training report of bsnl

8/4/2019 Training Report of BSNL

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ACKNOWLEDGEMENT

I acknowledge my gratitude and thank to all the well knowledge persons for giving meopportunity to avail all the best facilities available at this telecom centre through which I havegained knowledge thinking so as too just in the environment suitable for harmonicadjustment. I am grateful to the following persons for various help rendered by them duringthe training period.

Mr. Anoop Bajpai

Finally, a deep thanks to

Mr.

Last but not the least; I thank my teacher, friends and my family members for their constantencouragement.


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PREFACE

Since time immemorial, a man has tried hard to bring the world as close to himself aspossible. His thirst for information is hard to quench so he has continuously tried to developnew technologies, which have helped to reach the objective.The world we see today is aresult of the continuous research in the field of communication, which started with theinvention of telephone by Grahm Bell to the current avtar as we see in the form INTERNET

and mobile phones. All these technologies have come to existence because man continued itsendeavor towards the objective.

This project report of mine, STUDY OF TRENDS TECHNOLOGIES INCOMMUNICATION AND NETWORKING has been a small effort in reviewing thetrends technologies prevailing. For this purpose, no organization other than BAHRATSANCHAR NIGAM LIMITED could have been a better choice.

Table of contents

1. Acknowledgement2. Preface3. Table of contents

4. Introduction5. making a telephone call6. About the exchangea. computer unitb. power plantc. central air conditionerd. main distribution frame7. V-SAT networka. Design aspectsb. Operational factors8. Types of access V-SAT networks

a. fixed assignment time division multiple access(F-TDMA)


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b. Random accessc. Code division multiple access (CDMA)9. The Interneta. Introductionb. Internet connectivity

c.OSI modeld. Communication b\w the layerse. File transfer the internetf. National internet backbone10. Wireless in local loopa. Technical aspectsb. Advantages11. Global system for mobile communication (GSM)

BHARAT SANCHAR NIGAM LIMITED (BSNL)

An Introduction:-

Today, BSNL is the No. 1 telecommunication company and the largest public sectorundertaking of India and its responsibilities includes improvement of the already impeccablequality of telecom services, expansion of telecom services in all villages and instillingconfidence among its customers.

Apart from vast network expansions, especial emphasis has given for introducing latesttechnologies and new services like I-NET, INTERNET, ISDN (INTEGRATED SERVICESDIGITAL NETWORK), IN (INTELLIGENT NETWORK), GSM and WLL (WIRELESS INLOCAL LOOP) services etc. Now BSNL has also entered in mobile communication. BSNLhas all the new services send technological advantages, which are available with any well,developed Telecom network anywhere else in the country.Full credit for all above achievement goes to the officers and staff of the BSNL. Theadministration is fully aware of the challenges lying ahead and quite committed to providethe latest and best telecom services by their continued support and active co-operation.

BSNL Services:-

When it comes connecting the four corners of the country , and much beyond , one solitaryname lies embedded at the pinnacle- BSNL. A company that has gone past the number gamesand the quest to attain the position of the leader. It is working round the clock to take India into the future by providing excellent telecom services for people of India.Driven by the very best of telecom technology from global leaders, it connects each inch ofIndia to the infinite corners of the globe, to enable you to step in to tomorrow.The telecom services have been recognized the world over as an important tool for socio-economic development for a nation and hence telecom infrastructure is treated a crucialfactor to realize the socio-economic objectives in India. Accordingly the Department ofTelecom has been formulating developmental policies for the accelerated growth of thetelecommunication services in various cities. The department is also responsible for

frequency management in the field of radio connection in close coordination with theinternational bodies.


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MAKING A TELEPHONE CALL

A telephone call starts when the caller lifts the handsets of the base. Once the dial tone isheard, the caller uses a rotary or a push button dial mounted either on the handset or on thebase to enter a sequence of digits, the telephone number of called party. The switchingequipment from the exchange removes the dial tone from the line after the first digit isreceived and after receiving the last digit, determines the called party is in the same exchangeor a different ones. If the called is in the same exchange, burst of ringing current is applied tothe called partys line. Each telephone contains a ringer that responds to specific electric

frequency. When the called party answers the telephone by pocking up the handset, steadystart to flow in the called partys line and is detected by the exchange. The exchange thanstops applying ringing and sets up the connection between the caller and the called party. Ifthe called party is in different exchange from the caller, the caller exchange set up the

connection over the telephone network to the called partys exchange. The called party thenhandles the process of ringing, detecting an answer, and notifying the calling and billingmachinery when the call is completed. When conversation is over, one or both parties hangup by replacing their handset on the base, stopping the flow of current. The exchange wheninitiates the process of taking down the connection, including notifying billing equipment ofthe duration of the call if appropriate.

