BROADBAND SATELLITE COMMUNICATIONS : PROPAGATION INFLUENCE & SYSTEM ADAPTIVITY

Transcription

1 ASMS / EMPS Conference BROADBAND SATELLITE COMMUNICATIONS : PROPAGATION INFLUENCE & SYSTEM ADAPTIVITY Laurent CASTANET ESA / ESTEC, Noordwijk, The Netherlands, 20 September 2004 (ONERA/TéSA) 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 ADVANTAGES J Wide bandwidths : 1 GHz at Ka-band, 3 GHz at Q/V-band, 2 GHz at EHF band J Technology : reduced antenna and RF component size, J Narrow spot beams and high EIRP HIGH FREQUENCY BAND LIMITATIONS L Current technology not mature enough high development costs L Pointing accuracy more critical at equivalent antenna diameter L Propagation issue : influence of tropospheric effects CONTEXT RELATED TO BROADBAND SATCOM SYSTEMS NEXT GENERATION OF SATCOM SYSTEMS FOR MULTIMEDIA APPLICATIONS Access to mass market with Ku/Ka-band transparent payloads & star networks Access to corporate market with Ku/Ka-band OBP payloads & mesh networks Backbone satcom systems with Ka/Q/V-band payloads CRITICAL ISSUES FOR MULTIMEDIA SATCOM SYSTEMS RELATED 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 Techniques Objective : compensate propagation impairments in real time Need for adaptive resource management protocols Dynamic resource allocation to optimise system capacity with FMTs 1

2 OUTLINE OF THE PRESENTATION INTRODUCTION PROPAGATION EFFECTS Attenuation Scintillation Total impairment FADE MITIGATION TECHNIQUES (FMTs) Review of FMT concepts Impact of FMTs on FMT implementation issues CONCLUSION STRUCTURE OF THE 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 POWER BUDGET : PROPAGATION LOSS PROPAGATION ISSUES Ionospheric effects : important for frequencies lower than 5 GHz Tropospheric effects : dominant for frequencies higher than 10 GHz ATTENUATION EFFECTS Gas attenuation : dry air (oxygen) and water vapour Hydrometeor attenuation : clouds, rain and melting layer Scintillation : clear sky conditions, with clouds, during rain INFLUENCE ON SATELLITE COMMUNICATIONS Strong impairments : A tot = A gaz. A rain Lower availability when frequency increases EIRP G PR = L A FS tot R 2

3 OUTLINE OF THE PRESENTATION INTRODUCTION PROPAGATION EFFECTS Attenuation Scintillation Total impairment FADE MITIGATION TECHNIQUES (FMTs) Review of FMT concepts Impact of FMTs on FMT implementation issues CONCLUSION PROPAGATION LOSS : OXYGEN ATTENUATION - 1/5 OXYGEN ABSORPTION MODELLING Specific oxygen attenuation : γ Ο2 [db/km] Simplified expression for frequencies f [GHz] lower than 57 GHz : 3 2 γ O = f Total oxygen attenuation : A O2 [db] 6.09 f AO 2 2 ( f 57) = γ h O2 h O 6 km Equivalent height of Oxygen : = 2 More precise expressions in Recommendation ITU-R P.676 Dependency with respect to temperature Example of oxygen attenuation prediction O PROPAGATION LOSS : OXYGEN ATTENUATION - 1/5 3

4 PROPAGATION LOSS : OXYGEN ATTENUATION - 1/5 OXYGEN ABSORPTION MODELLING Specific oxygen attenuation : γ Ο2 [db/km] Simplified expression for frequencies f [GHz] lower than 57 GHz : 3 2 γ O = f Total oxygen attenuation : A O2 [db] 6.09 f AO 2 2 ( f 57) = γ h O2 h O 6 km Equivalent height of Oxygen : = 2 More precise expressions in Recommendation ITU-R P.676 Dependency with respect to temperature Example of oxygen attenuation prediction O PROPAGATION LOSS : WATER VAPOUR ATTENUATION - 2/5 WATER VAPOUR ABSORPTION MODELLING Specific water vapour attenuation : γ Η2Ο [db/km] Simplified expression for frequencies f [GHz] lower than 57 GHz : γ H O = + ρ f ρ ( f 22.2) ( f 183.3) ( f 325.4) More precise expression in Recommendation ITU-R P.676 Total water vapour attenuation : A H2O [db] A V γ = ρ sin E t H 2O H 2O sat PROPAGATION LOSS : WATER VAPOUR ATTENUATION - 2/5 4

