Bsnl Training Report

2012 BSNL TRAINING REPORT

Ishaan Gupta REG-BSE/24 Branch - Electronics Maharaja Agrasen Institute of Technology, psp Area, Sector22,Rohini, Delhi-110085 ALTTC, BSNL, GHAZIABAD

Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP

PREFACE Practical training in an industry is an essential part of an engineering curriculum towards making a successful engineer, as in an industry only a student can realize the theory thought in classroom and it also gives an exposure to modern technology. In the field of Electronics Computer Computer engineering there has been been rapid development to support the ever increasing volume information, so Electronics students has an opportunity during Training period to knowledge about the latest technologies. The training period of 6 weeks is not much sufficient to take complete knowledge of technology used but one is expected to identify components, the process flow in an industry for high efficiency and about the knowledge of product technology. Practical knowledge means the visualization of the knowledge, which we read in books. For this we perform experiments and get observations. Practical knowledge is very i mportant in every field. One must be familiar with the problems related to that field so that we may solve them and became successful person. After achieving the proper goal of life li fe an Engineer has to enter in professional life. According to this life he has to serve an industry, may be public or private sector or self-own. For the efficient work in the field he must be well aware of practical knowledge as well as theoretical knowledge. To be a good Engineer, one must be aware of the industrial environment & must know about management, working in industry, labor problems etc., so we can tackle them successfully. Due to all the above reasons & to bridge the gap between theory and practical, our engineering curriculum provides a practical training course of 28 days. During this period a student in industry and gets all type of experience and knowledge about the working and maintenance of various types of machinery. Since time immemorial, a man has tried hard to bring the world as close to himself as possible. His thirst for information is hard to quench so he has continuously tried to develop new technologies, which have helped to reach the objective.

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Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP The world we see today is a result of the continuous research in the field f ield of communication, which started with the invention of telephone by Graham Bell to the current avatar as we see in the form INTERNET and mobile phones. All these technologies have come to existence because man continued its endeavor towards the objective.

This project report of mine, STUDY OF TRENDS TECHNOLOGIES IN COMMUNICATION

AND NETWORKING has been a small effort in reviewing the trends technologies prevailing. For this purpose, no organization other than BAHRAT SANCHAR NIGAM LIMITED could have been a better choice. I have undergone by 6 weeks of training (after II yr.) at BAHRAT SANCHAR NIGAM

LIMITED, ADAVNACED LEVEL TELECOMMUNICATION TRAINING CENTER, GHAZIABAD (UP). This report has been prepared on the basis of the knowledge which I acquired during my 6 th

st

weeks (14 June to 21 July,2012) training at the Company.

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Acknowledgement: Acknow ledgement:Practical training has an important role in a shaping up an engineering student for practical knowledge how a keeping him update with latest technology. First of all, I would like to express my attitude towards Mr. Yogesh (Class In-charge for 4 weeks) and towards Mr. N.S.

Dham (Class In-charge for next two weeks) for providing me nearly everything I needed during our stay in BSNL. I Also thanks all the faculty members for a giving wonderful and interesting lectures on various topics in the field of Telecommunications.

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Table of Contents PREFACE ........................................................................................................................................................ 2 Acknowledgement:- ...................................................................................................................................... 4 Table of Contents .......................................................................................................................................... 5 Introduction .................................................................................................................................................. 8 COMPANY PROFILE ....................................................................................................................................... 9 DEPARTMENT OF TELECOMMUNICATIONS (DOT) ............................................................................... 9 VISION ............................................................................................................................................. 10 MISSION .......................................................................................................................................... 10 PROFILE OF THE COMPANY’S BUSINESS ..................................................................................................... 13 A.

3.

GLIMPSES GLIMPS ES OF MAIN SERVICES OFFERED ................................... ................. .................................... ................................... ............................ ........... 13 1.

BASIC AND LIMITED MOBILE TELEPHONE SERVICES .......................................... 13

2.

CELLULAR MOBILE TELEPHONE SERVICES........................................................... 13

INTERNET SERVICES ................................. ............... .................................... ................................... ................................... .................................... .................................... .................... .. 13

C.

NETWORK MANAGEMENT .................................................................................. 15

G.

COMPUTERISATION ............................................................................................ 17

CORPORATE SOCIAL RESPONSIBILITIES ...................................................................................................... 18 STRUCTURE AND ABOUT THE EXCHANGES ................................................................................................ 18 CONNECTING SYSTEM ................................................................................................................................. 26 Switching Systems ....................................................................................................................................... 28 Introduction ............................................................................................................................................ 28 Circuit Switching ..................................................................................................................................... 28 Packet Switching ..................................................................................................................................... 28 SWITCHING TECHNIQUES ........................................................................................................................... 29 1.

Time Switching .................................. ................ .................................... ................................... ................................... .................................... ................................... ....................... ...... 29 Output Associated Control .................................................................................................................. 29 Input Associated Control ..................................................................................................................... 29

2.

Space Switching ................................... ................. ................................... ................................... .................................... ................................... ................................... ..................... ... 30

Other Types are: ..................................................................................................................................... 30

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Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP EWSD ........................................................................................................................................................... 31

Contents.................................................................................................................................................. 32 Hardware ................................................................................................................................................ 32 Software ................................................................................................................................................. 32 Technical data......................................................................................................................................... 33 Fig. Time Stage group internal connections ............................................................................................... 45 Fig. Time Stage Group Internal connections ............................................................................................... 45 Transmission Media .................................................................................................................................... 53 Introduction ............................................................................................................................................ 53 Open Wire Systems ................................................................................................................................. 53 Open Wire Line ................................................................................................................................... 53 Twisted Pair Line ................................................................................................................................. 53 Unshielded Twisted Pair ..................................................................................................................... 54 Facts: ................................................................................................................................................... 54 Coaxial Cables ......................................................................................................................................... 54 Microwave Systems ................................................................................................................................ 54 Satellite Systems ..................................................................................................................................... 55 Optical Fiber Cable (OFC) ........................................................................................................................ 56 Development in Optical Fiber Communications ................................................................................. 56 Principle of Ray Propagation ............................................................................................................... 58 Transmission Characteristics ............................................................................................................... 58 Types of Fibers .................................................................................................................................... 59 Step Index Fibers ............................................................................................................................. 59 Graded Index Fibers ........................................................................................................................ 60 General Overview of OFC .................................................................................................................... 60 Primary Elements of O.F. Communications ........................................................................................ 61 Transmitter Section ......................................................................................................................... 62 L.E.D. vs. LASER as Optical Source ................................................................................................... 62 Drive Circuitry ................................................................................................................................. 62 Receiver Section .............................................................................................................................. 62

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Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP Applications of OFC ............................................................................................................................. 63 Internet ....................................................................................................................................................... 64 Introduction ............................................................................................................................................ 64 Functions of Internet .......................................................................................................................... 64 Transfer of File through Internet ........................................................................................................ 64 Common Term Used in Internet ......................................................................................................... 65 National Internet Backbone (NIB) ........................................................................................................... 65 CELLULAR MOBILE SERVICES ....................................................................................................................... 66 1.

Wireless Wirel ess in Local Loop(WLL) Loop(WL L) .................................. ................. ................................... .................................... ................................... ................................... .................... .. 66 Technical Aspects ................................................................................................................................ 66 Advantages of WLL .............................................................................................................................. 67

2.

CODE DIVISION MULTIPLE MULTIPL E ACCESS ACCES S (CDMA): .................................. ................ ................................... ................................... ................................ .............. 67 What is CDMA? ................................................................................................................................... 68

3.

GLOBAL SYSTEM FOR MOBILE COMMUNICATION COMMUNICATION (GSM) .................. ........................... ................... ................... .................. ................ ....... 68 OBJECTIVES OF GSM SYSTEM.............................................................................................................. 69 GSM NETWORK ELEMENTS AND ARCHITECTURE ............................................................................... 69

4.

rd

3 GENERATION TECHNOLOGY (3G) .............................................................................................. 70 Introduction ........................................................................................................................................ 70 Data Speed .......................................................................................................................................... 71 What is 3G? ......................................................................................................................................... 71

BSNL’s IPTV ............................................................................................................................................. 74 Conclusion ................................................................................................................................................... 76 Glossary ....................................................................................................................................................... 77

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Introduction Today, BSNL is the No. 1 telecommunication company and the largest public sector undertaking of India and its responsibilities includes improvement of the already impeccable quality of telecom services, expansion of telecom services in all villages and instilling confidence among its customers. Apart from vast network expansions, especial emphasis has given for introducing latest technologies and new services like I-NET, INTERNET, ISDN (INTEGRATED SERVICES SERVICES DIGITAL NETWORK), IN (INTELLIGENT NETWORK), CDMA, GSM and WLL (WIRELESS IN LOCAL LOOP), BROADBAND, BROADBAND, 3G services etc. Now BSNL has also entered in mobile communication. BSNL has all the new services send technological t echnological advantages, 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. The administration is fully aware of the challenges lying ahead and quite committed to provide the latest and best telecom services by their continued support and active co-operation.

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COMPANY PROFILE

Bharat Sanchar Nigam Limited (BSNL) is India's leading telecommunications provider and the country's largest public-sector firm. BSNL provides local-exchange access and domestic long-distance services through a network of more than 45 million access lines covering most of India. It also offers wireless communications, data and Internet services, as well as business voice and data services. The company is still controlled by the government, as is one of India's other large phone companies, Mahanagar Telephone Nigam Limited (MTNL). Plans to merge the two companies have been discussed but seem to be on hold.

HIGHLIGHTS 

Bharat Sanchar Nigam Limited has a vast reservoir o f highly skilled and

Experienced work force of about 3,57,000 personnel. 

We believe that our staff, which is one of the best trained manpower in the

telecom sector, is our biggest asset. 

To meet the technological challenges, employees are trained for technology up-gradation modernization, computerization, etc. in BSNL's training Centers spread across Country.



To apex training centers of BSNL i.e. Advance level Telecom Training Center (ALTTC) at Ghaziabad and Bharat Ratna Bhimrao Telecom Training Center at Jabalpur are comparable to any world class Telecom Training Center.

Moreover, 43 zonal training centers and a National Academy of Telecom Finance and Management have been running for several years now. 

Different curriculum runs in these centers to impart technology based training, Training for Attitudinal change, basic educational and skill development, Program etc.

DEPARTMENT OF TELECOMMUNICATIONS (DOT) Till 31st December, 1984, the postal, telegraph and telephone services were managed by the Posts and Telegraphs Department. In January 1985, two separate Departments

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Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP for the Posts and the Telecommunications Te lecommunications were created. The accounts of the department, initially, were maintained by the Accountant General of the P&T. However, by April 1972, the telecommunications accounts accounts were separated. Simultaneously the department also starte d preparing the balance sheet annually. With the takeover o f the accounts from the audit and delegation of larger financial powers to the field units, internal Financial Advisers were posted to all the circles and units.