ABOUT THE EXCHANGE

All telephone subscribers are served by automatic exchanges, which perform the functionsthe human operator. The number being dialed is stored and then passed to the exchanges

central computer, which in turns operates the switching to complete the call or routes it ahigher level switch for further processing. Todays automatic exchanges uses a pair of

computers, one running the program that provides services and the second monitoring theoperation of the first, ready to take over in a few seconds in the event of equipment failure.

Various exchanges present in BSNL are:

E-10BOCB283EWSD

All exchange has some purposes and some basic structural units, which are:

1. subscribers connection unit2. switching network (CX)

3. control unit4. OMC


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For smooth working of an exchange following unit are very important:-

1. Computer Unit: - it deals with additional services of the exchange to the customers withthe help of computers.

2. Power Plant:- to feed proper power supply to exchange

3. AC Plant: - to maintain the continuous temperature + or2 degree Celsius to the digitalswitch (exchange).

4. MDF: - to connect switch (exchange) with the external environment (subscriber) i.e. it isthe interface between subscribers and exchange.

Computer unit

As the name specified it is the main part of the exchange that deals with the all servicesprovided by the exchange to the customers with the help of computer. It also provides theupdated data to all other part of the exchange.

The customers are using the services of the exchange by using the internet also getsconnected 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 ofthis 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 therepairing of telephone. In this system when the user enters its 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 usingthis; 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 ofservice makes it enquiry using the internet, which gets connected to the main server at theinternet room in the exchange and further to the main server in the computer room.

POWERPLANT

As we know that, the power is the main source or any organization. It is the case of E-10B

exchange. That is the first requirement of any organization is the input.The main source of this exchange is AC supply. However, as soon as the power supply is


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gone off, then what is source? No one think on this that the telephone is always plays its rolein the human life. Even if the power supply gone off. Thus there must be adjustment sourceof power.The main parts of the power room are:

Batteries: - these are the instant sources of the power as soon as power is gone off.

UPS (Uninterrupted Power Supply):- the UPS must give supply to the computer. As we knowthere is some equipment which can withstand any type of power supply, but there are alsosome instruments which cannot withstand with this type of power supply, even amicrosecond delay will cause the loss of data.

Charging- Discharging Unit: - the batteries we are using in the power room need timelycharging. As soon as the AC power supply is on, we make use of the charging unit present inthe power room. The slowly charging of the batteries is known as the trickle charging. Butsometimes we need the BOOSTER charging. In this type of charging awe take of the

batteries from the load and charge separately, until it gets fully charged.The main work of the discharging unit is to control the discharging of the batteries.

Inverter and Converter Unit: - the main use of this system is to change AC mains to DC andvice versa as required by the parts of exchange.

Engine Room:-we know that the batteries are the instant source of supply but we cannot use itfor much larger time, thus for this, we have an engine to generate the power supply. They areof 885 KVA. Thus, this room controls the supply of the engine.

CENTRAL AIR CONDITIONER

For the function of electrical equipment, cooling system is basic requirement. The basicadvantages of cooling systems are following-It provides the thermal stability so that the temperature does not reach the tolerance limit ofelectronic equipment

It saves equipment from dust so to avoid malfunction of equipments.It protects equipment from excess humidity which can caused rusting of equipment.

The basic unit of measurement used in the industry is known as ton of refrigeration (TR)which is equivalent to the heat extracted in 24 hours for converting thousands kg of liquid toice at zero degree.The compressor is the heart of the AC system and the costliest. It increases the pressure andtemperature of the refrigerant gas coming from the evaporator coils by compressing it.Compressor comes in various types. The most widely used is simple reciprocal type acylinder and piston arrangement. For capacity more than 120 TR, centrifugal compressors areused. The condenser liquefies the refrigerant gas by a heat exchange process. The capillary

tube or the expansion valve pressurizes liquid refrigerant and meters it flows to theevaporator.


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The refrigerant then passes trough the evaporator coils, which extract heat out of theambience.

MAIN DISTRIBUTION FRAME

The primary function of MDF is:The fault of telephone number is removed in the MDF; it is called as Fault Remove Section.For removing the fault of telephone number, we use the testingThese testing are T.T.Y. testing, Group testing, etc.For any type of testing firstly we need the vertical no. or the live tester, printer and computertest N.E. number of that particular telephone number.The telephone numbers are also disconnected in the MDF because of some specific reason.

