Project Mtnl

8/3/2019 Project Mtnl

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ABOUT M.T.N.L

MTNL (Mahanagar Telephone Nigam Ltd.) was constituted in the yearApril,1986. Previously it was a government organization under the department of

Telecommunication.

The basic of MTNL is to provide best and fault free telephone services to the

subscribers so that they are satisfied with what they get.MTNL is fast emerging as

a global giant in the telecom sector in its endeavor to provide world class telecom

services, MTNL is equipping itself with the ‘state-of-art’ machines and acquiring

the latest gadgets to achieve the target of office automation.

MTNL is pioneering the introduction of information technology in the telecom-sector through human resource development, capacity building, computerization

of consumer services like telephone directory, integrated computer networks,

computer based scanning and signature recognition of subscribers, internet

and customer service management etc. For an organization like MTNL,

the customer support services like billing, Directory Enquiry, IVRS, FRS,

commercial etc. are very important. It plays an important role in the

implementation of these support services. Directory enquiry service is an essential

customer care service being provided by telecommunication service provider, It

helps the customers to find out the whereabouts of their associates. It comes to

their rescue in times of emergencies. MTNL New Delhi is regularly

updating telephone directory on CDROM. For national directory services also,

MTNL was the first to integrate and start the service. Presently directory enquiry

services system is being accused by nearly 250 cities of India.

MTNL was set up on 1st April, 1986 by the Government of India to upgrade the

quality of telecom services, expand the telecom network, introduce new services

and to raise revenue for telecom development needs of India’s key metros Delhi,

the political capital and Mumbai, the business capital of India. In the past 17

years, the company has taken rapid strides to emerge as India’s leading and one of

Asia’s largest telecom operating companies. Besides having a strong financial

base, MTNL has achieved a market share of approximately 13% of the Indian

telecommunication network with a customer base of over 4.74 million lines.



The company has also been in the forefront of technology induction by converting

100% of its telephone exchange network into the state-of-the-art digital mode.

The Govt. of India currently holds 56.25% stake in the company.In the year 2002-03, the company has not only consolidated the gains but also

focused on new areas of enterprise viz. Joint Ventures for projects outside India,

widened the cellular and CDMA-based WLL customer base, set up internet and

allied services on all India basis.

Services provided by the M.T.N.L

Basic services

Internet service

ISDN

Intelligent Network

INET

Dolphin Mobile

Garuda

Leased Circuits



HISTORY OF M.T.N.L

1986 Apr 1, 1986 -Mahanagar Telephone Nigam Limited (MTNL) MTNL

was set up.

1999 Feb 1999 - MTNL-Delhi became an Internet Service Provider (ISP)

2002 Oct 1, 2002 - New revenue sharing arrangements between the

Company and BSNL and MTNL are being negotiated

2004 Dec 2004 - The equipment was inducted in MTNL network after

thorough testing , imported equipment, which implies equipment supplied

by Motorola was used

2005 Jun 2005 - In June 2005, MTNL deployed Huawei's MPLS

backbone network solution. Multi Protocol Label Switching) backbone

network thus providing the Indian users with a variety of quality carrier-class services including Internet, VoIP and IPTV

2006 MTNL has received the national long distance license from the

government, a development that can start a fresh about of cuts in STD

rates, starting with Delhi and Mumbai, two of the most lucrative telecom

markets in the country.

2007 Jul 23, 2007 - MTNL's MPLS service was officially launched in

New Delhi on July 23, 2007, with dignitaries like Mr. RSP Sinha, CMD -

MTNL, Mr. Kuldeep Singh, Director - Technical, MTNL, Ms. Anita Soni,

Director - Finance, MTNL

2008 Dec 11, 2008 - MTNL is the first Indian mobile operator to launch

3G services in India and the services were formally inaugurated by

Hon'ble Prime Minister Mr. Manmohan Singh

2009 -MTNL to launch 3G Services in Mumbai

MAKING A TELEPHONE CALL

A telephone call starts when the caller lifts the handsets of the base. Once the dial

tone is heard, the caller uses a rotary or a push button dial mounted either on the

handset or on the base to enter a sequence of digits, the telephone number of

called party. The switching equipment from the exchange removes the dial tone

from the line after the first digit is received and after receiving the last digit,

determines the called party is in the same exchange or a different ones. If the



called is in the same exchange, burst of ringing current is applied to the called

party’s line. Each telephone contains a ringer that responds to specific electric

frequency. When the called party answers the telephone by picking up thehandset, steady start to flow in the called party’s line and is detected by the

exchange. The exchange than stops applying ringing and sets up the connection

between the caller and the called party. If the called party is in different exchange

from the caller, the caller exchange set up the connection over the telephone

network to the called party’s exchange. The called party then handles the process

of ringing, detecting an answer, and notifying the calling and billing machinery

when the call is completed. When conversation is over, one or both parties hang

up by replacing their handset on the base, stopping the flow of current.