Constitution: The Telecommunication Board consisted of the Secretary Telecommunications, who was the Chairman with Member (Finance), Member (Operations), Member (Development), Member (Personnel) and Member (Technology). The Telecom Commission Commission was constituted in 1989. The Commission has the the DoT Secretary as its Chairman with Member (Se rvices), Member (Technology) and Member (Finance) as its full time members. The Secretary (Finance), Secretary Secretary (DoE), Secretary (Industries) and Secretary (Planning Commission) are part time members of the Commission. The Department in 1986 reorganised the Telecommunication Circles with the Secondary Switching Switching Areas as basic units. This was implemented in a phased manner. Bombay and Delhi Telephones were separated to create the new entity called Mahanagar Telephone Nigam Ltd. (MTNL). On 1st October 2000, Department created BSNL, a new entity to operate services in different parts of the country as a public sector unit.

VISION To become the largest Telecom Service P rovider in South East Asia. 

It is defined as an organization’s dream, which it wants t o realize in the long run say 5-10 year time-frame.



A dream which a company sincerely attempts to make a reality.

While it is not necessary to have a Vision statement, it makes sense to have o ne so that all efforts, energy and resources get directed in realizing this Vision.

MISSION - To provide world class State-of-art technology telecom services on demand at affordable price. - To provide world class telecom infrastructure to develop country’s economy. 

Mission is the path taken to realize t he Vision. For example if leading a prosperous life after graduation is the vision of parents for their son, mission could be to get the son admitted in an engineering college so as to realize that vision.

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Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP PARTICULARS OF THE ORGANISATION Date of

Incorporated on 15.9.2000, vide Registration No. 55-107739, dated the

incorporation

15 September, 2000 and became entitled to commence business with

th

th

effect from 19 September, 2000. The Company (BSNL) took over the .business of providing telecom services and network management throughout the country except t he metro cities of Delhi and Mumbai of the e rstwhile service providing departments of the Govt. of India, i.e., the Departments of Telecom Services and Telecom Operations i.e. 1.10.2000 pursuant to an MOU signed between the BSNL and the Govt. of India.

Type of Company

Government Company under Section 617 of t he Companies Act, 1956.

Administrative

Govt. of India, Ministry of Communication and Information Technology,

Ministry

Department of Telecommunications. Telecommunications.

Details of

The entire share capital of the Company is held by the Govt. of India

Disinvestments Shareholding

Government of India is holding holding 100% of the share capital of the Company

pattern Listing with Stock

Not applicable, as the BSNL is an unlisted company

Exchanges

Share Capital

Authorized Capital – Rs.17,500 crores, divided into 1,000,00 ,00,000[One Thousand Crores] Equity Shares of Rs.10/- each; and 750,00,00,00 0 [Seven Hundred and Fifty Crores] Preference Shares of Rs.10/- each Paid Up Share Capital - Rs.5,000/- crores of Equity Shares Shares and Rs.7,500/crores of Preference Share Capital

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PROFILE OF THE COMPANY’S BUSINESS A. GLIMPSES OF MAIN SERVICES OFFERED 1. BASIC AND LIMITED MOBILE TELEPHONE SERVICES BSNL is the leading service provider in t he country in the Basic Telephone Services. As of now more than 35 million Direct Exchange Lines & more than 2.2.Million telephones in the Limited Mobile telephone Services are existing. BSNL has provides a number of attractive tariff packages & Plans which shall further strengthen its subscriber base.

2. CELLULAR MOBILE TELEPHONE SERVICES BSNL’s GSM Technology based Cellular Mobile Network has reached a long way, covering more st

than 6400 towns, with a subscriber base of over 1.54 crore as on 31 Jan. 2006 out of which 1.16 Crore cellular telephones are in the prepaid segment .

3. INTERNET SERVICES BSNL offers Dialup and Broad Band Internet services to the customers by Post-paid service with the brand name ‘Net one’, and pre-paid service with the brand name ‘Sancharnet’. The post-paid service is a CLI based access service, currently operational in 100 cities. Sancharnet is available on local call basis throughout India to ISDN and PSTN subscribers. The Internet Dhaba scheme of the Company aims to further promote Internet usage in rural and semi urban areas. To keep pace with the latest and varied value added services to its customers, BSNL uses IP/MPLS based core to offer world wor ld class IP VPN services. MPLS based VPNs is a very useful service for Corporate, as it reduces the cost involved as well as the complexity in setting up VP Ns for customers networking. As on 31.03.2005, your Company’s total Internet customer base was 17,98,089 and total Internet Dhabas were 4143. A total of 708594 dial up Internet connections have been given during 2004-2005, against a target of 7 Lakhs. BSNL plans to give 1215980 more dial up connections during the year 2005-06. As on 31.1.2006, there were 2367404 internet subscribers working in BSNL net work. BSNL has launched its Broadband Services under the brand name ‘DataOne’ on 14/1/ 2005. This offers services like High Speed Internet Access with speed ranging from 256 Kbps to 8 Mbps. Other services like streaming video, Video on Demand, Bandwidth on demand etc., have also been planned. As on 31.12.2005, there were more than 356000 broad band connection provided by the BSNL. There are plans to give 2 million and 3 million connections in 2006 and 2007 re spectively.

4. INTELLIGENT NETWORK

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Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP Intelligent Network Services is a service that incorporates several value added facilities, thoroughly designed to save time and money, and e nhance productivity. At present, your company offers Free Phone (FPH), Premium Rate Service (PRM), India Telephone Card (ITC), Account Card Calling (ACC), Virtual Private Network (VPN), Universal Access Number (UAN) and Tele voting IN services. With the commissioning of five numbers of new technology IN Platforms (Four General purpose and One Mass Calling) at Kolkata, Bangalore, Ahmadabad and Hyderabad, the India Telephone Card facility and new value added services are being provided throughout the country. Activation of these new IN platforms had increased the sale of ITC Cards taking the figure to Rs.265 crores in 2004 -05 alone.

5. IP TV Service First started in Japan in 2002. Popular in France, South Korea, Germany, Hongkong etc., France is leading in IPTV having more than 1.7 million IPTV viewers, Global IPTV subscribers base will reach 14 .5 million in 2007 and will be approximately 63 million by 2010.

6. Third Generation (3G) Wireless Technology Capability to support circuit and packet data at high bit rates: 

144 kilobits/second or higher in high mobility (vehicular) traffic



384 kilobits/second for pedestrian traffic



2 Megabits/second or higher for indoor traffic

Support of multimedia services/capabilities: 

Fixed and variable rate bit traffic



Bandwidth on demand



Asymmetric data rates in the forward and r everse links



Multimedia mail store and forward



Broadband access up to 2 Megabits/second

B. DEVELOPMENT OF RURAL TELECOM NETWORK 1. Rural DELs

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Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP As on 31.03.2005, in BSNL’s network, a total of 1.356 Crore rural te lephone connections were working. As on 31.1.2006, there are 1.425 Crore rural telephones working in BSNL network. network.

2. (a)Village Public Telephones (VPTs) & RCPs:BSNL, in its unstinted efforts to make the slogan ‘Connecting India’, a reality, had provided VPTs in 5,18,992 villages up to 31.03.2005. The Company entered into an agreement with USO Fund for expansion of rural telecom network by November 2007, by providing VPTs in 66,822 undisputed, undisturbed, accessible and inhabited villages having population more than 100 as per Census, 1991 in the country. BSNL provided VPTs in 5,28,886 villages up to 31.01.2006. There are plans to replace all MARR VPTs in the country . As of now total 123194 MARR VPTs already replaced in the country by BSNL. BSNL also committed to provide the Rural Community Phones as per the USO Fund agreement. As of now around 13713 RCPs already provided by BSNL.

2 (b)Public Telephones:There are more than 2 million PCOs working in the BSNL Network out of which around 1 million PCOs are having STD/ISD.

C. NETWORK MANAGEMENT BSNL is committed to provide a robust state of the art infrastructure that will provide stable and superior services to its customers. Accordingly, the MLLN network covering more than 2 00 cities was made operational in May 2004. Since then, about 22000 circuits have bee n provided on this network. This has provided high level of stability to the leased circuits and capability to offer N X 64 Kbps circuits. Keeping in view the growing demand of leased circuits, the network is being expanded to cover about 50 more locations and additional capacity at many existing locations is also being provided. To improve the operational efficiency of CCS 7 signaling, stand-alone signaling transfer point (SSTP) equipment is being procured. This will also enable the Company to measure signaling traffic of other operators, who are using its signaling network for exchanging messages, especially with regard to cellular services. BSNL has more than 4.7 Lakhs Route Kilometer s of optical fiber network in the country & has installed capacity more than 6.4 million lines for the TAX meant for the STD/ISD network.

D. Setting up KU Band VSAT network As regards the KU Band VSAT network equipment, the hub of this network is being set up at Bangalore, The equipment has been installed and expected to be commissioned shortly. This will help your Company, to become a service provider with all types of media equipment i.e. OFC, Microwave and satellite for provision of bandwidth, this will also enable the Company to offer composite solutions to its customers.

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Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP What is V-SAT? It can be defined as a class of very small aperture Intelligent Satellite Earth Station suitable for easy onpremise installation, usually operating in conjugation with a large size HUB earth station. Capable of supporting a wide range of two ways integrated Telecom Services. It has the following components: 1) Micro Earth Station 2) Mini Earth Station 3) Personal Earth Station 4) Roof Top Terminal 5) Customer Premises Terminal

ADVANTAGES OF V-SAT 1) Can be located in user premises/rooftop/backyard and hence eliminates last mile problems. 2) Superior quality satellite based data services. 3) Quick implementation time. 4) Reliable communication. 5) Broadcast feature on satellite communication. 6) Communication to different areas. 7) Flexibility for network and changes. 8) Service in distance insensitive. 9) Low cost.

E. Policy on transmission network maintenance Telecom Circles have large transmission networks. To improve the maintenance of transmission network, guidelines for route parties and ve hicles have been formalized. Telecom Territorial Circles are also being connected with computerized network for booking of transmission system faults, with a view to improve follow up and faster restoration of faults.

F. Annual Maintenance contracts for switching system & WLL Comprehensive AMC, which includes hardware and software maintenance and upgrade, has been arranged with the respective equipment suppliers. Initial feedback suggests that, as a result of preventive and corrective maintenance support, the performance of switches is improving. Difficulties in entering into AMC with rural WLL equipments suppliers have been resolved and procedures streamlined so that

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Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP adequate maintenance support becomes available. As a result, the performance of WLL network is improving. AMC arrangements have also been made with suppliers of FWTs and hand held terminals.

G. COMPUTERISATION Implementation of Inter Operator Billing and Accounting system (IOBAS) has been completed. Your Company plans to provide CDR based Customer Care and Convergent Billing system. This will help Company in providing effective and efficient billing & customer care solutions for its fixed line subscribers. It envisages building of country wide intranet to reduce the cost of operation, increase realization, stop leakage of revenue and minimize frauds, besides providing round the clock best customer care services to the Company’s subscribers.

Call center facility has been introduced for 71 SSAs, which is a single point approach for addressing all customer needs cum grievances. Web based Public grievance Management System has been implemented for speedy disposal and monitoring of public grievances. Web based Inventory Management package has also been introduced, through which, material management functions are being computerized gradually in different circles. Online Mobile Bill viewing facility has been made available to all Cell One Mobile Customers (all States) through Company’s Portal (http://bsnl.in). Duplicate Telephone bill viewing facility for landline telephone has also been made available at many places through Websites of respective telecom circles.

H. OBLIGATIONS 1. Towards customers and dealers To provide prompt, courteous and efficient service and quality of products/services at fair and reasonable services.