ORGANISATION OF THE MDF

PARTS OF THE MDF

Horizontal sideVertical side

HORIZONTAL SIDE:

It is again subdivided in to two partsExchange sideLine side

Description of the horizontal side:-

RACK: - On the rack, the tags are situated. One rack is having eight tags. The courting is

done from up (0) to down (7).

TAG: - Each rack consists of eight tags.1 tag = 4 core1 core = 4 bunch1 bunch = 2 line

N.E.:- The word NE stands for the NUMBER OF EQUIPMENT.It is a 128 pair cable. The EWSD and MDF connected by NE.

WEDGE:-If we want to disconnect any two numbers then we insert a wedge between

subscriber side and exchange side. Here wedge works as insulator made of plastic.


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VERTICAL SIDE:

The vertical aside connected to the underground cable. This cable is having 100 pairs.

These pair is distributed when we allot the telephone number to the subscriber.Vertical side is again subdivided in two parts:

One part is connected with the horizontal side and another with the subscriber line by using100 pair underground cable.

This is how the present day telephone system works. Different exchanges have differentarchitectures of switching call routing and other features.

Now let us see how BSNL has kept up with the changing world and provided the subscriberswith the latest facilities technologies, which include the V-SAT network, Internet, the WLL

(wireless in local loop) and the GSM mobile.

V-SAT NETWORK

What is V-SAT?

It can be defined as a class of very small aperture Intelligent Satellite Earth Station suitablefor easy on-premise installation, usually operating in conjugation with a large size HUB earthstation. Capable of supporting a wide range of two ways integrated Telecom Services.It has the following components:Micro Earth StationMini Earth StationPersonal Earth StationRoof Top TerminalCustomer Premises Terminal

ADVANTAGES OF V-SAT

Can be located in the user premises on roof top or backyard and hence eliminate last mileproblem.Superior quality satellite based data services.Quick implementation time.Reliable communication.Broadcast feature on satellite communication.Communication to different areas.Flexibility for network and changes.

Service in distance insensitive.Low cost.


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REASON FOR V-SAT EVOLUTION

The main reason for V-SAT evolution is due to advances in following areas:

Packet transmission and switching.Efficient multiple access protocol.Powerful microprocessor.KU and RF electronics.Antennae miniaturizationSpread spectrum techniques.Protocol standardization and implementation.LSI based FEC codec has and modems.Higher power satellites.

CLASSIFICATION OF V-SATs

V-SAT can be classified as following:1. Modulation type2. Application used for.3. Transmission rate.4. Cost.

CATEGORIES OF V-SATs

1. Broadcast/ point to multipointTypes of servicesa. Broadcast videob. Program quality audio.c. Packetised data.In this mode of operation V-SATs transmit/receive data through a centralized HUB. This typeof network is called star network.2. Point to pointTypes of servicesa. Voiceb. Datac. Image

In this mode of operation, V-SATs transmit/receive data without the help of hub station. Thistype of network is called a mesh network.3. Two way interactiveTypes of servicesa. Voiceb. Datac. ImageIn this configuration, V-SATs can communicate both on star as well as mesh topology.


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DESIGN FACTORS FOR V-SAT SYSTEMS

The capabilities of V-SAT system depend upon the following factors.

I. Satellite characteristicsII. Geographical and environmental factors.III. Transmission link properties.IV. Earth station characteristics.V. Information encoding and modulation.VI. Total system operation.

When evaluating V-SAT system each of the above attributes should be given attention.However, few of more important attributes are

Operational aspectsFrequency bandsSatellite access methods

OPERATIONAL ASPECTS

Considering a V-SAT system from its operational aspects, there are five broad functions thatdetermines how the system works. These are:Bandwidth allocationMultiplexingNetwork managementProtocol handlingTransmission

TYPE OF ACCESS FOR V-SAT DATA NETWORK

There are three types access available for V-SAT data networks. They are:

1. Fixed assignment time division multiple access (F-TDMA)2. Random accessa. Pure alohab. Slotted alohac. Reservationi. Implicitii. Explicit3. code division multiple access (CDMA)

FIXED ASSIGNMENT TIME DIVISION MULTIPLE ACCESS (F-TDMA)


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In a fixed assignment TDMA, each frame is divided in to slots of fixed time durations amongstations of network. The assignment of stations to slots is permanent similar to TDMAsystem carrying digitalized voice except FTDMA does not have synchronization. Packets are

sent asynchronously, with no frame sync signals.