ABOUT THE EXCHANGEAll telephone subscribers are served by automatic exchanges, which perform the

functions the human operator. The number being dialed is stored and then passed

to the exchange’s central computer, which in turns operates the switching to

complete the call or routes it a higher level switch for further processing. Today’s

automatic exchanges uses a pair of computers, one running the program that

provides services and the second monitoring the operation of the first, ready to

take over in a few seconds in the event.

COMPUTER UNIT AT EXCHANGE

As the name specified it is the main part of the exchange that deals with the all

services provided by the exchange to the customers with the help of computer. It

also provides the updated data to all other part of the exchange. The customers are using the services of the exchange by using the internet also

gets connected to the main server present this room via an internet room. It mainly consists of the servers that are providing the different services. The main

servers of this room are:- IVRS is used for the change number services provided by the exchange. CERS are provided by the exchange to avoid the problems that the users are

facing the repairing of telephone. In this system when the user enters it’s



complained it gets directly entered to the server and user is allotted with an id

number. LOCAL DIRECTORY ENQUIRY is another services provided by the exchange,by using this; subscribers calls the particular number and gets the directory

enquiry. The server present in the main computer room provides this service. INTERNET DIRECTORY ENQUIRY is the latest service by the exchange. In

this type of service makes it enquiry using the internet, which gets connected to

the main server at the internet room in the exchange and further to the main server

in the computer room.

Fig. 1924 PBX switchboard



Overview

Guided transmission media – wire (twisted pair, cable, fiber)

Unguided – wireless (radio wave, microwave, satellite)

Characteristics and quality determined by medium and signal

For guided, the medium is more important

For unguided, the bandwidth produced by the antenna is more important

Key concerns are data rate and distance



DESIGN FACTOR

Bandwidth

– Higher bandwidth gives higher data rate

Transmission impairments

– Attenuation

Interference

Number of receivers

– In guided media

– More receivers (multi-point) introduce more attenuation

–



Guided Transmission Media

Twisted Pair

Coaxial cable

Optical fiber



Twisted Pair

Twisted Pair –

Applications

Most common medium

Telephone network

Between house and local exchange (subscriber loop)

Within buildings

To private branch exchange (PBX)

For local area networks (LAN)

10Mbps or 100Mbps

Twisted Pair - Pros and Cons

It is much Cheap

Easy to work with

Low data rate

Short range cables



Explanation

In balanced pair operation, the two wires carry equal and opposite signals and the

destination detects the difference between the two. This is known as differential

mode transmission. Noise sources introduce signals into the wires by coupling of electric or magnetic fields and tend to couple to both wires equally. The noise

thus produces a common-mode signal which is cancelled at the receiver when the

difference signal is taken. This method starts to fail when the noise source is closeto the signal wires; the closer wire will couple with the noise more strongly and

the common-mode rejection of the receiver will fail to eliminate it. This problem

is especially apparent in telecommunication cables where pairs in the same cable

lie next to each other for many miles. One pair can induce crosstalk in another andit is additive along the length of the cable. Twisting the pairs counters this effect

as on each half twist the wire nearest to the noise-source is exchanged. Providing

the interfering source remains uniform, or nearly so, over the distance of a singletwist, the induced noise will remain common-mode. Differential signaling also

reduces electromagnetic radiation from the cable, along with the

associated attenuation allowing for greater distance between exchanges.

The twist rate (also called pitch of the twist, usually defined in twists per meter)

makes up part of the specification for a given type of cable. Where nearby pairshave equal twist rates, the same conductors of the different pairs may repeatedly

lie next to each other, partially undoing the benefits of differential mode. For this

reason it is commonly specified that, at least for cables containing small numbersof pairs, the twist rates must differ.[1]

In contrast to FTP (foiled twisted pair) and STP (shielded twisted pair)cabling, UTP (unshielded twisted pair) cable is not surrounded by any shielding.

