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 class room and it also gives an exposure to modern technology. In the field of Electronics Computer engineering there has 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 28 days 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 important 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 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. The world we see today is a result of the continuous research in the field 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. I have undergone by 28 days of training (after 3RD yr.) at BAHRAT SANCHAR NIGAM LIMITED (B.S.N.L), HISAR, (Haryana) . This report has been prepared on the basis of the
knowledge which I acquired during my 28 days training at Company.
Acknowledgement: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.AMIT SHARMA (Training cum placement officer, GPC, Kota) and towards Mr. GAJENDRA SUJEDIYA (H.O.D., Electronics department, SBCET, Jaipur) for providing me a great opportunity to undertake training at BSNL, Hisar. I would also like to thanks to Mr. Rajkishore Sharma (TTA EWSD, Hisar) and the cooperative management helpful staff for giving me a knowledge of their services and helping me time to time. Last but not least I would like to thanks to training incharge Mr. Balbir Singh (SDE SDOP1, Hisar), BSNL for arranging the training programmer for my practical training. With extreme regards and obligations.
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1.INTRODUCTION 1.1 Overview of the BSNL: BSNL is India's oldest and largest Communication Service Provider (CSP). Currently BSNL has a customer base of 64.8 million (Basic & Mobile telephony). It has footprints throughout India India except for the metropolitan cities of Mumbai and New Delhi which are managed by MTNL . As on March 31 , 2010 BSNL commanded a customer base of 33.7 million Wireline, 3.6 million CDMA-WLL and 27.5 million GSM Mobile subscribers. BSNL's earnings for the Financial Year ending March 31 , 2010 stood at INR 401.8b (US$ 9.09 b) with net profit of INR 89.4b (US$ 2.02 billion). Today, BSNL is India's largest Telco and one of the largest Public Sector Undertaking of the country with authorized share capital of US$ 3.95 billion (INR 17,500 Crores) and networth of US$ 14.32 billion.
1.2 History The foundation of Telecom Network in India was laid by the British sometime in 19th century. The history of BSNL is linked with the beginning of Telecom in India. In 19th century and for almost entire 20th century, the Telecom in India was operated as a Government of India wing. Earlier Earli er it was part of erstwhile Post & Telegraph Department (P&T). In 1975 the Department of Telecom (DoT) was separated from P&T. DoT was responsible for running of Telecom services in entire country until 1985 when Mahanagar Telephone Nigam Limited (MTNL) was carved out of DoT to run the telecom services of Delhi and Mumbai. It is a well known fact that BSNL was carved out of Department of Telecom to provide level playing field to private telecoms.Subsequently in 1990s the telecom sector was opened up by the Government for Private investment, therefore it became necessary to separate the Government's policy wing from Operations wing. The Government of India corporatised the operations wing of DoT on October 01 , 2000 and named it as Bharat Sanchar Nigam Limited (BSNL).BSNL operates as a public sector.
1.3 Interesting Facts:
There are 2 million BSNL mobile connections in rural India (a record, no other connection is as famous as bsnl in rural areas) BSNL is the 1 st company to introduce 3G in INDIA. BSNL supplies phone lines to all other network such as Airtel , Vodafone etc. Largest pan India coverage-over 11000 towns & 3 lakh Villages. India‘s No. 1 wireless service provider with more than 50 Million customers. An incredible speed of 2mbps is only offered by BSNL The only Mobile service available throughout the country including Jammu and Kashmir and NorthEastern states like Arunachal Pradesh, Nagaland , Mizoram etc. 3
2. PRODUCTS AND SERVICES
2.1 SERVICES When it comes to connecting the four corners of the nation, and much beyond one solitary name lies embedded at the pinnacle - BSNL. It is working round the clock to take India into the future by providing world – class telecom services for people of India. Here is an overview of the World Class Services offered by BSNL :
2.1.1 Basic Telephone Services The plain old, countrywide telephone service through 32,000 electronic exchanges, digitalized Public Switched Telephone Network (PSTN) with a host of phone plus value additions.
2.1.2 Internet Keeping the global network of networks connected, the countrywide Internet Services of BSNL under the brand SANCHAR.NET includes internet dialup/ leased access service, for web browsing and E-mail applications. Internet Telephony service is also started under the brand name WEB FONE recently.
2.1.3 ISDN Integrated Services Digital Network service of BSNL utilizes a unique digital network providing high speed and high quality voice, data and image transfer over the same line. It can also facilitate both desktop video and high quality video conferencing.
2.1.4 Intelligent Network Intelligent Network Service offers value added services, such as : 2.1.4.1 Free Phone Service (FPH) 2.1.4.2 India Telephone Card (prepaid card) 2.1.4.3 Account Card Calling (ACC) 2.1.4.4 Virtual Private Network (VPN) 2.1.4.5 Tele-voting 2.1.4.6 Premium Rate Service (PRM) 2.1.4.7 Universal Access Number (UAN) and many more
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2.1.5 I-Net India‘s x.25 based packet switched public data network is operational in 104 cities of the country. It offers x.25 leased, x.28 dial up (PSTN) connection and frame relay services.
