Industrial Training at BSNL

BHARAT SANCHAR NIGAM LIMITEDTYPE : COMMUNICATION SERVICE PROVIDERCOUNTRY : INDIAAVAILABLITY : NATIONAL EXCEPT DELHI & MUMBAIOWNER : THE GOVERNMENT OF INDIAWEBSITE : WWW.BSNL.CO.IN

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BSNL

BHARAT SANCHAR NIGAM LIMITED

Industrial Training at BSNL

Contents:1. History.2. About BSNL3. MDF4. OCB SWITCHING5. TAX (Trunk auto exchange)

6. TRANSMISSION1. Fiber Optic2. OFC SPLICING

7. BROAD BAND8. MOBILE SECTION

1. GSM2. CDMA

9. INTERNET10. Wi-Max11. Wireless In Local Loop12. Leased Lines13. National Internet Backbone (NIB)

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The foundation of telecom network in India was laid by British sometime in 19th century and history of BSNL is linked with the beginning of telecom in India was operated as a Government Of India wing. Earlier it was the part of Post & Telecom (P&T) department. In 1975 the Department of Telecom (DOT) was separated from P&T. In 1990 the telecom sector was opened up by Government for private investment, therefore it became necessary to separate the government policy wing from operations wings. The Government Of India corporatized the operations wing of DOT on October 01, 2000 and named it as Bharat Sanchar Nigam Limited (BSNL) .

BSNL Bharat Sanchar Nigam Ltd. formed in October, 2000, is World's 7th largest Telecommunications Company providing comprehensive range of telecom services in India: Wire line, CDMA mobile, GSM Mobile, Internet, Broadband, Carrier service, MPLS-VPN, VSAT, VoIP services, IN Services etc.

Bharat Sanchar Nigam Limited (known as BSNL, India Communications Corporation Limited) is a public sector communications company in India. It is the India's largest telecommunication company with 24% market share. Its headquarters are at Bharat Sanchar Bhawan, New Delhi. It has the status of Mini-ratna - a status assigned to reputed Public Sector companies in India.BSNL has installed Quality Telecom Network in the country and now focusing on improving it, expanding the network, introducing new telecom services with ICT applications in villages and wining customer's confidence. Today, it has about 47.3 million line basic telephone capacity, 4 million WLL capacity, 20.1 Million GSM Capacity, more than 37382

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fixed exchanges, 18000 BTS, 287 Satellite Stations, 480196 Rkm of OFC Cable, 63730 Rkm of Microwave Network connecting 602 Districts, 7330 cities/towns and 5.5 Lakhs villages. BSNL is the only service provider, making focused efforts and planned initiatives to bridge the Rural-Urban Digital Divide ICT sector. In fact there is no telecom operator in the country to beat its reach with its wide network giving services in every nook & corner of country and operates across India except Delhi & Mumbai including inaccessible areas of Siachen glacier and North-eastern region of the country.

BSNL cellular service, CellOne, has more than 17.8 million cellular customers, garnering 24 percent of all mobile users as its subscribers. That means that almost every fourth mobile user in the country has a BSNL connection. In basic services, BSNL is miles ahead of its rivals, with 35.1 million Basic Phone subscribers i.e. 85 per cent share of the subscriber base and 92 percent share in revenue terms. BSNL has more than 2.5 million WLL subscribers and 2.5 million Internet Customers who access Internet through various modes viz. Dial-up, Leased Line, DIAS, and Account Less Internet (CLI). BSNL has been adjudged as the NUMBER ONE ISP in the country.

BSNL has set up a world class multi-gigabit, multi-protocol convergent IP infrastructure that provides convergent services like voice, data and video through the same Backbone and Broadband Access Network. At present there are 0.6 million DataOne broadband customers. The company has vast experience in Planning, Installation, network integration and Maintenance of Switching & Transmission Networks and also has a world class ISO 9000 certified Telecom Training Institute. BSNL plans to expand its customer base from present 73 millions lines to 125 million lines and infrastructure investment plan to the tune of Rs. 733 crores (US$ 16.67 million) in the next three years. Today, BSNL is India's largest Telco and one of the largest Public Sector Undertaking with estimated market value of $ 100 Billion. The company is planning an IPO with in 6 months to offload 10% to public in the Rs 300-400 range valuing the company at over $100 billion.

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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 testing. These 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 computer test N.E. number of that particular telephone number. The telephone numbers are also disconnected in the MDF because of some specific reason.

PARTS OF THE MDF:

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-> Horizontal side -> Vertical side

HORIZONTAL SIDE: It is again subdivided in to two parts -> Exchange side -> Line 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 core 1 core = 4 bunch 1 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.

Fig: NE in MDF

-> 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.

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

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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 using 100 pair underground cable. This is how the present day telephone system works. Different exchanges have different architectures of switching call routing and other features.

fig: vertical frame in MDF

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SALIENT FEATURES:

OCB stands for organ control bhersion. Digital switching system developed by CIT ALCATEL of France. OMC & S/N duplicated. Varieties of service provided are: basic telephony, ISDN, Mobile, Videotext etc. Supports different types of signaling system. Max. no. of junctions may be 60000 and 35 types of cards can be used. Less space requirement. Automatic fault recovery and remote monitoring. Environmental requirement is not very stringent.

