FET(FACULTY OF ENGINEERING AND TECHNOLOGY )

GOMAL UNIVERSITY D I KHAN

SEMESTER 8TH (2012-2016)

DATE 08/12/2015

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By Engr Mateeullahshahid

OVERVIEW

VSAT

Introduction

Advantages

Applications

Network Architecture

Multiple Access Techniques

Distance Learning: an application

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M- Shahid

Introduction To VSAT

A Very Small Aperture Terminal (VSAT) is a

device known as a small private earth station

- that is used to transmit & receive data signal

through a satellite.

VSAT stands for Very Small Aperture Terminal

and refers to receive/transmit terminals

installed at dispersed sites connecting to a

central hub via satellite using small diameter

antenna dishes (0.6 to 3.8 meter). 3

INTRODUCTION (CONTD.)

• VSAT is used for both broadcast & interactive

applications of effective data, voice and

video transfer.

• It requires no staff or additional technology

to operate it.

• It simply plugs into existing terminal equipment

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VSAT INSTALLATION

Information is produced at the hub having a

very large 15 to 36 foot antenna. The hub

controls and monitors the network through

a network management system (NMS).

Information is sent up to the communication

satellite which receives, amplifies and

beams it back to earth for reception by the

remote VSATs.

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VSAT SITE INSTALLATION

• Ground Mount

This involves a tube lowered into a hole

which is then filled in with concrete. The pole

should be accurately vertical so that when you

swing the dish around to find the satellite the

elevation angle stays the same all the time.

The indoor data processing unit (DPU)

The indoor data processing unit (DPU)

should be located in a dry, cool and clean place.

The antenna needs to be mounted where it can 'see' the satellite and where it is safe from unauthorized access.

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SAFETYInstalling a dish is normally dangerous. Take care

not to fall down and not to drop tools on others

below. Be careful with ladders - always tie off

the top to some secure point. A small electric

shock may make you fall off a ladder so be extra

careful.

TIPS : ---- If you are a beginner, practice

the complete installation at ground level before

moving everything to the roof.

Accuracy

The dish pointing needs to be near

perfect as the transmit beam is narrower then

the receive beam.

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WHY VSAT?The dish is small, easily transportable andinstallation lead-time is much shorter ifcompared to terrestrial links.

VSAT network allows rapid, low-cost networkre-configuration and expansion to meet newor unexpected business requirements.

Cost effective transmission and networkoperations are made possible by use of theEx-C band satellite frequency and frequencytimes division multiple access (FTDMA),Frequency division multiple access (FDMA) orTime division multiple access (TDMA)transmission techniques.

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PARTS OF VSAT

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A VSAT SHOULD CONSISTS OF TWO PARTS

VSAT

Transceiver

Device such as

Personal Computer

(PC)

Short for “Small Aperture Terminal, an earthbound station used in satellite communications of data, voice and video signals, excluding broadcast television.

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CONT….

• A VSAT consists of two parts, a transceiver that is

placed outdoors in direct line of sight to the satellite

and a device that is placed indoors to interface the

transceiver with the end user's communications

device, such as a PC .

• The transceiver receives or sends a signal to a

satellite transponder in the sky.

• The satellite sends and receives signals from a

ground station computer that acts as a hub for the

system. 11

WORKING OF HUB STATION

• Each end user is interconnected with the hub

station via the satellite, forming a star topology.

• The hub controls the entire operation of the network

.

• For one end user to communicate with another,

each transmission has to first go to the hub station

that then retransmits it via the satellite to the other

end user's VSAT.

• VSAT can handle up to 56 Kbps.

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ADVANTAGES OF VSAT

Offer flexibility as adding a site is quick and

easy.

Service charges depend on the bandwidth,

which is allocated to network in line with

your requirements.

VSAT terminals prices are falling.

No last mile issues.

There are many advantages that VSAT offers, some of themare as follows:

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CONTD….

• Easy access to remote locations—Where

it would be difficult to facilitate a

•wire line arrangement, such as on an oil rig,

a VSAT can easily be set up.

As it is mobile, so be used for short term or

emergency communications.

Excellent for broadcast transmission. 14

DISADVANTAGES OF VSATS

• Transmission quality subject to weather

conditions—Stormy weather can

• cause disruptions. Most large users of VSAT networks have

some leased

• lines available to use as backup when disruptions occur.

• ■ Potentially high startup costs for small

installations—A small company

• may face a high startup cost if it does not have many nodes.

(If VSAT is the

• only available recourse—if there is no way to communicate

without it—

• then the installation cost is a moot point.)

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APPLICATIONS OF VSAT

• VSAT is an ideal satellite network that

provides

communications support for a wide range of

applications:

Distance Education

Retail Networks

• • Point-of-Sale(PoS) transaction, banking,

inventory, reservation system.

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CONTD….

Corporate Networks

• • Internet/Intranet access, corporate voice,

file transfer, video-conferencing.

High-speed Internet access

• • Browsing, E-mail, E-commerce .

Financial Management

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DISTANCE LEARNING USING VSATDistance education is an innovation that

allows educational content to be transmitted

from area to area and provides students in

rural areas also an opportunity to get

education.

Due to the need for high speed and high

quality educational messages,

communication satellites are often used

more for efficient transmission.

The main purpose of distance education is to

provide people greater access to education

without the limitations of distance and

boundaries.

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PROCESS OF DISTANCE LEARNING

At the teacher end the audio and video input is fed to

the Hub . A dummy student is also placed there to

see whether the information is sent correctly and in

order. Data from the hub is passed through the router

to the central hub, wherefrom it is transmitted to the

satellite.

At the user end, the user is given a particular IP

address and a login ID. Using this can access the

remote earth station which receives the data from the

central Hub via satellite.

Distance education requires a network, which has

broadband capability, so that the network is able to

carry large amount of video and audio data. Satellite

distribution can facilitate two-way transmission of

dense data traffic at speeds equal to or faster than

most wire-based systems.

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NETWORK ARCHITECTURE

• VSAT network can be of following two types:

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1.Hub type (VSAT Star Net with Star network topology)

2.Hub less type (VSAT Dial Net and VSAT Direct with

point-to-point or meshed network topology)

Most VSAT networks use a star configuration, which

composes a single Hub communicating with

remote VSATs. A VSAT Hub is a huge earth station

that is responsible for controlling & monitoring all the

activities of the geographical spread of VSATs. In

some cases all the remote VSATs communicate to one

central site, this central site is connected to the hub,

as hub is the switching element. This service supports

transmission bandwidth ranging from 9.6 kbps to 2

Mbps duplex.

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VSAT HUB NETWORK

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M- Shahid

• [1] Ha, Tri T., Digital Satellite Communications, 2nd ed., TMH,

2009.

• [2]http://en.wikipedia.org/wiki/Very-small-aperture_terminal

[accessed on 25/09/2013].

• [3]http://www.cse.iitb.ac.in/synerg/lib/exe/fetch.php?id=public%3ast

udents%3azahirk%3adm%3ainterfacing_to_pc&cache=cache&medi

a=public:students:zahirk:dm:vsat_doc.pdf [accessed on 29/10/2013]

• [4] http://novastars.com/vsat [accessed on 28/10/2013].

• [5] Rao, K.N. Raja, Fundamentals of satellite communication, PHI

pvt. Ltd., 2004.

• [6] Tseng, Yuh M., Cryptanalysis and Improvement of Key

Distribution System for VSAT Satellite Communications,

INFORMATICA, 2002, Vol. 13, No. 3, P 369–376.

REFERENCES

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M- Shahid

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