5 PROPAGATION LOSS : WATER VAPOUR ATTENUATION - 2/5 PROPAGATION LOSS : WATER VAPOUR ATTENUATION - 2/5 WATER VAPOUR ABSORPTION MODELLING Specific water vapour attenuation : γ Η2Ο [db/km] Simplified expression for frequencies f [GHz] lower than 57 GHz : γ H O = + ρ f ρ ( f 22.2) ( f 183.3) ( f 325.4) More precise expression in Recommendation ITU-R P.676 Total water vapour attenuation : A H2O [db] A V γ = ρ sin E t H 2O H 2O sat PROPAG. LOSS : CLOUD ATT. - 3/5 CLOUD ATTENUATION MODELLING Total cloud attenuation : A cl [db] Wt Kl AN = sin E W t : ILWC [kg/m 2 ] sat E sat : Elevation angle [ ] K l : Specific attenuation coefficient [(db/km)/(g/m 3 0 C K l ε" = 2 f GHz ( 1+ η ) 5

6 PROPAG. LOSS : CLOUD ATT. - 3/5 FIGURE 1 Specific attenuation by water droplets at various temperatures as function of frequency 10 More precise expression of K l in Rec. ITU-R P.840 Double-Debye model based on Rayleigh scattering Specific attenuation coefficient, K l ((db/km) / (g/m³)) 5 20 C 2 10 C 0 C 1 8 C Frequency (GHz) PROPAG. LOSS : CLOUD ATT. - 3/5 PROPAG. LOSS : CLOUD ATT. - 3/5 FIGURE 1 Specific attenuation by water droplets at various temperatures as function of frequency CLOUD ATTENUATION MODELLING Total cloud attenuation : A cl [db] Wt Kl AN = sin E sat W t : ILWC [kg/m 2 ] E sat : Elevation angle [ ] K l : Specific attenuation coefficient [(db/km)/(g/m 3 0 C K l ε" = 2 f GHz ( 1+ η ) Specific attenuation coefficient, K l ((db/km) / (g/m³)) C 2 10 C 0 C 1 8 C More precise expression of K l in Rec. ITU-R P.840 Frequency (GHz) Double-Debye model based on Rayleigh scattering

7 PROPAGATION LOSS : RAIN ATTENUATION - 4/5 ATTENUATION THROUGH A PRECIPITATION OF LENGTH L : where γ(x) : specific attenuation [db/km] A = L ( x) γ dx 0 SPECIFIC ATTENUATION : γ = k R α see Rec. ITU-R P.838 where k and α : coefficients, frequency and polarisation dependent TOTAL SLANT PATH ATTENUATION : through N rain cells, with R not constant Esat in most of the statistical models : L 001 = f(l ES, E sat,h r,r 001,F,γ 001 ) see Rec. ITU-R P.618 A L A = γ sin k = sin E E sat N L R i sat i= 1 α i PROPAGATION LOSS : RAIN ATTENUATION - 4/5 PROPAGATION LOSS : RAIN ATTENUATION - 4/5 7

8 PROPAGATION LOSS : RAIN ATTENUATION - 4/5 PROPAGATION LOSS : RAIN ATTENUATION - 4/5 PROPAGATION LOSS : RAIN ATTENUATION - 4/5 8