MAJOR UNITS OF OCB SYSTEM:1. Subscriber Connection Unit (CSN)

A CSN basically consists of 1 basic rack and 3 extension racks capacity of CSN is 5000.Subs may be analog and digital.

2. TRUNK & JUNCTION CONNECTION UNIT (SMT)

It is the interface between switching network and junctions from other exchanges (or remote connection unit).

3. SWITCHING MATRIX

The Switching matrix is a single stage ‘t’ made up of host switching matrix and branch selection & amplification function, SMX is duplicated.

4. AUXILLIARY EQUIPMENT CONTROL STATION (SMA)

It consists of frequency receiver/generator conference call CCTS, tone generators etc,

5. CONTROL UNIT (SMC):

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The six control units are as under: Multi register (MR) for connecting and disconnecting calls. Translator (TR) for storing exchange database. Charging unit (TX) for carrying out charging jobs. Marker (MQ) for performing connection & disconnection of subscribers. Ccs-7 controller (PC) for carrying out routing & traffic management

functions. Matrix system handler (GX) for monitoring connection in S/N.

It is OMC for supervising functions of different units and for taking suitable actions at the event of faults. Magnetic disks each of capability 1.2 GB for various stages.

5.TAX (Trunk auto exchange) This section deals when a caller picks up the receiver, gets the dial tone and how the call is made and processed.

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The call is transmitted from telephone to:

Caller /

D.P / Pillar

/ MDF /

Exchange /

Tax / Exchange /

MDF \

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Pillar \

D.P \

Receiver

There are two types of media:

Guided Media (OFC) Un-Guided Media.

6.1.Fiber Optics:

The use and demand for optical fiber has grown tremendously and optical-fiber applications are numerous. Telecommunication applications are widespread, ranging from global networks to desktop computers. These involve the transmission of voice, data, or video over distances of less than a meter to hundreds of kilometers, using one of a few standard fiber designs in one of several cable designs.

ADVANTAGES OF FIBRE OPTICS: Fiber Optics has the following advantages :

SPEED: Fiber optic networks operate at high speeds - up into the gigabits BANDWIDTH: large carrying capacity DISTANCE: Signals can be transmitted further without needing to be "refreshed" or

strengthened. RESISTANCE: Greater resistance to electromagnetic noise such as radios, motors or

other nearby cables. MAINTENANCE: Fiber optic cables costs much less to maintain.

Fiber Optic System : Optical Fibre is new medium, in which information (voice, Data or Video) is transmitted through a glass or plastic fibre, in the form of light, following the transmission sequence give below :

(1) Information is Encoded into Electrical Signals. (2) Electrical Signals are Coverted into light Signals. (3) Light Travels Down the Fiber. (4) A Detector Changes the Light Signals into Electrical Signals. (5) Electrical Signals are Decoded into Information.

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- Inexpensive light sources available. - Repeater spacing increases along with operating speeds because low loss fiber are used at high data rates.

Fig: 4.1 Fiber optic system

6.2.OFC SPLICING

Splices are permanent connection between two fibres. The splicing involves cutting of the edges of the two fibres to be spliced.

Splicing Methods The following three types are widely used :

1. Adhesive bonding or Glue splicing. 2. Mechanical splicing. 3. Fusion splicing.

Adhesive Bonding or Glue Splicing

This is the oldest splicing technique used in fibre splicing. After fibre end preparation, it is axially aligned in a precision V–groove. Cylindrical rods or another kind of reference surfaces are used for alignment. During the alignment of fibre end, a small amount of adhesive or glue of same refractive index as the core material is set between and around the fibre ends. A two component epoxy or an UV curable adhesive is used as the bonding agent. The splice loss of this type of joint is same or less than fusion splices. But fusion splicing technique is more

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reliable, so at present this technique is very rarely used.

Mechanical Splicing

This technique is mainly used for temporary splicing in case of emergency repairing. This method is also convenient to connect measuring instruments to bare fibres for taking various measurements. The mechanical splices consist of 4 basic components : (i) An alignment surface for mating fibre ends. (ii) A retainer (iii) An index matching material. (iv) A protective housing

A very good mechanical splice for M.M. fibres can have an optical performance as good as fusion spliced fibre or glue spliced. But in case of single mode fibre, this type of splice cannot have stability of loss.

Fusion Splicing The fusion splicing technique is the most popular technique used for achieving very low splice losses. The fusion can be achieved either through electrical arc or through gas flame.The process involves cutting of the fibres and fixing them in micro–positioners on the fusion splicing machine. The fibres are then aligned either manually or automatically core aligning (in case of S.M. fibre) process. Afterwards the operation that takes place involve withdrawal of the fibres to a specified distance, preheating of the fibre ends through electric arc and bringing together of the fibre ends in a position and splicing through high temperature fusion.