It is the primary wire type for telephone usage and is very common for computernetworking, especially as patch cables or temporary network connections due to

the high flexibility of the cables.

Twisted Pair - Transmission Characteristics

Analog

– Amplifiers every 5km to 6km

Digital

http://en.wikipedia.org/wiki/Twisted_pair#cite_note-dmray-0






– Use either analog or digital signals

– repeater every 2km or 3km

Limited distance

Limited bandwidth (1MHz)

Limited data rate (100MHz)

Susceptible to interference and noise

Twisted pair’s susceptibility to electromagnetic interference greatlydepends on the pair twisting schemes (usually patented by the

manufacturers) staying intact during the installation. As a result, twisted

pair cables usually have stringent requirements for maximum pulling

tension as well as minimum bend radius. This relative fragility of twistedpair cables makes the installation practices an important part of ensuring

the cable’s performance.

In video applications that send information across multiple parallel signal

wires, twisted pair cabling can introduce signaling delays known

as skew which results in subtle color defects and ghosting due to the

image components not aligning correctly when recombined in the displaydevice. The skew occurs because twisted pairs within the same cable often

use a different number of twists per meter so as to prevent common-mode

crosstalk between pairs with identical numbers of twists. The skew can becompensated by varying the length of pairs in the termination box, so as to

introduce delay lines that take up the slack between shorter and longer

pairs, though the precise lengths required are difficult to calculate and varydepending on the overall cable length.



Unshielded twisted pair (UTP)

Fig. Unshielded twisted pair

UTP cables are found in many Ethernet networks and telephone systems. For

indoor telephone applications, UTP is often grouped into sets of 25 pairsaccording to a standard 25-pair color code originally developed by AT&T. A

typical subset of these colors (white/blue, blue/white, white/orange, orange/white)

shows up in most UTP cables.

For urban outdoor telephone cables containing hundreds or thousands of pairs, the

cable is divided into smaller but identical bundles. Each bundle consists of twistedpairs that have different twist rates. The bundles are in turn twisted together to

make up the cable. Pairs having the same twist rate within the cable can still

experience some degree of crosstalk. Wire pairs are selected carefully to minimizecrosstalk within a large cable.

Fig. Unshielded twisted pair cable with different twist rates

UTP cable is also the most common cable used in computer networking.

Modern Ethernet, the most common data networking standard, utilizes UTP

http://en.wikipedia.org/wiki/File:UTP_cable.jpg

http://en.wikipedia.org/wiki/File:UTP-cable.svg

http://en.wikipedia.org/wiki/File:UTP_cable.jpg

http://en.wikipedia.org/wiki/File:UTP-cable.svg



cables. Twisted pair cabling is often used in data networks for short and medium

length connections because of its relatively lower costs compared to optical

fiber and coaxial cable.

UTP is also finding increasing use in video applications, primarily in securitycameras. Many middle to high-end cameras include a UTP output

with setscrew terminals. This is made possible by the fact that UTP

cable bandwidth has improved to match the baseband of television signals. Whilethe video recorder most likely still has unbalanced BNC connectors for standard

coaxial cable, a balun is used to convert from 100-ohm balanced UTP to 75-ohm

unbalanced.



Cable shielding

Fig. ScTP, also known as FTP

Fig. STP cable format

Fig. S/STP, also known as S/FTP.



Fig. S/UTP cable format

Fig. S/STP cable format

Twisted pair cables are often shielded in an attempt to prevent electromagnetic

interference. Because the shielding is made of metal, it may also serve as a

ground. However, usually a shielded or a screened twisted pair cable has a specialgrounding wire added called a drain wire. This shielding can be applied to

individual pairs, or to the collection of pairs. When shielding is applied to the

collection of pairs, this is referred to as screening. The shielding must begrounded for the shielding to work, and is improved by grounding the drain wire

along with the shield.

Shielded twisted pair (STP or STP-A)

150 ohm STP shielded twisted pair cable defined by the IBM Cabling System

specifications and used with token ring or FDDI networks. This type of shieldingprotects cable from external EMI from entering or exiting the cable and also

protects neighboring pairs from crosstalk.

