15-01-2013, 09:51 AM
Overview of Satellite Communication System
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Satellite Communication
In Satellite communication , signal transferring between the sender and receiver is done with the help of satellite.
Communication Satellite
A Communication Satellite can be looked upon as a large microwave repeater
It contains several transponders which listens to some portion of spectrum, amplifies the incoming signal and broadcasts it in another frequency to avoid interference with incoming signals.
Frequency Bands
Different kinds of satellites use different frequency bands.
L–Band: 1 to 2 GHz, used by MSS
S-Band: 2 to 4 GHz, used by MSS, NASA, deep space research
C-Band: 4 to 8 GHz, used by FSS
X-Band: 8 to 12.5 GHz, used by FSS and in terrestrial imaging, ex: military and meteorological satellites
Ku-Band: 12.5 to 18 GHz: used by FSS and BSS (DBS)
K-Band: 18 to 26.5 GHz: used by FSS and BSS
Ka-Band: 26.5 to 40 GHz: used by FSS
Communication link
Downlink
The link from a satellite down to one or more ground stations or receivers
Uplink
The link from a ground station up to a satellite.
Some companies sell uplink and downlink services to
television stations, corporations, and to other telecommunication carriers.
A company can specialize in providing uplinks, downlinks, or both.
How do Satellites Work ?
Two Stations on Earth want to communicate through radio broadcast but are too far away to use conventional means.
The two stations can use a satellite as a relay station for their communication
One Earth Station sends a transmission to the satellite. This is called a Uplink.
The satellite Transponder converts the signal and sends it down to the second earth station. This is called a Downlink.
How Satellites are used ?
Service Types
Fixed Service Satellites (FSS)
Example: Point to Point Communication
Broadcast Service Satellites (BSS)
Example: Satellite Television/Radio
Also called Direct Broadcast Service (DBS).
Mobile Service Satellites (MSS)
Example: Satellite Phones
Advantages of Satellite Communication
Can reach over large geographical area
Flexible (if transparent transponders)
Easy to install new circuits
Circuit costs independent of distance
Broadcast possibilities
Temporary applications (restoration)
Mobile applications (especially "fill-in")
Terrestrial network "by-pass"
Provision of service to remote or underdeveloped areas
User has control over own network
1-for-N multipoint standby possibilities
When to use Satellites
When the unique features of satellite communications make it attractive
When the costs are lower than terrestrial routing
When it is the only solution
Examples:
Communications to ships and aircraft (especially safety communications)
TV services - contribution links, direct to cable head, direct to home
Data services - private networks
Overload traffic
Delaying terrestrial investments
1 for N diversity
Special events
[attachment=46893]
Satellite Communication
In Satellite communication , signal transferring between the sender and receiver is done with the help of satellite.
Communication Satellite
A Communication Satellite can be looked upon as a large microwave repeater
It contains several transponders which listens to some portion of spectrum, amplifies the incoming signal and broadcasts it in another frequency to avoid interference with incoming signals.
Frequency Bands
Different kinds of satellites use different frequency bands.
L–Band: 1 to 2 GHz, used by MSS
S-Band: 2 to 4 GHz, used by MSS, NASA, deep space research
C-Band: 4 to 8 GHz, used by FSS
X-Band: 8 to 12.5 GHz, used by FSS and in terrestrial imaging, ex: military and meteorological satellites
Ku-Band: 12.5 to 18 GHz: used by FSS and BSS (DBS)
K-Band: 18 to 26.5 GHz: used by FSS and BSS
Ka-Band: 26.5 to 40 GHz: used by FSS
Communication link
Downlink
The link from a satellite down to one or more ground stations or receivers
Uplink
The link from a ground station up to a satellite.
Some companies sell uplink and downlink services to
television stations, corporations, and to other telecommunication carriers.
A company can specialize in providing uplinks, downlinks, or both.
How do Satellites Work ?
Two Stations on Earth want to communicate through radio broadcast but are too far away to use conventional means.
The two stations can use a satellite as a relay station for their communication
One Earth Station sends a transmission to the satellite. This is called a Uplink.
The satellite Transponder converts the signal and sends it down to the second earth station. This is called a Downlink.
How Satellites are used ?
Service Types
Fixed Service Satellites (FSS)
Example: Point to Point Communication
Broadcast Service Satellites (BSS)
Example: Satellite Television/Radio
Also called Direct Broadcast Service (DBS).
Mobile Service Satellites (MSS)
Example: Satellite Phones
Advantages of Satellite Communication
Can reach over large geographical area
Flexible (if transparent transponders)
Easy to install new circuits
Circuit costs independent of distance
Broadcast possibilities
Temporary applications (restoration)
Mobile applications (especially "fill-in")
Terrestrial network "by-pass"
Provision of service to remote or underdeveloped areas
User has control over own network
1-for-N multipoint standby possibilities
When to use Satellites
When the unique features of satellite communications make it attractive
When the costs are lower than terrestrial routing
When it is the only solution
Examples:
Communications to ships and aircraft (especially safety communications)
TV services - contribution links, direct to cable head, direct to home
Data services - private networks
Overload traffic
Delaying terrestrial investments
1 for N diversity
Special events