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Broadband in telecommunications refers to a signaling method that includes or handles a relatively wide range of frequencies, which may be divided into channels or frequency bins. Broadband is always a relative term, understood according to its context. The wider the bandwidth, the greater the information-carrying capacity. In radio, for example, a very narrow-band signal will carry Morse code; a broader band will carry speech; a still broader band is required to carry music without losing the high audio frequencies required for realistic sound reproduction. A television antenna described as "normal" may be capable of receiving a certain range of channels; one described as "broadband" will receive more channels. In data communications a modem will transmit a bandwidth of 56 kilobits per seconds (kbit/s) over a telephone line; over the same telephone line a bandwidth of several megabits per second can be handled by ADSL, which is described as broadband (relative to a modem over a telephone line, although much less than can be achieved over a fiber optic circuit, for example).

IN DATA COMMUNICATIONS:

Broadband in data communications can refer to broadband networks or broadband Internet and may have the same meaning as above, so that data transmission over a fiber optic cable would be referred to as broadband as compared to a telephone modem operating at 56,000 bits per second.

However, broadband in data communications is frequently used in a more technical sense to refer to data transmission where multiple pieces of data are sent simultaneously to increase the effective rate of transmission, regardless of actual data rate. In network engineering this term is used for methods where two or more signals share a medium.

IN VIDEO:

Broadband in analog video distribution is traditionally used to refer to systems such as cable television, where the individual channels are modulated on carriers at fixed frequencies. In this context, baseband is the term's antonym, referring to a single channel of analog video, typically in composite form with an audio subcarrier. The act of demodulating converts broadband video to baseband video.

However, broadband video in the context of streaming Internet video has come to mean video files that have bitrates high enough to require broadband Internet access in order to view them.

Broadband video is also sometimes used to describe IPTV Video on demand.

IN DSL:

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The various forms of Digital Subscriber Line (DSL) services are broadband in the sense that digital information is sent over a high-bandwidth channel above the baseband voice channel on a single pair of wires

IN ETHERNET:

A baseband transmission sends one type of signal using a medium's full bandwidth, as in 100BASE-T Ethernet. Ethernet, however, is the common interface to broadband modems such as DSL data links, and has a high data rate itself, so is sometimes referred to as broadband. Ethernet provisioned over cable modem is a common alternative to DSL

BSNL is in the process of commissioning of a world class, multi-gigabit, multi-protocol, convergent IP infrastructure through National Internet Backbone-II (NIB-II), that will provide convergent services through the same backbone and broadband access network. The Broadband service will be available on DSL technology (on the same copper cable that is used for connecting telephone), on a countrywide basis spanning 198 cities.

In terms of infrastructure for broadband services NIB-II would put India at par with more advanced nations. The services that would be supported includes always-on broadband access to the Internet for residential and business customers, Content based services, Video multicasting, Video-on-demand and Interactive gaming, Audio and Video conferencing, IP Telephony, Distance learning, Messaging: plain and feature rich, Multi-site MPLS VPNs with Quality of Service (QoS) guarantees. The subscribe will be able to access the above services through Subscriber Service Selection System (SSSS)portal. OBJECTIVES

To provide high speed Internet connectivity (upto 8 Mbps) To provide Virtual Private Network (VPN) service to the broadband customers To provide dial VPN service to MPLS VPN customers. To provide multicast video services, video-on-demand, etc. through the Broadband

Remote Access Server (BRAS). To provide a means to bill for the aforesaid services by either time-based or volume-

based billing. It shall provide the customer with the option to select the services through web server

To provide both pre-paid and post paid broadband services.

TECHNICAL CAPABILITY

The Broadband Service will be given through the state of the art Multi Protocol Label Switching (MPLS) based IP Infrastructure, which is designed to provide reliable routes to cover all possible destinations within and outside the country. Layer 1 of the network will consist of a high speed Backbone comprising of 24 powerful Core Routers connected with high speed 2.5 Gbps (STM-16) links. The routers are located on the national DWDM network interfacing at STM-16 optical level to provide for high transmission speeds.

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Advantage of MPLS over other Technologies

MPLS VPN is a technology that allows a service provider like BSNL to have complete control over parameters that are critical to offering its customers service guarantees with regard to bandwidth throughputs, latencies and availability.

Equipment's required in customer premises are• Filter:-The filter separates out the signal for telephone. (Called as Splitter) • Modem:-The modem directs the signal to PC and TV.• Set Top Box (STB)-The STB converts the digital IP based signal to a form

compatible with the TV set. • PC and TV

Equipment's required towards exchange side•DSLAM•BRAS•TIER 1

•TIER 2 • BNG

•MPLS •GATEWAYS

Digital subscriber loop (DSL)• A high speed digital communication line• Has several advantages over other high speed communication solutions.

• DSL runs on existing copper• DSL helps carriers reduce congestion on their voice-switching systems• Very high speed.

