Summar Traning Report AT
C-DOT MAXSUBMITTED IN PARTIAL FULFILLMENT
of the requirement for Practical Training In
B.Tech (ECE)
Bharat Sanchar Nigam Ltd. SUBMITTED BYKaran Singh Rana
Electronics&Communication5108113
KARNAL INSTITUTE OF TECHNOLOGY & MANAGEMENT
KUNJPURA, KARNAL
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ACKNOWLEDGEMENT
The author conveys his heartfelt gratitude to Dr.R.B. Sangwan the Director-Principal of
Karnal Institute of technology & Management Kunjpura, Karnal for the encouragement
and unstinted support given by him.
The author would like to convey heartiest thanks to the SDE of the Company B.S.N.L for
providing such an intensive and extensive training in the
project undertaken by me.
The author would like to convey heartiest thanks to the Er. Sachin Wadhwa, Academic
Incharge of KITM for providing such an intensive and extensive training in the project
undertaken by me.
The author acknowledges continuous guidance and incessant support rendered by Er.
Manisha Bangar Head of the Department of ECE not only for this project but also in my
overall career development. Without the help, guidance and support of Er.Rahul Panwar
under whose supervision I had the opportunity of working, it would have been absolutely
impossible for me to complete the project. His contribution is profusely acknowledged.
Moral, intellectual and very frequently required support from all the faculty members is
also hereby acknowledged.
Lastly the author would also like to thank each and every person who contributed directly
or indirectly for completion of this project.
KARAN SINGH RANA
5108113
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TO WHOM SO EVER IT MAY CONCERN
It is certified that Mr. Karan Singh Rana, a student of B.tech 2nd year (electronics & comm.) has training in BSNL for a period of 6 weeks.
During the period of training we find him very sincere, hard working, punctual and loyal to his work. We hope his future shall the same spirit of initiative and enthusiasm.
We wish him every success in the future.
VIJAY KUMAR
S.D.E.(C-DOT)
KARNAL
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Company Profile
BSNL
“BHARAT SANCHAR NIGAM LIMITED” Is Abbreviated As BSNL. It Is Fourth Largest
Department Of Tele Communication Company In Asia And Seventh In The World
Today. Which Is One Of The Most Earning Revenue In India. Above More Than3 Laces
Employees, Officer And Engineers Working In BSNL At Present . Previously Electro
Mechanically Exchanges For Use In India Namely Strowger Type Exchange, Cross
Bar Exchange Were There.
These Manual Telephone Exchanges Suffered From Some Disadvantages.
To Overcome These An Automatic Exchange Was Introduced In This System.
Now It Is “WLL” & “GSM” Mobiles Which Is Also Proved A Mild Stone In The Tele-
Communication Sector. It Was 31st March 2002 When BSNL Started These GSM
Mobile And Today It Has Provided Almost 35 Lacks Mobiles In All Over Country.
WLL System Which Is Also A Mobile With Limited Mobility In City & Can Have Tele
Communication Facility In That Area Almost. While GSM Can Cover Allcities Of The
Country.
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1 C-Dot Max
1.1INTRODUCTION
C-DOT MAX : C-Max is universal digital switch, which can be configured from different application on local, transit & transit concept. The advantage of family concept are standardized components, commonly in hardware, documentation, training, installation & field support for all products and minimization of inventory of spears.
C-DOT DSS :C-Max Dss is modular and flexible digital switch system, which provide economical means of serving metropolitan, urban and rural environment. It incorporates all important features and mandatory services, required by the user with the option of up gradation all new facilities and service in future. The architecture of the C-DOT DSS is such it is impossible to upgrade working C-DOT SBM or MBM exchange to provide ISDN service adding addition hardware modules while retaining existing hardware units. Another factor of the architecture is to support ISDN subscribers through remote switching unit (RSU). This unit is able to provide switching facility locally even in the case of failure of the communication path to the parent exchange.
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1.2FORWARD:
The design of C-DOT MAX has envisaged a family concept. The advantages of family concepts are standardized components , commonly in hardware, documentation, training, installation & field support for all products & minimization of inventory of spares.
The equipment processes provide modular packaging. Common cards & advanced components have been used in the system hardware in order to reduce the type and number of cards. Standard cards, racks, cabinets & distribution frames are used standardized at all levels equipment packaging.