FEATURES

No inter modulation problems.Transport utilization is better.Burst from different stations must arrive at satellite exactly in allocated slots.Throughput is 70% to 80%Delaymedium is too high.Complexity-medium.

RANDOM ACCESS

With TDMA schemes, signals are transmitted by earth stations in a burst mode. If noscheduling is provided b/w the transmitting station, this type of access is called time randommultiple access. This simplest method for the stations to transmit burst without regard forother station.

Random access id of two types:Pure alohaSlotted aloha

PURE ALOHA

Pure aloha, also called unslotted aloha is the simplest form of random access schema.In this form of access stations transmit packets\bursts randomly.

Packet from different stations may collide, thereby destroying information content.Station transmits the packet until they are received correctly.The aloha channel throughout can be analyzed in terms of traffic offered through thefollowing relationship:S=Ge-2gMaximum throughput is 13% to 18%.Delay- lowComplexity- very low

SLOTTED ALOHA


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The maximum throughput of an unslotted aloha channel is limited to 18% due to collision.To reduce probability of each collision time slots are introduced so that the transmissioncould only at the start of the slots.The above network discipline reduces the rate of collision by half and hence increases the

maximum throughput efficiency of the channel.In S-Aloha, each station has 2 queues.a. New packet queueb. Retransmit packet queue.Only if the retransmit packet queue is empty, a new packet queue is sent.The analysis of slotted aloha channel shows thatS = Ge2gMaximum channel throughput is 36%.Delay- low.Complexity- low- medium.

Reservation

The low bandwidth utilization of pure aloha and the slotted aloha has led to many proposalsfor increasing utilization by means of slot reservation schemes.The object of slot reservation schemes is to receive a particular time slot for a given station.This ensures that no collision takes place.This scheme has a higher throughput than either S- Aloha or F-TDMA depending on traffic.This increase in channel utilization efficiency is obtained at some overhead either in terms ofallocation of bandwidth for reservation purposes and\or increased complexity of the controlmechanism in transmitting stations.All reservation methods use some form of framing approach and the reservation scheme canbe either implicit or explicit.The implicit reservation method involves reservation by use. This is done whenever a stationsuccessfully transmit in a slot; all the stations internally assign that slot in sub-segmentframes for exclusive use by the successful station. This is called R-Aloha. In this there is noway to prevent a station capturing most or all of the slots in a frame for an indefinite time.The explicit reservation is a distinct and unique assignment of slots to a user by the networkscheduler.

CODE DIVISION MULTIPLE ACCESS (CDMA)

With CDMA transmission from earth station are spread over the time frequency plane by acode transformation. These techniques are referred to as Spread Spectrum Systems. Inaddition to their multiple access capabilities, they are useful in combating jamming, and are

for this reason principally used in military systems.


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Features

All stations operate on the same transponder frequency using a large bandwidth than needed

for the data rate.Network needs no time for frequency coordination.Provide anti jam capabilities or protection against interference.Provide for a graceful degradation of network performance as the number of simultaneoususers increases.Low spectral density compared to conventional emissions.It yields same capacity as FDMA.

Limitations of CDMA

Require large transponder ratio.Due to imperfect code orthogonalities, expected simultaneous users may be limited.Requires a highly central earth station called HUB using star configuration.VSAT technology using SSMA is presently available only for low bit rate application.

VSAT NETWORK IN DOT

Department of telecommunication entered the VSAT era in 1991 by commissioning its firstsatellite based low bit rate network known as REMOTE AREA BUSINESS MESSAGENETWORK (RABMN).This has been engineered for users located in remote areas for stable and reliable datacommunication.This service envisages installation of very small aperture terminals (VSAT) to work withsatellite based pocket switched network.

It has 3 main components:-

A large master earth station (hub)A satellite transponder located in geo stationary orbitA small micro earth station located at users premises

SERVICES OFFERED BY RABM NETWORK:-

Data communication up to 1200 bpsFax services.Access to Public Telex NetworkAccess to international data network through VSNL gateway.


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Tariff and billing:-

A RABMN customer availabling VSAT has to pay the following charges:-Registration charge Rs. 5000 per terminal

Cost of each VSAT Rs. 5.2 lakhsCost of each installation Rs. 15,000 per terminalLicense fees Rs. 100 per terminalMaintenance charges Rs. 25,000 per terminal annuallySatellite access charges Rs. 5000 per month per terminalTraffic charges Rs. 50 per kilo segment of data

Network users:

Some of the probable users are

Banking networkCivil aviationAirlines\railwaysPublic\private sector industriesMeteorological departmentPolice department

RABMN NETWORK

Introduction

Satellite communication plays a vital role in long distance communication.Satellite medium offers high bandwidth making it suitable for data communication andcomputer networking.Satellite communication is of distance and cost effective.Multi access nature of satellites.

