Satellite communications began in 1962 with the launch of Telstar 1, which demonstrated transmitting radio signals between Earth and a satellite. Since then, satellite technology has advanced, allowing international phone calls and television distribution globally. Satellites function as wireless repeaters in orbit, receiving and retransmitting signals. They provide communication links over large areas and distances independently. Various protocols like TDMA are used to manage communications over the delay-prone satellite links.

3. SATELLITE DATA
NETWORK
COMMUNICATIONS

4. OVERVIEW
• History of Satellite Network
• A Communication satellite
functions as an overhead
wireless repeater station
• It provides a microwave
communication link between
two geographically remote
sites

5. History of Satellite Network
In 1962, the world's first active communications
satellite, Telstar 1, was launched. This satellite was
built by Telesat's predecessors at AT&T and Bell
Laboratories. During its seven months in operation,
Telstar 1 dazzled the world with live images of sports,
entertainment and news. It was a simple single-
transponder low-earth-orbit (LEO) satellite, but its
technology of receiving radio signals from the ground,
and then amplifying and retransmitting them over a
large portion of the earth's surface, set the standard
for all communications satellites that followed.

6. History of Satellite Network
During the 1960s and 1970s, advances in satellite
performance came quickly and a global industry began
to develop. Satellites were mainly used at first for
international and long-haul telephone traffic and
distribution of select television programming, both
internationally and domestically. In 1973 the Canadian
Broadcasting Corporation began distributing its video
programming to Canadian customers using Telesat’s
Anik A satellite. Then in 1975 HBO began distributing
its video programming to US customers by satellite.
The commercial and technical success of these ventures
led to a greater use and acceptance of satellite
broadcasting. By the 1990s, satellite communications
would be the primary means of distributing TV
programs around the world.

7. TRANSPONDERS
• Each Satellite is equipped
with various “transponders”
consisting of a transceiver and
an antenna tuned to the part
of the allocated spectrum
• Most satellites simply
broadcast whatever they
receive and they are called as
“bent pipes”

8. DATA TRANSMISSION
• Use of satellites in packet
data transmission has been
on the rise
• They are typically used in
WAN networks which acts as
the backbone links to
geographically dispersed
LAN’s and MAN’s

9. SATELLITE COMMUNICATION
CHANNELS
• Wide Area coverage of the
earth's surface.
• Long transmission delays.
• Broadcast transmission.
• Large Channel Bandwidth.
• Transmission costs
independent of Distance.

10. MICROWAVE POWER
• The received microwave
power involved in satellite
links is typically very small
(of the order of a few
100picowatts).
• Specially designed earth
stations that keep C/N
(carrier to noise ratio) to a
minimum are used to
transmit/receive satellite
communications.

11. SATELLITE LINKS
• Satellite links can operate in
different frequency bands
and use separate carrier
frequencies for the up-link
and down-link or "spot
beam"
• The area of the earth's
surface covered by a
satellite's transmission
beam is referred to as the
"footprint" of the satellite
transponders.

12. EARTH SATELLITE
COMMUNICATION

13. SATELLITE CONSTELLATIONS
• Satellites can be positioned in
orbits with different heights
and shapes
• Depending on the shapes
they are of 3 types:
 LEO: Low Earth Orbit
 MEO: Medium Earth
Orbit
 GEO: Geostationary Earth
Orbit

14. SATELLITE CONSTELLATIONS
• Satellites are also classified in
terms of their payload.
• Satellites that weigh in the
range of 800-1000 kg fall in
the "Small" class
• The heavier class is named as
"Big" satellites. GEO
satellites are typically "Big"
satellites
• LEO satellites can fall in
either class

15. DIFFERENT SATELLITE
CONSTELLATIONS

16. MAC PROTOCOLS FOR SATELLITE
LINKS
• Satellite channels require special considerations at the
DLC (Data Link Control) layer of the OSI model they
are referred to as “Long Fat Pipes”
• Implementing CSMA/CD (Carrier Sense Multiple
Access/Collision Detection) protocol is not possible
• Delay occurs in the channel in which they cause
potential or multiple collisions in the satellite link

17. MAC SCHEMES
• Most satellite MAC schemes usually assign dedicated channels in time and/ or
frequency for each user
• ALOHA
 Pure Aloha allows every competing stations to transmit anytime
Its uses S-ALOHA (Slotted ALOHA) to increase its efficiency
• FDMA (Frequency Division Multiple Access)
The available satellite channel bandwidth is broken into
frequency bands for different earth stations
ES controls the microwave power in the band for not spilling
into other channels

18. MAC SCHEMES
• TDMA (Time Division Multiple Access)
Channels are time multiplexed in a sequential fashion.
Time synchronization is required between the Earth
Station
• CDMA (Code Division Multiple Access)
Uses a hybrid of time/frequency multiplexing
Form of spread spectrum modulation
No Time synchronization

19. : 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