2.1.6 Leased Lines and Datacom BSNL provides leased lines for voice and data communication for various applications on point to point basis. It offers a choice of high, medium and low speed data circuits as well as dial up lines. Bandwidth is available on demand in most cities. Managed Leased Line Network (MLLN) offers flexibility of providing circuits with speeds of nx64 kbps upto 2 Mbps, useful for internet leased lines and International Principles Leased Circuits (IPLCs).
2.1.7 Cellular Mobile Service BSNL‘s project of GSM cellular mobile service envisages a customer base of over 4 million and will support applications like Voice Mail, E-mail, Short Message Service (SMS), Cell Broadcast Service, International Roaming, IN Services like Prepaid Card, Premium rate, Free Phone, Universal Access Number (UAN), Split Charging, VPN etc.
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3. ABOUT THE EXCHANGE
All telephone subscribers are served by automatic exchanges, which perform the functions the human operator. The number being dialled is stored and then passed to the exchange‘s central computer, which in turns operates the switching to complete the call or routes it a higher level switch for further processing. Today‘s automatic exchanges uses a pair of computers, one running the program that provides services and the second monitoring the operation of the first, ready to take over in a few seconds in the event of equipment failure.
3.1 Various exchanges present in BSNL are:
3.1.2 E-10B 3.1.3 OCB283 3.1.4 EWSD
For smooth working of an exchange following unit are very important:-
3.2 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 of the exchange by using the internet also gets connected to the main server present this room via an internet room. It mainly consists of the servers that are providing the different services. The main servers of this room are:IVRS is used for the change number services provided by the exchange. CERS are provided by the exchange to avoid the problems that the users are facing the repairing of telephone. In this system when the user enters it‘s complained it gets directly entered to the server and user is allotted with an id number. LOCAL DIRECTORY ENQUIRY is another services provided by the exchange, by using this; subscribers calls the particular number and gets the directory enquiry. The server present in the main computer room provides this service. INTERNET DIRECTORY ENQUIRY is the latest service by the exchange. In this type of service makes it enquiry using the internet, which gets connected to the main server at the internet room in the exchange and further to the main server in the computer room.
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3.3 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 this 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: Batteries: - these are the instant sources of the power as soon as power is gone off. UPS (Uninterrupted Power Supply):- the UPS must give supply to the computer. As we know there is some equipment which can withstand any type of power supply, but there are also some instruments which cannot withstand with this type of power supply, even a microsecond delay will cause the loss of data. 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. Inverter and Converter Unit: - the main use of this system is to change AC mains to DC and vice versa as required by the parts of exchange. Engine Room:-we know that the batteries are the instant source of supply but we cannot use it for much larger time, thus for this, we have an engine to generate the power supply. They are of 885 KVA. Thus, this room controls the supply of the engine.
3.4 CENTRAL AIR CONDITIONER For the function of electrical equipment, cooling system is basic requirement. The basic advantages of cooling systems are followingIt provides the thermal stability so that the temperature does not reach the tolerance limit of 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. The basic unit of measurement used in the industry is known as ―ton of refrigeration‖ (TR) which is equivalent to the heat extracted in 24 hours for converting thousands kg of liquid to ice at zero degree. The compressor is the heart of the AC system and the costliest. It increases the pressure and temperature of the refrigerant gas coming from the evaporator coils by compressing it.
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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 the evaporator. The refrigerant then passes through the evaporator coils, which extract heat out of the ambience.
3.5 MAIN DISTRIBUTION FRAME The primary function of MDF is: The fault of telephone number is removed in the MDF; it is called as Fault Remove Section. For removing the fault of telephone number, we use the testing These testing are T.T.Y. testing, Group testing, etc. For any type of testing firstly we need the vertical no. or the live tester, printer and computer test N.E. number of that particular telephone number. The telephone numbers are also disconnected in the MDF because of some specific reason.
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4. OVERVIEW OF E-10B The main function of a Telephone Exchange is to connect a subscriber‘s link or a trunk to any other line or trunk out of the total number of lines and trunks connected to this exchange. The connection is brought about in accordance with the information given by the calling line (dial) or the incoming trunk (signaling code). In Electrochemical Exchanges, a free physical link (2 wires or sometimes 4 wires for transit) is established between the two junctions. This path is a voice frequency frequenc y circuit like a subscriber‘s line: lin e: In digital time division switching systems like E-10B, the same function is carried out but the analog circuits are first converted into PCM links before they are brought to the switching network. The switching network connects a time slot of any one PCM link of any one time slot of other PCM link connected to it. In this manner, the switching network carries only digital data. As a consequence of the general use of the PCM links in E10B system, the subscriber‘s connection unit can either be in the same location as the switching network or it may be remote.
4.1 General Description: Based on the functions carried out by different parts, an E-10B exchanges can be divided in four blocks as shown in the figure below: -
Fig.4.1
4.2 E-10B Exchange Structure Block 1: Connection Unit Block 2: Time Division Switching Network Block 3: Control Unit Block 4: Operation and maintenance center. This unit is able to handle several exchanges.
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4.2.1. Connection Units: The connection unit‘s compromise basically of equipment directly connected to external interfaces of the system, subscriber lines and circuits and equipment, which sends and receives audio-frequency signaling samples. These units are of following types: -
1. 2. 3. 4. 5.
