What is VSAT........................................................ ?

VSAT history .…………………………………………………………

VSAT application ……………………………………………………

Orbit type ………………………………………………………………

What are bands of v-sat......................................... ?

Equipments ……………………………………………………………

Concept …………………………………………………………………

SCPC- TDMA ..………………………………………………………

What is VSAT?

VSAT is the term (Very Small Aperture Terminal) refers to a small fixed earth station.

VSATs provide the vital communication link required to set up a satellite based

communication network. VSATs can support any communication requirement be it

voice, data, or video conferencing.

The VSAT comprises of two modules - an outdoor unit and an indoor unit. The

outdoor unit consists of an Antenna and Radio Frequency Transceiver (RFT) and

the antenna size is typically range from 1.8 meter to 3.4 meter in diameter,

although smaller antennas are also in use. The indoor unit functions as a modem

and also interfaces with the end user equipment like standalone PCs, LANs,

Telephones or an EPABX.

The antenna, along with the attached low-noise converter (LNB-which receives

satellite signals) and the transmitter (BUC-which transmits the radio waves signals)

make up the VSAT outdoor unit (ODU), one of the two components of a VSAT earth

station.

VSAT is a two-way satellite ground station or a stabilized maritime V-sat antenna, Data

rates typically range from 56 kbps up to 4 Mbps. VSATs access satellites

in geosynchronous orbit to relay data from small remote earth stations (terminals) to

other terminals (in mesh configurations) or master earth station "hubs" (in star

configurations).

VSATs are most commonly used to transmit narrowband data (point of sale transactions such as credit card, polling or RFID data; or SCADA), or broadband data (for the provision of Satellite Internet access to remote locations, VoIP or video). VSATs are also used for transportable, on-the-move (utilizing phased array antennas) or mobile maritime communications.

VSAT history

The first recorded fictional depiction of a satellite being launched into orbit is a short

story by Edward Everett Hale, The Brick Moon. The story was serialized in The Atlantic

Monthly, starting in 1869, the idea surfaces again in Jules Verne's The Begum's

Millions (1879).

In 1903 Konstantin Tsiolkovsky (1857–1935) published (The Exploration of Cosmic

Space by Means of Reaction Devices), which is the first academic treatise on the use

of rocketry to launch spacecraft.

He calculated the orbital speed required for a minimal orbit around the Earth at 8

km/s, and that a multi-stage rocket fueled by liquid propellants could be used to

achieve this. He proposed the use of liquid hydrogen and liquid oxygen, though other

combinations can be used.

In 1928 Herman Potočnik (1892–1929) published his sole book, (The Problem of Space

Travel — the Rocket Motor), a plan for a breakthrough into space and a permanent

human presence there. He conceived of a space station in detail and calculated its

geostationary orbit. He described the use of orbiting spacecraft for detailed peaceful

and military observation of the ground and described how the special conditions of

space could be useful for scientific experiments. The book described geostationary

satellites (first put forward by Tsiolkovsky) and discussed communication between

them and the ground using radio, but fell short of the idea of using satellites for mass

broadcasting and as telecommunications relays.

In a 1945 Wireless World article the English science fiction writer Arthur C. Clarke

(1917-2008) described in detail the possible use of communications satellites for mass

communications.

Clarke examined the logistics of satellite launch, possible orbits and other aspects of

the creation of a network of world-circling satellites, pointing to the benefits of high-

speed global communications. He also suggested that three geostationary satellites

would provide coverage over the entire planet.

Telstar, launched by NASA on board a Delta rocket from Cape Canaveral on July 10, 1962, was the first

Privately sponsored space launch and the first active satellite with a microwave receiver and transmitter to

Transmit live television and telephone conversations across the Atlantic.

In July 2004, one of the biggest communication satellites, Akin F2, was launched on board an Ariane 5G

Rocket. With a weight of almost 6 tons, Akin F2 carried 94 transponders (38 Ka-band, 32 Ku-band and 24 C-band transponders)

VSAT application

Applications:-

Communication (Trucking call)

Teleconference

Telemedicine

TV Broadcasting

Data communication

Telemetry (TEC, Remote sensing etc)

Weather telecast

Navigation

GPS

Security/Calamity monitoring

Standard Tm

Orbit type

Several typesLEOs - Low Earth Orbit

MEOs - Medium Earth Orbit

HEOs – Highly Elliptical Orbit

GEO - Geostationary Earth Orbit

LEOsLow Earth Orbit

200-3,000 km

High orbit speed

Many satellites

Predominately mobile

Iridium, Global star

(space shuttle orbit)

MEOs

Medium Earth Orbit

6,000 – 12,000km

New generation

About 12 satellites

Voice and mobile

ICO (Odyssey), Orbcomm , Ellipse

HEOs

HEOs – Highly Elliptical OrbitHEOs: Molnya and TundraMolnya TundraPeriod 12 h 24 hApogee 39500 km 46300 km

Perigee 1000 km 25300 kmInclination 63.4° 63.4°

GEOs

Originally proposed by Arthur C. Clarke

Circular orbits above the equator

Angular separation about 2 degrees - allows 180 satellites

Orbital height above the earth about23000 miles/35786.16km

Round trip time to satellite about 0.24 seconds

GEO satellites require more power for communications

The signal to noise ratio for GEOs is worse because of the distances involved

A few GEOs can cover most of the surface of the earth

Note that Polar Regions cannot be “seen” by GEOs

Since they appear stationary, GEOs do not require tracking

GEOs are good for broadcasting to wide areas

Currently 329 GEO are in orbit

What are bands of v-sat?