Another important feature of the design is the provision of both levels & centralized operation and maintenance. Beginnings with the local operation & maintenance, and maintenance. All these services are providing through a simple, interactive man-machine interface.
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1.3WORK DONE IN TRAINING PERIOD
In the period, in the department of telecommunication, I get knowledge about C-DOT exchange & R.S.U. (Remote Sensing System). R.S.U. is installed at various places according to areas. The exchange seen & studied is C-DOT (main exchange) & R.S.U.
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1.4HARDWARE ARCHITECTURE:
C-DOT EXCHANGE can be configured using four basic modules:
1) Base Module2) Central Module3) Administrative Module4) Input Output Module
BASE MODULEThe base module is basic growth unit of the system. It interfaces the external world to the switch.
● Analog to digital conversion of all signals on analog lines & trunks.
● Interface to digital trunks & digital subscriber.
● Switching the calls between the administrative module via the current module for the administrative and maintenance functions and majority of the inter BM switching function. ● Provision for the special circuits for call processing support, e.g. digital tones, announcements, MF/DTMF senders/receivers.
Terminals Units-1Terminals Units-2Terminals Units-3Terminals Units-4
Base Processor UnitTime Switching Unit
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1.5BASE MODULE (BM) CONFIGURATION:
For this function the base module hardware is spread over different
Types of unit.
1) ANALOG TERMINAL UNIT : It interface analog lines/trunks and provides special circuits as conference, announcements & terminals testers.
2) DIGITAL TERMINAL UNIT : It interface digital trunks i.e. 2MBPS E-1/PCM links. 3) #7 SIGNALING TERMINAL UNIT : It support SS7 protocol handlers & some call
processing for CCS7 calls.4) ISDN TERMINAL UNIT : It support termination of BRI/PRI interfaces &
implementation of lower layer of DSSI signaling protocol. 5) TIME SWITCHING UNIT : For voice & massage switching & provision of service
circuits.6) BASE PROCESSOR UNIT : For control massage communication & call processing
function.
ANALOG TERMINAL UNIT The analog terminal unit (ATU) is used to interfacing 1228 analog termination which may be lines & trunks. It consist of terminal cards may be combination of line circuits cards, CCB with material card, two wire trunk card and E & M four wire trunk cards, depending upon module configuration.
ANALOG SUBSCRIBERS LINE CARDS The variants of subscriber line cards as LCC or CCM with interfaces and subscribers, provide basic BORSCHT function of each line. Each CCM card has provision of battery reversal of all the 8-lines with the last two lines having provision to generate 16KHz metering pulses to be sent to subscribers metering equipments.The 8-digital output of the four LCC’s is multiplexed to form a 32-channel, 2-MBPS PCM-link also called a terminal group. Since a terminal unit has a maximum of 16 terminal cards, there are four such terminal groups. The signaling processor on four different scan/drivers signals.
ANALOG TRUNK CARDSThese trunk cards interface analog interface analog inter-exchange trunk which may be of three types as TWT, EMT & EMF. These interfaces are similar to subscriber line cards, with only difference that the interfaces are designed to scan/drive events on the trunks as per predefined signalling requirements.
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SIGNALING CARD (SP) CARDSIt processes the signalling information received from the terminal cards. This signalling information consist of scan/derive functions like origination detection, digit reception, reversal detection etc.
TERMINAL INTERFACE CONTROLLER (TIC) CARDIt controls the four terminals group (TG) of 32 channels and multiplex them to form duplicated 128-channel, 8 maps links towards time switch (TS).
SPECIAL SERVICE CARDS
A terminal unit provide certain special services card like TTC & ANN.1) Terminal Test Controller (TTC) Card : It is used to test analog terminal interface via
the test access relays on the terminal cards.2) Announcement Controller (ANN) Card : It provides 15 announcements on broadcast
basic.
CENTRAL MODULEIt consist of massage switch and a space switch to provide intermediate communication & perform voice data switching between base modules. It provide control massage communication between ant two base module & administrative module for operation and maintenance functions. It also provide clock & synchronous on a centralised basic.
ADMINISTRATIVE MODULEIt consist of 16/32 BIT controller called the administrative processor (IOP). It communicate with base processor via the central massage switch for control massage and with duplicate input/output processor in input/output module for interfacing peripheral devices.Administrative processor is responsible for global routing, translation, resource allocation & all other functions that are provided centrally in the C-DOT. The implementation of AM is similar to base processor complex of BM, using the same hardware configuration.