Local subscriber connection unit . Remote subscriber connection unit . Multiplex connection unit. Frequency sender/Receiver unit . Auxiliary Equipment Rack.
4.3 Time Division Switching Network : The time division-switching network is a 3-stage system (time space time). It provides a 4 W switching between the time slot allocated to the called party and the time slot allocated to the called party. For one call two sample connections are set up. The principal in the switching network is shown below: -
4.4 Control Units: The control units are partly based on dedicated mini-computers and are used to carry out all the switching operations required to set up release connections between subscribers and /or circuits. These units can be classified as follows: -
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4.4.1 Marker The marker is responsible for routing switching messages between the connection units, the switching network and the multi register.
4.4.2 Switching network control unit : The switching network control unit co-ordinates operations executed by the switching network (path finding, connection marking etc.). This involves: Checking the speech paths. Receiving transfer link status indications from each switch module. Connecting and disconnecting speech channels, tones, recorded announcements and signals when ordered to do so by multi-registers or charging units. Checking marking operations.
4.4.3 Multi-register : The multi-register is in charge of the setting up and releasing of calls. It is at the heart of the system and is only control unit, which can take initiative and send orders to other units in real time. It has access to all data from subscribers and trunk circuits (E & M wires) and to all units in the exchange. The main functions of the multi-register involve:
Servicing new call and on-hook conditions on subscriber lines and circuits, detected by connection units. Releasing subscriber lines and circuits. Receiving and sending signals from/to connection units. Ordering the transmission of various tones. Requesting the characteristics of a subscriber line or circuit. Requesting the translator to determine the connection address of the subscriber line or circuit at the exchange, on the basis of directory number. Sending and receiving messages to/from OMC.
The multi-register uses a programmed logic. A call processing register includes 1024 bits (extendable up to 1536 bits) stored in cyclic RAMs with a processing time of 8ms. Each multi-register comprises of 256 registers and can handle the setting up of releasing of 254 calls simultaneously. The two registers (0 & 255 are assigned to routine tasks, i.e., traffic observations. In an exchange the number of multi-registers varies from 2 to 6, depending upon the traffic load. These multi-registers are working on a traffic-sharing basis.
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4.4.4 Translator : The translator provides the multi-registers on request, with data on subscribers and trunks required to setup and release of calls. Data (categories, corresponding between directory number and subscriber or trunk equipment in the exchange) are held in TR files. This data may be written, deleted or modified from the operating and maintenance center with operating requirements. The translator executes the following operations: -
Seeking subscriber‘s lines or circuit class of service data when a new call or on-hook condition is detected. Translating pre-fixes or the first digits dialed by the calling party. Translating translation operations for chaining and overflow or circuit number. Handling translation operations for chaining and overflow routing functions. Managing additional services. Handling all management maintenance and test operations in conjunctions with OMC.
The total capacity of the translator files is 768k words, each of sixteen bits, i.e., 12288 Mbits.
4.4.5 Charging unit : The charging unit handles the subscriber line accounts, computes the number of basic metered units chargeable for a given telephone calls and outputs detailed billing data for subscribers entitled to this service. Multi-registers initiate the charging unit operations. At the start of each telephone call, on receiving instructions form MR, the charging unit seeks and assigns a charging register.
It receives charge-metering pulses from trunk circuits. It orders signal transmission where required. It sends detailed billing messages and observation messages to standby charge recording unit (DSF) where the OMC is down or unavailable. It sends subscriber meter readings (periodically demand from OMC), detailed billing messages and traffic observation messages to OMC. It stores traffic observation data.
Each charging unit can be configured as follows: 1000 charging registers of 512 bits, or 2000 charging registers of 256 bits or a combination of 256 & 512 bits charging registers. Each charging unit can therefore handle up to 2000 calls simultaneously. Charging registers compute the charge for a given telephone call. At the end of the call, the subscriber meter is incremented simultaneously in both changing units and these two values are read periodically by the OMC.
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4.4.6 Standby charge recording unit (DSF): In normal conditions, detailed billing and traffic observation messages are send from the exchange to OMC. In the event of failure of OMC or interruption of the link between the OMC and the monitoring unit, the standby charge-recording unit can receive these messages and record them onto magnetic tape. This unit can also reload the translator memories, the charge rates, and the charge-based data in the charging units. The DSF does not participate in traffic handling functions of the exchange.
4.4.7 Monitoring unit :The monitoring unit is an interface between the OMC and the other units of an E-10B exchange. It has access to all the units and handles the transfer of all the messages between the OMC and the exchange. The messages involve: Message from the OMC to the exchange units:
Operating messages (subscriber line creations, circuit creation etc.). Unit positioning messages. Maintaining messages. Control messages addressed to test modules.
4.5 Operation and Maintenance Center (OMC) (OMC): The E-10B exchange management functions are carried our at the OMC using a nondedicated computer. The main management functions are: 1. Operating functions – Translation memory management, charging functions. 2. Supervision functions – Lock out condition processing subscriber line and set tests, circuit tests, load and traffic observations. 3. Maintenance functions – Exchange equipment-positioning, anomaly and alarm processing, fault location.
