5
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BBSatCom ESTEC, Noordwijk, The Netherland, 20 September 2004
➢ 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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BBSatCom ESTEC, Noordwijk, The Netherland, 20 September 2004
➢ 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]
� Simplified expression for frequencies f [GHz] lower than 57 GHz :
� 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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PROPAGATION LOSS : WATER VAPOUR ATTENUATION - 2/5
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PROPAGATION LOSS : WATER VAPOUR ATTENUATION - 2/5
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BBSatCom ESTEC, Noordwijk, The Netherland, 20 September 2004
➢ 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]
� Simplified expression for frequencies f [GHz] lower than 57 GHz :
� 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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BBSatCom ESTEC, Noordwijk, The Netherland, 20 September 2004
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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BBSatCom ESTEC, Noordwijk, The Netherland, 20 September 2004
PROPAG. LOSS : CLOUD ATT. - 3/5
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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PROPAG. LOSS : CLOUD ATT. - 3/5
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PROPAG. LOSS : CLOUD ATT. - 3/5
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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BBSatCom ESTEC, Noordwijk, The Netherland, 20 September 2004
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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BBSatCom ESTEC, Noordwijk, The Netherland, 20 September 2004
PROPAGATION LOSS : RAIN ATTENUATION - 4/5
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PROPAGATION LOSS : RAIN ATTENUATION - 4/5
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PROPAGATION LOSS : RAIN ATTENUATION - 4/5
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PROPAGATION LOSS : RAIN ATTENUATION - 4/5
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PROPAGATION LOSS : RAIN ATTENUATION - 4/5
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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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BBSatCom ESTEC, Noordwijk, The Netherland, 20 September 2004
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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BBSatCom ESTEC, Noordwijk, The Netherland, 20 September 2004
❒ 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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PROPAGATION LOSS : SCINTILLATION - 5/5
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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 ••=
PROPAGATION LOSS : SCINTILLATION - 5/5
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BBSatCom ESTEC, Noordwijk, The Netherland, 20 September 2004
❒ 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 ••=
PROPAGATION LOSS : SCINTILLATION - 5/5
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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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BBSatCom ESTEC, Noordwijk, The Netherland, 20 September 2004
%
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
12
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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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BBSatCom ESTEC, Noordwijk, The Netherland, 20 September 2004
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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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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BBSatCom ESTEC, Noordwijk, The Netherland, 20 September 2004
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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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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BBSatCom ESTEC, Noordwijk, The Netherland, 20 September 2004
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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BBSatCom ESTEC, Noordwijk, The Netherland, 20 September 2004
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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BBSatCom ESTEC, Noordwijk, The Netherland, 20 September 2004
❒ 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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BBSatCom ESTEC, Noordwijk, The Netherland, 20 September 2004
❒ INTRA-SYST. INTERF.➢ Adjacent-channel
interference
INTERFERENCE SOURCES ON THE UPLINK
➢ Co-channel interf.Inter / intra beam
➢ Inter-beam cross-channelinterference
� At the input ofthe satellite transponder
UPLINKIntra-systemInterference
(with polar. re-use)
Useful ESInterfering ES
➢ Intra-beam cross-channelinterference
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BBSatCom ESTEC, Noordwijk, The Netherland, 20 September 2004
❒ INTRA-SYST. INTERF.➢ Adjacent-channel
interference
INTERFERENCE SOURCES ON THE UPLINK
➢ Co-channel interf.Inter / intra beam
➢ Inter-beam cross-channelinterference
➢ Intra-beam cross-channelinterference
❒ INTER-SYST. INTERF.➢ Adjacent satcom
system interference
Interfering ES
3°
� At the input ofthe satellite transponder
UPLINKAdjacentsystem
Interference
Useful ES
➢ Other system interference
InterferingadjacentFWBAsystem
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BBSatCom ESTEC, Noordwijk, The Netherland, 20 September 2004
INTERFERENCE SOURCES ON THE UPLINK
� 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.
➢ Co-channel interf.Inter / intra beam
➢ Inter-beam cross-channelinterference
➢ Multicarrier interf.
Orthogonalpolarisation
Useful ES
➢ Adjacent channel interf.
≠ frequencySame
polarisation
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BBSatCom ESTEC, Noordwijk, The Netherland, 20 September 2004
INTERFERENCE SOURCES ON THE DOWNLINK
❒ INTRA-SYST. INTERF.
➢ Co-channel interf.Inter / intra beam
➢ Inter-beam cross-channelinterference
➢ Intra-beam cross-channelinterference
➢ Multicarrier interf.
DOWNLINKIntra-systemInterference
(with polar. re-use)
� At the input ofthe ES receiver
Useful linkInterfering ES
➢ Adjacent channel interf.
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❒ INTRA-SYST. INTERF.
➢ Co-channel interf.Inter / intra beam
➢ Inter-beam cross-channelinterference
➢ Intra-beam cross-channelinterference
❒ INTER-SYST. INTERF.➢ Adjacent satcom
system interference
➢ Other system interference
INTERFERENCE SOURCES ON THE DOWNLINK
➢ Multicarrier interf.
3°
InterferingadjacentSatComsystem
InterferingadjacentFWBAsystem
DOWNLINKAdjacentsystem
Interference
� At the input ofthe ES receiver
Useful link
➢ Adjacent channel interf.
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BBSatCom ESTEC, Noordwijk, The Netherland, 20 September 2004
INTERFERENCE SOURCES ON THE DOWNLINK
� At the input ofthe ES receiver
❒ 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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BBSatCom ESTEC, Noordwijk, The Netherland, 20 September 2004
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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BBSatCom ESTEC, Noordwijk, The Netherland, 20 September 2004
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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BBSatCom ESTEC, Noordwijk, The Netherland, 20 September 2004
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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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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BBSatCom ESTEC, Noordwijk, The Netherland, 20 September 2004
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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BBSatCom ESTEC, Noordwijk, The Netherland, 20 September 2004
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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BBSatCom ESTEC, Noordwijk, The Netherland, 20 September 2004
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