15698 Introduction to Stallite

8/4/2019 15698 Introduction to Stallite

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INTRODUCTIONTO

SATELLITECOMMUNICATIONS

Manpreet kaur

Asst. Professor, LPU


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SATELLITES

A satellite is an object which has been placedinto orbit by human. Such objects are sometimescalled artificial satellites to distinguish themfrom natural satellites such as the Moon.

The basic component of a communications satellite isa receiver-transmitter, combination called atransponder.

Satellite orbits about the earth are either circular or

elliptical. Satellites are used for a large number of purposes.

Common types include military and civilian earthobservation satellites, communications satellites,navigation satellites, weather satellites, and researchsatellites.


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HISTORY OF SATELLITE

COMMUNICATION

1957 first satellite SPUTNIK I by USSR (didnot have communication capability)

1958 first satellite by US EXPLORER I (first

voice heard from space)

1960 first passive reflecting communicationsatellite ECHO I and II

1962 and 63 TELSTAR I and II, launched byBell Telephone Laboratories

1963 first geostationary satellite SYNCOM


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Cont

1965 first commercial geostationary satelliteEarly Bird (INTELSAT I): 240 duplextelephone channels and 1 TV channel, 1.5

years lifetime 1976 three MARISAT satellites for maritime

communication

1982 first mobile satellite telephone systemINMARSAT-A

1988 first satellite system for mobile phonesand data communication INMARSAT-C


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APPLICATIONS

weather satellites

radio and TV broadcast satellites

military satellites (replaced by fiber optics)

satellites for navigation and localization (e.g.,GPS)

global telephone connections

backbone for global networks

connections for communication in remote placesor underdeveloped areas

global mobile communication


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BASIC PRINCIPLE


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TRANSPONDER

Some satellites have (hundreds of)transponders for communication purposes

A transponder

1)receives transmissions from earth (uplink);2)changes signal frequency;3)amplifies the signal; and4)transmits the signal to earth (downlink)


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The Legal and Regulatory

Environment of Telecommunication

When the telegraph was first used in the UnitedStates and other nations, the systems werecompletely independent of one another.

All of the systems carried pulses of electricitywhich are encoded to represent the alphabets.

Cost to send the message is different from systemto system.

When these systems begun to be interconnected,the issues of technical compatibility and ofaccounting arose, prompting lawmakers andinternational organizations to set standards andprocedures


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The Legal and RegulatoryProblems

On the technical side, issues such as codingof letters and voltage levels that must beallowed to independent national system to be

connected to one another. On the business side, companies and nations

were forced to decide how to account andcharge for a telegram that oriented in onecountry for delivery in another.


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Telecommunication Issues

Telecommunication regulations deals with three majorkinds of Issues:- Technical issues such as codes, voltages, address, and

shape of connectors; these issues go under standards andprotocols.

Resource issues such as the limited spectrum, orbitalspace, and interference; these issues fall under allocationand coordination and

Money issues such as availability of capital, riskmanagement, insurance and who gets paid how much and

in what manner; these issues are comes under businessstrategy and tariffs.

Dealing with legal and regulatory issues among morethan 200 nations is much more difficult, time-consuming and money consuming than dealing with

technical details. Thus, man telecommunication services that are


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Satellite Telephone Call B/N Two

Countries

Telecommunication task go through many steps involving differentcompanies, technologies and nations


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Cont

The calling telephone is connected via a local loopto a local central office in country A.

The central office is connected by a long-distancecarrier to a international gateway established incountry A.

The call is carried through the satellite calledspace segment.

The call is passed through a long distancecompany in country Z to a central office near thecalled number.

The local loop is connected to the called

telephone.


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Cont.

Each of the above steps may involve adifferent company and thus may be subjectedto a different tariff.

Bill received be the calling party for a call willbe composed of telephone companys chargesfor local services, long-distance charges,uplink and downlink charges, space segmentcharges and termination charges from countryZ passed along the calling party.


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Standards and Protocols

Standards are the agreements that allowconnections to be made, called protocols.

Standards can be simple or complex.

Standards specifies that how many bits makeup a computer word, how many words makeup a frame, which bit represent the identity ofthe sender and receiver for a digital

transmission, the shape of the connectors, thevoltage and currents to be used, how tocompress video signal, and many otherdetails.


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The International

Telecommunication Union

In 1865, International Telegraph Union has beenestablished to coordinate the telegraph system in 20European nations.