Different types of DSL are1. ADSL2. SDSL3. VDSL

4. RADSl

Services available through Broadband:

High speed Internet Access: This is the always-on Internet access service with speed ranging from 256 kbps to 8 Mbps.

Bandwidth on Demand: This will facilitate customer to change bandwidth as per his / her requirement. For example a customer with 256 kbps can change to 1 Mbps during the video Conferencing session.

Multicasting: This is to provide video multicast services for application in distance education, telemedicine etc

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Dial VPN Service: This service allows remote users to access their private network securely over the NIB-II infrastructure.

Video and Audio Conferencing:

Content based Services: Like Video on Demand, Interactive Gaming, Live and time shifted TV

Mobile phones send and receive radio signals with any number of cell site base stations fitted with microwave antennas. These sites are usually mounted on a tower, pole or building, located throughout populated areas, then connected to a cabled communication network and switching system. The phones have a low-power transceiver that transmits voice and data to the nearest cell sites, normally not more than 8 to 13 km (approximately 5 to 8 miles) away.

When the mobile phone or data device is turned on, it registers with the mobile telephone exchange, or switch, with its unique identifiers, and can then be alerted by the mobile switch when there is an incoming telephone call. The handset constantly listens for the strongest signal being received from the surrounding base stations, and is able to switch seamlessly between sites. As the user moves around the network, the "handoffs" are performed to allow the device to switch sites without interrupting the call.

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Cell sites have relatively low-power (often only one or two watts) radio transmitters which broadcast their presence and relay communications between the mobile handsets and the switch. The switch in turn connects the call to another subscriber of the same wireless service provider or to the public telephone network, which includes the networks of other wireless carriers. Many of these sites are camouflaged to blend with existing environments, particularly in scenic areas.

The dialogue between the handset and the cell site is a stream of digital data that includes digitized audio (except for the first generation analog networks). The technology that achieves this depends on the system which the mobile phone operator has adopted. The technologies are grouped by generation. The first-generation systems started in 1979 with Japan, are all analog and include AMPS and NMT. Second-generation systems, started in 1991 in Finland, are all digital and include GSM, CDMA and TDMA.

The nature of cellular technology renders many phones vulnerable to 'cloning': anytime a cell phone moves out of coverage (for example, in a road tunnel), when the signal is re-established, the phone sends out a 're-connect' signal to the nearest cell-tower, identifying itself and signaling that it is again ready to transmit. With the proper equipment, it's possible to intercept the re-connect signal and encode the data it contains into a 'blank' phone -- in all respects, the 'blank' is then an exact duplicate of the real phone and any calls made on the 'clone' will be charged to the original account.

Third-generation (3G) networks, which are still being deployed, began in 2001. They are all digital, and offer high-speed data access in addition to voice services and include W-CDMA (known also as UMTS), and CDMA2000 EV-DO. China will launch a third generation technology on the TD-SCDMA standard. Operators use a mix of predesignated frequency bands determined by the network requirements and local regulations.

In an effort to limit the potential harm from having a transmitter close to the user's body, the first fixed/mobile cellular phones that had a separate transmitter, vehicle-mounted antenna, and handset (known as car phones and bag phones) were limited to a maximum 3 watts Effective Radiated Power. Modern handheld cell phones which must have the transmission antenna held inches from the user's skull are limited to a maximum transmission power of 0.6 watts ERP. Regardless of the potential biological effects, the reduced transmission range of modern handheld phones limits their usefulness in rural locations as compared to car/bag phones, and handhelds require that cell towers be spaced much closer together to compensate for their lack of transmission power.

Some handhelds include an optional auxiliary antenna port on the back of the phone, which allows it to be connected to a large external antenna and a 3 watt cellular booster. Alternately in fringe-reception areas, a cellular repeater may be used, which uses a long distance high-gain dish antenna or yagi antenna to communicate with a cell tower far outside of normal range, and a repeater to rebroadcast on a small short-range local antenna that allows any cell phone within a few meters to function properly.

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Mobile Section: In this section we learnt how mobile communication takes place. There are two ways by which mobile communication takes place,

GSM CDMA

8.1.GSM

INTRODUCTION A GSM system is basically designed as a combination of three major subsystems: the network subsystem, the radio subsystem, and the operation support subsystem. In order to ensure that network operators will have several sources of cellular infrastructure equipment, GSM decided to specify not only the air interface, but also the main interfaces that identify different parts. There are three dominant interfaces, namely, an interface between MSC and the base Transceiver Station (BTS), and an Um interface between the BTS and MS. GSM NETWORK STRUCTURE Every telephone network needs a well-designed structure in order to route incoming called to the correct exchange and finally to the called subscriber. In a mobile network, this structure is of great importance because of the mobility of all its subscribers [1-4]. In the GSM system, the network is divided into the following partitioned areas. • GSM service area; • PLMN service area; • MSC service area; • Location area;

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• Cells.;

Fig: 6.1 GSM Architechture

MS

The MS includes radio equipment and the man machine interface (MMI) that a subscribe needs in order to access the services provided by the GSM PLMN. MS can be installed in Vehicles or can be portable or handheld stations. The MS may include provisions for data communication as well as voice. A mobile transmits and receives message to and from the GSM system over the air interface to establish and continue connections through the system.

