Satellite Communications Overview

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© Copyright 2004 CapRock Communications – All Rights Reserved 1 Satellite Communications Overview Satellite 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

Transcript of Satellite Communications Overview

Page 1: Satellite Communications Overview

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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

Page 2: Satellite Communications Overview

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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