Satellite Communications Overview
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© Copyright 2004 CapRock Communications – All Rights Reserved 1
Satellite Communications OverviewSatellite Communications Overview• Why satellite?
– Radio/Microwave signals travel in straight lines – Earth is curved so “line of sight” is limited– Long distances or paths are impeded by curvature of the earth– Satellite provides a “repeater”, a place to bounce the signal off
• System consists of:– Transmitting Ground Station Terminal– Satellite– Receiving Ground Station Terminal
• Satellite Bands:– C Band 4 – 8 GHz– Ku Band 12 – 18 GHz
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CapRock Provides Communications for a Variety of CapRock Provides Communications for a Variety of Remote LocationsRemote Locations
CapRock Teleport
Internet
PSTN
Corporate Data & Voice
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Typical Deployments Support a Multitude of Voice Typical Deployments Support a Multitude of Voice & Data Broadband Applications& Data Broadband Applications
Phones Fax Machines PCs Wireless LAN
Satellite Network Gateway
Integrated Solutions For:• Secure Corporate Networking• Broadband Internet/Intranet• Voice over IP• Real-Time Data• Video Conferencing• Video Surveillance & Media
Antenna System
Video Surveillance
Applications & Appliances
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Brief HistoryBrief History
• 1957 – First launch of Sputnik I by the USSR
• 1958 - Explorer I launched by US
• December 1958 - First actual transmission from a satellite (Eisenhower’s Christmas address) was from a tape recorder on Score
– Score’s battery life allowed orbit for 35 days
• 1962 - First true commercial satellites - Telstar I – First true communications satellite
• 1964 – International Telecommunications Satellite Organization (Intelsat) formed by 12 countries.
• 1965 – First Intelsat satellite Early Bird launched in GEO orbit starting communications between US and Europe
– First geostationary satellite
• Currently around 200 satellites in GEO, over 175 for communications.
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The Satellite
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Geostationary OrbitGeostationary Orbit
• Geosynchronous Earth Orbit (GEO)– Majority of High Capacity Communications– 22,236 miles above equator– 24 hour orbit and since it takes Earth 24 hrs to
spin on its axis the earth and the satellite move together. Satellite appears over same spot on the Earth.
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GEO satellitesGEO satellites
•Minimum 2 deg. Spacing between satellites
•Cross-pol and adjacent interference compliance required
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Satellite FootprintSatellite Footprint• Footprint of the area of Earth on which the satellite antenna “projects”
a signal
• GEO satellites have no coverage on the poles.
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Satellite FootprintSatellite FootprintIA-6
Spot Beam(US Only)
SatMex V
Hemi Beam(Americas )
I-901
Global(Also shows
Hemi and Spot)
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TransponderTransponder• A package of physical hardware on the satellite that includes the
receiver, the frequency converter and the transmitter.
• Capacity : 24 - 72MHz Transponders– SatMex V : 24 Ku-band @ 36MHz – IA 6 : 24 Ku-band @ 27 MHz; 4 Ku-band @ 54 MHz; 24 C-band @ 36 MHz– Intelsat 901 Global beam: 18 C-band @36 MHz
• Signal to and from a transponder can be either linear polarity (horizontal/vertical) or circular (corkscrew). Allows for frequency re-use thus doubling the capacity.
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The Ground Station Terminal or Earth Station
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Antennas - FixedAntennas - Fixed
Antenna that is aligned to point at satellite and is fixed in that position.
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Antennas - Trailer Mounted Auto-AcquireAntennas - Trailer Mounted Auto-Acquire
Auto-acquire has pre-programmed control unit
to point to specific satellite based on
coordinates of antenna (GPS).
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Antennas - Quick DeployAntennas - Quick Deploy
Quick Deploy antennas can be disassembled
and transported in carrying cases
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Antennas - StabilizedAntennas - Stabilized
•Antenna that has mechanism to stay pointed at satellite even when moving.
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Typical Deployment Supports a Variety of Voice & Typical Deployment Supports a Variety of Voice & Data Customer ApplicationsData Customer Applications
CustomerCorporate Office
WAN & PBX
Teleport
Remote Customer Location
Internet
PSTN
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Earth StationEarth Station
Up Converter
Down Converter
Modulator
Demodulator
MODEM
Low Noise Block (LNB)
Block Up Converter (BUC)
End
Use
r D
ata/
Voi
ce
Power Amplifier
Low Noise Amplifier
Antenna & Feed
IF (Intermediate Frequency) High or Radio Frequency (RF)
Baseband
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Typical Maritime Remote SiteTypical Maritime Remote Site
iDirect Modem
Antenna Controller
Phone + Internet Connections
Iridium Satellite Phone(out of band management)
LNB
BUC
OM
T
Iridium Antenna
Feed
Receive IF
Transmit IF
Below Deck Above Deck Stabilised Antenna
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Link Design
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Satellite Link BudgetSatellite Link Budget• Calculation used to determine the optimum
system requirements based on the transmit power and receive capabilities of a given satellite at a particular place in its footprint.
• Takes into account a signal with all the losses and gains from end to end.
– Uplink (G/T) and Downlink (EIRP) Level of the Satellite
– Bandwidth requirements– Atmospheric conditions (rain fade)– BER threshhold of receiving modem
• Determines– Transmit Gain (Antenna size)– Power output required of the Power Amplifier
UplinkDownlinkUplink
Downlink
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Access Techniques
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Single Channel Per Carrier (SCPC)Single Channel Per Carrier (SCPC)
Carriers are not shared.
Satellite Transponder
RXTX TX RXTX
Cust. A
Cust. B
A
B
SCPC
Linkstar Hub IPXpress
A
B
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Time Division Multiple Access (TDMA)Time Division Multiple Access (TDMA)Outbound and Inbound are shared.
Remotes share assigned return carriers.
All remotes “listen” to the same outbound carrier. Remotes take turns to transmit back.
Satellite Transponder
RXRX TX
Cust. A
Cust. B
A
B
SCPC
Linkstar Hub IPXpress
A
B
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Typical Maritime System – Outbound TDMTypical Maritime System – Outbound TDM
Hub Line Card
Hub Antenna
Satellite
Remotes
Outgoing packets are merged into one single stream
Each remote takes its own packets and ignores all the rest
Outbound broadcaststo all remotes
Data streams for the remotes
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Typical Maritime System – Inbound TDMATypical Maritime System – Inbound TDMA
Hub Line Card Hub Antenna
Satellite
Remotes
Packets are separated according to their addresses and forwarded to their destinations
Each remote transmits in bursts (according to a schedule set by the hub) – bandwidth on demand
Bursts arrive at the hub on the same channel interleaved in time.
Data streams for the remotes