BASE STATION SYSTEM The BSS is a set of BS equipment (such as transceivers and controllers) that is in view by the MSC through a single A interface as being the entity responsible for communicating with MSs in a certain area. The radio equipment of a BSS may be composed of one or more cells. A BSS may consist of one or more BS. The interface between BSC and BTS is designed as an A-bis interface. The BSS includes two types of machines: the BTS in contact with the MSs through the radio interface and the BSC, the latter being in contact with the MSC. The function split is basically between transmission equipment, the BTS, and managing equipment at the BSC. A BTS compares radio transmission and reception devices, up to and including the antennas, and also all the signal processing specific to the radio interface. A single transceiver within BTS supports eight basic radio channels of the same TDM frame. A BSC is a

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network component in the PLMN that function for control of one or more BTS. It is a functional entity that handles common control functions within a BTS.

BTS

As stated, the primary responsibility of the BTS is to transmit and receive radio signals from a mobile unit over an air interface. To perform this function completely, the signals are encoded, encrypted, multiplexed, modulated, and then fed to the antenna system at the cell site. Trans-coding to bring 13-kbps speech to a standard data rate of 16 kbps and then combining four of these signals to 64 kbps is essentially a part of BTS, though, it can be done at BSC or at MSC. The voice communication can be either at a full or half rate over logical speech channel. In order to keep the mobile synchronized, BTS transmits frequency and time synchronization signals over frequency correction channel (FCCH and BCCH logical channels. The received signal from the mobile is decoded, decrypted, and equalized for channel impairments. Random access detection is made by BTS, which then sends the message to BSC. The channel subsequent assignment is made by BSC. Timing advance is determined by BTS. BTS signals the mobile for proper timing adjustment. Uplink radio channel measurement corresponding to the downlink measurements made by MS has to be made by BTS.

BTS-BSC Configurations There are several BTS-BSC configurations: single site; single cell; single site; multicell; and multisite, multicell. These configurations are chosen based on the rular or urban application. These configurations make the GSM system economical since the operation has options to adapt the best layout based on the traffic requirement. Thus, in some sense, system optimization is possible by the proper choice of the configuration. These include Omni directional rural configuration where the BSC and BTS are on the same site; chain and multidrop loop configuration in which several BTSs are controlled by a single remote BSC with a chain or ring connection topology; rural star configuration in which several BTSs are connected by individual lines to the same BSC; and sectorized urban configuration in which three BTSs share the same site amd are controlled by either a collocated or remote BSC.

BSC The BSC, as discussed, is connected to the MSC on one side and to the BTS on the other. The BSC performs the Radio Resource (RR) management for the cells under its control. It assigns and release frequencies and timeslots for all MSs in its own area. The BSC performs the intercell handover for MSs moving between BTS in its control. It also reallocates frequencies to the BTSs in its area to meet locally heavy demands during peak hours or on special

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events. The BSC controls the power transmission of both BSSs and MSs in its area. The minimum power level for a mobile unit is broadcast over the BCCH. The BSC provides the time and frequency synchronization reference signals broadcast by its BTSs. The BSC also measures the time delay of received MS signals relative to the BTS clock. If the received MS signal is not centered in its assigned timeslot at the BTS, The BSC can direct the BTS to notify the MS to advance the timing such that proper synchronization takes place.

MSC As stated, the main function of the MSC is to coordinate the set up of calls between GSM mobile and PSTN users. Specifically, it performs functions such as paging, resource allocation, location registration, and encryption. Specifically, the call-handling function of paging is controlled by MSC. MSC coordinates the set up of call to and from all GSM subscribers operating in its areas. The dynamics allocation of access resources is done in coordination with the BSS. More specifically, the MSC decides when and which types of channels should be assigned to which MS. The channel identity and related radio parameters are the responsibility of the BSS, The MSC provides the control of interworking with different networks. It is transparent for the subscriber authentication procedure. The MSC supervises the connection transfer between different BSSs for MSs, with an active call, moving from one call to another. This is ensured if the two BSSs are connected to the same MSC but also when they are not . In this latter case the procedure is more complex, since more then one MSC in involved. The MSC performs billing on calls for all subscribers based in its areas. When the subscriber is roaming elsewhere, the MSC obtains data for the call billing from the visited MSC. Encryption parameters transfers from VLR to BSS to facilitate ciphering on the radio interface are done by MSC. The exchange of signaling information on the various interface toward the other network elements and the management of the interface themselves are all controlled by the MSC. Finally, the MSC serves as a SMS gateway to forward SMS messages from Short Message Service Centers (SMSC) to the subscribers and from the subscribers to the SMSCs. It thus acts as a message mailbox and delivery system.