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5.OCB-283 (Organ Control Bhersion-283)
OCB-283 is digital switching system, which supports a variety of communication needs like basic telephony, ISDN, interface to mobile, data communication. ALCATEL of France has developed this system. The first OCB-283 exchange of R11 version were commissioned in Brest (France) and Beijing (China) in 1991, first OCB-283 exchange came to India in 1993. The system has been upgraded and current version R20 has fully validated in Jan 1994. The latest version is R24. All new technology switching system, are based on (SPC) stored program control concept. The call processing program is distributed over different control organs of the system and is stored in ROM/RAM of the units. Data required to handle the calls are also managed in RAM of different control units.
5.1 Salient Feature of the system: 1. It is digital switching system; maximum of 2048 PCM‘s can be connected. 2. It supports both analog and digital signal and it do not require separate OFC room. 3. The system supports all the existing signaling system e.g. MF (R2) for E10B, CAS, CCS7. 4. It provides telephony, ISDN, Data Communication. 5. The system has automatic recovery feature when serious fault occurs in control station it gives a message to SMM (OM), the SMM puts this unit O/S, load the software of this unit in a back up unit and brings it into service. 6. Version units of OCB-283 system are connected over token rings MIS, MAS, MAL for fast exchange of information and o avoid complicated links and wiring. 7. The charge accounts of subscriber are automatically saved on the disk once in case of information and to avoid complicated links and wiring 8. The traffic handling capacity of the system is huge depending on the traffic, 200,000 subscribers or 60,0000 circuits. 9. The system is made up of only 35 types of cards excluding CSN cards. 10. It has modular structure so expansive can easily be carried out by adding necessary software and hardware. 11. The SMM‘s are duplicated; one active and other hot stand by. 12. The hard disk is very small in size and has got memory of 1.2 Gb.
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5.2 EXCHANGE SWITCH
ANALOG
DIGITAL
NOKIA
SIEMENS ALCATEL ERICSON--------------
OCB-283
OCB-286
5.3 Main Divisions Of OCB-283 5.3.1 MDF (Main Distribution Frame) - this room is used to distribute the subscriber‘s call according to his request.
Any type of exchange, there is a unit called main distribution frame and is used for interconnection of exchange line and junction unit equipments to external physical lines coming to the exchange. The distribution frame provides easy and flexible interconnection, isolation point for testing, protective devices used for safety of exchange equipment etc.
In MDF, all lines are coming from subscribers, non exchange lines, telex lines and analog junction lines, are terminated on 100 pair pai r krone type tag blocks in which gas discharge disc harge tubes type protective devices are provided to tackle voltages and current surges. These tag blocks are located on one side of the MDF called ―line side‖. On the other side of the MDF called ―exchange side‖ tag blocks re provided for terminating the cables from CSE for subscriber lines and from transmission room for analog junction lines.
5.3.2 TRANSMISSION MEDIA In many communication systems, it is often necessary to interconnect points that are some distances apart from each other. The transmission of information as an electromagnetic signal always occur as a transverse electromagnetic wave. One of the media for transmission is :
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5.3.2.1 Optical Fiber Cable:
The Exploitation Room operates the whole OCB-283 exchange. So it is also known as operational room. My main responsibilities are come under this exploitation room. As in this room all the operations are done through system software by operating different commands over there. I have to operate some of these commands, which are named as under and discussed in detail with the help of example as under: IDABSE
INDIN
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6.COMPARISON BETWEEN OCB-283 AND E-10 B:
6.1CAPACITY 6.1 CAPACITY COMPARISON:
E 10-B 384 10000 49000 4000 No No
CHARACTERISTICS
PCMs Trunks Subscribers Traffic (Erl.) CCS#7 ISDN
OCB-283 2048 60000 200000 25000 Yes Yes
6.2HARDWARE: 6.2 HARDWARE:
CHARACTERISTICS
E 10-B
Subscriber Connection Unit
CSE
SwitchingNetwork
CX MR+TR+TX+ MQ
Call Processing
6.3SUBSCRIBER 6.3 SUBSCRIBER CONNECTION UNITS:
CHARACTERISTICS E 10-B OCB-283
Name Capacity (Erl.) Connected To
CSE 90 CS
CSN 384 SMX
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OCB-283
CSN
SMX MR+TR+T X+MQ+GX
7. EWSD 7.2 General Overview ähl s ystem Digital in German, Electronic Digital Switching EWSD ( ElektronischesW ähl 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 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.
7.3 INTROCDUCTION OF EWSD Switching network (SN) performs the switching function for speech as well as for messages 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.
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7.4 GENERAL FEATURES Switching network is provided in capacity stages SN: 63LTG to SN: 504LTG, 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 small internal blocking and can 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 time 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 each containing several (eight or sixteen) such internal highways, are used for each transmission direction. All externally 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.