2. Towards employees 

Develop their capability and advancement through appropriate training and career planning



Expeditious redressed of grievances



Fair dealings with recognized representatives of employees in pursuance of healthy trade union practices and sound personnel policies

3. Towards the Society –Corporate Social Responsibilities

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Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP CORPORATE SOCIAL RESPONSIBILITIES BSNL is committed to provide quality Telecom Services at affordable price to the citizens of the remotest part of the Country. BSNL is making all effort to ensure that the main objectives of the new Telecom Policy 1999 (salient points indicated below) are achieved:

Access to telecommunications is of utmost importance for achievement of the country's social and economic goals. Availability of affordable and effective communications for the citizens is at the core of the vision and goal of the new Telecom policy 1999. Strive to provide a balance between the provision of universal service to all uncovered areas, including the rural areas, and the provision of high-level services capable of meeting the needs of the country's economy encourage development of telecommunication telecommunication facilities in remote, hilly and tribal areas of the country;

Transform in a time bound manner, the telecommunications sector to a greater competitive environment in both urban and rural areas providing equal opportunities and level playing field for all players.

STRUCTURE STRUCTURE AND ABOUT THE EXCHANGES EXCHANGES All telephone subscribers are served by automatic exchanges, which perform t he functions the human operator. The number being dialed is stored and then passed to the exchange’s central computer, which in turns operates the switching to complete the call or routes it a higher level le vel switch for further processing. Today’s automatic exchanges uses a pair of computers, one running the program that provides services and the second monitoring the operation of the first, ready to take over in a few seconds in the event of equipment failure. Various exchanges present in BSNL are: C-DOT E-10B OCB283 (Exchange & TAX) EWSD (Exchange & TAX) All exchange has some purposes and some basic structural units, which are: 1. subscriber’s connection unit 2. Switching network (CX)

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Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP 3. Control unit 4. OMC (Operational & maintenance Control)

STRUCTURE OF THE EXCHANGE

ETM (Translator and Interpreter)

OMC

Switch

M.D.F. (Main Distribution Frame)

Exploitation Room

For smooth working of an exchange following unit are very important: 1. Computer Unit: Unit: - it it deals with additional services of the exchange to to the customers customers

with the

help of computers. 2. Power Plant:- to feed proper power supply to exchange 3. AC Plant: - to maintain the continuous temperature + or – 2 degree Celsius to the digital switch (exchange). 4. MDF: - to connect switch (exchange) with the ex ternal environment (subscriber) i.e. it is the interface between subscribers and exchange.

1.

Computer unit: as the name specified it is the main part of the exchange that deals with the all services

provided by the exchange to the customers with the help of computer. It also provides the updated data to all other part of the exchange. The customers are using the services se rvices of the exchange by using the internet also gets connected to the main server present this room via an internet room. It mainly consists of the servers that are providing the different services. The main servers of

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Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP this room are:IVRS is used for the change number services provided by the exchange. CERS are provided by the ex change to avoid the problems that the users ar e facing the repairing of telephone. In this system when the user enters its complained it gets directly entered t o the server and user is allotted with an id number. LOCAL DIRECTORY ENQUIRY is another services provided by the exchange, by using this; subscribers calls the particular number and gets the directory enquiry. The server pre sent in the main computer room provides this service. INTERNET DIRECTORY ENQUIRY is the latest service by the exchange. In this type of service makes it enquiry using the internet, which gets connected to the main server at the internet room in the exchange and further to the main server in the computer room.

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

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

ii.

Charging- Discharging Unit: - the batteries we are using in the power room need timely charging. As soon as the AC power supply is on, we make use of the charging unit present in the power room. The slowly charging of the batteries is known as the trickle charging. But sometimes 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.

iii.

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

iv.

Engine Room:-we know that the batteries are the instant source of supply but we cannot use it for much larger time, thus for this, we have an engine to generate the

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Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP power supply. They are of 885 K VA. Thus, this room controls the supply of the engine.

UPS OPERATING MODES: UPS system has three operating mode which can be designated as 1. Normal mode 2. Emergency mode 3. Recovery mode I.

NORMAL MODE: The rectifier charger draws power from the ac mains & convert it into DC. This DC power is

supplied to the inverter which converts it back into AC power to feed the critical load connected to the output of the inverter. A small amount of D C owner is also supplied to the battery which is connected to the output of the rectifier charger. The battery is thus kept in a fully charged condition by the rectifier charge. In this condition the battery is said to be o n float across the rectifier charger. In this mode the battery does not supply any power to the inverter.

II.

EMERGENCY MODE: Emergency mode occurs when there is an interruption in the AC input to the rectifier charger.

Interruption like voltage dips below the limit acceptable to the re ctifier charger to fall. But the input of the inverter cannot fall because the battery is across inverter input & it maintains the voltage. AC mains is interrupted, the source of the inverter input current gets instantaneously transferred from the

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Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP rectifier charger to the battery when the output voltage generated by the rectifier charger falls below the battery voltage. The battery which was earlier on float (charged) instantaneously goes into discharge & then supplies power to the inverter till the AC mains resumes or the battery gets fully discharged. During this mode current cannot flow back from the battery into the AC mains because the voltage reverse biases the diodes or THYRISTORS in the rectifier charger.

III.

RECOVERY MODE: The recovery mode commences when the AC mains resumes after the interruption. When the

generated voltage of the rectifier exceed the battery voltage. The input current of the inverter gets instantaneously transferred from the battery to t he rectifier charger. During this mode the r ectifier charger not only supplies power to the inverter but also supplies charging current to the battery to restore the charge lost by the battery during the emergency mode. When the battery gets fully charged, the charging current decreases progressively and the battery reverts to the float mode and the UPS to the normal mode. The duration of the recovery mode depends on the extent of battery discharged, approximately 10 to 20 hours depending on t he battery specifications and the design of the rectifier charger.

3. AC PLANT (CENTRAL AIR CONDITIONER) CONDITIONER) for the function of electrical equipment, cooling system is basic requirement. The basic advantages of cooling systems are followingIt provides provides the thermal stability stability so that the temperature temperature does not reach reach the tolerance limit limit electronic equipment. It saves equipment from dust so to avoid malfunction of equipment’s. It protects equipment from excess humidity which can caused rusting of equipment.

22

of

Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP The basic unit of measurement used in the industry is known as “ton of refrigeration” (TR) which is equivalent to the heat extracted extracte d in 24 hours for converting thousands kg of liquid to ice at zero degree. The compressor is the heart of the t he AC system and the costliest. It increases the pressure and temperature 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 a cylinder and piston arrangement. For capacity more than 120 TR, centrifugal compressors are used. 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 t he evaporator. The refrigerant then passes through t he evaporator coils, which extract heat out of the ambience.

4. 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 Se ction. For removing the fault of telephone number, we use the testing these testing are T.T.Y. testing, Group test ing, 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. 

ORGANISATION OF THE MDF PARTS OF THE MDF Horizontal side Vertical side a. HORIZONTAL SIDE: It is again subdivided in to two parts Exchange side Line side Description of the horizontal side:RACK: - On the rack, t he tags are situated. One rack is having eig ht 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

23

Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP 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. a.

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

FUNCTION OF MDF: A fixed means of terminating the ext ernal cables. A means for mounting the protective devices for incoming circuits. A convenient point of interception for locating of faults. A means for cross connecting the external circuits to the appropriate Internal circuits. The MDF is properly earthed for the protection of the equipment. The external pairs are area wise te rminated on the line side of the frame, while connection from the equipment is done on the e xchange side in a numerical order. By interconnections at this frame with the help of jumper wire s, any subscriber in any area can be given any exchange number. This MDF mounts De lay Fuses only. • • • •

PROTECTIVE DEVICES : Comprehensive protection against effects of lightning and power line contacts, is achieved in practice by fuses, arresters and he at coils. They are not affected by normal speech and signaling voltage and current but operates when the foreign voltage or current on the line is excessive. The line is then disconnected automatically from the equipment or a connection to earth is For safety precautions fuses are used. Every subscriber line has individual fuse. These fuses are made of GD (gas discharge) tube, which are connected in parallel. These fuses have two sides, one is exchange side and other is subscriber side. Connections between the different tag blocks are made using the jumper wires of red and white colors. GD tubes are connected in parallel while electrical fuses are connected in series. In electrical fuse, when high voltage appears across it, then it will break up the

24

Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP Connection and thus safeguard the system. If GD tube is connected in series, then due to high voltage across any line, the w hole exchange will be disconnected. Thus when GD tubes are connected in parallel, it w ill provide the required facility.

GASE DISCHARGE PROCTECTORS: In case of heavy lightning discharges, gas discharge protectors are used and more consistent voltage is obtained. The gas discharge protector essentially consists of two tungsten electrodes sealed in a special glass envelope containing a mixture of inert gases, mainly neon. One of the electrodes are for connections to the lines and the other is the e arth electrode. If the potential difference across the electrodes rises to a certain critical value (the Striking value) the gas is ionized and becomes conducting. This condition will Continue till the potential difference across the electrodes falls to the extinction voltage value. For voltages less than striking value it will not conduct. For normal operating voltages on the lines, it offers extremely high impedance and thus does not introduce any transmission loss. For equipment side: MDF has many tag blocks of 100 and that numbered from 1 to 100. In a tag block, there are 128 pair wire theoretically. Therefore, total number of Connecting wires are 1024 theoretically. But in practical, there are only 1000 pairs. For equipment side: From ground, a single pair of 400 wires originates, which is divided In 4 pairs of 100 w ires. Practically, each pair is provided with 102 wires. These Exact 2 wires are used in case of any manufacturing defect. For broadband connections, different colored tag blocks are provided. Broadband is used to provide different facilities on land-line phones with high Speed to access them. A grey colored tag block is used for line side while yellow Colored tag block is used on equipment side. These tag blocks has 0 to 47 pairs. In order to know the centre load point.: Cabinet and pillar are provided with capacity as per requirement. The D .P. box is Provided with 10 or 20 or 5 pairs. Now a days, a D.P. box of 5 pairs is used which is wall mount instead of being mounted on pole. To identify any telephone, we require t he following two addresses:1. Exchange/line address 2. Equipment address Exchange address is written in given manner: Vertical number-tag block number-pair number

25

Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP For example 7-5-15 Here, vertical no.=7 Tag block no.=5 Pair no.=15 This gives the address of a telephone in t he exchange. Equipment address is given as:Rack number-tag block number-pair number For example7-6-87 Here,rack no.=7 Tag block no.=6 Pair no.=87 This gives the information about the actual location of telephone equipment. This address is provided to lineman for repairing, in case of any fault. There is a section of fault repairing located in MDF section. When subscriber’s phone is not working, then subscriber call to exchange. For this he dial,198.