9 PROPAGATION LOSS : RAIN ATTENUATION - 4/5 ATTENUATION THROUGH A PRECIPITATION OF LENGTH L : where γ(x) : specific attenuation [db/km] A = L ( x) γ dx 0 SPECIFIC ATTENUATION : γ = k R α see Rec. ITU-R P.838 where k and α : coefficients, frequency and polarisation dependent TOTAL SLANT PATH ATTENUATION : through N rain cells, with R not constant Esat in most of the statistical models : L 001 = f(l ES, E sat,h r,r 001,F,γ 001 ) see Rec. ITU-R P.618 A L A = γ sin k = sin E E sat N L R i sat i= 1 α i OUTLINE OF THE PRESENTATION INTRODUCTION PROPAGATION EFFECTS Attenuation Scintillation Total impairment FADE MITIGATION TECHNIQUES (FMTs) Review of FMT concepts Impact of FMTs on FMT implementation issues CONCLUSION PROPAGATION LOSS : SCINTILLATION - 5/5 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, CLOUDS) 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 9

10 PROPAGATION LOSS : SCINTILLATION - 5/5 PROPAGATION LOSS : SCINTILLATION - 5/5 PROPAGATION LOSS : SCINTILLATION - 5/5 LONG-TERM STATISTICAL DISTRIBUTION where a & b = polynomial (Log 10 p, d 3) x x DEPENDENCY W.R.T. LINK CHARACTERISTICS Scintillation STD on the considered period (T >> stationarity period) where α = 7/12 & β = 1.20 and g(d) : antenna aperture factor χ renf ev σ = σ = a( p%) σ χ = b( p%) σ χ ref F g( D) α ( sinθ ) β METEOROLOGICAL DEPENDENCY Normalized scintillation STD : σ ref = fct (N wet ) see Rec. ITU-R P.618 Meteorological parameters : N wet, T, H, W hc 10

11 PROPAGATION LOSS : SCINTILLATION - 5/5 LONG-TERM QUIET ATMOSPHERE STATISTICAL DISTRIBUTION xrenf = a( p%) σ χ where a Stratified & b = polynomial atmosphere (Log: 10 pressure, p, d 3) temperature & humidity profiles Slow variation of n(p,t,h) with altitude (as x in the ev = b( p%) σ horizontal plane) χ Low elevation : curved rays and multipaths DEPENDENCY REFRACTION W.R.T. LINK effect CHARACTERISTICS α Scintillation STD on the considered period F (T >> stationarity period) σ χ = σ ref g( D) VERTICAL where α ATMOSPHERIC = 7/12 & β = 1.20 ( sinθ ) β AIR CURRENTS (CLEAR SKY, CLOUDS) and g(d) : antenna aperture factor Turbulent atmosphere instead of stratified atmosphere Small scale inhomogeneities of refractive index METEOROLOGICAL Atmospheric DEPENDENCY multipaths : with incident ray predominant w.r.t. diffracted ones Fast fluctuations of amplitude, phase & angle-of-arrival of received signals Normalized scintillation STD : σ SCINTILLATION effect ref = fct (N wet ) see Rec. ITU-R P.618 Meteorological parameters : N wet, T, H, W hc OUTLINE OF THE PRESENTATION INTRODUCTION PROPAGATION EFFECTS Attenuation Scintillation Total impairment FADE MITIGATION TECHNIQUES (FMTs) Review of FMT concepts Impact of FMTs on FMT implementation issues CONCLUSION TOTAL IMPAIRMENT : METHODOLOGY - 1 A O 2 A s Model % Temperature Nwet % A wv A t IWVC (0.3 %) IWVC (1 %) IWVC (3 %) IWVC (10 %) IWVC (30 %) % A c ILWC (0.1 %) ILWC (0.3 %) ILWC (1 %) ILWC (3 %) ILWC (10 %) % % RR(0.01 %) Rain height A r % & A ml % 11

12 TOTAL IMPAIRMENT : SINGLE LINK - 2 Predictions performed with Recommendation ITU-R P.618 Total 30 GHz Propagation 20 GHz TOTAL IMPAIRMENT : COVERAGE AREA - 3 Prediction performed for 0.5 % of an average year Total 30 GHz Propagation 20 GHz OUTLINE OF THE PRESENTATION INTRODUCTION PROPAGATION EFFECTS Attenuation Scintillation Total impairment FADE MITIGATION TECHNIQUES (FMTs) Review of FMT concepts Impact of FMTs on FMT implementation issues CONCLUSION 12

