satellite slides by sir haleem junejo(microwave & satellite communication)
TRANSCRIPT
8/3/2019 Satellite Slides by Sir Haleem Junejo(Microwave & Satellite Communication)
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Engineer Muhammad Haleem JunejoB.E( Electronics), MSc (Satellite Communication Engineering),CCNAMPEC
Microwave & Satellite
Communication
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Introduction
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Satellite Communications
Introduction & Systems Overview
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•Resources
–FrequenciesVhfL bandS band
C bandKu bandKa bandQ/V bands
–OrbitsGEOHEOLEO
MEO
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-Radio Regulations-
Why radio regulations?•Radio regulations rule the assignment and use of frequencies so as to
AVOID causing HARMFUL INTERFERENCE from one communicationsystem to another.•Two important aspects are to be considered:
–Allocation of frequency bands to the various services (WARC) –Standards for performance and compatible inter working of radiosystems (CCIR).•Space radio communication services are:
–Fixed satellite service
–Mobile satellite service –Broadcasting satellite service –Earth exploration satellite service –Space research service –Radio determination satellite service –
Amateur satellite service –Inter-satellite service
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Major system trends in Satellite Communications
•Fixed service –Telephony growing slowly –Video distribution, moderately
–VSATs slowly –IP for back haul increasing and interest inbroadband•Broadcast service
–Growing fast digital TV services-interactive –Radio, multicast and multimedia content•Mobile services
–Growing moderately for vehicles—reqt for broader
bandwidth
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The International Telecommunication Union (ITU)
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The International Telecommunication Union (ITU)
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Communication Fundamentals
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Interference considerations in satellite systems
Limited orbits & spectrum resources forceclose satellite spacing & sharing of spectrum
with other services (e.g. radio relay links).
Need to take account of interference, to &
from other satellite systems, existing &
planned.
Need to take account of interference, to &
from other services, existing & planned. Need to efficiently use resources so that
others can operate at future dates using some
of the remaining resources.
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Interference considerations
1.Terrestrial systems (restrictive if exclusive
bands not used).
2. Interference with same satellite network.
3. Interference with other satellite networks.
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Link Performance Interference
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Link Performance Interference
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Evolution of SatelliteCommunications
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1945 Arthur C Clarke
1956 First transatlantic telephone cable
1962 Telstar
1964 Intelsat founded1965 Early bird
1969 Intelsat completes global system
1976 Marisats launched
1977 Eutelsat created
1979 Inmarsat created
1982 Inmarsat starts operations
1983 EutelsatF1 launched
development of commercial satellite communication
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development of commercial satellite communication
