VSAT IMPLEMENTATION

8/3/2019 VSAT IMPLEMENTATION

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THE IMPLEMTATION OF A VERY SMALLL APERTURE

TERMINAL AND A LOCAL AREA NETWORK/OMINI RADIO

CONNECTION FOR SCHOOL OF ENGINEERING

BY

AARON OBUKOHWO PATRICK

DSPT/HND/COE/0910/620

BEING A PROJECT WORK SUBMITTED TO THE

DEPARTMENT OF COMPUTER ENGINEERING,

SCHOOL OF ENGINEERING, DELTA STATE

POLYTECHNIC,

OTEFE-OGHARA

IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE

AWARD OF HIGHER NATIONAL DIPLOMA IN COMPUTER

ENGINEERING

SEPTEMBER, 2011.

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CERTIFICATION

We hereby certify that this project work titled: THE

IMPLEMENTATION OF A VERY SMALL APERTURE

TERMINAL AND A LOCAL AREA NETWORK was carried out

by AARON OBUKOHWO PATRICK in the department of

Computer Engineering, Otefe-Oghara in partial fulfillment of the

requirements for the award of Higher National Diploma.

MR. ENOMATE .A. JOSEPH Date

Project Supervisor

ENGR. C. ONIYEMOFE Date

Head of Department

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DEDICATION

This project work is dedicated to God Almighty the doer of all things.

Also, I want to use this medium to dedicate this project to my mother

Mrs. AARON OMATIE for investing her resources, time, money,

energy and believing in my ability.

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ACKNOWLEDGEMENT

I thank God Almighty for making this project work a huge success. If

not for God who gave me the grace, strength and the gift of life, this

project work would not have being a reality. To Him be all the glory,

honour, power and praise.

I acknowledge my Project SupervisorMR. ENOMATE .A. JOSEPH

who took the pains to read through this project manuscripts and the

various correction made by him and also the fathering advice He gave

to me. Also I want to acknowledge the Head of Department ENGR.

C. ONIYEMOFE, MR. VICTOR OWEH. I wish to express my

profound gratitude to my mother Mrs. AARON OMATIE and my

Uncle, MR. ERIJITOMAH JACKSON for showing me the right

path to follow in life and my Lady EFUE JOSEPHINE for being

there for me during my hard time, for her courage, love and

intellectual support, she is a blessing to me. I will not fail to

acknowledge my brothers, sisters, and friends MRS. CAROLINE

IDAHOISE, IWESIKE COLLINS, BEST ATUMAH, MR.

OKPORHO DICK, EFEKUNU RAPHAEL, MOWETA JOHN,

EMUSI JOSEPH, ONORIODE HENRY, for their intellectual,

advice and financial support. And also to all my well-wishers who

have contributed to the success of this project.

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CONTENTS

Chapter 1. Introduction.....6

1.1. History....6

1.2 VSAT Network Definition......6

Chapter 2. VSAT Network Configuration.......11

2.1 Meshed Topology...........11

2.2 Star Topology.....13

Chapter 3. Constituent Part of VSAT Configuration...14

3.1 Antenna........14

3.2 Block Up Converter (BUC)....16

3.3 Low-Noise Block Converter (LNB).......17

3.4 Orthomode Transducer (OMT).......20

3.5 Interfacility Link Cable (IFL).22

3.6 Indoor Unit (IDU).......22

Chapter 4. Features of VSAT Networks..........23

4.1 DVB Technology........23

4.2 iDirect Technology ....23

4.3 VOIP over VSAT...24

Chapter 5. Automatic VSAT Network Management using Uplogix..........25

5.1 Local Control of Remote Network Equipment.......25

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5.2 Key Technical Benefit...26

Chapter 6. VSAT Network Configuration..27

6.1 Civilian Service......27

6.2 Military Service.........27

6.3 Private VSAT Network.29

Conclusion...30

References...31

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CHAPTER. 1

INTRODUCTION

A Very Small Aperture Terminal (VSAT), is a two-way satellite ground station or a

stabilized maritime Vsat antenna with a dish antenna that is smaller than 3 meters. The

majority of VSAT antennas range from 75 cm to 1.2 m. Data rates typically range from

56 Kbit/s up to 4 Mbit/s. 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 (utilising phased array antennas) or mobile maritime

communications.