13 FMT :POSITION OF THE PROBLEM SEVERE PROPAGATION EFFECTS! Total impairment > 10 db for p = 0.5 % of an average 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 OUTLINE OF THE PRESENTATION INTRODUCTION PROPAGATION EFFECTS Attenuation Scintillation Total impairment FADE MITIGATION TECHNIQUES (FMTs) Review of FMT concepts Impact of FMTs on FMT implementation issues CONCLUSION FMT : MAIN OBJECTIVES Link performance equation : C N 0 = Eb R N 0 b POWER CONTROL : aims at keeping constant C/N 0 Up-Link Power Control, End-to-End PC, Down-Link PC, On-Board Beam Shaping Ru 1 User 1 ADAPTIVE WAVEFORM : aims at reducing the required C/N 0 at constant BER Ru Adaptive 2 User Coding 2 or Modulation : allows the required E b /N 0 to be decreased Coding Modulation Data Rate Reduction : aims at decreasing the information data rate (R b ) DIVERSITY Ru User : aims N at adopting Rb a re-route Rc strategy of the network Rs N Site Diversity, Satellite Diversity, Frequency Diversity LAYER 2 : aims at retransmiting Automatic Repeat request, Time Diversity 13

14 POWER CONTROL - 1 DLPC UPLINK (ULPC) ex : ULPC compensates for uplink propagation impairments allows operating at low power in clear sky cond. to limit 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 OBBS EEPC (transparent repeater operated far from saturation) maintains a constant margin on the overall link budget mitigates downlink impairments if sufficient repeater margin keeping reasonable non-linear effects (intermodulation noise & capture effects) POWER CONTROL - 2 ON-BOARD BEAM SHAPPING Objective : maintaining up - down and overall link budgets Action : adapting the size of spot beams to the propagation 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 to be respected DOWN-LINK POWER CONTROL Objective : maintaining the downlink budget Action : adapting TWTA output power (weak extra power allocation) Limitations : no channel or intermodulation products ground power flux density specification to be respected ADAPTIVE WAVEFORM AC, AM : Adaptive Coding or Modulation Adaptive PSK Modulation BER 10-3 M 2 M 1 M 0 OPERATION MODE : Perf. objective : BER = C te 10-6 Threshold Constant bandwidth & variable info data rate (R b ) (Additional mitigation due to DR adjustment) Variable bandwidth & constant info data rate (R b ) 10-9 ρ 0 ρ 1 ρ 2 E b /N 0 (db) 14

15 DIVERSITY FMT SITE DIVERSITY (SD) Principle : 2 ES inter-connected by 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 (3 rd ES) LAYER 2 FMT RETRANSMISSION TECHNIQUES Objective : waiting for good propagation conditions interesting 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 area mid-term weather forecast (Meteorological Nowcasting) Necessary in complement to FMTs, but High system complexity : CAC, DAMA, JOINT FMT Fade depth (db) 1 OBBS 2 OBBS + ULPC 40 db 5 3 OBBS + ULPC + AM 30 db 4 OBBS + ULPC + AM + SatD 20 db 10 db 5 db AM AC SD 4 SatD ULPC 3 FD OBBS DLPC 0.01 % 0.1 % 1 % 10 % % of year 5 2 OBBS + ULPC + AM + SatD + SD 1 15

16 OUTLINE OF THE PRESENTATION INTRODUCTION PROPAGATION EFFECTS Attenuation Scintillation Total impairment FADE MITIGATION TECHNIQUES (FMTs) Review of FMT concepts Impact of FMTs on FMT implementation issues CONCLUSION INTERFERENCE SOURCES ON THE UPLINK INTRA-SYST. INTERF. Adjacent-channel Co-channel interf. Inter / intra beam Inter-beam cross-channel At the input of the satellite transponder UPLINK Intra-system Interference (no polar. re-use) Orthogonal polarisation Useful ES frequency Same polarisation INTERFERENCE SOURCES ON THE UPLINK INTRA-SYST. INTERF. Adjacent-channel Co-channel interf. Inter / intra beam Inter-beam cross-channel Intra-beam cross-channel At the input of the satellite transponder UPLINK Intra-system Interference (with polar. re-use) Interfering ES Useful ES 16