1984 PanAmSat founded
1985 SES Astrain corporated1987 Iridium conceived
1988 First transatlantic fiber cable
1988 First PanAmSat launch
1989 First SES Astra launch1995 PanAmSat completes global system
1998 Iridium service launch
2001 Intelsat & Eutelsat privatisations
2002 SDR operation US –
SIRIUS/XM
2004 DMB in Japan/Korea
2005 INTELSAT PANAMSAT Merger
2006 SES/New Skies merger – one manufacturer in Europe!
HYLAS new UK o erator launched
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Evolution of Satellite Communications
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Evolution of Satellite Communications
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I4 Wid b
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I4 Wide-beam coverage
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I4-Narrow-beam
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Orbit Options
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Satellite Communications
Systems Architecture
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Ground Segment Functions
Track satellite motion with antenna system Boot Telemetry signal with high gain antenna Process, record and analyse Telemetry data Transmit commands to satellite using high power -
unblock able' uplink signal Provide Ranging data Perform scheduled operations Maintain communications with spacecraft under all
possible circumstances Data Distribution Satellite Health data to Satellite Control Centre Experimental data to user groups/investigators Alarm/Alert warning messages
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Single Ground Station Model
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Ground Station Components
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Typical Ground Station
MCC – plansand operates
the entire
space mission
SOCC – satellite
bus and
communication
systems
POCC – onboard
payload
instruments
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Location of Ground Segment The number and location of TT&C stations will vary
according to the orbit and mission Geo-stationary Orbit Once on station only one TT&C facility, which may also be the
Satellite Control Centre (SCC) is required in satellite servicearea e.g. ASTRA/SES Luxembourg EUTELSAT Paris
Large organizations with multiple service areas INTELSAT,INMARSAT maintain remote or multiple TT&C facilities
Deep Space Network A network of very large installations (often multiple antennas)
maintained in varying longitudes to provide near continuous
coverage of the plane of the solar system. – The system is US led and maintained by NASA/JPL locations
Australia,Mexico,Hawaii ESOC - network controlled from Darmstadt Jet Propulsion Laboratory
National Aeronautics and Space Administration
Locations of STDN Stations
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Locations of STDN Stations STDN - NASA’s Satellite Tracking and Data Network
Earth Station Technology
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Earth Station Technology
-Earth Station Architecture
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Earth Station Technology
Earth Station Architecture
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Space Segment
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Space Segment Functions
Maintain Earth coverage for antenna low gain omni directional antennas
high gain directional antennas for stabilizedplatform
Receive commands from authorized sources
Transmit spacecraft Telemetry and status
Receive ranging signals and retransmit in
coherent mode Maintain communications with Earth
stations under all possible circumstances
Transmit payload data
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Satellite Subsystems
• Communications Payload• –Antennas• –Repeater
• Bus• –Structure• –Electrical power subsystem
• –Satellite attitude control subsystem• –Propulsion subsystem• –Thermal control subsystem
• –Telemetry, tracking and command (TTC)
Attit d /O bit C t l
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Attitude/Orbit Control Satellites experience external forces which can disturb
orbits and attitude
Compensation uses rocket propulsion (jets)
Disturbing torques? –solar pressure and magneticdisturbances
Techniques used -Spin stabilization (old INTELSAT‘s)
Three axis momentum (momentum wheels)(most modern/satellites)
Gravity gradient (SSTL/Orbcom) Reaction controlMagnetic control Solar sailing (EurostarSeries)
St t l
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Structural
Spacecraft frame and skeleton
Mechanical support and rigidity
shock loads
Rigours of launch (vibration table)Temperature cycling.
Radiation fields –vacuum.
Minimum mass and cost.Pyrotechnics –deployments.
Tracking Telemetry and command
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Tracking, Telemetry and command
(TT&C)
Transmits/receives house keeping data to/from satellite
allowing ranging, Doppler, tracking and commands from
ground control
Measures temperature, pressure, voltages, currents,
GPS, etc.
Formats data – command and data handling (C&DH)
Dedicated TTC transponder
Commands to initiate mode changes, turn on/off
equipment, fire thrusters, etc.
P S l
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Power Supply
Solar photovoltaic cells –Si & GaAs –sized toproduce average power requirements –10-25%efficient –lifetime degradation due to spaceradiation. BOL and EOL power
Batteries (clinical) –eclipse and peak powerrequirements Nicad Lithi-ion
Regulation and conditioning (need to survivemillions of charge/discharges and distribution tovarious parts of the bus).
Th l
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Thermal
On earth –Radiation/conduction/convectionIn space -only radiation
Objects > 273K radiate heat energy
Thermal control is achieved by using externalsurface properties together with heaters,thermostats, heat pipes and interface fillers
Sun shields, black paint, heat shields etc.