1.1 HISTORY

The first commercial VSATs were C band (6 GHz) receive-only systems by Equatorial

Communications using spread spectrum technology. More than 30,000 60 cm antenna

systems were sold in the early 1980s. Equatorial later developed a C band (4/6 GHz) 2

way system using 1 m x 0.5 m antennas and sold about 10,000 units in 1984-85. In 1985,

Schlumberger Oilfield Research co-developed the world's first Ku band (1214 GHz)

VSATs with Hughes Aerospace to provide portable network connectivity for oil field

drilling and exploration units. Ku Band VSATs make up the vast majorty of sites in use

today for data or telephony applications. The largest VSAT network (more than 12,000sites) was deployed by Spacenet and MCI for the US Postal Service.

1.2 VSAT NETWORK DEFINITION

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VSAT, now a well established acronym for Very Small Aperture Terminal, was initially

a trademark for a small earth station marketed in the 1980s by Telcom General in the

USA. Its success as a generic name probably comes from the appealing association of its

first letter V, which establishes a victorious context, or may be perceived as a friendly

sign of participation, and SAT which definitely establishes some reference to satellite

communications. The use of the word terminal which appears in the clarification of the

acronym will be replaced by earth station, or station for short, which is the more

common designation in the field of satellite communications for the equipment assembly

allowing reception from or transmission to a satellite. The word terminal will be used to

designate the end user equipment (telephone set, facsimile machine, television set,

computer, etc.) which generates or accepts the traffic that is conveyed within VSAT

networks. This complies with regulatory texts, such as those of the International

Telecommunications Union (ITU), where for instance equipment generating data traffic,

such as computers, are named Data Terminal Equipment (DTE).

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CHAPTER. 2

VSAT NETWORK CONFIGURATION

VSATs are connected by radio frequency (RF) links via a satellite, with a so-calleduplinkfrom the station to the satellite and a so-called downlinkfrom the satellite to thestation. The overall link from station to station, sometimes called hop, consists of an

uplink and a downlink. A radio frequency link is a modulated carrier conveying

information. Basically the satellite receives the uplinked carriers from the transmitting

earth stations within the field of view of its receiving antenna, amplifies those carriers,

translates their frequency to a lower band in order to avoid possible output/input

interference, and transmits the amplified carriers to the stations located within the field of

view of its transmitting antenna.

Present VSAT networks use geostationary satellites, which are satellites orbiting in theequatorial plane of the earth at an altitude above the earth surface of 35,786 km. that the

orbit period at this altitude is equal to that of the rotation of the earth. As the satellite

moves in its circular orbit in the same direction as the earth rotates, the satellite appears

from any station on the ground as a fixed relay in the sky.

2.1 MESHED TOPOLOGY

Mesh networking is a type of networking wherein each node in the network may act as an

independent router, regardless of whether it is connected to another network or not. It

allows for continuous connections and reconfiguration around broken or blocked paths by

hopping from node to node until the destination is reached. A mesh network whose

nodes are all connected to each other is a fully connected network. Mesh networks differ

from other networks in that the component parts can all connect to each other via

multiple hops, and they generally are not mobile.

As all VSATs are visible from the satellite, carriers can be relayed by the satellite from

any VSAT to any other VSAT in the network, as illustrated by Figure 1.3.

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Figure 2.1 Meshed VSAT network

Regarding meshed VSAT networks, as shown in Figure 1.3, one must take into account

the following limitations:

typically 200 dB carrier power attenuation on the uplink and the downlink as a result of

the distance to and from a geostationary satellite.

limited satellite transponder radio frequency power, typically a few tens of watts.

small size of the VSAT, which limits its transmitted power and its receiving sensitivity.

Therefore direct links from VSAT to VSAT may not be acceptable. The solution then is

to install in the network a station larger than a VSAT, called the hub. The hub station has

a larger antenna size than that of a VSAT, say 4 m to 11 m, resulting in a higher gain than

that of a typical VSAT antenna, and is equipped with a more powerful transmitter. As a

result of its improved capability, the hub station is able to receive adequately all carriers

transmitted by the VSATs, and to convey the desired information to all VSATs by means

of its own transmitted carriers.