Provides two way communications.Dynamic assignment of channels between geographically dispersed users.Satellite network provides point to point and point to multipoint communication needs.

Frequency division multiple access (FDMA):-

Bandwidth is split in to narrow frequency bands with multiple users each allocated afrequency range within the larger bandwidth.


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Time division multiple access (TDMA):-

Each terminal is allotted a short time slot in which to transmit on a sequential basis. This time

slot is usually a fraction of a second.

Code division multiple access (CDMA)

Each terminal is allotted a unique encryption code. The transmitted signals are encoded and

only the terminal intended to receive it, can decode it. This is also known as Spread SpectrumMultiple Access.

Statistical time division multiplexing (STDM):-

In TDM, time slots are allotted to the multiplexed lines even if they have no data transmit. InSTDM, a time slot is allotted to the multiplexed line only if there is data to be sent. Themultiplexed circuit is used more efficiently.

VSAT (very small aperture terminal)

It is also called Micro Earth Station or Personal Earth Station.

Its main features are as follows:-

Independent of terrain can be installed in hilly regions, islands and remote places.Flexible service carrying data, Telex.No last mile problems of cable pair\overhead lines.Interference immunity.Data security

The main services offered by VSAT are as follows:-

Interactive data communication.

Connection to public telex network.Connection to Packet Switched Data NetworkINET.


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Connection to international gateway packet switch.

The different technologies used in VSAT are-

Satellite basedSpread spectrumPacket switching

Tariffs:-

Cost of VSAT : about Rs. 7,00,000Installation cost : Rs. 15,000Maintenance cost : Rs. 25,000Satellite access charge : Rs. 5,000 per month

Charges for using VSAT are as follows:

National : Rs. 50 per kilo segment of data: Rs. 10 per min in addition to vol. of telex International : Rs.200 per Kilo segment of data: Rs. 240 per hour duration.

Dialing codes for VSAT are as follows:

Within RABMN:o 12 digit codeo 4041xxxxxxxx

to other data networks:

o I-NETo 4043xxxxxxxxo international networkso DNICxxxxxxxx

To telex networksNATIONALQ008/area code/telex number

INTERNATIONAL0009/country code/telex number

TELEX TO RABMIN


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09841xxxxx (last 5 digits of telex number)

Specifications for master earth station:

There are two types of master earth stations:

OutboundInbound

Outbound:

Each VSAT and host computer is allotted an HCL portNPG polls HCL ports and generates a 153.6 Kbps demand based STDM data streamData stream contains variable length packets of data addressed to various VSATsOutmux chips the data @1:16 resulting in 2.4576 MB stream.BPSK modulator produced 5 MHz of spectrumUpconvertor converts to 5GHz RFMes transmits 153.6KBps STDM/BPSK/SS carriersNPG provides FEC encoding for outbound data

Inbound:

Inbound signals originates from VSATsVSAT has a unique PN codeData spread by its PN code and transmitted to satellite in 6 GHz bandMES resolves the signal in 4 GHz band, converts to 70 MHz IF and sends to Demod sectionDemod cards compare the pattern of the to other PN code for its associated VSAT. When thecorrect pattern is detected, the original signal is extracted from the IF signal and transmitted

to INMUXNPG polls INMUX for I\C data packets and transmits the packets to HCL

VSAT specifications


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Antennae module

Reflector : 1.2M X 1.8M Weight : 60 KGs Tracking : fixed

Amb. Temp : -40 to +50 deg. Cel. Wind speed : operating 100 kmph

Controller module

Size : 15 cm(h) x 43 cm(w) x 55 cm (d) Weight : 15 kgs Power supply : 220V\60Hz, 300 watts Oper. Temp. : -5 to 50 deg. Cel. Humidity : up to 95%

Controller module :

INPUT\OUTPUT PROCESOR Converts raw data to packets Customer protocol to network protocol

NETWORK PROCESSORTRANS SIDE: generates BFEC & FCS Retains packets in buffer until ACKs receives and transmits if required.

RECIEVER SIDE: checks BFEC & FCS ACKs the packets and requests retransmission of missing packets

SPACE PROCESSORTRANS SIDE Encodes the packets with PN sequence to 2.45MBps stream BPSK modulation of IF

RECIEVER SIDE Demodulates IF signal to 2.45MBps Dispreads to 153.6KBps stream Checks destination link address in the header Discards packets addressed to other links.