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Propulsion
Need thrusters to create momentum –propellants
Cold gas –precise, low thrust, simple
Liquid propellant -Hydrogen, hydrogen peroxide
-Higher thrust –more complex
Bipropellants -Liquid hydrogen, oxygen etc-very high thrust –complex and expensive
-high mass propellant
Electric Propulsion -electrostatic –electro –thermal-ion engines
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Access Schemes in Satellite Networks
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Satellite Network organisation
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Satellite Network organisation
Satellite Networks
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Satellite Networks
Fixed and Demand Assignment
Satellite Networks
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Satellite Networks
Fixed and Demand Assignment
Basic multiple access techniques
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Basic multiple access techniquesFREQUENCY DIVISION MULTIPLE ACCESS
(FDMA)
Basic multiple access techniques
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Basic multiple access techniquesTime Division Multiple Access (TDMA)
Basic multiple access techniques
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Basic multiple access techniquesCode Division Multiple Access (CDMA)
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Various layers of multiple access
FDMA (1 carrier per link)
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FDMA (1 carrier per link)
FDMA(1 carrier per station)
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FDMA(1 carrier per station)
FDMA throughput
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FDMA throughput
FDMA S
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FDMA Summary
Access Channel: give frequency band
Advantages
Use of existing hardware to a greater extent than other techniques Network timing not required
Disadvantages
As the number of accesses increases, intermodulation noise reduces
the usable repeater output power (TWT back-off). Hence there is a lossof capacity relative to single carrier/transponder capacity
The frequency allocation may be difficult to modify Uplink power coordination is required
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TDMA Satellite System
• In a TDMA system, each earth station transmitstraffic bursts, synchronized so that they occupyASSIGNED NON-OVERLAPPING time slots. Timeslots are organized within a periodic structurecalled TIME FRAME.
• A burst is received by all stations in the downlinkbeam and any station can extract its traffic from
any of the bursts• a BURST = link from one station to several
stations (TDMA=one-link-per-station scheme)
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TDMA Satellite System
Principles of Time Division Multiple
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Principles of Time Division MultipleAccess (TDMA)
TDMA throughput
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TDMA throughput
TDMA summary
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Access Channel: given time slot within time frame
Advantages
Digital signaling provides easy interfacing with developing digitalnetworks on ground
Digital circuitry has decreasing cost Higher throughput compared to FDMA when number of accesses is
large
Disadvantages
Stations transmit high bit rate bursts, requiring large peak power
Network control is required Generation and distribution of burst time plans to all traffic stations Protocols to establish how stations enter the network Provision of redundant reference stations with automatic switchover to
control the traffic stations Means for monitoring the network
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CDMA Spread spectrum communications
Direct sequence systems
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Direct sequence systems
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-power spectrum of data and of spread signal-
CDMA
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Frequency hopping systems
Multiple access
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pComparison of multiple access techniques
Advantages/disadvantages
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g g
Random Access Schemes (1)
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( )
FDMA/TDMA/CDMA fixed access have
been designed for circuit/stream traffic
Bursty data traffic –e.g. packets-moreefficiently dealt with via random access
schemes
In random access there is no permanent
assignments –resource is allocated when
needed on a random basis
R d A S h (1) td
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Random Access Schemes (1) ctd
In random access or contention methods, no station is superior to another station and none is assigned the
control over another. No station permits, or does not
permit, another station to send. At each instance, a
station that has data to send uses a procedure defined by the protocol to make a decision on whether or not to
send.
Random Access Schemes (2)
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Simplest system is ALOHA –transmit packets andif collide, retransmit with random time difference.
Performance via ‗throughput versus delay‘
Throughput = N λL/R –N= no transmissions
–λ= packet generation rate (S-1)
–L= packet length (bits) –R= transmission bit rate (bits/s)
ALOHA doesn‘t need synchronization
Maximum throughput 18%
Frames in a pure ALOHA
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a es a pu e O
network
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Random Access Schemes (3)
SLOTTED-ALOHA confinestransmission to slot boundariesand needs time synchronization
Maximum throughput isincreased to 36%
As system rapidly becomesunstable as collisions build up,usual to operate below maxima
Frames in a slotted ALOHA network
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Frames in a slotted ALOHA network
R d A S h (4)
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Random Access Schemes (4)
For variable length messages need toemploy more complex scheme e.g.
slotted reject ALOHA
Use multi-packet message and onlyre-transmit sub-packets that collide
Increases throughput (≈0.37)independent of message length
Random Access Schemes (5)
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Random Access Schemes (5)
Slotted Reject-Aloha
Comparison of random access
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p
Summary
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Summary
Select RA scheme for traffic type and
delay/throughput (α number of tx’s)
Take care to achieve stability
ALOHA: short bursty traffic
S-ALOHA: short bursty traffic –better
throughputS-R.ALOHA: variable length messages
DA-TDMA: stream or file transfers
VSATs
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VSATs
Why VSAT? –advantages and disadvantages
Structure of VSAT networks -star/mesh
Traffic types and their description
Choice and comparison of multiple accesssystems
Capacity and throughput analysis -protocolsand network interfaces
VSAT system design drivers Regulatory and licensing aspects.