The links from the hub to the VSAT are named outbound links. Those from the VSAT to

the hub are named inbound links.

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2.2 STAR TOPOLOGY

Star networks are one of the most common computer network topologies. In its simplest

form, a star network consists of one central switch, hub or computer, which acts as a

conduit to transmit messages. Thus, the hub and leaf nodes, and the transmission lines

between them, form a graph with the topology of a star. If the central node is passive, the

originating node must be able to tolerate the reception of an echo of its own transmission,

delayed by the two-way transmission time (i.e. to and from the central node) plus any

delay generated in the central node. An active star network has an active central node that

usually has the means to prevent echo-related problems.

The star topology reduces the chance of network failure by connecting all of the systems

to a central node. When applied to a bus-based network, this central hub rebroadcasts all

transmissions received from any peripheral node to all peripheral nodes on the network,

sometimes including the originating node. All peripheral nodes may thus communicate

with all others by transmitting to, and receiving from, the central node only. The failure

of a transmission line linking any peripheral node to the central node will result in the

isolation of that peripheral node from all others, but the rest of the systems will be

unaffected.

Figure 2.2 Two-way star-shaped VSAT network

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CHAPTER. 3

CONSTITUENT PART OF VSAT CONFIGURATION

The different parts used in a VSAT canfiguration are

* Antenna

* Block Up Converter (BUC)

* Low-Noise Block Converter (LNB)

* Orthomode Transducer (OMT)

* Interfacility Link Cable (IFL)

* Indoor Unit (IDU)

3.1 ANTENNA

An antenna (or aerial) is a transducer that transmits or receives electromagnetic waves. In

other words, antennas convert electromagnetic radiation into electric current, or vice

versa. Antennas generally deal in the transmission and reception of radio waves, and are a

necessary part of all radio equipment. Antennas are used in systems such as radio and

television broadcasting, point-to-point radio communication, wireless LAN, cell phones,

radar, and spacecraft communication. Antennas are most commonly employed in air or

outer space, but can also be operated under water or even through soil and rock at certain

frequencies for short distances.

Physically, an antenna is an arrangement of one or more conductors, usually called

elements in this context. In transmission, an alternating current is created in the elements

by applying a voltage at the antenna terminals, causing the elements to radiate an

electromagnetic field. In reception, the inverse occurs: an electromagnetic field from

another source induces an alternating current in the elements and a corresponding voltage

at the antenna's terminals.

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The antenna used in VSAT are parabolic antennas or dish antenna. A parabolic antenna is

an antenna that uses a parabolic reflector, a surface with the shape of a parabola, to direct

the radio waves. The most common form is shaped like a dish and is popularly called a

dish antenna or parabolic dish. The main advantage of a parabolic antenna is that it is

highly directive; it is able to direct the radio waves in a narrow beam (like a searchlight),

or receive radio waves from one particular direction only. Parabolic antennas have some

of the highest gains, that is they can produce the narrowest beamwidth, of any antenna

type. They are used as high-gain antennas for point-to-point radio, television and data

communications, and also for radiolocation (radar), on the UHF and microwave (SHF)

parts of the electromagnetic spectrum. The relatively short wavelength of electromagnetic

radiation at these frequencies allows reasonably sized reflectors to exhibit the desired

highly directional response for both receiving and transmitting.

Figure 3.1 Parabolic antenna

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Figure 3.2 Main types of parabolic antennas

3.2 BLOCK UP CONVERTER

A block upconverter (BUC) is used in the transmission (uplink) of satellite signals. It

converts a band (or "block") of frequencies from a lower frequency to a higher frequency.

Modern BUCs convert from the L band to Ku band, C band and Ka band. Older BUCs

convert from a 70 MHz intermediate frequency (IF) to Ku band or C band.

Most BUCs use phase-locked loop local oscillators and require an external 10 MHz

frequency reference to maintain the correct transmit frequency.

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BUCs used in remote locations are often 2 or 4 W in the Ku band and 5 W in the C band.

The 10 MHz reference frequency is usually sent on the same feedline as the main carrier.

Many smaller BUCs also get their direct current (DC) over the feedline, using an internal

DC block.