Screened twisted pair (ScTP or F/TP)

http://en.wikipedia.org/wiki/File:S-STP-cable.svg

http://en.wikipedia.org/wiki/File:S-UTP-cable.svg

http://en.wikipedia.org/wiki/File:S-STP-cable.svg

http://en.wikipedia.org/wiki/File:S-UTP-cable.svg



ScTP cabling offers an overall sheath shield across all of the pairs within

the 100 Ohm twisted pair cable. F/TP uses foil shielding instead of a

braided screen. This type of shielding protects EMI from entering or

exiting the cable.

Screened shielded twisted pair (S/STP or S/FTP)

S/STP (Screened Shielded Twisted Pair) or S/FTP (Screened Foiled

Twisted Pair) cabling offer shielding between the pair sets and an overall

sheath shield within the 100 Ohm twisted pair cable. This type of

shielding protects EMI from entering or exiting the cable and also protects

neighboring pairs from crosstalk.

S/STP cable is both individually shielded (like STP cabling) and also has an outermetal shielding covering the entire group of shielded copper pairs (like S/UTP).This type of cabling offers the best protection from interference from external

sources, and also eliminates alien crosstalk .

Note that different vendors and authors use different terminology (i.e.

STP has been used to denote both STP-A, S/STP, and S/UTP). Seebelow for the ISO/IEC attempt to internationally standardise the

various designations.

Comparison of some old and new abbreviations, according toISO/IEC 11801:

Old name New name cable screening pair shielding

UTP U/UTP None None

STP U/FTP None Foil

FTP F/UTP Foil None



S-STP S/FTP Braiding Foil

S-FTP SF/UTP foil, braiding None

The code before the slash designates the shielding for the cable itself, while the

code after the slash determines the shielding for the individual pairs:

TP = twisted pair

U = unshielded

F = foil shielding

S = braided shielding

Most common cable categories

Categor

y Type

Frequency

Bandwidt

h Applications Notes

Cat1 0.4 MHz Telephone and modem lines

Not described inEIA/TIA

recommmendations. Unsuitable for

modern systems.

Cat2 ? MHzOlder terminal systems,e.g.IBM 3270

Not described inEIA/TIA

recommmendations

. Unsuitable for

modern systems.

Cat3 UTP 16MHz10BASE-T and 100BASE-

Described in

EIA/TIA-568.

http://en.wikipedia.org/wiki/Category_1_cable











T4 Ethernet Unsuitable for

speeds above 16

Mbit/s. Now

mainly fortelephone cables

Cat4 UTP 20MHz 16 Mbit/s Token RingNot commonlyused

Cat5 UTP 100MHz100BASE-TX & 1000BASE-

T Ethernet

Common in most

current LANs

Cat5e UTP 100MHz100BASE-TX & 1000BASE-

T Ethernet

Enhanced Cat5.

Same construction

as Cat5, but withbetter testing

standards.

Cat6 UTP 250MHz 1000BASE-T Ethernet

Most commonlyinstalled cable in

Finland accordingto the 2002standard. SFS-EN

50173-1

Cat6e

250MHz(500MHz

according

to some)

Not a standard; a cable

maker's own label.

Cat6a

500MHz 10GBASE-T Ethernet

ISO/IEC

11801:2002

Amendment 2.


















Cat7

S/FTp 600MHz

Telephone, CCTV,1000BASE

-TX in the samecable. 10GBASE-T Ethernet.

Four pairs, U/FTP

(shielded pairs).Standard under

development.

Cat7a

1000MHz

Telephone, CATV,1000BASE

-TX in the same

cable. 10GBASE-T Ethernet.

Four pairs, S/FTP

(shielded pairs,

braid-screened

cable). Standardunder development.

Cat8 1200MHzUnder development, no

applications yet.

Four pairs, S/FTP

(shielded pairs,braid-screened

cable). Standard

under development.

Coaxial CableCoaxial cable, or coax, is an electrical cable with an inner conductor surrounded

by a flexible, tubular insulating layer, surrounded by a tubular conducting shield.

The term coaxial comes from the inner conductor and the outer shield sharing the




http://en.wikipedia.org/w/index.php?title=Category_8_cable&action=edit&redlink=1







same geometric axis. Coaxial cable was invented by English engineer and

mathematician Oliver Heaviside, who patented the design in 1880.