Micro earth station transmits 1.2KBps\9.6KBps BPSK/CDMA carriers bursts in absolutelyrandom access mode in the same frequency.


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INTERNET

Introduction:

The Internet is not a program, not software, not hardware or a big system. It is a group ofvarious co-operating computers worldwide interconnected by computer based on TCP\IPcommunication protocols. People use it to get information over a standard communicationlink. The hundreds or thousands or millions of computer network are connected to each otherfor exchanging the information which is based on the unique identity and set of procedures.

Internet is a series of interconnected networks providing global link to information.

GIAS: BSNL launched the Gateway Internet Access Service (GAIS) through dialup/leased/ISDN network. Users can access GAIS from 99 cities in India by this means.

INTERNET CONNECTIVITY

INTERNET TECHNOLOGY

The basic function of Internet can be summarized as under-

Interconnecting of computers to form a network.Interconnecting of computers to form a network of networks.To establish a communication link between two computers within as network.To provide alternate communication link among the networks, even if one network is notworking. These are based on TCP/IP communications protocol.

Transfer of a file through Internet:-

Suppose a file is to be transmitted on Internet from one computer to other ones

Break the file in to small packetsAttached destination and source address in o packetsMultiplexed and transmit these packets

At destination de-multiplex the packetsRemove address bits from the packets and assemble the data in to the original file


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Make source bits as destination address and send the acknowledgement in to the source

Therefore, it is clear that network hardware sends the packets to specified destination andnetwork software reassembles of communications, the computer network performs thefollowing functions-

Addressing and routingFragmentation and error correctionData error checkingConnectivity controlMultiplexing and de-multiplexingData flow controlEnd users interface etc.The data handling

A single module cannot handle the entire process. One that adopted as a standard is an opensystem interconnection (OSI) model.

OSI NETWORKING MODEL: The open systems interconnection model defines all themethods and protocols needed to connect one computer to any other over a network.

The OSI model separates the methods and protocols needed for a network connection in toseven different layers. Each higher layer relies on services provided by a lower level layer.

The OSI model is sometimes called the seven layer model. It was developed by the

International Standards Organization (ISO) in 1983 and is documented as standard 7498.

Layers are:

Application layerPresentation layerSession layerTransport layerNetwork layer

Data link layerPhysical layer

PHYSICAL LAYER:

The physical layer defines the properties of the physical medium used to make a networkconnection. It includes a network cable that can transmit a stream of bits between nodes onthe physical network. The physical connection can be either point to point or multipoint, and

it can consist of either half duplex (one direction at a time) or full duplex (both directionssimultaneously) transmissions. Moreover, the bits can be transmitted either in series or in


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parallel (most network use a serial stream of bits, but the standard allows for both serial andparallel transmission). The specification for the physical layer also defines the cable used, thevoltages carried on the cable, the timing of the electrical signals, the distance that can be run,and so on. For example, a NIC network interface network) is part of the physical layer.

DATA LINK LAYER: the data link layer, layer 2, defines standard that assign meaning tothe bits carried by the physical layer. It establishes a reliable protocol through the physicallayer, so the network layer (layer 3) can transmit its data. The data link layer typicallyincludes error detection and correction to ensure a reliable data stream. The data elementscarried by the data link layer are called frames.Examples of frame types include x.25 and 802.x (802.x includes both Ethernet and TokenRing networks).

The data link layer is usually subdivided in to two sub layers, called the Logical link control(LLC) and Media Access Control (MAC) sub layers. The LLC sub layer performs tasks such

as call set up and termination and data transfer. The MAC sub layer handles frame assemblyand disassembly, error detection and correction, and addressing. The two most commonMAC protocols are 802.3 Ethernet and 802.5 Token ring .Other MAC protocols include802.12 100 Base VBG, 802.11 Wireless, and 802.7 Broadband.

Network Layer: The network layer, Layer-3, is where a lot of action goes on for mostnetworks. The network layer defines how data packets get from one point to another onnetwork. The Network layer is also known as packet layer, it defines different packetprotocols, such as Internet Protocol (IP) and Internet Protocol Exchange (IPX). These packetprotocols include source and destination routing information. The routing information in eachpacket tells the network where to send the packets to reach its destination and tells thereceiving computer from where the packet originated.