Genesis of VSATs: WHAT IS A VSAT?
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Genesis of VSATs: WHAT IS A VSAT?
VSAT is an acronym for Very Small Aperture Terminal.
It is a small satellite terminal that can be used for one-way and/or interactive communications.
ETSI (the European Telecommunications StandardsInstitute) define, in brief, a VSAT as a one or two-wayterminal used in a star, mesh or point to point network.
Antenna size is restricted to being less than or equal to1.8 m at Ka band, 3.8 m at Ku band and 7.8 m at C band
Genesis of VSATs: ETSI VSAT Ku-Band
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Frequency Bands
The VSATs are operating in one or more frequencyranges in part of the following bands allocated:-
exclusively to the Fixed Satellite Services (FSS):
14,00 GHz to 14,25 GHz (earth-to-space); 12,50 GHz to 12,75 GHz (space-to-earth).
or in the shared parts of the following bands,
allocated to the FSS and Fixed Services (FS): 14,25 GHz to 14,50 GHz (earth-to-space);
10,70 GHz to 11,70 GHz (space-to-earth).
Genesis of VSATs
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Ge es s o S s VSATs were first employed for data distribution to a
large number of locations.
They provided a means to avoid the highly regulated(monopoly based) communications infrastructure as wellas the associated high charges for such networks (alsoknown as ‗by-pass‘).
Most early use was in private networks.
VSAT networks first appeared in the early 1980‘s whenEquatorial Communications, a start-up company launchedby Ed Parker and Dean Mack in a warehouse near PaloAlto, initiated the first use of really small dish antennas forreceive-only applications.
Data distributors like ―wire services‖ were quick tojump to using the technology to economically distributeinformation to thousands of receive only VSAT‘s.
Genesis of VSATs: WHY USE A VSAT?
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Genesis of VSATs: WHY USE A VSAT?
Genesis of VSAT Systems
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Early Equatorial Communications Inc.VSAT (CDMA)
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VSAT (CDMA)
Mid 1980sC-Band
2 way
Current day outdoor unit
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Genesis of VSAT Systems: Hardware
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SATELLITE SERVICE EVOLUTION
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VSAT evolution
More than 30,000 Equatorial C-band (4/6 GHz)60 cm antenna systems were sold in the early1980s.
Equatorial later developed a C-band (4/6 GHz)2 way system using 1m x 0.5 m antennas andsold about 10,000 units in 1984-85.
2005 around 1.4 million VSAT terminal in useglobally.
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VSAT Network Topologies
Star –employs a large hub Large antenna hub enables
small VSAT with low powerVSAT transmitter
Typical of networks in the
1980s and 1990sMesh –VSAT to VSAT
Need higher VSAT andsatellietransmit powers buteliminates double delay
Typical of networks in thelast 5 years
VSAT Network Topologies
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VSAT Network Topologies
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p g
VSAT Network Topologies: TCP/IP
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VSAT Network Topologies: Extensionwith Wireless Distribution
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with Wireless Distribution
SAMPLE OF VSAT USERS (1984-1994)
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SAMPLE OF VSAT USERS (1995-1999)
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Geographic location of VSAT terminals
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Internet Protocol (IP) over Satellite
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( )
TCP/IP consists of TCP -Transmission Control Protocol and IP -Internet Protocol which form a protocol stack.
TCP/IP is primarily oriented mostly to terrestrial based networks, whenSatellite Internet access and VSAT systems are yet to be utilized commercially.Despite significant optimizations and enhancements proposed over the manyyears, TCP/IP operation has not changed significantly since RFC 793,
published in 1981.
Applying standard TCP/IP to Satellite Internet access circuits leads to theunder-utilization of the link and degraded performance.
There is the issue of round trip latency due to the fact that geostationary
satellites are 30,000 km above the earth surface: it takes approximately half asecond for the signal to travel from the user to the satellite and back to thehub.