CONNECTING SYSTEM EXCHANGE

MDF

Exchange Side

CABINETS

Line Side

SUBSCRIBERS

•

Cables from all the Exchanges reach the MDF

•

From the MDF Underground Jumper Cables go to the Cabinets

* The Capacity of the Cabinets is large around 2000 pairs * If the number of subscribers is small then there is no need for the Cabinets •

26

PILLARS

From the Cabinets the cables go to the Pillars

DISTRIBUTION

Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP *the position of the pillars is chosen such that the le ngth of the wires going to t he DPs is equal in all directions •

From the Pillars the wires go to the DPs

* the capacity capacity of each of the Pillars is about 10 or 15 •

From the DPs the wires go to the subscribers’ homes

When a fault like Phone dead is r eported then first check is made at the MDF

(i)

a Phone Set is inserted on the Line Side, some number is dialed and it is checked

if the conversation takes place properly

(ii)

if the conversation takes place properly then the fault is said to be on the Line

Side (Outdoors)

(iii)

But if there is no Dial Tone then the fault is said to be o n the Exchange side

(Indoors)



The fault in the Outdoors is checked first of all at the DP

If there is dial tone at the Pillar but not in the subscribers home then the fault is in between the DP and the subscribers phone set. 

Otherwise at the Pillar If there is dial tone at the Pillar but not at the DP then

the fault is in between the DP and the Pillar 

Otherwise the phone is checked at the Cabinet If there is dial tone at the t he

Cabinet but not at the Pillar then the fault is in between the Cabinet and the Pillar 

Cabinet

27

Otherwise the only option left is that the fault is in between the MDF and the


Switching Systems Introduction Switching is basically transfer of information from one point to another point with some intelligence or control

or Switching is basically establishing a temporary path or connection between two points or writing at one point of time and reading at another point of time. There are two modes of switching employed in our network.

Circuit Switching In normal service, basically, a circuit between the calling party and the called party is se t up and this circuit is kept reserved till the call is completed. Here two speech time slots are involved i.e one of the caller and the other of the called party. This is called as circuit switching. This is based on the sampling theorem. Voice Frequency Range: 3KHz to 3400KHz According to sampling theorem, Fs>=2*Fh Sampling frequency: 2*4 KHz = 8000 Hz = 8000sample/second Time Period: 125µs On using a PCM Channel Cable, where 3 2 Time slots are available(2 for signaling), So we have 30 Speech time slots available in 125µs. So for one time slot, we have : 3.90µs 32 Time Slots make up one Time Frame.

Packet Switching The information (speech, data etc.) is divided into packets. Each packet containing piece of information also bears source and destination address. These packets are sent independently through the network with the destination address in them. Each packet may follow different path de pending upon the network.

28

Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP SWITCHING TECHNIQUES

1. Time Switching Time Switching involves the interconnection of different - slots on the incoming and outgoing highways by reassigning the channel sequence. Basically it is a Time Slot changer. Time Switch can be operated in two modes: •

Output associated control

•

Input associated control.

Output Associated Control 32 samples of I/C PCM are written cyclically in the speech memory locations in order of time slots of I/C PCM, i.e TS1 is written in location 1, TS2 is written in location 2, and …. The contents of speech memory are read on output PCM in the order specified by control memory. Each location of control memory is rigidly associated with the corresponding time slot of the O/G PCM and contains the address of the TS of incoming PCM to be connected.

Figure 1:OAC

Input Associated Control

Here location of control memory is rigidly associated with the corresponding TS of I/C PCM and contains the address of the TS of O/G PCM to be connected.

29


Figure 2:IAC

2. Space Switching Though the electronic cross points are not so expensive, the cost of accessing and selecting them from external pins in space switch becomes the limitation as the switch size increases.

Other Types are: • Two Dimensional Swithing (Ex: TST,TSSST) • Multiple Stage Time and Space Switching

BSNL uses: EWSD OCB 283 5ESS

30

AXE-10 C- DOT E – 10B


EWSD

EWSD Main Processor and Office Switch

1. General Overview EWSD (E lektronisches lektronisches W ähl ähl system Digital in German, Electronic Digital Switching System/Electronic World Switch Digital in English) is one of the most widely installed telephone exchange systems in the world. EWSD can work as a local or tandem switch or combined local/tandem, and for landline or mobile phones. It is manufactured by Siemens AG, who claims that EWSD switches perform switching for over 160 million subscriber lines in more than 100 countries. DeTeWe bought its first EWSD under license in 1985 for remote switching. Bosch built its first EWSD as a local exchange in 1986. Deutsche Telekom, formerly Deutsche Bundespost, the largest German telephone company, uses EWSD and System 12 (Alcatel), the former more than the t he latter. In 2007, Nokia Corporation and Siemens AG formed the new company Nokia Siemens Networks, and responsibility of further development and shipments of the EWSD system is dependent on this new company.

31

Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP Contents • • •

1 Hardware 2 Software 3 Technical data

Hardware Main subsystems are: • • • • • • •

CP (Central Processor) MB (Message Buffer) CCNC (Common Channel Network Control) LINE (Analog Line Group) LTG (Line Trunk Group) DLU (Digital Line Unit) SN (Switching Network)

All system units are redundant so the inactive side can take over immediately in case of an error. DLU handles analog and ISDN lines and includes codec’s for analog lines, one of the BORSCHT functions for subscriber lines. Digital signals are assigned a time slot. DLU concentrates traffic onto a Line B unit, as well as Primary ISDN and V5.2 connections. Supervision and address signaling (dial pulse, DTMF) are also integrated in the DLU. For PCM-30 (E-1) connections to other exchanges, Line C Units are used, which also handle signaling including SS7, MFC R2 signaling, IKZ (dial pulse), and E&M. he Switching Network consists of 4 space division stages of 16x16 switches, and a time division section with 16 stages of 4x4 switches. Control is provided by the CP Co-ordination Processor. There are the following kinds of Co-ordination Processors: • • • • •

CP103 with max 22,000 call attempts in the busy hour CP112 with max 60,000 call attempts in the busy hour CP113D with max one million call attempts in the busy hour CP113C with max six million call attempts in t he busy hour CP113E with max ten million call attempts in t he busy hour

Software The software of EWSD is called APS (Automatic Program System). The APS is on a hard drive and includes the operating system, developed by Siemens in cooperation with Bosch. It is predominantly written in the CHILL language. Application software is switch specific and serves among other things traffic management, path search, and call charging. Support software serves translating programs,

32

Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP binding modules as well as administration of libraries for generating data. Operating and data communication software serve for co-operation of maintenance centers and switching centers.

Technical data • • • • • • • • •

Number of access lines: to 250,000 Number of feeder lines: 240,000 Traffic connection: 25,200 Call attempts in busy hour: 10 million Operating voltages: -48V -60V -90V Rate zones: 127, for each zone of 6 tariffs Tariff change-over at 15 minute intervals Space requirement with 10,000 access lines: 35 square meters 15-25 *C Temperature

1. INTRODUCTION OF EWSD Switching network (SN) performs the switching function for speech as well as for m essages in an EWSD exchange. For this purpose it is connected to LTGs and CCNC for speech/data and to CP (through MB) for exchange of control information. Switching network with ultimate capacity up to 63 LTGs is called SN DE4. For larger exchanges SN DE5.1 is used which can connect up to 126 LTGs. Similarly SN DE5.2 can connect up to 252 and SN DE5.4 up to 504 LTGs.

DLU

LTG(B)

LTG(C) CCNC

MB SYP

CP CCG

OMT MDD

PRINTER

MTU

SN

Figure 1. Position of Switching Network in EWSD

33

Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP 2. BLOCK DIAGRAM OF EWSD EWSD switching system structure chart

DLU

LTG

SN

SSNC

CCNC

MB

CP

CCG

Net Manager

34

Digital line unit •

SLM(A,D,X,I) - subscriber line modules

•

DLUC - Digital line unit controller

Line trunk group

Switching network

Signaling system network control

Common channel network control

Message buffer

Coordinating processor •

BAP - base processor

•

CAP - call processor

•

CMY - common memory

•

IOC- I/O controller

•

AMP - ATM bridge processor

•

B:CMY0(1) - common memory access bus

Central clock generator

Network management system

Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP 3. GENERAL FEATURES Switching network is provided in capacity stages SN: 63LTG to SN: 5 04LTG, i.e. up to 63 LTGs can be connected or, via other intermediate capacity stages, up to 504 LTGs can be connected. The modularly expandable SN has negligibly negligibly small internal blocking and can be be used in EWSD exchanges of all types and sizes. The self-monitoring switching network uses a uniform through connection format. Octets (8 bit speech samples) from the incoming time slots are switched to the outgoing time slots leading to the desired destination fully transparently. This means that each bit of all octets is transmitted to the output of the switching network in the way that it appears at the input (bit integrity). For each connection made via the switching network, the octets have the same sequence at the output as at the input (digit sequence integrity). The switching network’s full availability makes it possible for each incoming octet to be switched at any time to any outgoing highway at the output of the switching network. The t ime slots used in switching network for making through-connections make up a 64 Kbit/s connection path. All of the switching network’s internal highways have a bit rate of 8192 bits/s (Secondary Digital Carriers, SDCs). 128 time slots with a transmission capacity of 64 Kbits/s each (128x64 = 8192 Kbits/s) are available on each 8192 Kbits/s highway. Separate cables e ach containing several (eight or sixteen) such internal highways, are used for each transmission direction. All exte rnally connected highways also have the same uniform bit rate. The switching network combines the numerous switching network functions in a few module types. These modules work at very high through-connection bit rates; 8192 Kbits/s and some even at 32768 Kbit/s. For example 1024 connections can be switched simultaneously through a space stage with 16 inputs and 16 outputs. Although these highly integrated switching network modules switch a large number of connections with a high degree of reliability, the EWSD switching networks are always duplicated. The amount of space needed for the switching network in the EWSD exchange is still very low despite this duplication. Two different switching network versions have been supplied in India: *

Switching network

[SN]

supplied with first 110K order.

*

Switching network B

[SN (B)] supplied with subsequent orders.

4. Position and Functional Structure Switching network is connected to LTGs and CCNC for speech/data and to CP (through MB) for exchange of control information. Figure 1 shows the position of switching network in EWSD exchange with reference to other equipment.

35

Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP For security reasons, entire SN is duplicated. The two sides of SN (SN0 and SN1) are called planes. The external highways for both transmission directions i.e. between the switching network and one LTG or between t he switching network and one Message Buffer Unit (MBU) are identified as follows as shown in figure 2. *

message exchange between the LTG SDC: LTG interface between SN and LTG: time slot 0 for message and coordination processor (CP) as well as between two LTGs, time slot 1 to 127 for subscriber connections.

*

SDC: CCNC interface between the SN and the common channel signaling network (CCNC):

for common channel signaling. *

SDC: TSG interface between SN and a message buffer unit unit assigned to CP (MBU: LTG) for message exchange between the CP and the LTGs as well as between the LTGs.

*

SG C of the CP for setting up and clearing SDC: SGC between the SN and an MBU: SGC connections.

Switching network in EWSD exchanges uses time and space switching and therefore it is functionally divided into Time Stage Group (TSG) and Space Stage Group (SSG). SN D E4 with capacity stage SN: 63LTG has a TST structure and TSG/SSG division is not applicable in this case. TSGs and SSGs are interconnected through internal 8 Mb/s interfaces called SDC:SSG. TSGs of both planes are connected to SSGs of both planes, and thus these provide further security. Each TSG and SSG have its own ow n Switch Group Control(SGC) that is connected to CP via MB through interfaces SDC:SGC.

