Frequency bands are groupings of radio frequencies that are used by mobile networks to communicate with mobile phones. The frequency bands that a phone supports determine to a large degree where and on which networks it can be used.a continuous range of frequencies, especially in the radio spectrum, between two limiting frequenciesIn telecommunication, a band - sometimes called a frequency band - is a specific range of frequencies in the radio frequency (RF) spectrum, which is divided among ranges from very low frequencies (vlf) to extremely high frequencies (ehf). Each band has a defined upper and lower frequency limit.
The principle of communication by passive satellite is based on the properties of distribution of electromagnetic waves from different surface areas. Thus an electromagnetic wave incident on a passive satellite is scattered back towards the earth and a receiving station can receive the scattered wave. The passive satellites used in the early years of satellite communications were both artificial as well as natural.
It transmitted a pre-recorded message of Christmas Greetings from US President Eisenhower. However, the satellite did not function as a true repeater.. It accepted and stored up to 360,000 Teletype words as it passed overhead and rebroadcast them to ground station farther along its orbit. It operated with 3 watts of on-board output power and it was also the first satellite to use solar cells for generating electrical power
One way link from transmitter Tx to receiver Rx on earth’s surfaceIn two-way Satellite Communications link the exchange of information between two distant users takes place through a pair of transmit and receive earth stations and a satellite.
Space operations service, (Tracking, Telemetry, Command)Earth Exploration Satellite Service (Remote Sensing)Standard frequency and time signal satellite service
A new class of two-way fixed satellite network service known as Very Small Aperture Terminal (VSAT) service has became very popular among business and closed users group communities.
UNIVERSAL: Satellite communications are available virtually everywhere. A small constellation of satellites can cover the Earth's entire surface. And even the reach of a single satellite is far more extensive than what any terrestrial network can achieve.VERSATILE: Satellites can support all of today's communications needs - transactional and multimedia applications, video, voice, cellular networks, entertainment and breaking news.
RELIABLE: Satellite is a proven medium for supporting a company's communications needs. Whereas terrestrial IP networks are often a mix of different networks and topologies, with different level of congestion and latency. Satellite networks are extremely predictable allowing constant and uniform quality of service to hundreds of locations, regardless of geography.SEAMLESS: Satellite's inherent strength as a broadcast medium makes it ideal for the simultaneous distribution of bandwidth-intensive information to hundreds or thousands of locations.FAST: Unlike most terrestrial alternatives, satellite networks can be rolled out quickly and inexpensively to hundreds or thousands of locations, connecting cities or remote locations across a large landmass, where copper or fiber is cost prohibitive. Since satellite networks can be set up quickly, companies can be fast-to-market with new services.
EXPANDABLE: Satellite networks are easily scalable, allowing users to expand their communications networks and their available bandwidth easily. In coordination with local vendors, expanding a network on the ground requires the ordering of new terminal components and the commissioning of increased bandwidth at each site.FLEXIBLE: Satellites can be easily integrated to complement, augment or extend any communications network, helping overcome geographical barriers, terrestrial network limitations and other constraining infrastructure issues.Wide coverageSuitable for both Digital and Analog TransmissionHigh QualityFlexibilityQuick Provision of ServicesMobile and Emergency Communication
Satellites are having some disadvantages till now. If they are improved to an extent that the delay will be minimized then I will be a golden achievement of science in our life.
What is satellite?
What is satellite communication?
Elements for satellite communication.
Orbits for satellite communication.
Evolution of satellite communication.
Services of satellite communication.
Frequency Bands and Beams.
Advantages of satellite communication.
Applications of satellite communication.
The future of satellite communication.
An artificial body placed in orbit around the
For example, Earth is a satellite because it
orbits the sun.
A communications satellite is a radio relay
station in orbit above the earth.
It receives, amplifies, and redirects analog and
digital signals carried on a specific radio
Satellite communications play a vital role in
the global telecommunications system.
Two major elements of Satellite Communications
Space Segment includes:
Means for launching satellite
Electrical Power System
Attitude and orbit control
Satellite Control Centre function:
Tracking of the satellite
Eclipse management of satellite
Commanding the Satellite for station keeping.
Determining Orbital parameters from Tracking
and Ranging data
Switching ON/OFF of different subsystems as per
the operational requirements
The ground segment consists of
Rear Ward Communication links
User terminals and interfaces
Network control centre
The path a Satellite follows around a planet is
defined as an orbit.