Coaxial cable is used as a transmission line for radio frequency signals. Itsapplications include feedlines connecting radio transmitters and receivers withtheir antennas, computer network (Internet) connections, and distributing cable

television signals. One advantage of coax over other types of radio transmission

line is that in an ideal coaxial cable the electromagnetic field carrying the signalexists only in the space between the inner and outer conductors. This allows

coaxial cable runs to be installed next to metal objects such as gutters without the

power losses that occur in other types of transmission lines. Coaxial cable also

provides protection of the signal from external electromagnetic interference.

Coaxial cable differs from other shielded cable used for carrying lower frequencysignals, such as audio signals, in that the dimensions of the cable are controlled to

give a precise, constant conductor spacing, which is needed for it to functionefficiently as a radio frequency transmission line.

Coaxial cable conducts electrical power using an inner conductor (usually a

flexible solid or stranded copper wire) surrounded by an insulating layer and all

enclosed by a shield layer, typically a woven metallic braid; the cable is often

protected by an outer insulating jacket. Normally, the shield is kept at ground

potential and a voltage is applied to the center conductor to carry electrical power.

The advantage of coaxial design is that the electric and magnetic fields are

confined to the dielectric with little leakage outside the shield. Conversely,

electric and magnetic fields outside the cable are largely kept from causing

interference to signals inside the cable. This property makes coaxial cable a good

choice for carrying weak signals that cannot tolerate interference from the

environment or for higher power signals that must not be allowed to radiate or

couple into adjacent structures or circuits.



Common applications of coaxial cable include video and CATV distribution, RF

and microwave transmission, and computer and instrumentation data connections.

The characteristic impedance of the cable ( Z 0) is determined by the dielectricconstant of the inner insulator and the radiuses of the inner and outer conductors.A controlled cable characteristic impedance is important because the source and

load impedance should be matched to ensure maximum power transfer and

minimum Standing Wave Ratio. Other important properties of coaxial cableinclude attenuation as a function of frequency, power and voltage handling

capability, and shield quality.

Uses

Short coaxial cables are commonly used to connect home video equipment,in ham radio setups, and in measurement electronics. They used to be common forimplementing computer networks; in particular Ethernet, but twisted pair cables

have replaced them in most applications except in the growing consumer cable

modem market for broadband Internet access.

Long distance coaxial cable was used in the 20th century to connect radionetworks, television networks, and Long Distance telephone networks though this

has largely been superseded by later methods (fibre optics, T1/E1, satellite).

Shorter coaxials still carry cable television signals to the majority of televisionreceivers, and this purpose consumes the majority of coaxial cable production.

Micro coaxial cables are used in a range of consumer devices, military equipment,

and also in ultra-sound scanning equipment.

The most common impedances that are widely used are 50 or 52 ohms, and 75

ohms, although other impedances are available for specific applications. The 50 / 52 ohm cables are widely used for industrial and commercial two-way

radio frequency applications (including radio, and telecommunications), although

75 ohms is commonly used for broadcast television and radio.



Optical Fiber

Optical fiber communication Optical fiber can be used as a medium for telecommunication and computer

networking because it is flexible and can be bundled as cables. It is especially

advantageous for long-distance communications, because light propagates

through the fiber with little attenuation compared to electrical cables. This allowslong distances to be spanned with few repeaters. Additionally, the per-channel

light signals propagating in the fiber have been modulated at rates as high as

111 gigabits per second by NTT, although 10 or 40 Gbit/s is typical in deployedsystems. Each fiber can carry many independent channels, each using a different

wavelength of light (wavelength-division multiplexing (WDM)). The net data rate

(data rate without overhead bytes) per fiber is the per-channel data rate reducedby the FEC overhead, multiplied by the number of channels (usually up to eighty

in commercial dense WDM systems as of 2008). The current laboratory fiber

optic data rate record, held by Bell Labs in Villarceaux, France, is multiplexing

155 channels, each carrying 100 Gbit/s over a 7000 km fiber. Nippon Telegraphand Telephone Corporation has also managed 69.1 Tbit/s over a single 240 km

fiber (multiplexing 432 channels, equating to 171 Gbit/s per channel). Bell Labs

also broke a 100 Petabit per second kilometer barrier (15.5 Tbit/s over a single

7000 km fiber).