VLR The VLR is collocated with an MSC. A MS roaming in an MSC area is controlled by the VLR responsible for that area. When a MS appears in a LA, it starts a registration procedure. The MSC for that area notices this registration and transfers to the VLR the identify of the LA where the MS is situated. A VLR may be in charge of one or several MSC LA’s. The VLR constitutes the databases that support the MSC in the storage and retrieval of the data of subscribers present in its area. When an MS enters the MSC area borders, it signals its arrival to the MSC that stores its identify in the VLR. The information necessary to manage the MS is contained in the HLR and is transferred to the VLR so that they can be easily retrieved if so required.HLR

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The HLR is a database that permanently stores data related to a given set of subscribers. The HLR is the reference database for subscriber parameters. Various identification numbers and addresses as well as authentication parameters, services subscribed, and special routing information are stored. Current subscriber status including a subscriber’s temporary roaming number and associated VLR if the mobile is roaming, are maintained. The HLR provides data needed to route calls to all MS-SIMs home based in its MSC area, even when they are roaming out of area or in other GSM networks. The HLR provides the current location data needed to support searching for and paging the MS-SIM for incoming calls, wherever the MS-SIM may be. The HLR is responsible for storage and provision of SIM authentication and encryption parameters needed by the MSC where the MS-SIM is operating. It obtains these parameters from the AUC. The HLR maintains record of which supplementary service each user has subscribed to and provides permission control in granting services. The HLR stores the identification of SMS gateways that have messages for the subscriber under the SMS until they can be transmitted to the subscriber and receipt is knowledge. Some data are mandatory, other data are optional. Both the HLR and the VLR can be implemented in the same equipment in an MSC (collocated). A PLMN may contain one or several HLRs.

AUC

The AUC stores information that is necessary to protect communication through the air interface against intrusions, to which the mobile is vulnerable. The legitimacy of the subscriber is established through authentication and ciphering, which protects the user information against unwanted disclosure. Authentication information and ciphering keys are stored in a database within the AUC, which protects the user information against unwanted disclosure and access. In the authentication procedure, the key Ki is never transmitted to the mobile over the air path, only a random number is sent. In order to gain access to the system, the mobile must provide the correct Signed Response (SRES) in answer to a random number (RAND) generated by AUC.

Also, Ki and the cipher key Kc are never transmitted across the air interface between the BTS and the MS. Only the random challenge and the calculated response are transmitted. Thus, the value of Ki and Kc are kept secure. The cipher key, on the other hand, is transmitted on the SS7 link between the home HLR/AUC and the visited MSC, which is a point of potential vulnerability. On the other hand, the random number and cipher key is supposed to change with each phone call, so finding them on one call will not benefit using them on the next call.

The HLR is also responsible for the “authentication” of the subscriber each time he makes or receives a call. The AUC, which actually performs this function, is a separate GSM entity

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that will often be physically included with the HLR. Being separate, it will use separate processing equipment for the AUC database functions.

EIR (EQUIPMENT IDENTIFY REGISTER)

EIR is a database that stores the IMEI numbers for all registered ME units. The IMEI uniquely identifies all registered ME. There is generally one EIR per PLMN. It interfaces to the various HLR in the PLMN. The EIR keeps track of all ME units in the PLMN. It maintains various lists of message. The database stores the ME identification and has nothing do with subscriber who is receiving or originating call. There are three classes of ME that are stored in the database, and each group has different characteristics. • White List: contains those IMEIs that are known to have been assigned to valid MS’s. This is the category of genuine equipment. • Black List: contains IMEIs of mobiles that have been reported stolen. • Gray List: contains IMEIs of mobiles that have problems (for example, faulty software, wrong make of the equipment). This list contains all MEs with faults not important enough for barring.

8.2.CODE DIVISION MULTIPLE ACCESS (CDMA):INTRODUCTION

Access network, the network between local exchange and subscriber, in the Telecom Network accounts for a major portion of resources both in terms of capital and manpower. So far, the subscriber loop has remained in the domain of the copper cable providing cost effective solution in past. Quick deployments of subscriber loop, coverage of inaccessible and remote locations coupled with modern technology have led to the emergence of new Access Technologies. The various technological options available are as follows :

1. Multi Access Radio Relay

2. Wireless In Local Loop

3. Fibre In the Local Loop

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Different Codes

Walsh Code :

In CDMA the traffic channels are separated by unique “Walsh” code. All such codes are orthogonal to each other. The individual subscriber can start communication using one of these codes. These codes are traffic channel codes and are used for orthogonal spreading of the information in the entire bandwidth. Orthogonality provides nearly perfect isolation between the multiple signals transmitted by the base station.

The basic concept behind creation of the code is as follows:

(a) Repeat the function right

(b) Repeat the function below

(c) Invert function (diagonally)

Long code :

the long pseudo random noise (PN) sequence is based on 242 characteristic polynomial. With this long code the data in the forward direction (Base to Mobile) is scrabled. The PN codes are generated using linear shift registers. The long code is unique for the subscribers and is known as users address mask.

Short Code :

The short pseudo random noise (PN) sequence is based on 215 characteristic polynomial. This short code differentiates the cells & the sectors in a cell. It also consists of codes for I & Q channel feeding the modulator.