36

Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP SN LTG 1

TIME STAGE GROUP

SDC:LTG

SPACE STAGE GROUP

OF SN:DE 5 SDC:SSG

OF SN:DE5

LTG n

OR

SDC:LTG

SN:DE4 SDC:SSG

CCNC

CP

SDC:CCNC

MB SDC:TS MBU

MBU

SDC:SG C

SGC

SDC:SG C MBU

Figure 2: SN Internal and External Interfaces

37

SGC

Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP TABLE 1: SN Capacity Stages

Capacity stages of

SN:63LTG

SN:126LTG

SN:252LTG

SN:504LTG

switching network

(DE 4)

(DE 5.1)

(DE 5.2)

(DE 5.4)

Switchable traffic(E)

3150

6300

12600

25200

30000

60000

125000

250000

No. of trunks

7500

15000

30000

60000

Structure

TST

TSSST

TSSST

TSSST

Connectable no. of

63

126

252

504

or

or

or

or

62+1

125+1

251+1

503+1

Local Exchanges No. of lines Transit Exchanges

LTGs or LTG+CCNC

5.

Capacity Stages The present version of SN is available in capacity stages SN:63LTG, SN:126LTG, SN:252 LTG and

SN:504LTG. Modular structure permits partially equipped equipped SN. Up gradation from DE5.1 to DE5.2 and from DE5.2 to DE5.4 is possible with the help of supplier. SN DE4 is not upgradable to DE5.1 as TSG and SSG are not separate ly identified in SN DE4. The traffic handling capacity, connect ability for various capacity stages of SN are shown in Table 1.

6. Functional Units of SN 7.1

Switching path

The switching network is subdivided into time stage groups (TSG) and space stage groups (SSG). Due to its modular structure, the EWSD switching network can be partially equipped as needed and expanded step by step. The switching network uses the following switching stages:

•

38

one time stage incoming (TSI)

Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP three space stages (SS) and One time stage outgoing (TSO). These time and space stages (functional units), shown in figure 3, are located in the following

• •

module types: • • • • •

Link interface module between TSM and LTG (LIL) time stage module (TSM) link interface module between TSG and SSG (LIS) space stage module 8|15 (SSM8|15) space stage module module 16|16 (SSM16|16)

The switching network capacity stage SN:63LTG, however has a TST structure with only one space stage as shown in figure 4. Module types LIS and SSM 8|15 are not there t here in SN:63 LTG. Further, the modules and the TSGs/SSGs are interconnected A list of the various modules used in SN is given in Table 2.

TSG1

SSG1

TSG0.0 TS0

SS M

LTG

SN0

SSG0.0 LTG

TSO

15|8

MBU:

MBU:

Figure 3: The seven module types in SN: DE5

39

MBU:SG Figure 4: The five module

Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP 7.1.1 LIL & LIS: The receiver components of the LIL and LIS compensate for differences in propagation times via connected highways. Thus, they produce phase synchronization between the incoming information on the highways. These differences in propagation times occur because an exchange’s racks are set up at varying v arying distances to each other. Module LIL is connected on the interface to L TGs and has 4 inputs and 4 outputs while module LIS is connected on the interface to SSG and has 8 inputs and 8 outputs.

6.1.2. TSM: The number of TSMs in a switching network is is always equal to the the number of LILs. Each TSM contains one time stage incoming (TSI) and one time stage outgoing (TSO) (Figure 5). The The TSI and the TSO handle the incoming or outgoing information in the switching network. Between input and output, octets can change their time slot and highway via time Stages. Octets on four incoming highways

TSM

are cyclically cyclically written into into the speech memory of a 512 different time slots). The speech memory areasLIL 0 and 1 are used alternately in consecutive 125-

•

connections to be made determine the octet

0

sequence during read-out. The stored octets are transferred via four outgoing highways.

•

• •

microseconds periods for writing the octets. The

read-out to any one of 512 time slots and then

0

0

TSI or TSO (4x128 = 512 locations corresponding to

LIL

•

TSO

•

0 •

• •

•

SSM16|16 or LIS

•

SSM16|16 or LIS

•

3

Figure 5 : Time stage module (TSM)

6.1.3. SSM8|15 and SSM 16|16: The SSM 8|15 contains contains two space stages as shown in in figure 6. One One space stage is used for for transmission direction LIS  SSM 8|15  SSM 16|16 and has 8 inlets and 15 outlets while a second space stage is used for transmission direction SSM 16|16  SSM 8|15  LIS and has 15 inlets and 8 outlets. Via space stages, octets octets can change their highways between between input and output, but but they retain the same time slot. Space stages 8|15, 16|16 and 15|8 switch the received octets synchronously with the time slots and the 125-microsecond periods. The The connections to be switched change in consecutive consecutive time slots. In this process, the octets arriving on incoming highways are “spatially” distributed to

40

Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP outgoing highways . In capacity capacity stages with a TST structure, the SSM 16|16 Switches the octets received from the TSIs directly to the TSOs.

SSM16|16

SSM8|15

0

0 LIS

TSM

0

0

•

•

•

•

SSM16|16

•

•

SS 8|15

or TSM

0

0

or

LIS SSM8|15

•

• •

•

•

SSM16|16

•

7

14

Figure 6 : Space stage modules (SSM16|16 and SSM8|15)

TABLE 2: List of Modules used in SN

PCB

No. of

No. of

No. of

cards in

cards in

cards in

SN:63

TSG of

SSG of

SN:DE5

SN:DE5

16

-

LTG LIL

16

Remarks

One LIL can connect up to 4 LTGs. The cards LIL and TSM

TSM

16

16

-

are always used in pairs

LIS

-

8

16

This PCB has 8 inlets and 8 outlets. LIS and SSM8|15

41

Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP SSM8|15

-

-

16

are always used in pairs

SSM16|16

4

-

15

Used to cross connect outlets of 16 SSM8/15 to inlets of SSM15/8

LIM

1

1

1 These two PCBs are used

SGC

1

1

1

in the SGC

DCC(B)

2

2

2

Separate shelf is provided for the DCC(B)s in the rack

7.2 Control section: Each TSG, each SSG, and with SN: 63LTG, each switching network side has its own control. These controls each consist of two modules viz. switch group control (SGC) and link interface module between SGC and MBU: SGC (LIM). An SGC consists of a microprocessor with accompanying memory and peripheral components. The main tasks of an SGC are to handle CP commands (such as connection setup and clear down), message generation and routine test execution. Apart from the interface to the me ssage buffer unit (MBU: SGC), an LIM has a hardware controller (HWC) and a clock generator for clock distribution.

7.3Firmware 7.3Firmware The firmware for the switching network is permanently stored in the program memory of each SGC. For this reason, it does not have to be loaded or initialized by the coordination processor (CP). SN firmware is organized in the following manner: • • • •

42

executive control programs call processing programs maintenance programs startup and safeguarding programs

Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP 7.

Switching network (B ) Switching network (B) is a special compact version of switching network wherein a number o f

functional units are integrated over a single module. This arrangement has the following advantages: *

Reduction in shelf space

*

Reduction in number of PCB types

*

Utilization of available space in SN rack for accommodating LTGs

Functionally SN(B) is entirely similar to SN. However, only the following five types of modules are used in SN(B) as shown in table 3 . TSMB: LISB:

Two LILs and two time stage stage modules modules TSMs are combined to form one TSMB. This is formed by combining two LIS functional units in a TSG.

SSM8B: Two LIS and two SSM8|15 functional units in a SSG are combined combined to form one SSM8B. SSM16B: This is formed by combining eight SSM16|16 functional units. SGCB:

TABLE 3:

PCB

Functional units LIM and SGC are combined to form one SGCB.

SN(B) Modules

No. of

No. of cards

No. of cards

cards in

in TSG of

in SSG of

SN(B)

SN(B):DE5

SN(B):DE5

8

-

Equivalent modules in SN

:63LTG TSMB

8

2 X TSM + 2 X LIL

LIS

-

43

4

-

2 X LIS of TSG

Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP SSM8B

-

-

8

2 X LIS of SSG + 2 X SSM8|15

SSM16B

1

-

2

8 X SSM16|16

SGCB

1

1

1

LIM + SGC

DCCMS

1

1

1

Provided in same shelf containing SN/TSG/SSG

8.

Module Frame Layout

10.1

SN:63LTG

One plane of SN: SN: 63LTG is accommodated accommodated in one frame consisting consisting of two shelves. The arrangement of of modules in module frame for SN:63LTG SN:63LTG is shown in in figure 9. SN0 or SN1

T L T L T L T L S S I S I S I S I M L M L M L M L S

L I M

S S

M

M

16

16

T L T L T L T L S S I S I S I S I S M L M L M L M L

S G C

S S

M

M

16

16

T L T L T L T L S I S I S I S I M L M L M L M L

T L T L T L T L S I S I S I S I M L M L M L M L

Figure 9: Module Locations (SN:63LTG)

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TSGx-x

SDC: LTG 0

0

1

2

1 2

2

2

14

3

3

3

3

1

1

1

0

0

0

15

TSMB-0 4

0

0

0 1

5

1

6

2

2

7

3

3

1

0

1

2 14 3 15

0 1

56

0

0 1

57

0

1 14

58

2

2

2

59

3

3

3

15

TSMB-7 60

0

61

0 0

0 1

1

1

1 14

62

2

2

2

63

3

3

3

15

Fig. Time Stage group internal connections

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Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP 11.Interconnection of Switching Modules Switching modules in EWSD switching network are connected in a manner so as to ensure nearly full availability. One module LIL, which can handle highways coming from 4 LTGs is connected to 4 inlets of a module TSM on one-to-one basis. Thus these 4 highways coming from 4 LTGs undergo a T-switching function and are then connected to inlets of 4 different LIS modules. The 8 inlets of a LIS module are connected to outlets of 8 different TSMs. Two such groups form a Time Stage Group wherein 63 LTGs can be connected. The TSG has 64 outlets coming out of 8 LIS modules. Eight outlets of LIS modules in TSG are connected to 8 inlets of LIS modules in SSG on one-to-one basis. One SSG consists of 16 LIS modules and therefore two TSGs can be connected to one SSG. There i s again one-to-one connection between 8 outlets of LIS modules and 8 inlets of SSM8|15 modules. Fifteen outlets of SSM8|15 and 16 inlets of SSM16|16 are cross connected. Similarly 16 outlets of SSM16|16 and 15 inlets of SSM15|8 are cross connected. All the TSGs of SN are connected to all the SSGs in such a manner as to ensure nearly full availability. The interconnection of TSGs with SSGs in case of SN:504 LTG is shown in figure f igure 15, and that for SN:252 LTG and SN:126 LTG are shown in figure 16.

Interconnection of the modules in SN DE4 is simpler as there are no TSG or SSG. The TSMs are directly connected to SSM16|16 as shown in fi gure 17.