BUCs are generally used in conjunction with low-noise block converters (LNB). The

BUC, being an up-converting device, makes up the "transmit" side of the system, while

the LNB is the down-converting device and makes up the "receive" side. An example of a

system utilizing both a BUC and an LNB is a VSAT system, used for bidirectional

Internet access via satellite.

The block upconverter is assembled with the LNB in association with an OMT,

orthogonal mode transducer to the feed-horn that faces the reflector parabolic dish.

Figure 3.3 Block up converter, ku band

3.3 LOW NOISE BLOCK CONVERTER

A low-noise block converter (LNB, for low-noise block, sometimes LNC, for low-noise

converter, or, rarely, LND for low-noise downconverter) is the (receiving, or downlink)

antenna of what is commonly called the parabolic satellite dish commonly used for

satellite TV reception. It is functionally equivalent to the dipole antenna used for most

other TV reception purposes, although it is actually waveguide based. Whereas the dipole

antenna is unable to adapt itself to various polarization planes without being rotated, the

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LNB can be switched electronically between horizontal and vertical polarization

reception. The LNB is usually fixed on or in the satellite dish, for the reasons outlined

below. The corresponding component in the uplink transmit link is called a Block

upconverter (BUC).

The purpose of the LNB is to use the superheterodyne principle to take a wide block (or

band) of relatively high frequencies, amplify and convert them to similar signals carried

at a much lower frequency (called intermediate frequency or IF). These lower frequencies

travel through cables with much less attenuation of the signal, so there is much more

signal left on the satellite receiver end of the cable. It is also much easier and cheaper to

design electronic circuits to operate at these lower frequencies, rather than the very high

frequencies of satellite transmission.

The low-noise part means that special electronic engineering techniques are used, that the

amplification and mixing takes place before cable attenuation and that the block is free of

additional electronics like a power supply or a digital receiver. This all leads to a signal

which has less noise (unwanted signals) on the output than would be possible with less

stringent engineering. Generally speaking, the higher the frequencies with which an

electronic component has to operate, the more critical it is that noise be controlled. If

low-noise engineering techniques were not used, the sound and picture of satellite TV

would be of very low quality, if it could even be received at all without a much larger

dish reflector. The low-noise quality of an LNB is expressed as the noise figure or noise

temperature.For the reception of wideband satellite television carriers, typically 27 MHz

wide, the accuracy of the frequency of the LNB local oscillator need only be in the order

of 500 kHz, so low cost dielectric oscillators (DRO) may be used. For the reception of

narrow bandwidth carriers or ones using advanced modulation techniques, such as 16-

QAM, highly stable and low phase noise LNB local oscillators are required. These use an

internal crystal oscillator or an external 10 MHz reference from the indoor unit and a

phase-locked loop (PLL) oscillator.

LNBF : Direct broadcast satellite (DBS) dishes use an LNBF (LNB with feedhorn),

which integrates the antenna feedhorn with the low noise block converter (LNB). Small

diplexers are often used to distribute the resulting IF signal (usually 950 to 1450 MHz)

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piggybacked in the same coaxial cable jacket which carries lower-frequency terrestrial

television from an outdoor antenna. Another diplexer then separates the signals to the

receiver of the TV set, and the integrated receiver/decoder (IRD) of the DBS set-top box.

Newer Ka band systems use additional IF blocks from the LNBF, one of which will cause

interference to UHF and cable TV frequencies above 250 MHz, precluding the use of

diplexers. In the case of DBS, the voltage supplied by the set-top box to the LNB

determines the polarization setting. With multi-TV systems, a dual LNB allows both to

be selected at once by a switch, which acts as a distribution amplifier. The amplifier then

passes the proper signal to each box according to what voltage each has selected. The

newest systems may select polarization and which LNBF to use by sending DiSEqC

codes instead. The oldest satellite systems actually powered a rotating antenna on the

feedhorn, at a time when there was typically only one LNB or LNA.

Universal LNB : A universal LNB can receive both polarisations (Vertical and

Horizontal) and the full range of frequencies in the satellite Ku band. Some models can

receive both polarisations simultaneously (known as a quattro LNB and used with a

multiswitch) through four different connectors Low/Hor, Low/Ver, High/Hor, High/Ver,

and others are switchable (using 13 volt for Vertical and 17 or 18 volt for Horizontal) or

fully adjustable in their polarisation (this is relatively rare as this requires a separate

polarisor, and it's also not part of the Universal LNB specification).