Additionally, there is a packet loss possible due to the error rate of the link.
Internet Protocol (IP) over Satellite
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There are a number of solutions available in order toovercome TCP/IP performance degradation.
Usually, these solutions are named TCP accelerators andPerformance Enhancing Proxies (PEP).
TCP accelerators use various techniques to substituteTCP/IP with a protocol set which is more optimized for SatelliteInternet access.
Most of solutions use UDP as the primitive IP packetstransport while speed and window size negotiations are done
inside the TCP accelerator protocol.
Most of the TCP accelerators also bundle a number of wellknown techniques in order to improve the performance of theSatellite Internet circuit. These techniques usually include DNScaching, HTTP pre-fetching and on-the-fly traffic compression.
ACCESS TECHNIQUES
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FDMA -Frequency Division Multiple Access TDMA -Time Division Multiple Access CDMA -Code Division Multiple Access
MF-TDMA -Multi-Frequency Time Division Multiple Acces
DAMA with SCPC –Demand Assigned Multiple Access with Single Channel Per Carrier
DAMA with MF-TDMA
–Demand Assigned Multiple Access with Multi-Frequency Time Division Multiple Access
PCMA -Paired Carrier Multiple Access
Optimizing the Access System
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Different VSAT platforms use various technologies in order
to access the satellite radio space segment and share it amongmultiple subscribers.
Many of sharing techniques are based on TDMA technology.
The concept of sharing the satellite space segment amongmultiple subscribers is based on allocating a group of users
the same transmit and/or receive frequencies and dividing itinto many timeslots.
Simple approaches allow users to transmit randomly,decreasing the overall performance of the network down toalmost 15-20% while more complex concepts dedicatetimeslots to every subscriber, raising the performance to near80%.
Multiple Access Schemes
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TDMA► Packet-based
► Star and mesh Topology► Large volume (1000s) for Star► Small volume (10s to 100s) for Mesh► Efficient for random/Bursty Traffic and Bandwidth on Demand
SCPC-DAMA
► Circuit switched► Star and Mesh topology► Small to medium volume (10s to 100s)► Efficient for dedicated/continuous data transfers
SPREAD SPECTRUM (CDMA)► Packet-based► Star topology► Large volume (1000s)► Efficient for random /bursty Traffic•
Single Channel per carrier (SCPC)A
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Access.
Multi-Frequency TDMA (MF-TDMA)
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q y ( )
The conventional TDMA uses only one frequency andall Earth stations transmit and receive on a singlefrequency, whatever the destination of the bursts is.
Therefore, it does not provide power efficiency and thesatellite link speed is limited.
To solve this inefficiency, the MF-TDMA was proposed.The MF-TDMA reduces satellite antenna sizes andtransmission power, and increases satellite networkbandwidth.
Most of the future broadband satellite networks will useMF-TDMA or MF-TDMA-like schemes.
DAMA with MF-TDMA
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In order to achieve a greater efficiency in broadbandsatellite networks, the DAMA scheme can be used with
other access schemes such as MF-TDMA.
By exchanging signaling packets, the process of call
setup involves the negotiation among the Earth station anda master control station (MCS) which controls the satellitenetwork.
The signaling packets are transmitted in the
synchronization area which is a fixed portion in the MF-TDMA frame.
Once the connection is established, a certain amount ofmemory and bandwidth is allocated to the new connection.
MF-TDMA
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MF-TDMA
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MF-TDMA
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MF-TDMA
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Paired Carrier Multiple Access
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Paired Carrier Multiple Access
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Bandwidth saving is by the overlaying of the twochannels
No power is saved as we still need to transmitboth carriers across the transponder
We can re-use up to twice the availablebandwidth limited by
►The point where we have bandwidth and power parityon the Transponder
►A need for asymmetry of the two carriers
Available from ViaSat, HNS, TranscendentTechnologies (DoubleTalk)
Standards
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In the early years of VSATs the lack of compliance toany specific standards and the shortage of agreed
standards were significant impediments to thedevelopment of a thriving VSAT market.