17 INTERFERENCE SOURCES ON THE UPLINK 3 INTRA-SYST. INTERF. Adjacent-channel Co-channel interf. Inter / intra beam Inter-beam cross-channel Intra-beam cross-channel At the input of the satellite transponder Interfering adjacent FWBA system UPLINK Adjacent system Interference INTER-SYST. INTERF. Adjacent satcom system Other system Interfering ES Useful ES INTERFERENCE SOURCES ON THE UPLINK INTRA-SYSTEM INTERFERENCE Adjacent-channel : Co-channel : Inter-beam cross-channel : Intra-beam cross-channel : IES in the same spot beam, frequency, same polarisation At the input of the satellite transponder IES in a spot beam, same freq., same polar. (TDMA) IES in the same spot beam, same freq., same polar. (CDMA) IES in a spot beam, same frequency, orthogonal polarisation IES in the same spot beam, same frequency, orthogonal polarisation INTER-SYSTEM INTERFERENCE Adjacent satcom system : the same frequency & polarisation Other systems : Fixed Broadband Wireless Access systems, radar systems : negligible INTERFERENCE SOURCES ON THE DOWNLINK INTRA-SYST. INTERF. Adjacent channel interf. Multicarrier interf. Co-channel interf. Inter / intra beam Inter-beam cross-channel At the input of the ES receiver DOWNLINK Intra-system Interference (no polar. re-use) Orthogonal polarisation Useful ES frequency Same polarisation 17

18 INTERFERENCE SOURCES ON THE DOWNLINK INTRA-SYST. INTERF. Adjacent channel interf. Multicarrier interf. Co-channel interf. Inter / intra beam Inter-beam cross-channel Intra-beam cross-channel At the input of the ES receiver DOWNLINK Intra-system Interference (with polar. re-use) Interfering ES Useful link INTERFERENCE SOURCES ON THE DOWNLINK 3 INTRA-SYST. INTERF. Adjacent channel interf. Multicarrier interf. Co-channel interf. Inter / intra beam Inter-beam cross-channel Intra-beam cross-channel DOWNLINK Adjacent system Interference At the input of the ES receiver Interfering adjacent FWBA system Interfering adjacent SatCom system INTER-SYST. INTERF. Adjacent satcom system Other system Useful link INTERFERENCE SOURCES ON THE DOWNLINK INTRA-SYSTEM INTERFERENCE Multi-carrier : Adjacent channel : intermodulation noise, carrier suppression effects carrier to the same spot beam same frequency, same polarisation At the input of the ES receiver Co-channel : 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 : Intra-beam cross-channel : carrier to a spot beam, same frequency, orthogonal polarisation carrier to the same spot beam, same frequency, orthogonal polarisation INTER-SYSTEM INTERFERENCE Adjacent satcom system : Other systems : the same frequency the same polarisation Fixed Broadband Wireless Access systems, radar systems : coordination 18

19 IMPACT OF POWER CONTROL ON INTERFERENCE LEVEL ULPC : maximum Tx power fixed from SoA & technology Objective : c t carrier transponder input Static compensation : Gr sat->es - Lup ES Dynamic compensation : Aup Clear sky conditions Lower nominal power to limit uplink Rain conditions Constant uplink during activation inside ULPC dynamic range DLPC (analysis for unicast) : Objective : c t power flux ground level? Static compensation? Ldwn ES Dynamic compensation : Adwn Clear sky conditions Limited IM (w.r.t. system saturation) Rain conditions Higher during activation IMPACT OF ADAPTIVE WAVEFORM ON INTERFERENCE LEVEL ADAPTIVE CODING / MODULATION Objective : improve spectral efficiency in clear sky conditions Higher 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 the transponder input variable uplink C/I Variable bandwidth : constant information data rate During AC or AM activation variable (I 0 ) DATA RATE REDUCTION Objective : adjust data rate to meet the required E b /N 0 Constant transmitted data rate : possible if fade spreading Impact on : Depends if bandwidth is kept constant or not IMPACT OF OTHER FMT ON INTERFERENCE LEVEL DIVERSITY Site Diversity : 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 : to be each frequency band No clear tendency, scenario dependent LAYER 2 ARQ & Time Diversity : No change on the physical layer transparent w.r.t. 19