For short distance applications, such as a network in an office building, fiber-optic

cabling can save space in cable ducts. This is because a single fiber can carry

much more data than electrical cables such as standard category 5 Ethernet

cabling, which typically runs at 1 Gbit/s. Fiber is also immune to electrical



interference; there is no cross-talk between signals in different cables, and no

pickup of environmental noise. Non-armored fiber cables do not conduct

electricity, which makes fiber a good solution for protecting communications

equipment in high voltage environments, such as power generation facilities, ormetal communication structures prone to lightning strikes. They can also be used

in environments where explosive fumes are present, without danger of ignition. Wiretapping (in this case, fiber tapping) is more difficult compared to

electrical connections, and there are concentric dual core fibers that are said to be

tap-proof.

Comparison of optical fibre with electrical transmission

The choice between optical fiber and electrical (or copper) transmission for a

particular system is made based on a number of trade-offs. Optical fiber isgenerally chosen for systems requiring higher bandwidth or spanning longer

distances than electrical cabling can accommodate.

The main benefits of fiber are its exceptionally low loss (allowing long distancesbetween amplifiers/repeaters), its absence of ground currents and other parasite

signal and power issues common to long parallel electric conductor runs (due to

its reliance on light rather than electricity for transmission, and the dielectricnature of fiber optic), and its inherently high data-carrying capacity. Thousands of

electrical links would be required to replace a single high bandwidth fiber cable.

Another benefit of fibers is that even when run alongside each other for long

distances, fiber cables experience effectively no crosstalk, in contrast to sometypes of electrical transmission lines. Fiber can be installed in areas with

high electromagnetic interference (EMI), such as alongside utility lines, power

lines, and railroad tracks. Nonmetallic all-dielectric cables are also ideal for areasof high lightning-strike incidence.

For comparison, while single-line, voice-grade copper systems longer than a

couple of kilometers require in-line signal repeaters for satisfactory performance;

it is not unusual for optical systems to go over 100 kilometers (62 mi), with noactive or passive processing. Single-mode fiber cables are commonly available in

12 km lengths, minimizing the number of splices required over a long cable run.

Multi-mode fiber is available in lengths up to 4 km, although industrial standards

only mandate 2 km unbroken runs.

In short distance and relatively low bandwidth applications, electricaltransmission is often preferred because of its

Lower material cost, where large quantities are not required



Lower cost of transmitters and receivers

Capability to carry electrical power as well as signals (in specially-designedcables)

Ease of operating transducers in linear mode.

Optical fibers are more difficult and expensive to splice than electrical

conductors. And at higher powers, optical fibers are susceptible to fiber fuse,resulting in catastrophic destruction of the fiber core and damage to transmission

components.

Because of these benefits of electrical transmission, optical communication is not

common in short box-to-box, backplane, or chip-to-chip applications; however,

optical systems on those scales have been demonstrated in the laboratory.

In certain situations fiber may be used even for short distance or low bandwidth

applications, due to other important features:

Immunity to electromagnetic interference, including nuclear electromagnetic

pulses (although fiber can be damaged by alpha and beta radiation).

High electrical resistance, making it safe to use near high-voltage equipmentor between areas with different earth potentials.

Lighter weight — important, for example, in aircraft.

No sparks — important in flammable or explosive gas environments.

Not electromagnetically radiating, and difficult to tap without disrupting the

signal — important in high-security environments.

Much smaller cable size — important where pathway is limited, such as

networking an existing building, where smaller channels can be drilled andspace can be saved in existing cable ducts and trays.

Optical fiber cables can be installed in buildings with the same equipment that is

used to install copper and coaxial cables, with some modifications due to thesmall size and limited pull tension and bend radius of optical cables. Optical

cables can typically be installed in duct systems in spans of 6000 meters or more

depending on the duct's condition, layout of the duct system, and installationtechnique. Longer cables can be coiled at an intermediate point and pulled farther

into the duct system as necessary.



Microwave transmission

Microwave transmission refers to the technology of transmitting information or

power by the use of radio waves whose wavelengths are conveniently measured in

small numbers of centimeters; these are called microwaves. This part of the radio

spectrum ranges across frequencies of roughly 1.0 gigahertz (GHz) to 30 GHz.

These correspond to wavelengths from 30 centimeters down to 1.0 cm.