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SN1 SN0 SSM

SSM 0

0

0 1

LIS

8

15

To inputs 0

16 16

of SSM1-13

0

0

0

15

15

14 0

0

0

0 1

LIS

8

15

To inputs 15

16 16

of SSM1-13

LIM

SGC

MBU:SGC

Figure 14: Space Stage Group Internal connections

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LIS

TSGx.0

0

0 1

TSG1 TSG2 TSG3 TSG4

2 3

0

TSG5 TSG6

1

TSGx.1 2

LIS

1 2 3

SSGx.0

4 5 6

3 0

0 1

TSGx.2

TSG1 TSG2 TSG3 TSG4

2 3 0

TSG5 TSG6

1

TSGx.3 2

LIS

1 2 3

SSGx.0

4 5 6

3 0

0 1

TSGx.2

2 3 0 1

TSGx.3 2

> SSG

TSG1 TSG2 TSG3 TSG4 TSG5 TSG6

LIS

1 2 3

SSGx.0

4 5 6

3 0

0 1

TSGx.2

2 3

LIS

TSGx.3

0 1 2

TSG1 TSG2 TSG3 TSG4 TSG5 TSG6

LIS

1 2 3 4

SSGx.0

5 6

3

Figure 15: TSG-SSG interconnection for SN: 504LTG

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LIS

TSGx.0

0

0 1

TSG1

2

TSG2

3

TSG1

5

2

TSG2

6

3

7

0

0

2

TSG1 TSG2

TSGx.3

2

LIS

TSGx.0

LIS

TSGx.0

LIS

1 2 3

SSGx.1

4

0 1

SSGx.0

4

3

LIS

2

1

1

TSGx.2

1

3 0

TSGx.1

LIS

TSG1

5

TSG2

6

3

7

0

0

1

1

2

2

3

3

0

4

1

5

2

6

3

7

LIS

SSGx.0

Figure 16: TSG-SSG interconnection for SN:252 and 126 LTG

49

Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP 12. Functions Three essential functions of switching network namely speech path switching, message path switching and changeover to standby are described below: -

12.1 Speech path switching The switching network switches single channel and broadcast connections with a bit rate of 64 Kbit/s and multichannel connection with nx64 Kbits/s. Two connection paths are necessary per single channel connection (e.g. from calling to called party and from called to calling party). For a multichannel connection, nx2 connection paths are necessary. In broadcast connections, the information is passed from one signal source to a number of signal sinks (no opposing direction). The coordination processor (CP) searches for free paths through the switching network according to the busy status of connection paths stored at that moment in the switching network’s memory. The path selection procedure is always the same and is independent of the capacity stage of the switching network. During path selection, the two connection paths of a call are always chosen so that they will be switched via the same space stage section. A space stage section is a quarter of the space stage arrangement; with an SN: 252 LTG, for example, this corresponds to half a space stage group SSG. After path selection, the CP causes the same connection paths to be switched through in both switching network sides of an SN. The SGCs are responsible for switching the connection paths. In a capacity stage with 63 LTGs, one switch group control participates in switching a connection path; however in a capacity stage with 504, 252, or 126 LTGs, two or three switch group controls are involved. This depends on whether or not the subscribers are connected to the same TSG. The CP gives every involved switch group control setting instructions necessary for the through-connection. These setting instructions always have the same data format. An SGC receives the setting instruction from the CP via the message buffer unit MBU: SGC, the secondary digital carrier SDC: SGC, n an SGC and the CP are exchanged via an LIM. The SGC calculates the setting data using the call processing programs and service routines. The SGC loads the data into registers in the hardware controller (HWC) of the LIM and, via the HWC, controls the setting of desired connection paths in

50

Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP LTG

SN0 TSG0.0

SSG0.0

S

TSO

SSM

E

15|8

E

SN 1 TSG 1.0

SSG 1.0

E TSO

S SSM 15|8

Figure 19 :Example of possibilities for changeover to standby in the switching network capacity stage SN:504LTG, SN:252LTG and SN:126LTG

51

Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP 12.2 Message path switching.

Apart from the connections determined by subscribers by inputting dialing information, the switching network also makes connections between the LTG and the CP. These connections are used to exchange control information; they are setup only once, and then they are always available. For this reason, they are called semi-permanent connections. Via these same connections, the LTGs also interchange message without having to burden the CP’s processing unit. In this manner, a separate line network for the exchange of messages within an e xchange is not necessary. Nailed-up connections and connections for common channel signaling are made on a semi-permanent basis as well.

12.3 Changeover to standby All connection paths are duplicated, i.e. switched through in SN0 and SN1. This provides an alternative route for each e ach connection in case of failure. Figure 19 provides a simplified illustration of the various alternative routes possible in capacity stages with 504, 252, and 126 LTGs. The connection paths are switched in the same manner over both switching network sides (SN0 and SN1). The LTGs accept the incoming octets of the effective e ffective connections (subscriber/ subscriber connections) from only one switching network side. In figure 19, the effective connections lead over SN0. Of note is the duplicated routing between the time stage groups (TSG) and space stage group (SSG). This makes it possible for the TSGs and SSGs to be individually switched over to standby. Switching over to standby is implemented only if errors occur simultaneously in both switching network sides. The effective connections are then lead over routed TSGs and SSGs of both switching network sides 0 and 1. In the switching network capacity stage with 63 L TGs, it is only possible to route the connections over SN0 or SN1. If an error occurs in the switching network, the CP initiates corresponding measures for switching over to standby and issues the corresponding messages. Change over to standby do not interrupt existing connections. Thanks to this duplication principle, all operational measures are easily carried out without impairing traffic (e.g. adding new modules or replacing defective modules).

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Transmission Tr ansmission Media Introduction There are mainly 7 types of o f transmission media through which data is transferred or received. They are: •

Open Wire Systems (OWS)

•

Coaxial Cables

•

UHF System

•

Microwave Systems (µwave)

•

Digital Transmission System(DTS)

•

Satellite System (SAT Comm.)

•

Optical Fibre Cable(OFC)

Open Wire Systems Open Wire Line •

An open wire transmission line is made up of two parallel wires. Nonconductive spacers are used between the wires to separate and support them. The distance between the conducting wires is anywhere between 2 to 6 inches. The advantage of the open wire line is its simplicity in construction. The major disadvantage of the open wire line pair is its high energy loss. Since the wires are not shielded, energy loss via radiation is immense. Additionally, the wire pair is capable of picking up random signals, resulting in inte rference (crosstalk). The open wire transmission line pair is typically used to transmit acoustic waves for telephone applications.

Twisted Pair Line •

A twisted pair transmission line is formed when two individual insulated wire conductors are twisted around one other. The twisting cancels out all electromagnetic interference from ne ighboring sources, such as crosstalk between nearby wire pairs and radiation generate d from a pair of unshielded twisted pair (UTP) transmission lines. Twisted pair lines are shielded to prevent energy loss and external interference. The shielding offered is typically metallic. The advantages of a twisted pair transmission line are its size, flexibility and cost. A pair of twisted transmission lines is less expensive than other types of cables. The disadvantages of a twisted pair cable include stringent installation requirements. This type is not effective during transmission of video data for it is known to cause delays and color defects. The various types of twisted pair cables include loaded twisted pair, unloaded twisted pair, bonded twisted pair and twisted ribbon cables.

53

Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP Unshielded Twisted Pair •

An unshielded twisted transmission line pair consists of two copper wires that are individually insulated. insulated. The insulation is provided by a polyvinyl chloride coating. The wires are twisted more than two times around each other to further reduce re duce external interference and crosstalk. The bandwidth of an unshielded twisted pair is increased by the number of tw ists per segment and the way in which the wires have been twisted. An unshielded twisted pair transmission line is used for te lephonic applications and to connect computer networks. Its major advantage is its flexibility and installation ease. Its major disadvantages include increased external interference and energy loss.

Facts: •

The long distance voice communication till 1950s was almost entirely transported over Open Wire Carrier system.

•

The voice signals for these systems were modulated to a higher frequency and carried through open wire systems.

•

These open wire systems are capable of carrying traffic of three to twelve subscribers at a time.

Coaxial Cables Open-wire transmission lines have the property that the electromagnetic wave propagating down the line extends into the space surrounding the parallel wires. These lines have low loss, but cannot be bent, twisted, or othe rwise shaped without changing their characteristic impedance, causing reflection of the signal back toward the source, cannot be run along or attached to anything conductive, as the extended fields will induce currents in the nearby conductors causing unwanted radiation and detuning of the line. Coaxial lines solve this problem by confining virtually all of the electromagnetic wave to the area inside the cable. They can therefore be bent and moderately twisted without negative effects, and they can be strapped to conductive supports without inducing unwanted currents in them. These cables may be viewed as a type of waveguide. Power is transmitted through the radial electric field and the circumferential magnetic field in the TEM00 transverse mode. This is the dominant mode from zero frequency (DC) to an upper limit determined by the electrical dimensions of the cable.

Microwave Systems

54

Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP Microwaves are widely used for point-to-point communications because their small wavelength allows conveniently-sized antennas to direct them in narrow beams, which can be pointed directly at the receiving antenna. This allows nearby microwave equipment to use the same frequencies without interfering with each other, as lower frequency radio waves do. Another advantage is that the high frequency of microwaves gives the microwave band a very large informationcarrying capacity; the microwave band has a bandwidth 30 times that of all the rest of t he radio spectrum below it. A disadvantage is that microwaves are limited to line of sight propagation; they cannot pass around hills or mountains as lower frequency radio waves can. Microwave radio transmission is commonly used in point-topoint communication systems on the surface of the Earth, in satellite communications, and in deep space radio communications. Other parts of the microwave radio band are used for radars, radio navigation systems, sensor systems, and radio astronomy. In wide band of frequencies around 60 GHz, the radio waves are strongly attenuated by molecular oxygen in the atmosphere. The electronic technologies needed in the millimeter wave band are also much more difficult to utilize than those of the microwave band. The first Microwave system was installed between Calcutta and Asansole. Microwave systems with 60, 300 and 1800 voice channels capacity were inducted into the telecom network subsequently.

Satellite Systems It works for connecting far flung, inaccessible area and island community started in late seventies by Department of Telecommunication. The first Domestic Satellite Network was e stablished by connecting Port-Blair and Car-Nicobar in Andaman & Nicobar Islands, Kavaratti in Lakshadweep islands, Leh in Ladakh region and Aizwal in North Eastern region. These stations were simultaneously linked to the gateway at Delhi and Chennai. This satellite network was commissioned in November 1980 through International Telecommunication Satellite. Satellite Communication capacity increased with launch of INSAT-1 and INSAT-2 series satellites. MCPC - VSAT (Multi Channel per Car rier - Very Small Aperture Terminals) Te rminals) systems were developed and deployed in remote and inaccessible areas of Garhwal region Uttar Pradesh, Himachal Pradesh, Arunachal Pradesh, J&K, Orissa, Sikkim etc. for providing STD

55

Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP facilities. These terminals are linked to earth station generally co-located with the TAX (Trunk Automatic Exchange).

