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8/2/2019 Chapter 1 Introduction to Satellite Communication System
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BEE 4243 SATELLITE COMMUNICATION SYSTEMDept. Of Communication Engineering,FacultyOf Electrical And Electronics,
UniversitiTun Hussein OnnMalaysia
The space race, legacy of the
SPUTNIK
Oct 4th 1957, Sputnik 1, launch
from Tyurastam, USSR Means “Friendly Traveller”, weighed
just 184.3 pounds (83.6kg) continue
to send signals for 21 days before
decaying 3 months after launch on
Jan 4th 1958
Spirited the technological
competition in the space race
BEE 4243 SATELLITE COMMUNICATION SYSTEMDept. Of Communication Engineering,FacultyOf Electrical And Electronics,
UniversitiTun Hussein OnnMalaysia
Next was Explorer 1 on Jan 31st 1958 USA answers to Sputnik
Carried scientific equipment to study the
Earth atmosphere
Found the van Allen belt
Transmitted telemetry for nearly 5 months
SCORE, Signal Communication by Orbiting
Relay Equipment
Dec 18, 1958 by the USA, 150 pounds conical-shaped satellite
The first artificial satellite used for relaying
terrestrial communication
First bent pipe repeater
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BEE 4243 SATELLITE COMMUNICATION SYSTEMDept. Of Communication Engineering,FacultyOf Electrical And Electronics,
UniversitiTun Hussein OnnMalaysia
1960, ECHO (USA)
First communicating satellite (passive) into space
100 ft diameter plastic balloon with aluminium coating
1962, Telstar
First active communication satellite
1962, Relay (USA)
First comm. satellite to transmit TV signal worldwide
1963, Syncom II (USA)
First geosynchronous communications satellite
Jul 1964, IntelSat formed
1965, INTELSAT 1 (Early Bird) launched
68 kg, 480 telephone channels, annual cost $32,500 perchannel
Caused by launch cost, satellite, short lifetime and lowcapacity
1965, MOLNYA series launched
BEE 4243 SATELLITE COMMUNICATION SYSTEMDept. Of Communication Engineering,FacultyOf Electrical And Electronics,
UniversitiTun Hussein OnnMalaysia
Important Milestone
1000 AD, Chinese invented the rocket
1903, Konstantin Tsiokovsky, publishes his ideas on space flight
1926, first liquid propellant rocket launched by R.H. Goddard in the USA
1942, first successful launch of V-2 rocket in Germany
1945, Arthur C. Clarke published his ideas on geostationary satellite for
worldwide communications Today, satellite communications is very much a fact of everyday life
Form an essential part of telecommunications systems worldwide carrying
large amount of data and telephone traffic in addition to television signals
Cost is distance insensitive, it cost about the same to provide a satellite
communication link over a short distance as it does over a longer distance
due to its wide coverage
According to the Union of Concerned Scientists, there are around 900
satellites currently in operation (not including the secret/ classified
satellite).
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BEE 4243 SATELLITE COMMUNICATION SYSTEMDept. Of Communication Engineering,FacultyOf Electrical And Electronics,
UniversitiTun Hussein OnnMalaysia
ARCHITECTURE OF SATELLITE
COMMUNICATION SYSTEM Space segment Satellite
All terrestrial facilities for the control and monitoring of the satellite
Tracking, telemetry and command (TT&C) station
Satellite control centre
Station keeping
Check vital function of the satellite
Satellite can be divided into two parts
Payload
Consists of the receiving and transmitting antennas and all theelectronic equipment which support the transmission of
carriers and information Platform (bus)
All the subsystems which permit the payload to operate such asstructure, electrical power supply, temperature control, attitudeand orbit control, propulsion equipment, TT&C equipment
BEE 4243 SATELLITE COMMUNICATION SYSTEMDept. Of Communication Engineering,FacultyOf Electrical And Electronics,
UniversitiTun Hussein OnnMalaysia
Ground segment All the earth stations; receive, or both transmit and receive
The simplest is Home TV receive-only (TVRO)
Most complex – Terminal station used for international communicationnetwork
Stations are distinguished by
Size : varied according to volume of traffic to be carried on space
links Type of traffic : telephone, television or data
Satellite can link network of ground station in three ways:
Point-to-point : signal transmitted in one part of the world toanother individual stations
Point-to-multipoint : From one stations to an unlimited number of independent receiving stations (e.g. satellite TV broadcasting
Multipoint-to-point : From many point to a single controllingstation (e.g. environmental data-collection
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BEE 4243 SATELLITE COMMUNICATION SYSTEMDept. Of Communication Engineering,FacultyOf Electrical And Electronics,
UniversitiTun Hussein OnnMalaysia
The performance of a satellite link is typically specified in terms of itchannel capacity
Definition
A channel is one-way link from transmitting earth station through thesatellite to the receiving earth station