Microwaves are widely used for point-to-point communications because their

small wavelength allows conveniently-sized antennas to direct them in narrow

beams, which can be pointed directly at the receiving antenna. This allows nearby

microwave equipment to use the same frequencies without interfering with each

other, as lower frequency radio waves do. Another advantage is that the high

frequency of microwaves gives the microwave band a very large information-

carrying capacity; the microwave band has a bandwidth 30 times that of all the

rest of the radio spectrum below it. A disadvantage is that microwaves are limited

to line of sight propagation; they cannot pass around hills or mountains as lower

frequency radio waves can.

Microwave radio transmission is commonly used in point-to-point communication

systems on the surface of the Earth, in satellite communications, and in deep

space radio communications. Other parts of the microwave radio band are used

for radars, radio navigation systems, sensor systems, and radio astronomy.

The next higher part of the radio electromagnetic spectrum, where the frequencies

are above 30 GHz and below 100 GHz, are called "millimeter waves" because

their wavelengths are conveniently measured in millimeters, and their

wavelengths range from 10 mm down to 3.0 mm. Radio waves in this band are

usually strongly attenuated by the Earthly atmosphere and particles contained in

it, especially during wet weather. Also, in wide band of frequencies around

60 GHz, the radio waves are strongly attenuated by molecular oxygen in theatmosphere. The electronic technologies needed in the millimeter wave band are

also much more difficult to utilize than those of the microwave band.



Properties

Suitable over line-of-sight transmission links without obstacles

Provides large useful bandwidth when compared to lower frequencies (HF,

VHF, UHF)

Affected by the refractive index (temperature, pressure and humidity) of the

atmosphere, rain (see rain fade), snow and hail, sand storms, clouds, mist and

fog, strongly depending on the frequency.

Uses

[Wireless]] Transmission of information

One-way (e.g. television broadcasting) and two-way telecommunication

using communications satellite

Terrestrial microwave radio broadcasting relay links in telecommunications

networks including e.g. backbone or backhaul carriers in cellular

networks linking BTS-BSC and BSC-MSC

Fig. A parabolic antenna for Erdfunkstelle Raisting, based

in Raisting, Bavaria, Germany.

http://en.wikipedia.org/wiki/File:Erdfunkstelle_Raisting_2.jpg



Proposed systems e.g. for connecting solar power collecting satellites to

terrestrial power grids

Parabolic (microwave) antenna

To direct microwaves in narrow beams for point-to-point communication links or

radiolocation (radar, a parabolic antenna is usually used. This is an antenna that

uses a parabolic reflector to direct the microwaves. To achieve narrow

beamwidths, the reflector must be much larger than the wavelength of the radio

waves. The relatively short wavelength of microwaves allows reasonably sized

dishes to exhibit the desired highly directional response for both receiving and

transmitting.

Microwave power transmission

Microwave power transmission (MPT) is the use of microwaves to transmit

power through outer space or the atmosphere without the need for wires. It is a

sub-type of the more general wireless energy transfer methods.

Satellite Microwave

• Satellite is relay station

• Satellite receives on one frequency, amplifies or repeats signal and

transmits on another frequency

• Requires geo-stationary orbit

– Height of 35,784km

• Television

• Long distance telephone

• Private business networks



Satellite Point to Point Link

Satellite Broadcast Link

Direct-broadcast satellite Direct broadcast satellite (DBS) is a term used to refer to satellite

television broadcasts intended for home reception.

A designation broader than DBS would be direct-to-home signals, or DTH. This

has initially distinguished the transmissions directly intended for home viewers



from cable television distribution services that sometimes carried on the same

satellite. The term DTH predates DBS and is often used in reference to services

carried by lower power satellites which required larger dishes (1.7m diameter or

greater) for reception.

In Europe, prior to the launch of Astra 1A in 1988, the term DBS was commonly

used to describe the nationally-commissioned satellites planned and launched to

provide TV broadcasts to the home within several European countries

(e.g. BSB in the UK, TV-Sat in Germany). These services were to use the D-Mac

and D2-Mac format and BSS frequencies with circular polarization from orbital

positions allocated to each country. Before these DBS satellites, home satellite

television in Europe was limited to a few channels, really intended for cabledistribution, and requiring dishes typically of 1.2m SES Astra launched the Astra

1A satellite to provide services to homes across Europe receivable on dishes of

just 60 cm-80 cm and, although these mostly used PAL video format and FSS

frequencies with linear polarization, the DBS name slowly came to applied to all

Astra satellites and services too.

Documents

Project Mtnl