INPUT/OUTPUT MODULEIt consist of duplicated input/output processor (IOP). The IOP is general purpose computer with unit operating system.It is used as a front end processor in the C-DOT. The IOP is connected to AP/BP via HDLC links. During normal operations, the two IOP’s interconnected by HDLC links, operate in the duplex configuration. Working as the front end processor, it provide initial code download to the system, man machine interface & data storage for billing & other administrative information.
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REMOTE SWITCHING UNITIn case of remote switch unit the time switch switch (TSS) cards in BM are replaced by enhanced switch cards. This card implemented certain different functions like HDM3 to HRZ conversion, clock extraction, time slot interchange on PCM links to the host exchange, digital trunk interface, fault handling on digital interface etc.In case the link of RSU gets broken from the main exchange, the RSU offers the facility to the subscribers to remain connected locally. Also it can withstand high temperature of about 42 degree. So it most suitable exchange of villages.
INTERCONNECTED OF THE VARIOUS UNITS
RECOGNISING THE TERMINAL EQUIPMENT NUMBER (TEN)
Terminal equipment number can be easily being recognized. For e.g.
10 - 1 - 4 - 4 - 7
RSU NO. RACK NO. FRAME NO. CARD NO. PORT NO.
SUBSCRIBER AND SYSTEM FEATURESThe C-DOT digital switching system offers a wide range of telephony features and supplementary features:
INTEGRATED SERVICES DIGITAL NETWORK (ISDN)
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CENTER MODULE
(C.M.)
BASE MODULE TRUNK
E-10-B
EWSD
BASE MODULE 2
BASE MODULE 6
BASE MODULE 4
BASE MODULE 32
The ISDN traffic is of two different types:
1) Circuit switched voice & data2) Packaged switching data
In case of circuit switched voice data, the traffic is routed through ISDN network. In the case of packaged switch data, traffic is routed to PSPDN where packet processing takes place processing take place. This is a economical solution & meant for quick implementation & development of ISDN services.
PSTN (ANALOG) AND ISDN SUBSCRIBER SERVICES
NUMBER IDENTIFICATION SERVICES
1) CALLING LINES IDENTIFICATION PRESENTATION (CLIP):Here all the incoming calls are offered to the user along with the detail of calling party identity.
2) CALLING LINE IDENTIFICATION RESTRICTION (CLIR) :This service is offered to the calling party to restrict presentation of its number to the called party.
3) CALLING LINE IDENTIFICATION RESTRICTION OVERRIDE (CLIRO) :Subscribers instead of CLIP receives the call with the calling line identification should not presented to the caller user.
4) MALICIOUS CALL IDENTIFICATION (MCID) :This facility is used for ascertaining the origin of malicious calls.
1- SDH (SYNCHRONOUS DIGITAL HERARCHY)
It Is An International Standard Networking Principle And A Multiplexing Method.
The Name Of Hierarchy Has Been Taken From The Multiplexing Method Which Is 4.
It Is A Standardized Architecture For Use In Digital Transmission Network. It Is
Based On A Synchronous Multiplexing Structure, Which Has Several Advantages.The
FIBCOM FOCUS AC1 Product Family Is Part Of The FIBCOM Product Range For
Access And Regional Telecom Transmission Network Based On The Standards And
Recommendations On SDH From EISI And ITU .
ADVANTAGE :
SDH Supports The Following Services :
• Low/High Speed Data.
• Voice
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• Interconnection Of LAN
• Computer Links
• Broadband ISDN Transport
1.1-OCB-283
All New Technology Switching Systems Are Based On Stored Program Control
Concept . The Call Processing Programmes Are Distributed Over Different Control
Organs Of The System And Are Stored In ROM / RAM Of Different Control Units.
Processor In The Control Units By Using The Programme And Data Stored In Unit
ROM / RAM Process And Handle Calls. Handling Or Processing Call Means To
Ultimately Establish A Connection In A Switch Between I/C And O/G Ends. Depending
On The Name And Architecture Of Control Units And Switch May Change But Criterion
For Switching Remains More Or Less The Same.
OVERVIEW OF OCB-283
INTRODUCTION:-
OCB-283 Is Digital Switching System Which Supports A Variety Of
Communication Needs Like Basic Telephony, ISDN, Etc. This System Has Been Developed
By CIT ALCATEL Of France And Therefore Has Many Similarities To Its Predecessor E-
10B
(Also Known As OCB-181 In France).