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8. Call Processing
LOCAL EXCHANGE
Exchange Side
TELE PHO NE
MDF
CSE O/G
COMMON CONTROL EQUIPMENT
OCB TAX EXCH ANGE
MR, MQ, TR, TX
Exchange Side LOCAL EXCHANGE
OCB TAX EXCH ANGE
CSE
Common Control Equipment MR, MQ, TR, TX
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MDF
TELE PHO NE
8.1 Steps Of Call Processing: a) When a subscriber goes off book, it is detected by line equipment. The change in loop state is detected by micro processor during its scanning. The CSNL allots free TS on LR for this call. The CSNL prepares a new call message and sends it to PU/PE (in SMA) over a signaling link through MCX. The message is sent in local version of CCS7. b) PU/PE receives this message and sends it to MR over MAS. It indicates UR no. UT no. (line card no.) and equipment no. And T/S allotted. c) MR allots a free register to handle this call. It notes down UR no. Equipment number And T/S allotted for the subscriber. Now MR obtains UR-LR to SMX-LRX correspondence from MQ. d) MR obtains class of service date from TR. e) MR orders COM to connect dial tone to the free T/S allotted to subscriber. If subscriber has DTMF instruments it orders for connection of RGF to the T/S of subscriber and then orders for dial tone connection. f) MR also sends acknowledgement message to CSN. g) On receipt of dial tone, the subscriber dials called party‘s number. The UT (Terminal Unit i.e. subscriber line card) disconnects dial tone from the calling subscriber. h) CSN sends these digits to PU/PE through the same path and signaling system. i) PU/PE sends these digits to MR over MAS. j) On reception of first digit, MR orders COM to disconnects dial tone from the calling sub. k) On receipt of first two digits, MR calls TR for pre-analysis. TR, after analysis of first two digits tells MR, the type of call (i.e. local, STD etc.). l) After receipt of adequate number of digits (or all the digit in case of local call) MR again calls TR for analysis. TR supplies called party‘s address and charging information to MR. m) MR carries out party‘s test to know whether it is free, or not. (Pat h MR-U/PE-CSN). n) CSN tests the called party‘s equipment. If this is free, it connects ringing current to called subscriber. It also allots free TS to LR and sends a message to MR indicating LR-T/S of called subscriber. o) MR orders COM for connection of ring back tone to calling subscriber. It also obtains UR-Lr to SMX LRX correspondence for called subscriber. MR walls for called sub‘s reply. p) When called subscriber replies, the concerned CSN sends a message to PU/PE. PU/PE sends the message to MR. q) MR orders COM to disconnect ring back tone. MR orders MQ for connection of calling and called subscriber time slot. MR also orders TX for charging the calling subscribers. As per data supplied by TR. MQ and TX give compliance. r) The subscribers are now in conversation phase. MR hands over the surveillance of calling and called subscriber to retrieve CSNs and releases. s) When calling subscribers goes off-hook, CSN informs PU/PE. PU/PE informs MR. MR releases the connection. If called subscriber goes off hook, MR sets a 1-minute timer and releases the connection after expiry of this time.
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9. CDMA Technology 9.1 Access Network: Access network, the network between local exchange and subscriber, in the Telecom Network accounts for a major portion of resources both in terms of capital and manpower. So far, the subscriber loop has remained in the domain of the copper cable providing cost effective solution in past. Quick deployments of subscriber loop, coverage of inaccessible and remote locations coupled with modern technology have led to the emergence of new Access Technologies. The various technological options available are as follows: 8.1.1. Multi Access Radio Relay 8.1.2. Wireless in Local Loop 8.1.3. Fiber in the Local Loop
9.2 Wireless in Local Loop: Fixed Wireless telephony in the subscriber access network also known as Wireless in Local Loop (WLL) is one of the hottest emerging market segments in global telecommunications today. WLL is generally used as ―the last mile solution‖ to deliver basic phone service
expeditiously where none has existed before. Flexibility and expediency are becoming the key driving factors behind the deployment of WILL. WLL shall facilitate cordless telephony for residential as well as commercial complexes where people are highly mobile. It is also used in remote areas where it is uneconomical to lay cables and for rapid development of telephone services. The technology employed shall depend upon various radio access techniques, like FDMA, TDMA and CDMA. Different technologies have been developed by the different countries like CT2 from France, PHS from Japan, DECT from Europe and DAMPS & CDMA from USA. Let us discuss CDMA technology in WLL application as it has a potential ability to tolerate a fair amount of interference as compared to other conventional radios. This leads to a considerable advantage from a system point of view.
9.3 Spread Spectrum Principle: Originally Spread spectrum radio technology was developed for military use to counter the interference by hostile jamming. The broad spectrum of the transmitted signal gives rise to ―Spread Spectrum‖. A Spread Spectrum signal is generated by modulating the radio
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frequency (RF) signal with a code consisting of different pseudo random binary sequences, which is inherently resistant to noisy signal environment. A number of Spread spectrum RF signals thus generated share the same frequency spectrum and thus the entire bandwidth available in the band is used by each of the users using same frequency at the same time.