In the early 1990s there were some 27 vendors offeringVSAT products with around 20 different interfaces, service
quality levels and network management approaches. Looseassociation with protocols such as X25.
On the other hand, Standards Bodies were not veryinterested in spending resources to develop standards if
the market was not mature and significant.
In the late 1990s the market had matured sufficiently forthe open standards to be developed ( the need forproprietary systems to protect high investment values had
diminished).
STANDARDISATION OF SATELLITETERMINALS IN ETSI
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TERMINALS IN ETSI
The relevant standardization body for Standards fallingunder
the scope of the R&TTE Directive is the EuropeanTelecommunications Standards Institute (ETSI), which isresponsible for all telecommunication-related standards.
The focal point for all satellite-related activities within ETSIis
the Technical Committee for Satellite Earth Stations andSystems(TC-SES).
ETSI publishes DVB standards within its range of standardsand reports.
DVB
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The Digital Video Broadcasting Project(DVB) is an industry-led consortium of over270 broadcasters, manufacturers, networkoperators, software developers, regulatorybodies and others in over 35 countries
committed to designing global standards forthe global delivery of digital television anddata services.
Services using DVB standards areavailable on every continent with more than
120 million DVB receivers deployed. DVB publishes it standards via ETSI.
www.dvb.org
DVB Return Channel via Satellite (DVB-RCS)
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• In 1995 SES/Astra began working with various
industry bodies (ETSI, DAVICS, DVB and others)to establish a standards-based return channeldesign for the DVB system (DVB-RCS).
• DVB-RCS was adopted as a standard by ETSIduring mid-2000 joining a range of DVB standardswhich include return channels for wireless, cableand other media.
• DVB-RCS offers high bandwidth on the forwardand return links -with a 45 Mbps outbound channeland an inbound channel of 2 Mbps working with amultiple-frequency TDMA access scheme.
Political Aspects
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The USA led the way in competition policies for thetelecommunications industry during the late 1970s andearly 1980s.
Restrictive legislation was reduced and regulation
minimized with market forces encouraged. This resulted in an expansion of telecommunicationservice companies and associated growth ofentrepreneurial developments and products.
VSAT systems owe a great deal to these developments
as a catalyst to their market places. The UK followed by Western Europe lagged but were
not far behind.
Political Aspects
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Elsewhere in the world, politics have molded the shape of VSAT
services in many countries.
Competition in domestic services is one thing, but manygovernments maintained their monopoly on international services.
1994 saw Europe in the interim stages of liberalization and this was
only really completed by 2000.
During the early 1990s, Latin America was probably exhibiting thefastest rates of deregulation. Services were relatively free in Chile,Argentina, Colombia, Ecuador, Venezuela and Mexico.
Africa has been hard for a number of reasons, but now many of thekey economies in the region have liberalized, the market has begun tolook more attractive and some limited regional services are possible.
Political Aspects
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Difficult economic conditions and the swift market correction whichtook place in early 2001 left many operators and system vendors in aprecarious position.
Manufacturers and operators went searching for customers able topay a commercial rate for a service and found them in the SMEsegment.
Broadband access services targeted at enterprises -as opposed toenterprise networks which also connected IP services -finally becamea reality and Europe in particular saw wholesalers begin to developprogrammers for value added resellers in order to address smallercustomer sales.
As the major markets of Asia and Latin America struggled, Africasuddenly assumed the role of golden opportunity and a gold rushensued and, mostly, still remains.
Political Aspects
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Where VSAT platforms have moved on is in the
integration of products around a core IP-centricdesign.
Having established IP as the primary elementof the system architecture, all of the vendors have
gone on to build router capabilities into theirsystems as an inherent part of their feature set. Various features have been added -
acceleration, QoS, classes of service, encryption,web page acceleration and, in some instances,support for VoIP.
With increased processing power VoIPimplementations have grown beyond the clumsyservices of a few years ago and are now hard to
distinguish from a toll-quality terrestrial line
Political Aspects
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Nearly all VSAT systems are now based on IP,with a very broad spectrum of applications. At December 2004, the total number of VSAT
terminals ordered stood at over 1 million withnearly 650,000 sites in service.