Figure 3.4 LNBF disassembled

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Figure 3.5 Ku band LNB with both sides uncovered

Figure 3.6 Ku band linear polarised LNBF

3.4 ORTHOGONAL TRANSDUCER

An orthomode transducer is a microwave duct component of the class of microwave

circulators. It is commonly referred to as an OMT, and commonly referred as a

polarisation duplexer. Such device may be part of a VSAT antenna feed Orthomodetransducers serve either to combine or to separate two microwave signal paths. One of the

paths forms the uplink, which is transmitted over the same waveguide as the received

signal path, or downlink path. For VSAT modems the transmission and reception paths

are at 90 to each other, or in other words, the signals are orthogonally polarised with

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respect to each other. This orthogonal shift between the two signal paths provides

approximately an isolation of 40dB in the Ku band and Ka band radio frequency bands.

Hence this device serves in an essential role as the junction element of the outdoor, unit

(ODU) of a VSAT modem. It protects the receiver front-end element (the low-noise

block converter, LNB) from burn-out by the power of the output signal generated by the

block up converter (BUC). The BUC is also connected to the feed horn through a wave

guide port of the OMT junction device.

Orthomode transducers are used in dual-polarised Very small aperture terminals VSAT,

in sparsely populated areas, radar antennas, radiometers, and communications links. They

are usually connected to the antenna's down converter or LNB and to the High Power

Amplifier (HPA) attached to a transmitting antenna.

Wherever there are two polarisations of radio signals (Horizontal and Vertical), the

transmitted and received radio signal to and fro the antenna are said to be orthogonal.

This means that the modulation planes of the two radio signal waves are at 90 degrees

angles to each other. The OMT device is used to separate two equal frequency signals, of

high and low signal power. Protective separation is essential as the transmitter unit would

seriously damage the very sensitive low (V) micro-voltage, front-end receiver amplifier

unit at the antenna.

The transmission signal of the up-link, of relatively high power (1, 2,or 5 watts for

common VSAT equipment) originating from BUC,(block up converter) and the very low

power received signal power (-volts) coming from the antenna (aerial) to the LNB

receiver unit, in this case are at an angle of 90 relative to each other, are both coupled

together at the feed-horn focal-point of the Parabolic antenna. The device that unites both

up-link and down-link paths, which are at 90 to each other, is known as an Orthogonal

Mode Transducer OMT.

In the VSAT Ku band of operation case, a typical OMT Orthomode Transducer provides

a 40dB isolation between each of the connected radio ports to the feed horn that faces the

parabolic dish reflector (40dB means that only 0.01% of the transmitter's output power is

cross-fed into the receiver's wave guide port). The port facing the parabolic reflector of

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the antenna is a circular polarizing port so that horizontal and vertical polarity coupling of

inbound and outbound radio signal is easily achieved.

The 40dB isolation provides essential protection to the very sensitive receiver amplifier

against burn out from the relatively high-power signal of the transmitter unit. Further

isolation may be obtained by means of selective radio frequency filtering to achieve an

isolation of 100dB (100dB means that only a 1010 fraction of the transmitter's output

power is cross-fed into the wave guide port of the receiver).

Figure 3.7 Orthomode transducer

3.5 INTERFACILITY LINK CABLE

An Inter-Facility Link (IFL) is the set of coaxial cables that connect the indoor equipment

to the outdoor equipment of a satellite earth station. In a VSAT terminal, the IFL is

usually one or two co-axial cables carrying IF signals, control signals, and DC power.

3.6 INDOOR UNIT

The Indoor Unit (IDU) is the component of the VSAT terminal that is located indoors. It

is usually the satellite router. The IDU is connected to the Outdoor Unit (ODU) via Inter-

Facility Link (IFL) cables.