20 IMPACT OF FMT ON INTERFERENCE LEVEL SUMMARY Impact of FMT on if in presence of fading : Real time adjustment of power : No adjustment of C/N 0 : Real time adjustment of bandwidth : ULPC, EEPC, DLPC, OBBS AC, AM, DRR 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 : Only for re-transmission FMTs OUTLINE OF THE PRESENTATION INTRODUCTION PROPAGATION EFFECTS Attenuation Scintillation Total impairment FADE MITIGATION TECHNIQUES (FMTs) Review of FMT concepts Impact of FMTs on FMT implementation issues CONCLUSION DETECTION & DECISION SCHEMES (D&D) OBJECTIVES Estimate of variable parameters impacting the physical 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 / contributions Uplink / downlink propagation impairments POSSIBLE D&D SCHEMES Open-loop : Closed-loop : Hybrid-loop : Retrieval of propagation fades from direct measurements QoL estimation from physical layer performance Rx Combination of both open-loop & closed-loop techniques 20

21 DISTRIBUTED D&D SCHEMES Open-loop Closed-loop Measurement, signalling, com. link Hybrid-loop CENTRALIZED D&D SCHEMES : BENT-PIPE SYSTEM Open-loop Closed-loop Hybrid-loop GES UES NCC UES Measurement, signalling, com. link NCC GES FADE ESTIMATION TECHNIQUES 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) 21

22 FMT CONTROL LOOP CONFIGURATION DETECTION OF State THE of the CHANNEL art : design BEHAVIOUR of only very simple loop Purpose : real-time estimate of current fade level Real-time estimate of overall SNIR Monitored signal 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 EVENT-BASED ANALYSIS WITH FMT 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 GHz GHz Coding rate 2/3 2/3 Uplink information data rate 2272 kbit/s 2272 kbit/s Nominal SSPA output power 600 mw 2 W Uplink E b/(n 0+I 0) 6.35 db 11.5 db Required E b/ N 0 (BER = 1.4*10-9 ) 4.6 db 4.6 db Uplink margin 1.75 db 6.9 db ULPC dynamic range / 5.2 db Required availability = 99.8 % 22

23 JOINT FMT IMPLEMENTATION DEFINITION OF THE JOINT FMT ULPC : from 800 mw to 2 W AC : Constant Tx DR : R c = 3019 kbit/s DRR : DR / 2 and DR / 4 FMT dynamic range : 16.0 db Frequency GHz GHz GHz GHz Coding rate 3/4 1/2 1/3 1/3 Uplink info. data rate 2272 kbit/s 1515 kbit/s 1010 kbit/s 505 / 252 kbit/s SSPA output power 0.8 / 2 W 2.0 W 2.0 W 2.0 W Uplink Eb/(N0+I0) 7.0/11.0 db 12.7 db 14.5 db 17.5 / 20.5 db Req. Eb/ N0 (1.4*10-9 ) 5.4 db 3.6 db 2.9 db 2.9 db Uplink margin 1.6 / 5.6 db 9.1 db 11.6 db 14.6 / 17.6 db FMT dynamic range - / 4.0 db 7.5 db 10.0 db 13.0 / 16.0 db Required availability = 99.8 % OUTLINE OF THE PRESENTATION INTRODUCTION PROPAGATION EFFECTS Attenuation Scintillation Total impairment FADE MITIGATION TECHNIQUES (FMTs) Review of FMT concepts Impact of FMTs on FMT implementation issues CONCLUSION FMT PRINCIPLE & IMPLEMENTATION : SUMMARY Availability User data rate Affected nb of users Reaction time Complexity Signalling / cost ULPC ++ 0 local DLPC + 0 beam OBBS + 0 beam AC + - channel/tdm AM + - channel/tdm DRR local Already used Planned Not mature SD local/global SatD + 0 global FD ++ 0 global TD ++ - global

24 SYSTEM PERFORMANCE PERFORMANCE ASSESSMENT User point of view : Service availability : function of link 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 24