Fig-1 CDMA ACCESS – A CONCEPT
On the receive side only the signal energy with the selected binary sequence code is accepted and original information content (data) is recovered. The other users signals, whose codes do not match contribute only to the noise and are not ―despread‖ back in bandwidth (Ref Fig-1) This transmission and reception of signals differentiated by ―codes‖ using the same frequency
simultaneously by a number of users is known as Code Division Multiple Access (CDMA) Technique as opposed to conventional method of Frequency Division Multiple Access and Time Division Multiple Access. In the above figure, it has been tried to explain that how the base band signal of 9.6 Kbps is spread using a Pseudo-random Noise (PN) source to occupy entire bandwidth of 1.25 MHz. At the receiving end this signal will have interference from signals of other users of the same cell, users of different cells and interference from other noise sources. All these signals get combined with the desired signal but using a correct PN code the original data can be reproduced back. CDMA channel in the trans and receive direction is a FDD (Frequency Division Duplexing) channel. The salient features of a typical CDMA system are as follows: Frequency of operation:
824-849Mhz and 869-894 MHz
Duplexing Method:
Frequency Division Duplexing (FDD)
Access Channel per carrier:
Maximum 61 Channels 23
RF Spacing:
1.25 MHz
Coverage:
5 Km with hand held telephones and approx. 20 Km with fixed
units.
9.4 Introduction to CDMA: Network entity description: Base station subsystem (BSS) Base station subsystem is the
general term for the wireless devices and wireless channel control devices that serve one or several cells. Generally, a BSS contains one more base station controllers (BSC) and base transmitter stations (BTS).
9.5 Mobile switch center (MSC) MSC is a functional entity that performs control and switching to the mobile stations within the area that it serves, and an automatic connecting device for the subscriber traffic between the CDMA network and other public networks or other MSCs. MSC is the kernel of the CDMA cellular mobile communication system, and it is different from a wired switch in that an MSC must consider the allocation of the wireless resources and the mobility of subscribers, and at least it must implement the follows processing activities:
1. Location Registration processing. 2. Handoff.
9.6 Gateway MSC (GMSC) When a non-CDMA subscriber calls a CDMA subscriber, the call will first be routed to an MSC, which will inquires the corresponding HLR and further route the call to the called party‘s MSC. This kind of MSC is called Gateway MSC (GMSC). It is up to the network
operator to select which MSCs as GMSCs.
9.7 Visitor location register (VLR) VLR is responsible for the storage and updating of the subscriber data of mobile stations that roamed to the service area of this VLR. The VLR is generally configured together with the MSC. When the mobile station enters a new location area, the MSC will notice the VLR, which will initiate registration processing to the HLR to update the subscriber location 24
information. The VLR also stores necessary information for the establishment of calls in the database for the MSC to search. One VLR can cover one or more MSC areas.
9.8 Home location register (HLR) The HLR provides subscriber information storage and management functions for the mobile network, including mobile subscriber subscription and cancellation and service authorization and cancellation. At the same time, it helps in the implementation of subscriber‘s call and
service operations. A CDMA can contain one or more HLRs based on the number of subscribers, equipment capacity and network organization mode, with multi-HLR mode realized in the form of virtual HLRs. The subscriber information stored in the HLR includes the following two types in information: 1. Subscription information 2. Subscriber-related information stored in the HLR
9.9 Authentication center (AUC) Authentication center is a function entity for the management of authentication information related to the mobile station. It implement mobile subscriber authentication, stores the mobile subscriber authentication parameters, and is able to generate and transmit the corresponding authentication parameters based on the request from MSC/VLR. The authentication parameters in the AUC can be stored in the encrypted form. The authentication center is generally configured together with the HLR. The authentication parameter stored in the AUC includes: 1. Authentication key (A_KEY); 2. Share secret data (SSD); 3. Mobile identification number/international mobile subscriber identity (MIN/IMSI); 4. Authentication algorithm (AAV); 5. Accounting (COUNT).
9.10 Short message center (MC or SC) As an independent entity in the CDMA cellular mobile communication system, the short message center works in coordination with other entities such as MSC, HLR to implement
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the reception, storing and transfer of the short messages from CDMA cellular mobile communication system subscribers, and store subscriber-related short message data.
9.11 Short message entity (SME) SME is a function entity for synthesis and analysis of short messages.
9.12 Operation and maintenance Center (OMC) The OMC provides the network operator with network operation and maintenance services, manages the subscriber information and implements network planning, to enhance the overall working efficiency and service quality of the system. There two type of operation and maintenance centers: OMC-S and OMC-R. An OMC-S is mainly used for the maintenance work at the mobile switching subsystem (MSS) side; an OMC-R is mainly used for the maintenance work at the base station subsystem (BSS) side.
9.13 Third Generation Standards
CDMA2000/FDD-MC — CDMA2000 Multicarrier
using
Frequency
Division
Duplexing-
(FDD-MC) mode. Here multicarrier implies N x 1.25 MHz channels
overlaid on N existing IS-95 carriers or deployed on unoccupied spectrum. CDMA2000 includes: 1. 1x — using using a spreading rate of 1.2288 Mcps 2. 3x — using using a spreading rate of 3 x 1.2288 Mcps or 3.6864 Mcps — using 3. 1xEV-DO (1x Evolution - Data Optimized) — using a spreading rate of 1.2288
Mcps optimized for data
WCDMA/FDD-DS — Wideband Wideband CDMA (WCDMA) Frequency Division DuplexingDirect Sequence spreading (FDD-DS) mode. This has a single 5 MHz channel. WCDMA uses a single carrier per channel and employs a spreading rate of 3.84 Mcps.