Advantages

CDMA wireless access provides the following unique advantages:

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1. Larger Capacity :

let us discuss this issue with the help of Shannon’s Theorem. It states that the channel capacity is related to product of available band width and S/N ratio.

C = W log 2 (1+S/N)

Where C = channel capacity

W = Band width available

S/N = Signal to noise ratio.

It is clear that even if we improve S/N to a great extent the advantage that we are expected to get in terms of channel capacity will not be proportionally increased. But instead if we increase the bandwidth (W), we can achieve more channel capacity even at a lower S/N. That forms the basis of CDMA approach, wherein increased channel capacity is obtained by increasing both W & S/N. The S/N can be increased by devising proper power control methods.

2. Vocoder and variable data rates:

As the telephone quality speech is band limited to 4 Khz when it is digitized with PCM its bit rate rises to 64Kb/s Vocoding compress it to a lower bit rate to reduce bandwidth. The transmitting vocoder takes voice samples and generates an encoded speech/packet for transmission to the receiving vocoder. The receiving Vocoder decodes the received speech packet into voice samples. One of the important feature of the variable rate vocoder is the use of adaptive threshold to determine the required data rate. Vocoders are variable rate vocodes. By operating the vocoder at half rate on some of the frames the capacity of the system can be enhanced without noticeable degradation in the quality of the speech. This phenomenon helps to absorb the occasional heavy requirement of traffic apart from suppression of background noise. Thus the capacity advantage makes spread spectrum an ideal choice for use in areas where the frequency spectrum is congested.

3. Seamless Hand-off :

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CDMA provides soft hand-off feature for the mobile crossing from one cell to another cell by combining the signals from both the cells in the transition areas. This improves the performance of the network at the boundaries of the cells, virtually eliminating the dropped calls.

4. No Frequency Planning :

A CDMA system requires no frequency planning as the adjacent cells use the same common frequency. A typical cellular system (with a repetition rate of 7) and a CDMA system is shown in the following figures which clearly indicates that in a CDMA network no frequency planning is required.

Fig: 7.1 CDMA frequency

Fig: 7.2GSM Frequency

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5. High Tolerance to Interference :

The primary advantage of spread spectrum is its ability to tolerate a fair amount of interfering signals as compared to other conventional systems. This factor provides a considerable advantage from a system point of view.

INTRODUCTION

• Smaller private version of Internet. It uses Internet protocols to create enterprise-wide network which may consists of interconnected LANs. • It may or may not include connection to Internet. • Intranet is an internal information system based on Internet technology and web protocols for implementation within a corporate organization. • This implementation is performed in such a way as to transparently deliver the immense informational resources of an organization to each individual’s desktop with minimal cost, time and effort. • The Intranet defines your organization and display it for everyone to see.

WHO NEEDS AN INTRANET:

In an Intranet environment is used to communicate over two or more networks across different locations.

1. Users having multi-locations with multi-networks. 2. Users having single locations with multi-networks. 3. Users having single locations with single networks.

WHAT’S REALLY COOL ABOUT INTRANET: From a technology point of view, an Intranet is simply beautiful Because:

1. It is saleable. 2. It is Interchangeable. 3. It is platform independent 4. It is Hardware independent. 5. It is vendor independent.

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WHY INTRANET FOR AN ORGANIZATION:

• Quick access to voice, video, data and other resources needed by users. • Variety of valuable applications of Intranet applications improve communication and productivity across all areas of an enterprise.

An Intranet can give immediate access to products specifications, pricing charts and new collateral’s, sales lead, competitive information and list of customer wins Including profit/loss analysis, thus boosting the success of the business.

APPLICATIONS OF INTRANET

1. Publishing Corporate documents Corporate documents such as newsletters, annual reports, maps, company facilities, price lists, product’s information literature can be easily published and propagated across an organization. Intranet technology facilitates efficient, timely and accurate communication across the entire corporate organization and cuts down on the cost of publishing the information on paper every now and then. 2. Access into searchable directories Intranet provides rapid access to corporate phone books and the like. By using this technology, information can be made more widely available. Excellent Mailing Facilities .With Intranet mail products mailing attachment of documents, sound, vision And other multimedia is facilitated. With the evolution of this web technology one-to-many communication has become more effective.

3. Proper Sharing of Information Using Intranet technology, applications such as Bulletin Board Services can help every individual in an organization to put forth his views on various topics and discuss it with others in the organization.

4. Developing Groupware Applications The flow of documents can be automated by incorporating intranet in an organization. Thus the overall efficiency of an organization increases as less manual and paper involvement will be required. Typical examples are sanctioning of expense reports/travel reports, Conference room booking, etc.