It is the world oldest technical organization.

For the telephone systems that was invented only adecade after telegraph system International TelegraphUnion set up a standard committee called theConsultative Committee For International Telegraphyand Telephony (CCITT).

In the year 1932, a separately formed body, theInternational Radiotelegraph Union, merged with theTelegraph Union and the overall body becameInternational Telecommunication Union (ITU).

The radiotelegraph functions became a committee

called Consultative Committee For International RadioCCIR .


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ITU Regions

The ITU considers the world divided into threelarge geographic regions, referred to ITU regionsor WRC (World Radio Conference). Regulationsand standards may be set differently in deferent

regions. The three regions are ITU region 1 consists of all the Africa, Europe, the

Middle East, and the Soviet Union.

ITU region 2 includes the America, Greenland (but notIceland), and the ocean region adjacent to North and

South America. ITU region 3 encompasses everything else, including

most of Asia, the East Indies, India, Australia and NewZealand, Japan, Korea.


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Other Standards and Regulatory

Organization

Each nation has some standard-settingorganizations and telecommunication regulations.

ISO International Standard Organization- covers the

area of telecommunication. Its technical committee 97set standards for data processing and datacommunication.

OSI Open System Interconnection model is its best knownstandard which defines seven layers of data handling

during transmission.

IEEE Institute of Electrical and ElectronicsEngineering- many of its standards have gone on tobecome global standards.

IEC International Electrotechnical Commissions which


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Satellite Services

The satellite delivered telecommunication applicationsfall into 12 service categories with somesubcategories designed by ITU. Of these only five areof major interest of commercial end users: fixed satellite service (FSS)

Broadcast satellite service (BSS)

Mobile satellite service (MSS)

Radio Determination satellite service (RDSS)

Radio Navigation satellite service (RNSS)

One service is primarily important to the operators ofsatellite system Inter-satellite service (ISS)


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Cont

Six designated services are which are primarilyimportant to specialized users such as scientificresearchers, space exploration agencies andsatellite operators:

Amateur Satellite Services

Earth-exploration Satellite Services

Meteorological Satellite Services

Space operation Services Space research Services

Standard Frequency and Time Signal SatelliteServices


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Fixed Satellite Service (FSS)

This is the oldest and most used of all the satelliteservices.

It is intended for communication through a satellitebetween earth stations and are fixed (not usually

moving when are in use), or which are with in aspecific area.

E.g. point-to-point communication.

The FSS frequency allocations also specify the

direction of the signal travel, assigning one frequencyband for uplink, and another complimentary band tothe downlinks

FSS services are intended for television, telephonyand data signals.

FSS fre uenc allocation are in the C Ku Ka band.


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Broadcast satellite service (BSS)

BSS is designed to provide audio and videoservices directly to end users: BSS-TV, BSS-HDTV, BSS-sound.

Theses services specify orbital slot,frequencies and channels.

Also specifies interference ratio, minimum

power sent to user. Also called Direct Broadcast Services or Direct

to home Services (DTH).


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Mobile satellite service (MSS)

Satellite delivers the services to the users onthe go and are divided into three majorcategories, depending upon the location ofuser. MMSS- Maritime Mobile satellite service (MSS)

AMSS- Aeronautical Mobile satellite service (MSS)

LMSS- Land Mobile satellite service (MSS)

All these services are primarily to carry telephonecalls, while sometimes carrying low speed digitalservices such as: facsimile.

Highly compressed data can be transmitted throughthese services.


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Radio Determination satellite service(RDSS)

RDSS is designed to provide the ability to theusers to determine and if desired report therelocation to some one else.

In some cases mobile unit uses radio navigation

services such as LORAN, to find its position. The unit relays the information via RDSS satellite

service back to the office.

The links from the mobile user to and from the

satellite operate in L-band for uplink and S-bandfor the downlink.

While the link from the satellite to the controlfacility uses C-band frequencies.


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Radio Navigation satellite service(RNSS)

These services are designed specifically forthe navigation, in contrast to radiolocation andposition reporting.

These services are little used at present.


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Inter-satellite service (ISS)

Radio communication between satellites.

This service is not for end users but one wayfor satellite operators to route traffic.

It is authorized in the Ka- band.

Until the late 1990s, ISS also called satellite tosatellite links (SSL)

15698 Introduction to Stallite

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