Satellite Orbits are classified in two broad
Non-Geostationary Orbit (NGSO)
Geo Stationary Orbit (GSO)
satellites in Non-geostationary low earth orbits due to the
technical limitations of the launch vehicles in placing
satellites in higher orbits.
Classification of NGSOs as per the orbital plane
Polar Orbit: In polar orbit the satellite moves from pole to pole
and the inclination is equal to 90 degrees.
Equatorial Orbit: In equatorial orbit the orbital plane lies in the
equatorial plane of the earth and the inclination is zero or very
Inclined Orbit: All orbits other than polar orbit and equatorial
orbit are called inclined orbit.
Advantages of NGSO
Less booster power required
Less delay in transmission path
Reduced problem of echo in voice communications
Suitability for providing service at higher latitude
Lower cost to build and launch satellites at NGSO
Disadvantages of NGSO
Complex problem of transferring signal from one
satellite to another.
Less expected life of satellites at NGSO
frequent replacement of satellites
compared to satellite in GSO.
Problem of increasing space trash in the outer space.
Requirement of a large number of orbiting satellites for
As each low earth orbit satellite covers a small portion of
the earth’s surface for a short time.
There is only one geostationary orbit
possible around the earth
Lying on the earth’s equatorial plane.
The satellite orbiting at the same speed as the
rotational speed of the earth on its axis.
Simple ground station tracking.
Nearly constant range
Very small frequency shift
Transmission delay of the order of 250 msec.
Large free space loss
No polar coverage
Satellite orbits in terms
of the orbital height:
According to distance from
Geosynchronous Earth Orbit
Medium Earth Orbit (MEO)
Low Earth Orbit (LEO)
During early 1950s, both passive and active satellites
were considered for the purpose of communications over
a large distance.
Passive satellites though successfully used in the early
years of satellite communications, with the advancement
in technology active satellites have completely replaced
the passive satellites.
A satellite that only reflects signals from one Earth
station to another, or from several Earth stations to
It reflect the incident electromagnetic radiation without
any modification or amplification.
It can't generate power, they simply reflect the incident
The first artificial passive satellite Echo-I of NASA was
launched in August 1960.
Earth Stations required high power to transmit signals.
Large Earth Stations with tracking facilities were expensive.
A global system would have required a large number of passive
satellites accessed randomly by different users.
Control of satellites not possible from ground.
The large attenuation of the signal while traveling the large
distance between the transmitter and the receiver via the
satellite was one of the most serious problems.
In active satellites, it amplify or modify and retransmit the
signal from the earth.
Satellites which can transmit power are called active satellite.
Have several advantages over the passive satellites.
Require lower power earth station.
Not open to random use.
Directly controlled by operators from ground.
World’s first active satellite was SCORE (Satellite
Communication by Orbiting Relay Equipment)
Launched by US Air force in 1958.
At orbital height of 110 to 900 miles.
The first fully active satellite was Courier
Launched into an orbit of 600 - 700 mile,
By Department of Defense in 1960.
Requirement of larger and powerful rockets to launch
heavier satellites in orbit.
Requirement of on-board power supply.
Interruption of service due to failure of electronics
One-way satellite services are:
Satellite Service: Radio, TV, Data
Safety services : Search & Rescue, Disaster Warning
Radio Determination Satellite Service(Position location)
Standard frequency and time signal satellite service
Space Research Service.
Space operations service.
Earth Exploration Satellite Service.
Two-way satellite services are:
Fixed Satellite Service: Telephone, fax, high bit rate
Mobile Satellite Service: Land mobile, Marine time
mobile, Aero-mobile, personal communications.
Satellite News Gathering.
Inter Satellite Service.
available virtually everywhere.
Versatile: Satellites can support all of today's
communications needs .
supporting a company's communications needs.
broadcast medium makes it perfect.
FAST: Since satellite networks can be set up
quickly, companies can be fast-to-market with new
Quick Provision of Services
Mobile and Emergency Communication
Suitable for both Digital and Analog Transmission
Future communication satellites will have
more onboard processing capabilities,
more power, and
that will enable satellites to handle more bandwidth.
The demand for more bandwidth will ensure the longterm viability of the commercial satellite industry well
into the 21st century.
reusable launch vehicles are in development.
Further improvements in satellites’ propulsion and power systems
will increase their service life to 20–30 years from the current 10–15
By going through the above slides we came to
know that satellite is mostly responsible for:
Reception of television signals
Which is very important in our daily life.