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CHAPTER. 4

FEATURES OF VSAT NETWORKS

4.1 DVB TECHNOLOGY

Digital Video Broadcast (DVB) is a satellite-based standard that was primarily designed

to use in broadcast video applications. The standard has been widely adopted due to its

simplicity, easily available chipsets, and cost. DVB based technology is widely deployed

and understood by most network operators. DVB was primarily designed for one waybroadcast of video and MPEG traffic. Recently a new standard DVB-RCS (Return

Channel via Satellite) was completed to allow for a standard based return channel for

two-way traffic. The intent of the open standard is to accelerate economies of scale,

thereby generating lower-cost solutions and opening the market in a shorter timeframe

than could be possible with competing proprietary solutions.

Advantages of DVB based system:

- High bandwidth outbound or broadcast

- Designed and built for Video Broadcast

- Lower Cost of Remote Terminals

Disadvantages of DVB based system:

- Generally Power-Limited satellite requirement.

- Very inefficient when use of transponder capacity and very high Hub equipment cost

- Not designed for TCP/IP traffic. IP is encapsulated within MPEG

4.2 IDIRECT TECHNOLOGY

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iDirect has pioneered TCP/IP over satellite technology in the industry to ensure the most

efficient use of satellite bandwidth. As demand for IP over satellite continues to grow

more Network Operators would want to start offering IP services over satellite. iDirect

technology is designed to allow Network Operators implement these networks at a much

lower cost, at the same time provide a business class service with all the TCP/IP

enhancements over satellite.

Advantages of iDirect Technology

- Primarily Bandwidth limited, thus much lower service costs

- Extremely responsive TDMA channels

- Queue depth checked 5 times/sec

- All remotes have a minimum CIR

- Multiple-inroutes Network Capability

- Frequency Hopping Capability Dynamically Assigned based on demand

- Very scalable hub equipment, with multiple network support within a chassis

4.3 VOIP OVER VSAT

iDirect Technologies broadband IP VSAT network system effectively transports VoIP

traffic over satellite. The obstacles associated with this challenge have been addressed

using iDirects highly differentiated real time traffic management (RTTM) feature set.

The RTTM feature set is an inherent part of iDirects operating system software (iDS)

and has been specifically designed to support applications such as voice that are not

tolerant of delay, requiring specific network conditions to perform properly.

Traditionally, transporting voice over satellite has been supported through

implementation of Single Channel Per Carrier (SCPC) technology ostensibly creating a

continuously connected environment similar to a dedicated private line circuit. Using

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SCPC to support enterprise VoIP needs is bandwidth inefficient and therefore a costly

solution.

CHAPTER. 5

AUTOMATIC VSAT NETWORK MANAGEMENT USING

UPLOGIX

5.1 LOCAL CONTROL OF REMOTE NETWORK EQUIPMENT

Uplogix offers a new approach to reducing the cost and complexity of supporting satellite

network environments. Uplogix Automated Remote Management (ARM) appliances

enable operators to remotely monitor and control both satellite and terrestrial-based

network equipment. The appliances co-locate and connect serially with network and

satellite communications equipment to provide non-stop local management and control.

Uplogix appliances automate numerous network support, maintenance, configuration and

recovery proceduresreducing the time, cost and error associated with manual support.

Administrators can manage all Uplogix appliances via the Uplogix Control Center- a

centralized, web-based portal that presents a full inventory of both Uplogix appliances

and the infrastructure equipment connected to them. Working via the Control Center

console, operations staff can schedule and coordinate all network maintenance and

management operations to be performed by Uplogix appliances. In addition, the Control

Center serves as the central repository and reporting interface for all data collection and

audit logs provided by the appliances.

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Figure 5.1 Uplogix Remote Management Platform for Satellite Communications

5.2 KEY TECHNICAL BENEFITS

- Immediately diagnoses and repairs service failures through intelligent automation.

- Minimizes on-site tech support and engineer visits to remote locations.

- Provides a single point of management control for both terrestrial and satellite-based

network equipment.

-Delivers continuous monitoring data and management control even during outages LEO

Antenna LEO.

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CHAPTER. 6

VSAT NETWORK APPLICATION

VSAT networks have both civilian and military applications. These will now be

presented.