UTRA TDD/ TD-SCDMA — Universal Mobile Telephone Services Terrestrial Radio Access (UTRA) and TD-SCDMA. These are Time Division Duplexed (TDD) standards aimed primarily at asymmetric services used in unpaired (i.e., no separate uplink and downlink) bands. TD-SCDMA is based on a synchronous Time Division scheme for TDD and wireless local loop applications. The frame and slot structure are the same as W-CDMA. However, in TDD mode each slot can be individually allocated either the uplink or the downlink.
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10. WIRELESS-FIDELITY (WI-FI) 10.1 Scope: Wi-Fi is a registered trademark by the Wi-Fi Alliance. The products tested and approved as "Wi-Fi Certified" are interoperable with each other, even if they are from different manufacturer. It is Short form for “Wireless-Fi “Wireless-Fidelity” delity” and is meant to generically refer to any type of ‗802.11‘ network, whether ‗802.11‘b, ‗802.11‘a, dual -band, etc.
10.2 General description of Wi-Fi Network: A Wi-Fi network provides the features and benefits of traditional LAN technologies such as Ethernet and Token Ring without the limitations of wires or cables. It provides the final few meters of connectivity between a wired network and the mobile user thereby providing mobility, scalability of networks and the speed of installation. WIFI is a wireless LAN Technology to deliver wireless broad band speeds up to 54 Mbps to Laptops, PCs, PDAs , dual mode wi-fi enabled phones etc.
In a typical Wi-Fi configuration, a transmitter/receiver (transceiver) device, called the Access Point (AP), connects to the wired network from a fixed location using standard cabling. A
wireless Access Point combines router and bridging functions, it bridges network traffic, usually from Ethernet to the airwaves, where it routes to computers with wireless adapters. The AP can reside at any node of the wired network and acts as a gateway for wireless data to be routed onto the wired network as shown in Figure-1. It supports only 10 to 30 mobile devices per Access Point (AP) depending on the network traffic. Like a cellular system, the Wi-Fi is capable of roaming from the AP and re-connecting to the network through another AP. The Access Point (or the antenna attached to the Access Point) is usually mounted high but may be mounted essentially anywhere that is practical as long as the desired radio coverage is obtained.
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Figure -1: A typical Wi-Fi Network.
Like a cellular phone system, the wireless LAN is capable of roaming from the AP and reconnecting to the network through other APs residing at other points on the wired network. This can allow the wired LAN to be extended to cover a much larger area than the existing coverage by the use of multiple APs such as in a campus environment as shown in Figure 2.
Figure -2: Extending Wi-Fi coverage with multiple APs.
An important feature of the wireless LAN is that it can be used independent of a wired network. It may be used as a stand alone network anywhere to link multiple computers together without having to build or extend a wired network. Then a peer to peer workgroup
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can be established for transfer or access of data. A member of the workgroup may be established as the server or the network can act in a peer to peer mode as Shown in Figure-3.
Figure-3: Wireless LAN workgroup.
End users access the Wi-Fi network through Wi-Fi adapters, which are implemented as cards in desktop computers, or integrated within hand-held computers. Wi-Fi wireless LAN adapters provide an interface between the client Network Operating System (NOS) and the airwaves via an antenna. The nature of the wireless connection is transparent to the NOS. WiFi deals with fixed, portable and mobile stations and of course, the physical layers used here are fundamentally different from wired media.
10.3 Wi-Fi Network Configuration: A Wireless Peer-To-Peer Network:This mode is also known as ADHOC mode.Wi-Fi
networks can be simple or complex. At its most basic, two PCs equipped with wireless adapter cards can set up an independent network whenever they are within range of one another. This is called a peer-to-peer network. It requires no administration or preconfiguration. In this case, each client would only have access to the resources of the other client and not to a central server as shown in Figure-4.
Figure-4: A Wi-Fi Peer-To-Peer Network.
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10.4 Client and Access Point: This is known as INFRASTUCTURE mode and is normally employed. However, wireless gateway can be configured to enable peer to peer communication in this mode as well. In this mode, oneAccess Point is connected to the wired network and each client would have access to server resources as well as to other clients. The specific number client depends on the number and nature of the transmissions involved. Many real-world applications exist where a single Access Point services from 15 to 50 client devices as shown in Figure-5.
Figure-5: A Server and Clint Wi-Fi Network.
10.5 Multiple Access Points and Roaming: Access points can be connected to each other through UTP cable or they can be connected to each other over radio through wireless bridging. There is an option to connect access points in a mesh architecture where in event of a fault in an access point the network heals itself and connectivity is ensured through other access point. This changeover takes place dynamically. Access Points have a finite range, of the order of 500 feet indoor and 1000 feet outdoors. In a very large facility such as a warehouse, or on a college campus, it will probably be necessary to install more than one Access Point. Access Point positioning is done by a site survey. The goal is to blanket the coverage area with overlapping coverage cells so that clients might range throughout the area without ever losing network contact. The ability of clients to move seamlessly among a cluster of Access Points is called roaming. Access Points hand the client off from one to another in a way that is invisible to the client, ensuring unbroken connectivity as shown in Fig-6. 30
Figure-6: Multiple Access Points and Roaming.