Annual VSAT service revenues were $3.88billion, with TDMA & DAMA hardware revenues at$746.9 million
Some political will is being expended to
identify if Satellite Broadband can close the socalled ‗Digital Divide‘, but the key questions arewill funding be assured and the market not beeradicated in terms of timescales and competition.
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Communications PayloadEngineering
Constraints on the Communications PayloadDesign
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Design Constraints from the Platform
Accommodation - Physical size, must fit on spacecraft platform, compatibility withlaunch vehicle fairing
Thermal Dissipation - Limited ability of spacecraft to radiate heat, radiator area Mass
- Launcher capability and spacecraft platform set absolute limit - Payload Mass Contends with: - Life (Mass of station keeping fuel) - Cost (Launch cost) - Payload Power ( Mass of the Power Sub-system)
Available Electrical Power - Mass and accommodation of power sub-system Temperature Control - Comms. performance versus mass and power consumption of
thermal control hardware Electromagnetic Compatibility with the Platform
Constraints on the Communications PayloadDesign
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Design
Constraints from the Environment
Received Earth Noise - Sets lower limit to the communications payload system noise
temperature
- Typically 100 to 300 Kelvin depending on frequency and
location viewed on the Earth Ionising Radiation
- Materials and active electronics must survive for the designedlifetime
Vacuum
- No convective heat transfer
- Multipaction Breakdown
- Air to vacuum frequency shift for vacuum cavity filters
Constraints on the Communications PayloadDesign
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es g
Communications Payload Function
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Communications Payload
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Essential Communication Payload Functions
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Satellite Communication Frequencies
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Key Communications Requirements
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A Satellite Antenna
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Antenna Types and Functions
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Typical Spacecraft Antennas
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Satellite Antenna - Side deployed
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Typical Repeater Functions
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Receive and filter uplink signals
Provide minimum C/No degradation
Provide variable high gain amplification
Down convert Frequency for re-transmission
Filter high power downlink signal and re-transmit
Provide high reliability in functionality
Beam-to-beam interconnectivity Functional re-configurability
Beam forming
Why High Reliability?
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Quality of the Receive System – G/T
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Noise Temperature
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E.I.R.P
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Payload Configurations - Basic Elements
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Why Filter?
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Why Chanalised Amplification?
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Payload Configurations - Channelisation
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Input De-Multiplexer – (IMUX)
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Payload Equipment - Input Multiplexers
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Payload Equipment - Input Multiplexers
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Choice of HPA
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Dual Travelling Wave Tube Amplifier(TWTA)
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Payload Configurations – Trends
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Payload Configurations – Trends
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On-board Processing – Why?
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On-board Processing – Why Not?
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Transparent Or Regenerative
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Typical Digital Processor Architecture
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Inmarsat 4
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Payload Equipment - Receivers
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Payload Equipment – Multi-Chip Module(MCM) Technology
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Payload Equipment – Integrated Down converterHi-Modular Microwave Hybrid Technology (Hi-MMHT)
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Payload Equipment - Channel Amplifier
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Payload Equipment - Frequency Generator
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INMARSAT 4 Digital Signal Processor
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Anechoic Chamber
• An anechoic chamber is a shielded room designed
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An anechoic chamber is a shielded room designed
to attenuate waves. Anechoic chambers wereoriginally used in the context of acoustic (sound)echoes caused by reflections from the internalsurfaces of the room, but more recently anechoicchambers have been used to provide a shieldedenvironment for radio frequency (RF) andmicrowaves. An RF anechoic chamber is designedto suppress the electromagnetic wave analogy ofechoes: reflected electromagnetic waves, from theinternal surfaces. Both types of chamber areconstructed with echo suppression features andwith effective isolation from the acoustic or RFnoise present in the external environment.
Astra In Anechoic Chamber
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Astra Repeater in Assembly andIntegration
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Typical Repeater Panel Layout
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Astra Repeater Panels
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Future Trends
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Future Trends – Next GenerationGeneric Flexible Payloads
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An introduction to Inmarsat
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