Optical Fiber Cable (OFC) Development in Optical Fiber Communications The visible optical carrier waves or light has been commonly used for communication purpose for many years. Alexander Graham Bell transmitted speech information using a light beam for the first time in 1880. Just after four years of the invention of the telephone Bell proposed his photophone which was capable of providing a speech transmission over a distance of 200m. In the year 1910 Hondros and Debye carried out a theoretical study and in 1920 Schriever reported an experimental work. Although in t he early part of twentieth century optical communication was going through some research work but it was being used only in the low capacity communication links links due to severe affect of disturbances in the atmosphere and lack of suitable optical sources. However, low frequency (longer wavelength) electromagnetic waves like radio and microwaves proved to be much more useful for information transfer in atmosphere, being far less affected by the atmospheric disturbances. With the LASER coming into the picture the research interest of optical communication got a stimulation. A powerful coherent light beam together with the possibility of modulation at high frequencies was the key feature of LASER. Kao and Hockham proposed the transmission of information via dielectric waveguides or optical fiber cables fabricated from glass almost simultaneously in 1966. In the earlier stage optical fibers exhibited very high attenuation (almost 1000 dB/km) which was incomparable with coaxial cables having attenuation of around 5 to 10dB/km. Nevertheless, within te n years optical fiber losses were reduced to below 5dB/km and suitable low loss jointing techniques were perfected as well. The first generation optical fiber links operated at around 850 nm range. Systems operating at 1550nm provided lowest attenuation and these links routinely carry traffic at around 2.5Gb/s over 90 km repeater less distance. The introduction of optical amplifiers like Erbium-doped fiber amplifiers (EDFA) and Praseodymium-doped fiber amplifiers (PDFA) had a major thrust to fiber transmission capacity. The use of Wavelength Division Multiplexing (DWDM) along with EDFA proved to be a re al boost in fiber capacity. Hence developments in fiber technology have been carried out rapidly over recent years. Glass material for even longer wavelength operation in the mid-infrared (2000 to 5000nm) and far-infrared (8000 to 12000nm) regions have been developed. Furthermore, the implementation of active optoelectronic devices and associated fiber components (i.e. splices, connectors, couplers etc.) has also accelerated ahead with such speed that optical fiber communication technology would seem to have reached a stage of maturity within its developmental path.

56


57


Principle of Ray Propagation When light ray is passing from denser (refractive index is higher) dielectric medium to a rarer (refractive index is lower) dielectric medium then from the point of incidence at the interface it bends away from the normal. When the incidence angle is sufficiently high such that the angle of refraction is 90º then it is called critical angle. If light ray falls at the interface of the two m ediums at an angle greater than the critical angle then the light ray gets re flected back to the originating medium with high efficiency (around 99.9%) i.e. total internal reflection occurs.

Transmission Characteristics The transmission characteristics of optical fiber cables play a major role in determining the performance of the entire communication system. Attenuation and bandwidth are the two most important transmission characteristics when the suitability of optical fiber for communication is analysed. The various attenuation mechanisms are linear scattering, non linear scattering, material absorption and fiber bends etc. The bandwidth determines the number of bits of information transmitted in a given time period and is largely limited by signal dispersion within the fiber.

58


Types of Fibers According to the refractive index profile optical fibers can be divided into two categorie s namely Step index fibers and Graded index fibers which are described below.

Step Index Fibers If the refractive index profile of a fiber makes a step change at the core cladding interface then it is known as step index fiber. The core diameter of which is around 50µm. Some physical parameters like relative refractive index, index difference, core radius etc determines the maximum number of guided modes possible in a multimode fiber. A single mode fiber has a core diameter of the order of 2 to 10µm ad it has the distinct advantage of low intermodal dispersion over multimode step index fiber. On the other hand multimode step index fibers allow the use of spatially incoherent optical sources and low tolerance requirements on fiber connectors.

59

Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP Graded Index Fibers The graded index fibers have decreasing core index n(r) with radial distance from a maximum value of n1 at the axis to a constant value n2 beyond the core radius a in the cladding as shown in figure8. The graded index fiber gives best results for multimode optical propagation for parabolic refractive index profile. Due to this special kind of refractive index profile multimode graded index fibers exhibit less intermodal dispersion than its counterpart i.e. multimode step index fibers.

General Overview of OFC Like all other communication system, the primary objective of optical fiber communication system also is to transfer the signal containing information (voice, data, video) from the source to the destination. The source provides information in the form of electrical signal to t he transmitter. The electrical stage of the transmitter drives an optical source to produce modulated light wave carrier. Semiconductor LASERs or LEDs are usually used as optical source here. The information carrying light wave then passes through the transmission medium i.e. optical fiber cables in this system. Now it reaches to the receiver stage where the optical detector demodulates the optical carrier and gives an electrical output signal to the electrical stage. The common types of optical detectors used are photodiodes (p-i-n, avalanche), phototransistors, photoconductors etc. Finally the electrical stage gets the real information back and gives it to the concerned destination.

60

Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP It is notable that the optical carrier may be modulated by either analog or digital information signal. In digital optical fiber communication system the information is suitably encoded prior to the drive circuit stage o f optical source. Similarly at the receiver end a decoder is used after amplifier and equalizer stage.

Primary Elements of O.F. Communications As we can see the t he transmitter stage consists of a light source and associated drive circuitry. Again, the receiver section includes photo-detector, signal amplifier and signal restorer. Additional components like optical amplifier, connectors, splices and couplers are also there. The regenerator section is a key part of the system as it amplifies and reshapes the distorted signals for long distance links.

61

Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP Transmitter Section The main parts of the transmitter section are a source (either a LED or a LASER ), efficient coupling means to couple the output power to the fiber, a modulation circuit and a level controller for LASERs. In present days, for longer repeater spacing, the use of single mode fibers and LASERs are seeming to be essential whereas the earlier transmitters operated within 0.8µm to 0.9µm wavelength range, used double hetero structure LASER or LED as optical sources. High coupling losses result from direct coupling of the source to optical fibers. For LASERs, there are two types of lenses being used for this purpose namely discrete lenses and integral lenses.

L.E.D. vs. LASER as Optical Source A larger fraction of the output power can be coupled into the optical fibers in case of LASERs as they emit more directional light beam than LEDs. That is why LASERs are more suitable for high bit rate systems. It is obvious that LASER is more temperature dependent than LED. LASERs have narrow spectral width as well as faster response time. C onsequently, LASER based systems are capable of operating at much higher modulation frequencies than LED based systems. Typical LEDs have lifetimes in excess of 10^7 hours, w hereas LASERs have only 10^5 hours of lifetime. Another thing is that LEDs can start working at much lower input currents which is not possible for LASERs. So, according to the situation and requirements either LED or LASER can be utilized as an optical source. Now there are a number of factors that pose some limitations in transmitter design such as electrical power requirement, speed of response, linearity, thermal behavior, spectral width etc.

Drive Circuitry These are the circuits used in the transmitters to switch a current in the range of ten to several hundred mili-amperes required for proper functioning of optical source. For LEDs there are drive circuits like common emitter saturating switch, low impedance, emitter coupled, trans-conductance drive circuits etc. On the other hand for LASERs, shunt drive circuits, bias control drive circuits, ECL compatible LASER drive, etc. are noticeable.

Receiver Section It is clear that it includes Photo-detector, low noise front end amplifier, voltage amplifier and a decision making circuit to get the exact information signal back. High impedance amplifier and Transimpedance amplifier are the two popular configurations of front end amplifier, the design o f which is very critical for sensible performance of the receiver. The two most common photo-detectors are p-in diodes and avalanche photodiodes. Quantum efficiency, responsivity and speed of response are the key parameters behind the decision of photo-detectors. The most important requirements of an optical receiver are sensitivity, bit rate transparency, bit patter n independence, dynamic range, acquisition time etc. As the noise contributed by receiver is higher than other elements in the system so, we must put a ke en check on it.

62

Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP Applications of OFC Telecommunications • Long-Distance Transmission • Inter-exchange junction loop (FITL) -- FTTC, FTTB, FTTH • Fiber in the loop • Video Transmission • Television broadcast, cable television (CATV), remote monitoring, etc. • Broadband Services Provisioning of broadband services, such as video request service, home study courses, medical facilities, train timetables, etc. • High EMI areas Along railway track, through power substations can be suspended directly from power line towers, or poles. • Military applications Non-communication fiber optic: e .g. fiber sensors. • Non-communication •

63


Internet Introduction The Internet is not a program, pro gram, not software, not hardware or a big system. It is a group of var ious cooperating computers worldwide interconnected by computer based on TCP\IP communication protocols. People use it to get information over a standard communication link. The hundreds or thousands or millions of computer network are connected to each other for 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 dial up/leased/ISDN network. Users can access GAIS from 99 cities in India by this means.

INTERNET CONNECTIVITY INTERNET TECHNOLOGY

Functions of Internet 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 not working.

These are based on TCP/IP Protocols.

Transfer of File through Internet Suppose a file is to be transmitted on Internet from one computer to o ther ones. •

Break the file in to small packets.

•

Attached destination and source address in o packets

•

Multiplexed and transmit these packets

•

At destination de-multiplex the packets

•

Remove address bits from the packets and assemble the data in to the original file

•

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

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Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP Therefore, it is clear that network hardware sends the packets to specified destination and network software reassembles of communications, the computer network performs the following functions•

Addressing and routing

•

Fragmentation and error correction

•

Data error checking

•

Connectivity control

•

Multiplexing and de-multiplexing

•

Data flow control

•

End users interface etc.

•

The data handling

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

Common Term Used in Internet •

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

•

HTTP: Hypertext transmission Protocol (HTTP) is the communication protocol used to transfer documents 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 of web documents to tell the browser software how to display the document text, link gr aphics and link media.

•

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

•

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

National Internet Backbone (NIB) Networking is a key component of any Internet S ervices Provider (ISP) operations. The networking equipment 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 equipment as given below. 1. Access server 5. Security server .

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2. Router 6. Rack, console & power supply

3. Modem bank 7. Network management

4. LAN components 8. Help desk


CELLULAR MOBILE SERVICES Cellular is one of the fastest growing and most demanding telecommunication applications. 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 and nearly 50% of those subscribers are located in USA. It is forecasted that cellular system using a digital technology will become the universal method of telecommunications. By the year 2005, forecasters predict that t here will be more than 100 million cellular subscribers worldwide.

1. Wireless in Local Loop(WLL) WLL is a communication system that connects customers to the Public Switch Telephone Network (PSTN) using radio frequency signals as substitutes of conventional wires for all part of connection between the subscribers and the telephone exchange. It works on CDMA technique. The local loop is access part of telecommunication network i.e. the part between PSTN switch and subscribers. WLL network application involves uses of radio to replace of the wire link betwe en PSTN switch and subscriber. The radio technology is able to provide same quality of services as that provided by the wires line. Application of wireless loop technology 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 cellular mobile telephone system are available.

Technical Aspects WLL is based on CDMA technique and is entire ly different from GSM. The system for WLL se rvices can be divided in two following parts:-

BSC (Base Switching Centre):- It provides links between BTS & B SM; it consists of different processors, in BSNL it is of SUN Po laris of LG Company. In LG 1 BSC can have 48 BTS? In BSNL we have two types of BSC:-

I.

V-5.2:- This type of BSC cannot switch by itself so it is dependent on local exchange / PSTN for

switching and keeping records of billing etc. BSNL uses this type of BSC for rural areas.

ii.

CCS-7 / R2:- These types of BSC are totally automatic it doesn’t depend on local exchange 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 as receive signal, it

66

Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP works as an amplifier (router) to overcome t he loss in signal in transmission.

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

Advantages of WLL WLL •

The Country wide induction of WLL underway of areas t han are non-feasible for the normal network

•

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

•

Limited the mobility without any airtime charges

•

It has improved signal and reducing the interference

•

Greater capacity than mobile

•

Provides ease of operation, administration & maintenance at lower cost.