FIG: 10.1 TYPICAL INTERANET SETUP

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TECHNICAL OVERVIEW OF THE INTRANET TECHNOLOGY

Intranet runs on open TCP/IP network, enable companies to employ the same type of servers and browser used for World Wide Web for internal applications distributed over the corporate LAN . A typical Intranet implementation involves a high end machine called a server which can be accessed by individual PCs commonly referred to as clients, through the network. The Intranet site setup can be quite inexpensive, especially if your users are already connected by LAN. Most popular Intranet web servers can run on a platform widely found in most organizations. Basic requirements for setting up an intranet site are:

REQUIREMENTS :

Software : • Server : OS can be Windows server, Unix, LINUX .Web Server s/w should be installed • Client : OS can be Windows workstation, LINUX .Web Browser software

HARDWARE:

• Server: 4 GB RAM, 360 GB secondary storage, Pentium processor with CD ROM . • Client: 1GB RAM, 180 GB Secondary storage, Pentium processor .

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SCOPE:

The Wi-MAX certification mark is given to product that pass conformity and Interoperability test for the IEEE 802-16 standard which caters for the Air interface standard for point-to-multipoint broad-band Internet access over a wireless connection. GENERAL DETAILS OF WI-MAX:

Wi-MAX is an acronym that stands for World-wide Interoperability for Microwave Access. It is an ideal method for ISP to deliver high speed broadband to locations where wired connections would be difficult or costly. Wi-MAX delivers a point-to-multipoint architecture. It doesn't require a direct line of sight between the source and endpoint and it has a service range of 50 Kms. It provides a shared data rate of up to 70 Mbps, which is enough to service up to a thousand homes with high-speed access.

THE MAIN ADVANTAGES OF WI-MAX ARE:

• High speed of broadband service upto 70 Mbps. • Wireless rather than wired access, so that it would be a lot less expensive than cable or Digital Subscriber Line (DSL) and much easier to extend to suburban and rural areas. • Broad coverage like the cell phone network instead of small Wi-Fi hotspots , 50 Kms.

There are following, two corresponding Wi-MAX standards:

1. IEEE 802.16-2004 is for fixed point-to-point and point-to-multipoint wireless access. It is akin to a faster, airborne version of Digital Subscriber Line (DSL) or cable-modem services, It is also called first Non Line of Sight (NLOS), Broad-Band Wireless access (BWA) standard. 2. IEEE 802.16e is for mobile wireless access from laptops and hand held. It is analogous to a faster version of third-generation (3G) telecommunications technology. (Wi-Max proponent Intel Corp. has promised 802.16e-enabled laptops by early 2007)

WORKING OF WI-MAX:

Wi-MAX operates similar to Wi-Fi but at higher speeds, over greater distances and for a greater number of users. It consists of following two parts: a) A Wi-MAX tower, similar in concept to a cell-phone tower, and which can provide coverage to a very large area as big as 3,000 square miles (~8,000 square km). b) A Wi-MAX receiver, and antenna could be like a PCMCIA (Personal Computer Memory Card International Association) card, or they could be built into a laptop similar to Wi-Fi access.

It can provide two forms of wireless service:

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a) The non-line-of-sight, Wi-Fi sort of service, where a small antenna on your computer connects to the tower. In this mode, Wi-MAX uses a lower frequency range - 2 GHz to 11 GHz (similar to Wi-Fi). As lower-wavelength transmissions are not as easily disrupted by physical obstructions they provided non line of sight coverage.

b) The line-of-sight service, where a fixed dish antenna points straight at the Wi-MAX tower from a rooftop or pole. The line-of-sight connection is stronger and more stable, so it is able to send a lot of data with fewer errors. Line-of-sight transmissions use higher frequencies, with ranges reaching a possible 66 GHz. At higher frequencies, there is less interference and lots more bandwidth as shown in Figure 12(b).1

Fig 12(b).2 Working of Wi-Max

WI-MAX (IEEE 802.16) SPECIFICATIONS:

• Range: 30 miles (50-kms) radius from base station. • Speed: 70 Mbps. • Line-of-sight not needed between user and base station. • Frequency bands: 2 to 11 GHz and 10 to 66 GHz (licensed and unlicensed Bands)

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This is a communication system that connects customers to the Public Switched Telephone Network (PSTN) using radio frequency signals as a substitute for conventional wires fsor all or part of the connection between the subscribers and the telephone exchange.

Countrywide WLL is being offered in areas that are non-feasible for the normal network.

Helping relieve congestion of connections in the normal cable/wire based network in urban areas.

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1. Connecting the remote and scattered rural areas.2. Limited mobility without any air-time charge

BSNL provides leased lines for voice and data communication for various application on point to point basis. It offers a choice of high, medium and low speed leased data circuits as well as dial-up lines. Bandwidth is available on demand in most cities. Managed Leased Line Network (MLLN) offers flexibility of providing circuits with speeds of nx64 kbps upto 2mbps, useful for Internet leased lines and International Principle Leased Circuits (IPLCs).

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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 successful functioning of ISP. An ISP node where subscribers enter internet, consists of a set of equipments as given

below.1. Access server2. Router3. Modem bank4. LAN (Local Area Network) components5. Security server6. Rack, console & power supply7. Network management agent.8. Help desk

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