Transport Layer: The Transport Layer, layer-4, manages the flow of information from onenetwork node to another. It identifies each computer or node on a network uniquely. Itensures that the packets are decoded in the proper sequence and that all packets are received.Transport layer protocols include Transmission Control Protocol (TCP) and SequencedPacket Exchange (SPX).Each is used in concert with IP and IPX respectively.

Session layer: The session layer, layer-5, defines the connection from a user to a networkserver, or from a peer on a network to another peer. These virtual connections are referred toas sessions. They include negotiation between the client and the host, or peer and peer, onmatters of flow and control, transaction- processing, transfer of user information, andauthentication to the network.

Presentation Layer: The presentation layer, layer-6, takes the data supplied by the lowerlevel layer and transform so it can be presented to the system. The Presentation layer caninclude data compression and decompression as well as data encryption and decryption.

Application Layer: The Application layer, layer 7, controls how the operating system and its


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application interact with network.As mentioned earlier, data flows from an application program or the operating system, andthen goes through the protocols and devices that make up the seven layers of the OSI modelone by one until the data arrives at the physical layer and is transmitted over the networkconnection. The computer at the receiving end reverses this process. At each stage of the OSI

model, the data is wrapped with new control information related to the work done at theparticular layer. This control information is different for each layer, but it includes headers,trailers pre-ambles, and post-ambles.Therefore, for example, when the data goes into the networking software and componentsmaking up the OSI model, it starts at the application layer and includes an application headerand application data. Next, at the presentation layer, a presentation header is wrapped aroundthe data and it is passed to the session layer, where a session header is wrapped around all thedata, and so on, until it reaches the physical layer. At the receiving computer this process isreversed.

COMMON TERMINOLOGY USED IN INTERNET:

WWW:

World Wide Web (WWW) is a wide area hypermedia information retrieval aiming to giveuniversal access to a large universe of documents.

HTTP:

Hyper text transmission Protocol (HTTP) is the communication protocol used to transferdocuments from the server to client over the WWW (http:// www).

HTML:

Hyper Text Markup Language (HTML) is a system of marking or tagging the various parts ofweb documents to tell the browser software how to display the document text, link graphicsand link media.

ISDN:

Integrated Service Digital Network (ISDN) is a digital phone connection technology thatprovides both voice and data services over the same connection.

ISP:

Internet Service Provider (ISP) is an agency that provides Internet access and other netrelated services.


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NATIONAL INTERNET BACKBONE (NIB)

Networking is a key component of any Internet Services Provider (ISP) operations. The

networking equipments like access servers, routers and modems are critical to the successfulfunctioning of ISP.An ISP node where subscribers enter internet, consists of a set of equipments as given below.Access serverRouterModem bankLAN (Local Area Network) componentsSecurity serverRack, console & power supplyNetwork management agent.Help desk

WIRELESS IN LOCAL LOOP (WLL) MOBILE

WLL is a communication system that connects customers to the Public Switch TelephoneNetwork (PSTN) using radio frequency signals as substitutes of conventional wires for allpart of connection between the subscribers and the telephone exchange. It works on CDMAtechnique. The local loop is access part of telecommunication network i.e. the part betweenPSTN switch and subscribers. WLL network application involves uses of radio to replace ofthe wire link between PSTN switch and subscriber. The radio technology is able to providesame quality of services as that provided by the wires line. Application of wireless looptechnology has just been started in the worldwide. There is no standard for this so far.However, a number of national and international air interface standards for digital cellularmobile telephone system are available.

TECHNICAL ASPECTS:

WLL is based on CDMA technique and is entirely different from GSM. The system for WLLservices can be divided in to following parts:-

BSC (Base Switching Centre):- It provides links between BTS & BSM; it consists ofdifferent processors, in BSNL it is of SUN Polaris of LG Company. In LG 1 BSC can have48 BTS? In BSNL we have two types of BSC:-

V-5.2:- This type of BSC cannot switch by itself so it is dependent on local exchange / PSTNfor switching and keeping records of billing etc. BSNL uses this type of BSC for rural areas.

CCS-7 / R2:-These types of BSC are totally automatic it doesnt depend on local exchange


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for its functions, it is complete in itself. BSNL uses this type of BSC for urban areas.

BTS (Base Transreceiver System):- As it is clear from its name it transmits as well asreceive signal, it works as an amplifier (router) to overcome the loss in signal in transmission.

BSM (Base Station Management):- It controls and manages the WLL services. It cantroubleshoot the problem; add new users as well as capable to block service given to user. Itis basically a computer system, which manages the whole process of WLL service. In BSNLBSM are two UNIX based computer system.