A circuit is full duplex link between two earth station
A half circuit is a two-way link between an earth station and thesatellite only
The capacity of a link is specified by these types and number of channelsand the performance requirement of each channel
the term channel may also apply to televisions and data circuits
The quality of a radio link is specified by it carrier-to-noise ratio (C/N)
The quality of the total link determines the quality of the signals deliveredto the end user in accordance with the type of modulating and coding used
BEE 4243 SATELLITE COMMUNICATION SYSTEMDept. Of Communication Engineering,FacultyOf Electrical And Electronics,
UniversitiTun Hussein OnnMalaysia
The satellite has dual role
To amplify the received carriers for retransmission downlink
The carrier power input at the satellite receiver is in the order of
100pW to 1nW
The carrier power at the output of the transmission amplifier is of
the order of 10 to 100W The power gain is thus of the order of 100 to 300dB
To change the frequency of the carrier to avoid re-injection of a
fraction of the transmitted power to the receiver
The rejection capability of the input filters at the downlink
frequency combines with the low antenna gains between the
transmitting output and the receiving input to ensure isolation of
the order of 150dB
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BEE 4243 SATELLITE COMMUNICATION SYSTEMDept. Of Communication Engineering,FacultyOf Electrical And Electronics,
UniversitiTun Hussein OnnMalaysia
Conventional satellite
Regenerative satellite
Figure 1.1 Conventional and regenerative satellite
BEE 4243 SATELLITE COMMUNICATION SYSTEMDept. Of Communication Engineering,FacultyOf Electrical And Electronics,
UniversitiTun Hussein OnnMalaysia
Definitions Local communications
Communications limited in distance e.g. few tens of kilometres
Regional communications
Communications over a specific region of the world such as groupsof countries or continent
Global communications
World wide established link
Communications can be classified into two main categories
Real time communications
Delayed communications
This distinction is essential for identifying the type of service that canbe performed, since it will affect the system design
Possible mix of the two concept within the constrain of a cost-effectivedesign e.g. LEO satellite systems can well be adopted for providing
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BEE 4243 SATELLITE COMMUNICATION SYSTEMDept. Of Communication Engineering,FacultyOf Electrical And Electronics,
UniversitiTun Hussein OnnMalaysia
(a) Typical Vista application (b) domestic/regional Vista network with standard Aor B gateway
BEE 4243 SATELLITE COMMUNICATION SYSTEMDept. Of Communication Engineering,FacultyOf Electrical And Electronics,
UniversitiTun Hussein OnnMalaysia
The design of a satellite communications system present many
interesting alternatives and tradeoffs
Choice of orbits
Method of multiple access
Method of modulation and coding
Trade off between power and bandwidth
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BEE 4243 SATELLITE COMMUNICATION SYSTEMDept. Of Communication Engineering,FacultyOf Electrical And Electronics,
UniversitiTun Hussein OnnMalaysia
The most favourable orbits for satellite communication LEO (Low Earth Orbit)
Altitude : 300 km – 2,000 km (more common : 600 km – 1,000 km) Either elliptical or (more usual) circular
Many different type, no firm decision as to what constitutes a LEO
Polar (inclination = 90o, circular) Near polar ( inclination ~90o, circular)
Circular inclined
LEqO ( inclination = 0o, circular)
Period : 90 minutes 2 hours
Negligible transmission delay between end-users and satellite
Radius of the footprint varies from 3,000 to 4,000 km
The maximum time during which a satellite above a local horizon for an
observer on the ground is up to 20 minutes Large Doppler shift
Affected by atmospheric drag which cause the orbit to gradually deteriorate
BEE 4243 SATELLITE COMMUNICATION SYSTEMDept. Of Communication Engineering,FacultyOf Electrical And Electronics,
UniversitiTun Hussein OnnMalaysia
ICO ( Intermediate Circular Orbit) or MEO (Medium Earth Orbit)
Altitude : between 10,000 – 20,000 km
Orbit period depends on altitude, e.g. ~10,000 km altitude period ~ 6hours
Stable orbits, allowing more accurate long term orbital predictions
Large area of coverage
Slower Doppler shift
Some radiation effect (high electron dose)
GEO ( Geostationary Earth Orbit Satellites)
Altitude 35, 786
Circular prograde orbit in the equatorial plane
Orbital period 23 hours 56 minutes
Appear fixed above the surface of the earth
Footprint cover almost 1/3 of the earth surface ( from ~75oS to ~75oN)
Roundtrip delay ~250ms
Doppler shift non or low
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BEE 4243 SATELLITE COMMUNICATION SYSTEMDept. Of Communication Engineering,FacultyOf Electrical And Electronics,
UniversitiTun Hussein OnnMalaysia
Tomasi
Electronic Communications Systems, 5eCopyright ©2004 byPearson Education, Inc.