There are 3 bands for the V-Sat which are C-band, KU-band and the Ka-band.

All Satellite communication systems are subject to international agreements and

regulations. The International Telecommunication Union (ITU) regulates frequency

use and defines "bands"

The C-Band:

C-band was the first band to be used for satellite communication systems.

However, when the band became overloaded (due to the same frequency being

used by microwave links) satellites were built for the next available frequency

band, the Ku-band.

Today C-Band also gets disturbed by wireless radio links in particular uncontrolled

spreading in Africa. Interferences can get reduced by cost intensive microwave

filters level 421 generally recommends each customer who plans to use C-Band.

The C-band frequency range has one significant problem. It is the frequency

region assigned to microwave radio communication systems. There are an

emerging number of these microwave systems located all over the world and

they carry a large volume of commercial communications. Consequently, the VSAT

locations needed to be restricted in order to prevent interference with the

microwave communication systems. As mobile phones get used more and more in

countries all over Africa as well, the use of C-Band in future will possibly certainly

rather decrease than increase. At the current point of time - C Band nevertheless

is widely used. In particular as KU band capacity over some regions is quite

limited.

Commercially it is fact that hardware for C Band is significantly more expensive

while the capacity is cheaper. So customers with large bandwidth requirements

preferably choose this technology.

Downlink: 3.7 – 4.2 GHz

Uplink: 5.9 – 6.4 GHz

Advantages:

- Less disturbance from heavy rain fade

- Cheaper Bandwidth

Disadvantages:

- Needs a larger satellite dish (diameters of minimum 2-3m)

- Powerful expensive RF unit

- More expensive hardware

- Possible Interference from microwave links

Ku-band:

Ku-band is typically used for broadcasting and 2-way Internet connections

The Ku-band frequency range is allocated to be exclusively used by satellite

communication systems, thereby eliminating the problem of interference with

microwave systems. Due to higher power levels at new satellites Ku-band allows

for significantly smaller earth station antennas and RF units to be installed at the

VSAT location.

KU Band on the other hand operates with small antennas and less expensive

equipment, while the capacity price is higher than C Band.

Downlink: 11.7 – 12.2 GHz

Uplink: 14.0 – 14.5 GHz

Advantages:

- No interference from microwave links and other technologies

- Operates with a smaller satellite dish (diameters from 0.9m) -> cheaper and

more easy installation

- Needs less power -> cheaper RF unit

Disadvantages:

- More expensive capacity

- Sensitive to heavy rain fade (significant attenuation of the signal) / possibly can

be managed by appropriate dish size or transmitter power.

The Ka band:

The Ka band is a portion of the K band of the microwave band of the

electromagnetic spectrum.

Ka-band roughly ranges from 18 to 40 GHz. The 20/30 GHz band is used in

communications satellites, downlink 18.3–18.8 GHz and 19.7–20.2 GHz. The term

Ka-band is frequently used to refer to the recommended operating frequencies of

WR-28 rectangular waveguide, which is 26.5 to 40.0 GHz.

Ka band in future will allow a broader application field in the V-SAT Industry. At the

moment only very few capacity possibilities are available in Ka Band.

Those commercial projects available suffer from the global warming and

the resulting climatic change.

You will ask why? Very simple: The increase of rain and strong weather

conditions terrible affect service stabilities in KA band. Due to stronger and longer

bad weather periods outages of services in KA Band have dramatically increased

in the last 3 years.

However it's quite exciting to get more bandwidth out of a smaller required space

segment - KA band related services still will have to proof that they really will play

a major role in futures satellite communication business.

Equipments

- Mobile

-

- THURAYA

- BJAN

- SNG

- Marine system

- Satellite dish

-

The Satellite Dish Consists of:-

Dish

BUC

LNB

How does VSAT works?

HERE’S HOW THE PROCESS WORKS - IN 5 EASY STEPS TO

UNDERSTAND:

End user computer is connected to your network, which in turn is connected to

the Internet by VSAT Systems. You open a web browser, and type in a web

address. End user computer sends a request for a transfer of data both

transmit and receive.

That request is sent from the end user PC, through their home network, to the

indoor satellite modem which modulates the signal and passes it to the VSAT

dish. The VSAT dish converts this signal to an RF signal and sends it to a

satellite located in the geostationary orbit at the speed of light - 186,000 miles

per second.

The satellite in the geo-stationary orbit receives this signal and sends it to one

of the VSAT Systems teleports This illustrates the fact that although the

packets of information travel tremendous distances via the space segment,

the packets hop fewer networks due to the large reduction in the number of

inter domain and intra domain routers giving an opportunity to minimize

latency.

The request then goes to VSAT Systems’ NOC, which retrieves the requested

website from the web server, across the Internet backbone.

The whole cycle is then reversed and the requested data is available to the

user. A 90,000 mile journey, through millions of dollars of infrastructure and

sophisticated equipment, all in less than 700 milliseconds.