6.1 CIVILIAN SERVICE

It can be noted that most of the services supported by two-way VSAT networks deal with

interactive data traffic, where the user terminals are most often personal computers. The

most notable exceptions are voice communications and satellite news gathering. Voicecommunications on a VSAT network means telephony with possibly longer delays than

those incurred on terrestrial lines, as a result of the long satellite path. Telephony services

imply full connectivity, and delays are typically 0.25 s or 0.50 s depending on the

selected network configuration, as mentioned above. Satellite news gathering (SNG) can

be viewed as a temporary network using transportable VSATs, sometimes called fly-

away stations, which are transported by car or aircraft and set up at a location where

news reporters can transmit video signals to a hublocated near the companys studio. Of

course the service could be considered as inbound only, if it were not for the need to

check the uplink from the remote site, and to be in touch by telephone with the staff at the

studio. As fly-away VSATs are constantly transported, assembled and disassembled, they

must be robust, lightweight and easy to install. Today they weigh typically 100 kg and

can be installed in less than 20 minutes.

6.2 MILITARY APPLICATION

VSAT networks have been adopted by many military forces in the world. Indeed the

inherent flexibility in the deployment of VSATs makes them a valuable means of

installing temporary communications links between small units in the battlefield and

headquarters located near the hub. Moreover, the topology of a star-shaped network fits

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well into the natural information flow between field units and command base. Frequency

bands are at X-band, with uplinks in the 7.98.4 GHz band and downlinks in the 7.25

7.75 GHz band. The military use VSAT must be a small, low weight, low power station

that is easy to operate under battlefield conditions. As an example, the manpack station

developed by the UK Defence Research Agency (DRA) for its Milpico VSAT military

network is equipped with a 45 cm antenna, weighs less than 17 kg and can be set up

within 90 seconds. It supports data and vocoded voice at 2.4 kbs1. In order to do so, the

hub stations need to be equipped with antennas as large as 14 m. Another key

requirement is low probability of detection by hostile interceptors. Spread spectrum

techniques are largely used.

Figure 6.1 Fly-away VSAT station

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6.3 PRIVATE VSAT NETWORKS

* Private VSAT offers organisational level connectivity solutions and bandwidth.

* Pricing have been simplified and more complex network can be engineered.

* Higher bandwidth at lower cost available on demand.

* High level business applications can be supported.

International and internert connectivity

* Web browsing and E-mail.

* Web browsing and server hosting.

* VPN connectivity available-including IPSEC.

* Multicast services.

Figure 6.2 Private VSAT Network

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CONCLUSION

VSAT networking has been developed into a sophisticated technique that can provide

remote access to the small antennas through satellite. Most of research on VSAT has

been conducted for environment and engineering applications. However VSAT networks

has very important application in communication field . A VSAT network offers

communications between remote terminals. As a result of the power limitation resulting

from the imposed small size and low cost of the remote station. VSAT has a number of

advantages like asymmetrty of data transfer, flexibility, low bit error, distance insensitive

cost and private corporate. VSAT networking an focus on a discussion of how this

service integration could take place and the possible performance improvements that

could be achieved. As has been discussed previously, end to end management is

becoming a critical requirement for most customers, and the ability to both intelligently

manage the VSAT component, while cleanly integrating with management systems for

other components and providing full end-to-end class based monitoring is the ultimate

challenge, but can also provide great opportunities for time saving, automation, customer

satisfaction and generating additional revenues. In modern future the VSAT network can

be used for remote access to very small antennas and provide better signal reception.

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REFERENCES

1. Gerard Maral , VSAT Networks, John Wiley & Sons Ltd.

2. Timothy Pratt, Satellite Communication , Wiley India Pvt. Ltd.

3. Raychaudhuri, D., Joseph, K., Ku-Band Satellite Networks using VSATs-Part1:Multi-

access Protocols, Int. Jrnl. Sat. Comms.

4.www.uplogix.com.

5.http://en.wikipedia.org/wiki/VSAT

6.http://www.crystalcommunications.net/satellite/vsat/about_vsat.htm
http://www.uplogix.com/http://en.wikipedia.org/wiki/VSAThttp://www.crystalcommunications.net/satellite/vsat/about_vsat.htmhttp://www.uplogix.com/http://en.wikipedia.org/wiki/VSAThttp://www.crystalcommunications.net/satellite/vsat/about_vsat.htm

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VSAT IMPLEMENTATION