The telecommunication is the biggest factor in influencing the speed of life in the moder n age. Today we can get connection with any corner of world through the push button of computer; with the small mobile phone we can send not only the me ssages but also the secret document. As we know that there is positive view behind any mention that it should be helpful in the development of society. But humans have diverted mentality some of them of positive view and some of them of negative view. Where use any invention for the welfare of society but some uses for the satisfaction their disturbed mentality and to earn more and more money whether it may be harmful for the society. They infringe the norms of society and their behavior is condemned as antisocial, immoral and sinful.

2. CODE DIVISION MULTIPLE ACCESS (CDMA): Multiple access system allows a large number of users to share a common pool of radio telephone circuits, like sharing of trunked radio facility. Multiple access radio has similarity to the LAN in which the common channel is available to all users. The circuits are demands assigned i.e. assigned on demand first-cum-first-served basis. The provision of access to t he radio circuits methods of multiple accesses are:

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

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Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP What is CDMA? CDMA, a cellular technology originally known as IS-95, competes with GSM technology for dominance in the cellular world. There are now different variations, but the original CDMA is known as CdmaOne. Latest CDMA global subscriber & operator’s numbers As of December 2002, there were 120 m illion 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 . They refer to variant of usage of a 1.25 MHz channel. 3X uses a 5 MHz channel. Wide band CDMA forms that the basis of UMTS 3G networks, developed originally by Qualcomm, high capacity and small cell radius, employing spread-spectrum technology and special coding scheme characterized by CDMA.

The Telecommunication Industry Association (TIA) in 1993 adopted CDMA. May 2001 there 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 22 countries using cdmaOne technology. Enhancing today’s data capabilities is the 1XRTT CDMA standard this next evolutionary step for cdmaOne operators will provide data rates up to 300 kbps, significant capacity increases as well as extended batteries life for handsets. Worldwide resources are being devoted to r oll out third generation CDMA technology, including multicarrier (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 designed to double current voce capacity and support always on data transmission speed 10 times faster than ty pically available today, some 153.6 kbps on both the forward and re verse links.

3. GLOBAL SYSTEM FOR MOBILE COMMUNICATION (GSM) The GSM Association is a unique organization, with a truly global reach, offering a full range of 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 wireless wire less communication. Throughout the evolution of cellular t elecommunications, various systems have been developed without the benefit of standardized specifications. This presented many problems directly 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 to create a

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Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP common European mobile telephone standard that would formulae the specifications for a panEuropean mobile cellular radio system operating at 900 MHz it is e stimated that many countries outside of Europe will join the GSM partnership.

OBJECTIVES OF GSM SYSTEM One of the important objectives of GSM group is to evolve a unified standard to provide seamless roaming across Europe. Another landmark decision taken by the group is to standardize standardize a digital radio interface for the communication between the mobile handset handset and the radio transmitter / receiver. The design objectives of the GSM system can be briefly states as below: •

Excellent speech quality

•

High security and privacy

•

Low module terminal cost

•

Low service and facilities cost

•

Design of sleek and handled mobile terminals

•

International roaming

•

Wide range of services and facilities

•

Ability to adopt to new and innovative features

•

Narrowband ISDN compatibility

•

Digital Radio

•

High Spectral efficiency

GSM NETWORK ELEMENTS AND ARCHITECTURE 1. i. ii.

Mobile Station (MS) Mobile Terminal or Equipment (MT) Subscriber Identity Module (SIM) Card

2. Base Station Subsystem (BSS) Base transceiver Station (BTS) i. Base Station Controller (BSC) ii. iii.

iv.

Main Station Controller (MSC) Transcoding and Rate Adoption Unit (XCDR/TRAU)

3. Network Switching Subsystem (NSS) Registration i. Authentication and security ii. Location updating iii. Handovers and iv. Routing to roaming subscribers v. 4. Operation and Maintenance Subsystem (OMS)

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Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP i. ii.

Operation and Maintenance Centre – Switch Operation and Maintenance Centre – Radio

5. Enhanced Services Subsystem (ESS) 6. Billing and Customer Care System (B&CCS)

Figure 3: GSM Architecture

rd

4. 3 GENERATION TECHNOLOGY (3G) Introduction Third generation (3G) networks were conceived from the Universal Mobile Telecommunications Service (UMTS) concept for high speed networks for enabling a variety of data intensive applications. 3G systems consist of the two main standards, CDMA2000 and W-CDMA, as well as other 3 G variants

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Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP such as NTT DoCoMo's Freedom of Mobile Multimedia Access (FOMA) and Time Division Synchronous Code Division Multiple Access (TD-SCDMA) used primarily in China.

Data Speed The data speed of 3G is determined based on a combination of factors including the chip rate, channel structure, power control, and synchronization. An example of calculating the theoretical 3G data speed is as follows: W-CDMA assigned code 400-500 Kbps/code. Kbps/code. 6 codes X 400 > 2Mbps (UMTS target for 3G data speed in fixed location)

•

Actual data speeds will vary in accordance with several factors including: •

Number of users in cell/sector

•

Distance of user from cell

•

User is moving or stationary

•

Network operator capacity and network optimization requirements

EV-DO Solutions •

1xEV-DO is a data-only solution, supporting a theoretical data speed of up to 2.457 Mbps

•

1xEV-DV is a data and voice solution, supporting a theoretical data speed of up to 3.072 Mbps

FOMA has two operational modes, supporting a dedicated 64 Kbps connection or a 384 Kbps downlink/64 Kbps uplink best-effort connection.

•

•

TD-SCDMA can operate in 1.6 MHz or 5 MHz mode for 2 Mbps or 6 Mbps respectively.

What is 3G? 3G is the short form for third-generation technology. It is one of the popular mobile phone standards. The services utilizing 3G provide the ability to transmit both voice data such as calls and nonvoice data such as instant messaging, email and video telephony at the same time. Japan was the first country to introduce 3G on a wide scale commercially. In 2005, almost 40 per cent of the subscribers in Japan used 3G services. On t he technical front, 3G services are wide area are a cellular telephone networks unlike IEEE 802.11 networks, which are short range networks meant for Internet access. Now, 3G is being used to provide various services. You have to plug in 3G Data Card into your laptop and can get the fastest available connection, with mobile broadband speeds of up to 1.8 Mbps. It’s neat, compact design makes it easy to use; you can easily swap it between laptops for use at work, home or on the move. m ove. Laptops have a PC Card slot (also known as a PCMCIA slot), or an Ex press Card slot. There is PCMCIA to Express C ard Converter for using 3G broadband; you need 3G Data card, ne twork SIM card, software, user guide.

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72


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Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP BSNL’s IPTV •

First started in Japan in 2002.

•

Popular in France, South Korea, Germany, Hong Kong etc.

•

France is leading in IPTV having more than 1.7 million IPTV viewers

Global IPTV subscriber’s base will reach 14.5 million in 2007 and will be approximately 63 m illion by 2010.

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Conclusion

Hence in the last I can say that taking training in such an organization proved to be very beneficial for me. I learnt quite a lot about electronic exchange, Internet, Land line, WLL, Mobile GSM & 3G, and the basis of processing Exchange. I also got firsthand knowledge of how a Telephone Exchange works. The first phase of training has proved to be quite fruitful. It provides an opportunity to encounter with such huge machines. The architecture of company has various units. They are linked and working of whole plant is controlled make the student realized that engineering is not just learning the structure description and working of various machines. But the greater part is planning proper management.

-------×-------

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Glossary ADM

Add/Drop Multiplexers

ANALOGUE

An electrical signal which is analogous to changing physical quantity measured

BSC

Base Station Controller

BTS

Base Tran receiver Station

C-DOT

Centre for Development of Telemetric

CD Cabinet

Cable Distribution Cabinet

CDMA

Code Division Multiple Access

CKM

Cable conductor kilometer – cable sheath kilometers multiplied by the number of conductor pairs in each cable

CLIP

Calling Line Identification Identification Processing P rocessing

COAXIAL CABLE

A cable with a single wire in the centre of cylindrical conductor forming a pair of carrying electrical signals

CT BOXES

Cable Termination Boxes

DECT

Digital Enhanced Cordless Telecommunications

DEL

Direct exchange lines, one each for every telephone connection

DIGITAL EXCHANGE

The exchange having signals coded into binary pulses and having little or no moving parts

DIU

DECT interface unit

DLC

Digital Loop Carrier

DWDM

Dense Wavelength Multiplexing Terminal

EDX

Electronic Data Exchange

EPABX

Electronic Private Automatic Branch Exchange

ETRP

Electronic Trunk Relay Plates

EWSD TAX

Electronic Wheeler System of Digital Trunk Automatic Exchange

GHz

Giga Hertz

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Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP GSM

Global System for Mobile Communications

HDPE

High density polyethylene

HDSL

High bit rate Digital Subscriber Line

Hertz or Hz

Frequency (cycles per second), named after Heinrich Hertz - usually in ranges of kilo 1000 - KHz, mega 1,000,000 MHz or giga 1,000,000,000 - GHz

IDR

Intermediate Data Rate

ISDN

Integrated Services Digital Network

LDST

Long Distance Satellite Telephone

LOI

Letter of Intent

MARR

Multi Access Rural Radio

MBM

Multi Base Module

Mbps

Mega bits per second denoting digital frequency

MCPC

Multi Channel Per Carrier

MDF

Main Distribution Frame

MUX

Multiplex

NIT

Notice Inviting Tender

NE Lines

Non Exchange Lines

OFC

Optical Fiber Cable

Optical Fiber (OF)

Glass fibers using light waves for transmission transmission of signals

OLA

Optical Line Amplifiers

OYT

Own your telephone

PABX

Private Automatic Branch exchange

PBX

Private branch exchange

PCM

Pulse Code Modulation

PCO

Public Call Offices

PDH

Plesiochronous Digital Hierarchy

PERT Chart

Programmed Evaluation Review Technique Chart

PIJF Cable

Polyethylene Insulated Jelly Filled Cable

PSPDN

Packet Switch Public Data Network

PST

Progressive Stock Taking

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Ishaan Gupta Reg-BSE/24 BSNL,ALTTC,Ghaziabad,UP PSTN

Public Switched Telephone Network

PVC

Polyvinyl chloride

PW

Private Wires

RLU

Remote Line Unit

RSU

Remote Switching Unit

SACFA

Standing Advisory Committee on Radio Frequency Allocation

SDH

Synchronous Digital Hierarchy

SMPS

Switch Mode Power Supply

SRCs

Subscriber Record Cards

SSAs

Secondary Switching Areas

STD

Subscriber trunk dialing

STM

Synchronous Transport Module

TAX

Trunk automatic exchange

TDMA

Time Division Multiple Access – A transmission technique used in digital radio transmission in which the use of a frequency is divided into time slots that are shared amongst several users.

TELEX

TelePrompTer exchange

TTH

Triangular Tubular Hybrid

UHF

Ultra high frequency (300 to 3000 MHz)

VHF

Very high frequency

VPT

Village Public Telephones

VSAT

Very small aperture terminal

WLL

Wireless-in-Local Wireless-in-Local Loop

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79


Certificate This is to certify that ISHAAN GUPTA of ECE from Maharaja Agrasen Insitute of th

Technology, Delhi has successfully completed 6 weeks of Training from 14 June th

to 25 July, 2012 under my guidance and observation.

NP Faculty Niranjan Singh Dhama

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Bsnl Training Report

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