Use of an Extension Point: To solve particular problems of topology, the network designer
some times uses Extension Points (EPs) to augment the network of Access Points (APs). Extension Points look and function like Access Points, but they are not tethered to the wired network as are APs. EPs function just as their name implies: they extend the range of the network by relaying signals from a client to an AP or another EP. EPs may be strung together in order to pass along messaging from an AP to far-flung clients as shown in Figure-7.
Figure -7: Wi-Fi network with Extension Point (EP).
The Use of Directional Antennae: One last item of wireless LAN equipment to consider is
the directional antenna. Let‘s suppose you had a Wi-Fi network in your building-A and
wanted to extend it to a leased building-B, one mile away. One solution might be to install a directional antenna on each building, each antenna targeting the other. The antenna on ‗A‘ is connected to your wired network via an Access Point. The antenna on ‗B‘ is similarly connected to an Access Point in that building, which enables Wi-Fi network
connectivity in that facility as shown in Figure-8.
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Figure-8: A Wi-Fi network using Directional Antennae.
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11. INTERNET 11.1 Introduction: The Internet is not a program, not software, not hardware or a big system. It is a group of various co-operating 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.
11.2 The basic function of Internet can be summarized as under1. Interconnecting of computers to form a network. 2. Interconnecting of computers to form a network of networks. 3. To establish a communication link between two computers within as network. 4. To provide alternate communication link among the networks, even if one network is not working. 4. These are based on TCP/IP communications protocol.
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12.COMMON TERMINOLOGY USED IN INTERNET: 12.1 WWW: World Wide Web (WWW) is a wide area hypermedia information retrieval aiming to give universal access to a large universe of documents.
12.2 HTTP: Hyper text transmission Protocol (HTTP) is the communication protocol used to transfer documents from the server to client over the WWW (http:// www).
12.3 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 graphics and link media.
12.4 ISDN: Integrated Service Digital Network (ISDN) is a digital phone connection technology that provides both voice and data services over the same connection.
12.5 ISP: Internet Service Provider (ISP) is an agency that provides Internet access and other net related services.
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13.WIRELESS IN LOCAL LOOP (WLL) MOBILE
13.1 INTRODUCTION: 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 between 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
13.2TECHNICAL ASPECTS: WLL is based on CDMA technique and is entirely different from GSM. The system for WLL services can be divided in two following parts:-
13.2.1 BSC (Base Switching Centre):- It provides links between BTS & BSM; it consists of different processors, in BSNL it is of SUN Polaris 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.
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13.2.2 BTS (Base Transreceiver System):-As it is clear from its name it transmits as well as receive signal, it works as an amplifier (router) to overcome the loss in signal in transmission.
13.2.3 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 service. In BSNL BSM are two UNIX based computer system.
13.2.3 ADVANTAGES OF WLL: 1. Country wide induction of WLL underway of areas than are non-feasible for the normal network 2. Helping relieves congestion of connections in the normal cable / wire based network in urban areas 3. Limited the mobility without any airtime charges 4. It has improved signal and reducing the interference 5.Greater capacity than mobile 6. Provides ease of operation, administration & maintenance at lower cost.
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14. GLOBAL SYSTEM FOR MOBILE COMMUNICATION (GSM): 14.1 INTRODUCTION: 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 communication. Throughout the evolution of cellular telecommunications, 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 common European mobile telephone standard that would formulae the specifications for a pan-European mobile cellular radio system operating at 900 MHz it is estimated that many countries outside of Europe will join the GSM partnership.
14.2 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 a digital radio interface for the communication between the mobile 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 . 37
14.3 GSM NETWORK ELEMENTS AND ARCHITECTURE: 1. Mobile Station (MS) i. Mobile Terminal or Equipment (MT) ii. Subscriber Identity Module (SIM) Card 2. Base Station Subsystem (BSS) i. Base transceiver Station (BTS) ii. Base Station Controller (BSC) iii. Main Station Controller (MSC)
3. Network Switching Subsystem (NSS) i. Registration ii. Authentication and security iii. Location updating iv. Handovers and v. Routing to roaming subscribers 4. Operation and Maintenance Subsystem (OMS) i. Operation and Maintenance Centre – Switch ii. Operation and Maintenance Centre – Radio 5. Enhanced Services Subsystem (ESS) 6. Billing and Customer Care System (B&CCS)
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15.THIRD GENERATION 3G TECHNOLOGY : 15.1 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 3G variants 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.
15.2 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. 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
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
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16.ABBREVIATIONS: 16.ABBREVIATIONS: 1. LAN:
Local Area Network.
2. AP:
Access Point.
3. EP:
Extension Point.
4. ISM:
Industrial scientific & medical
5. MAC:
Media Access Control.
6. CSMA/CA: Carrier Sense multiple Access with Collision Avoidance. 7. CDMA 2000 1x EV-DO: CDMA 2000 1x Evolution Version Data Only. 8. IEEE:
Institute of Electrical & Electronics Engineers.
9. OSI:
Open systems Interconnect.
10. WEP:
Wireless Equivalent Privacy.
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17.REFERENCE 17.1 WEBSITES: 17.1.1 WWW.BSNL.CO.IN 17.1.2 WWW.WIKIPEDIA.COM 17.1.3 en.wikipedia.org/wiki/Bharat_Sanchar_Nigam_Limited 17.1.4 www.indiabroadband.net 17.1.5 www.cellone.in
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