Upper Saddle River, New Jersey 07458
Allrights reserved.
Three satellite used to cover the inhabited world
BEE 4243 SATELLITE COMMUNICATION SYSTEMDept. Of Communication Engineering,FacultyOf Electrical And Electronics,
UniversitiTun Hussein OnnMalaysia
Satellites in geosynchronous earth orbits
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BEE 4243 SATELLITE COMMUNICATION SYSTEMDept. Of Communication Engineering,FacultyOf Electrical And Electronics,
UniversitiTun Hussein OnnMalaysia
HEO ( Highly Elliptical Orbit)
Have a perigee at about 500 km above the surface of the earth and
apogee as high as 50,000 km
The orbits are inclined at 63.4o in order to provide communications
services to location at high northern latitude
Orbit period varies from 8 to 24 hours
Owing to the high eccentricities of the orbit, a satellite will spend about
two-third of the orbital period near apogee and during that time it
appears to be almost stationary for an observer on the earth
Free space loss and propagation delay is comparable to that of GEO
Large Doppler shift (due to large movement of satellite in HEO)
BEE 4243 SATELLITE COMMUNICATION SYSTEMDept. Of Communication Engineering,FacultyOf Electrical And Electronics,
UniversitiTun Hussein OnnMalaysia
Example of HEO
Russian Molniya
Employs 3 satellite in three 12 hours orbits separated by 120o
around the earth
Apogee : 39, 354 km, Perigee : 1000 km
Russian Tundra 2 satellites in two 24 hour orbits separated by 180o around the
earth
Apogee : 53, 622 km, Perigee : 17, 951 km
Loopus system
Achimedes System (ESA)
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BEE 4243 SATELLITE COMMUNICATION SYSTEMDept. Of Communication Engineering,FacultyOf Electrical And Electronics,
UniversitiTun Hussein OnnMalaysia
Highly elliptical orbit
Various type of orbits
BEE 4243 SATELLITE COMMUNICATION SYSTEMDept. Of Communication Engineering,FacultyOf Electrical And Electronics,
UniversitiTun Hussein OnnMalaysia
The appropriate orbit is often suggested by The nature of the service
The business plan, or
The constraints of the communication link
Example : Satellite Mobile Telephony System
Iridium Inclination 86.4o , 6 plane , 11 per plane
LEO constellation of 66 satellites in polar orbit at an altitude of 780 km The orbital period is 100 minutes and a given satellite is in view for only 10
minutes before handover of a call to a following satellite
Has extensive on-board processing and telephone call is routed throughconstellation via inter-satellite links
The choice of LEO was dictated by the desire to : minimize power on both the satellite and the mobile handset minimize satellite antenna size minimize time delay, or latency for a two-way signal
maximize the angle of elevation
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BEE 4243 SATELLITE COMMUNICATION SYSTEMDept. Of Communication Engineering,FacultyOf Electrical And Electronics,
UniversitiTun Hussein OnnMalaysia
GlobalStar A constellation of 48 satellites ( 8 plane , 6 per plane) in orbit inclined
at 52°at an altitude of 1,414km
Concentrates coverage over the temperature regions of the earth from70°S to 70°N
Employed spatial diversity - signal are combined in the receiver tomitigate losses due to blockage and multipath effects
The inclined, non-polar orbit constellation was chosen to ensure that atleast two satellites are visible at all times
Uses non-processing, or "bent-pipe" satellite
Relay communications between the user and a gateway- the party beingcall will be connected with the gateway. Through the PSTN(maximizing the use of existing, low cost communication service or
back through a satellite if the party is another Globalstar user.
BEE 4243 SATELLITE COMMUNICATION SYSTEMDept. Of Communication Engineering,FacultyOf Electrical And Electronics,
UniversitiTun Hussein OnnMalaysia
ICO Consists of 10 operational satellites in MEO at an altitude of 10,390km The orbit is an excellent compromise between LEO and GEO The satellite antenna size and power are relatively modest and the
latency is still small The number of satellite required for global coverage is significantly
less than LEO and the dwell time is considerably longer Has a period of revolution of six hours and the time a satellite is visible
is on the order of two hours ECCO
- circular orbit constellation in the equatorial plane, design forcommunication in tropical region
Ellipse elliptical orbit to maximize coverage over northern hemisphere
AceS Asia Cellular Satellite system GEO orbit Serve Pacific rim Satellite antenna ~12m across