CODE DIVISION MULTIPLE ACCESS (CDMA):

CONCEPT OF MULTIPLE ACCESSES: - Multiple access system allows a large number

of users to share a common pool of radio telephone circuits, like sharing of trunked radiofacility. Multiple access radio has similarity to the LAN in which the common channel isavailable to all users. The circuits are demands assigned i.e. assigned on demand first-cum-first-served basis. The provision of access to the radio circuits methods of multiple accessesare:

CDMA: - Where large number of transmission are combined on the same channel at thesame time and separated by the codes.

FDMA (Frequency Division Multiple Access):- Where individual transmission separatedby each other by the time.

WHAT IS CDMA?

CDMA, a cellular technology originally known as IS-95, competes with GSM technology fordominance in the cellular world.There are now different variations, but the original CDMA is known as CdmaOne.

Latest CDMA global subscriber & operators numbersAs of December 2002, there were 120 millions users worldwide, with 55 million of these in

the USA.See other cellular technology in the world.

We now have CDMA2000 and its variant like 1X EV, 1XEV-DO and MC 3X. The refer ofvariant of usage of a 1.25 MHz channel. 3X uses a 5 MHz channel. Wide band CDMA formsthat the basis of UMTS 3G networks, developed originally by Qualcomm, high capacity andsmall cell radius, employing spread-spectrum technology and special coding schemecharacterized by CDMA.

The Telecommunication Industry Association (TIA) in 1993 adopted CDMA. May 2001there were 35 million subscribers on cdmaOne system worldwide. Over 35 countries have

either commercial or trial activity ongoing. There were already 43 WLL systems in 22countries using cdmaOne technology.


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Enhancing todays data capabilities is the 1XRTT CDMA standard this next evolutionarystep for cdmaOne operators will provide data rates up to 300 kbps, significant capacityincreases as well as extended batteries life for handsets.Worldwide resources are being devoted to roll out third generation CDMA technology,including multi-carrier (cdmaOne2000 1xMC and HDR in 1.25 MHz bandwidth and 3xMC

in 5 MHz bandwidth) and direct spread (WCDMA in 5 MHz bandwidth).This first phase of cdmaOne2000 variously called 1XRTT, 3G1X or just plain 1X is designedto double current voce capacity and support always on data transmission speed 10 timesfaster than typically available today, some 153.6 kbps on both the forward and reverse links.

ADVANTAGES OF WLL:

Country wide induction of WLL underway of areas than are non-feasible for the normalnetwork

Helping relieves congestion of connections in the normal cable / wire based network in urbanareasLimited the mobility without any airtime chargesIt has improved signal and reducing the interferenceGreater capacity than mobileProvides ease of operation, administration & maintenance at lower cost.The telecommunication is the biggest factor in influencing the speed of life in the modernage. Today we can get connection with any corner of world through the push button ofcomputer; with the small mobile phone we can send not only the messages but also the secretdocument. As we know that there is positive view behind any mention that it should behelpful in the development of society. But humans have diverted mentality some of them ofpositive view and some of them of negative view. Where use any invention for the welfare ofsociety but some uses for the satisfaction their disturbed mentality and to earn more and moremoney whether it may be harmful for the society. They infringe the norms of society andtheir behavior is condemned as antisocial, immoral and sinful.

CELLULAR MOBILE SERVICES:

Cellular is one of the fastest growing and most demanding telecommunication applications.Today, it represents a continuously increasing percentage of all new telephone subscriptions

around the world. Currently there are more than 45 million subscribers in worldwide andnearly 50% of those subscribers are located in USA. It is forecasted that cellular system usinga digital technology will become the universal method of telecommunications. By the year2005, forecasters predict that there will be more than 100 million cellular subscribersworldwide.

GLOBAL SYSTEM FOR MOBILE COMMUNICATION (GSM)

The GSM Association is a unique organization, with a truly global reach, offering a full rangeof business and technical services to its members. Now as the wireless family unfolds the

association is deriving forward its vision of seamless, limitless, world of wirelesscommunication.


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Throughout the evolution of cellular telecommunications, various systems have beendeveloped without the benefit of standardized specifications. This presented many problemsdirectly related to compatibility, especially with the development of digital radio technology.The GSM standard is intended to address these problems.Global system for mobile communication (GSM) is a globally accepted standard for digital

cellular communication. GSM is the name of a standardization group established in 1982 tocreate a common European mobile telephone standard that would formulae the specificationsfor a pan-European mobile cellular radio system operating at 900 MHz. It is estimated thatmany country outside of Europe will join the GSM partnership.

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