ECE 5233 - Lecture 1 (Introduction)

Florida Institute of technologies

ECE 5233 Satellite Communications Prepared by:

Dr. Ivica Kostanic

Lecture 1: Introduction to Satellite Systems(Sections 1.1-1.4)

Spring 2014


Class overviewConfiguration of a satellite systemsElements of a satellite systemTypes of satellite systemsBrief history of satellite communication

Outline


Satellite communication system

Satellite system consists ofo Earth segment (traffic and control)o Space segment

Earth segmento Service provider hub (ground)

o User terminals

Space segmento Satellite (s)o Communication links to and from

satellites

1. Data center of the sat-com provider

2. Central hub (receives data stream and sends it toward satellite)

3. Satellite (receives data stream, amplifies and sends it back towards ground)

4. End user antenna – critical part (small size, high performance)

5. Modem – receives data stream

6. User end network – usually IP network


Ground segment Consists of earth stations Satellite network may have one or more earth stations Earth station may be transmit-receive or receive only Earth stations are connected to terrestrial networks (PSTN

for CS traffic or Internet for PS) Usually have very large antennas (up to 30m in diameter) Earth stations have high quality and redundant links to

terrestrial networks

Functional block diagram of an earth station

Example of a Ku band earth station antenna


Space segment Satellite consist of

o Payload – used in communicationo Platform – facilitates operation of payload

Payloado Receive antennao Electronics for communicationo Transmit antenna

Two types of satelliteso “Bent pipes” (transparent) o Regenerative (base band processing)

Smallest assignable recourseo Satellite transpondero Satellite usually hosts multiple transponderso Satellite usually operates in single band (although

there are some multiband satellites)

Transmit antenna may be o Single beam – one area of the Eartho Multi beam – multiple areas of the Earth

Basics of “bent pipe” architecture

Satellite with onboard processing


End user segment User stations

o Mobile stations (mobile terminals)o VSAT terminals o Gateways (connect space segment to

terrestrial networks)

User equipment mayo Connect to user stations

Example: Satellite TV

o Integrate with user stations Example: Satellite phone

Heavily dependent on the end application

Globstar satellite phones

Marine satellite antennas Satellite on the moveSatellite TV equipment


Types of satellite orbits

Orbit heighto Low Earth Orbit (LEO)

Attitude 160-2,000km Satellite speed ~ 8km/sec Orbital period ~ 90 min Example: Globstar, 48 satellites in six planes, 1413km

o Medium Earth Orbit (MEO) Altitude 2,000km -35,786km Satellite speed 8km/sec to 3 km/sec Orbital period 2 to 24h Example: GPS, 24 satellites in 6 planes, 20,200km

o Geosynchronous orbit (GSO) Altitude 35,768km Satellite speed ~ 3km/sec Non zero inclination Orbital period 24 hours

o Geostationary orbit (GEO) GSO satellite in zero inclination orbit

Constellation of Globstar system

Constellation of GPS system


Satellite services

Fixed satellite services (FSS)o PTP or PTMP delivery of signal across the

Globe

Mobile satellite services (MSS)o Delivery of satellite signal to mobile platforms

(either terrestrial, marine or aeronautical)

Broadcast satellite services (BSS)o Broadcast of satellite signal (TV, radio)

Navigation satellite services (NAV) Earth exploration services (ESS) Space research services (SRS) Space operations services (SOS) Radio determination satellite services

(RSS) Inter-satellite services (ISS)


Frequency bands used for sat-comm Satellites operate in microwave frequency range Two links

o Uplink – ground to satelliteo Downlink – satellite to ground

Each link uses its own band Uplink operates on higher frequency Microwave frequency bands

o L band: 1-2GHzo S band: 2-4GHzo C band: 4-8GHzo X band: 8-12GHzo Ku band: 12-18GHzo K band: 18-26.5GHzo Ka band: 26.5-40GHz

Majority of existing systems operate in C and Ku Higher frequencies

o More available spectrumo Better antenna directivityo Higher propagation losseso More sophisticated technology

Frequency chart for communication

satellite services


Frequency management

Responsibility of International Telecommunication Union ITU

Insures:o Non-interference condition between different

satellite systemso Fairness between nations in access to the

satellite frequencies

Frequency allocation may be o exclusive for given serviceo shared between services

Service provisioning usually requires consent of all countries within coverage area of the satellite

Frequency is usually allocated in pairso One frequency for ULo One frequency for DL

UL frequency is higher

ITU Regions

Example: VIASAT license in Ka band as of 2010

http://upload.wikimedia.org/wikipedia/en/4/46/International_Telecommunication_Union_region.svg

http://upload.wikimedia.org/wikipedia/en/4/46/International_Telecommunication_Union_region.svg


Beginnings of satellite communication

Origins: Arthur Clarke’s article in Wireless World in 1945 WW-II stimulated development of two key technologies

o Microwave communicationo Missile technology

First satellite launched in 1957 by USSR o Sputnik, 83.6kg, LEO, atmospheric studieso Mission duration 3 months

First commercial communication satellite 1967o Intelsat I - EarlyBird, 34.5kg, GEO, communication satelliteo Coverage between US and Europeo Operated 4 years (deactivated in 1969)o Launched from KSCo Could handle 240 voice and 1 TV channelo Owned by Intelsat (52 countries)

Sputnik 1

Intelsat- EarlyBird


Development of satellite communication

Imagination (1945-1960)o Early days of extensive scientific research o “Dreaming” of what is possible

Innovation (1960-1970)o Establishment of governmental space exploration

agencies and international satellite consortia o Development of communication and rocket technologyo First launches

Commercialization (1970-1980)o Satellite communication becomes commercial technologyo Applications: cross continental telephony and satellite TV

Liberalization (1980-1990)o Transformation of international governmental consortiao Market led approach allowed private investmentso Regulatory framework changes that allowed all of the

transformations to take place

Privatization and private ventures (1990 – on)o Communication satellites become mainstream technology led

by private businesso Leading applications: broadcast TV, data backhaul, mobile

communications in the air and on the sea, navigation, etc.o Future – integration of satellite technology with Internet

Satellite applications (values in B$)

History channel documentary: Satellites – how they work

https://www.youtube.com/watch?v=eYUxkSFCKZQ

ECE 5233 - Lecture 1 (Introduction)

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