SYSTEM APPLICATIONS:
1. Local Subscribers Exchange
2. Remote Subscribers Unit
3. Transit Exchange
4. Hybrid Local/Transit Exchange
5. Tandem Exchange
6. Centrex(Private Or Public)
1.2-MAIN DISTRIBUTION FRAME
INTRODUCTION
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The Switching Equipment, Common To All The Subscribers Of The Area Is Located In An
Exchange.To Make Possible For Subscriber To Communicate With Remaining Subscribers,
Telephone Of Each And Every Subscriber Must Be Connected To The Exchange. The
Function Of MDF Is To Provide A Means For Connecting Side Is Terminated At OCB
Where The Switching Take Place. From OCB, Through Pcmconnected To Various Sections
Like WLL,TAX Etc. A Line From The Subscriber’s
Telephone Set Involves :
FUNCTION OF MDF :
• A Fixed Means Of Terminating The External 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 Terminated On The Line Side Of The Frame, While
Connection From The Equipment Is Done On The Exchange Side In A Numerical Order. By
Interconnections At This Frame With The Help Of Jumper Wires, Any Subscriber In Any
Area Can Be Given Any Exchange Number. This MDF Mounts Delay Fuses Only.31
1.3-ABBREVIATIONS
IN-Intelligent Network
SCP-Service Control Point
SSP-Service Switching Point
IP-Intelligent Peripheral
PRM-Premium Rate Service
ACCS-Account Card Calling Service
VCC-Virtual Card Calling
UAN-Universal Access Number
CIN-Change In Number
VPN-Virtual Private Network Service
GSM-Global System Of Mobile
HLR-Home Location Register
VLR-Visitor Location Register
CCS-Common Cell Signal
OSS-Operation Support System
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WLL-Wireless Local Loop
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CDMA-Code Division Multiple Access
SDH-Synchronous Digital Hierarchy
DWDM-Dense Waveleangth Division Multiplexing
GPRS-General Pocket Radio Service
MMS-Multi Media Service
STM-Synchronous Transport Modules
TAX – Trunk Automatic Exchange
ADM-Add Drop Mux
OCB-Organ Control Base
SDH-Synchronous Digital Hierarchy
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Principle Of Mobile Communication:-
1-Introduction
In Telecom Network Conventionally Each User Is Connected To The Telephone Exchange
Individually. This Dedicated Pair Starts From MDF, Where It Is Connected To The
Appropriate Equipment Point And Ends At The Customer Premises Telephone. (With
Flexibility At Cabinet/Pillar/ Distribution Points Dps)
The Connectivity From Exchange To Customer Premises Is Called “Access Network Or
Local Loop”, And Mostly Comprises Of Underground Cable From Exchange Up To DP’s
And Insulated Copper Wires (Drop Wires)Later On This Type Of Access Network Does Not
Require Separate Authentication Of Customer Before Extending Services.
Duplexing Methodology.
1. Multiple Access Methods.
2. Cellular Principle Or Reuse Concept.
3. Techniques To Cope With “Mobile” Environment.
2.1Duplexing Methodology:
Duplexing Is The Technique By Which The Send And Receive Paths Are Separated Over
The Medium, Since Transmission Entities (Modulator, Amplifiers, Demodulators) Are
Involved.
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There Are Two Types Of Duplexing.
Frequency Division Duplexing FDD
Time Division Duplexing TDD
A)- Frequency Division Duplexing FDD
Different Frequencies Are Used For Send And Receive Paths And Hence There Will Be A
Forward Band And Reverse Band. Duplexer Is Needed If Simultaneous Transmission (Send)
And Reception (Receive) Methodology Is Adopted .Frequency Separation Between Forward
Band And Reverse Band Is Constant
B)- Time Division Duplexing (TDD)
TDD Uses Different Time Slots For Transmission And Reception Paths. Single Radio
Frequency Can Be Used In Both The Directions Instead Of Two As In FDD.GSM And
CDMA Systems Use Frequency Division Duplexing And Cordect Uses Time Division
Duplexing.
2.2-Multiple Access Methodology:
The Technique Of Dynamically Sharing The Finite Limited Radio Spectrum By Multiple
Users Is Called Multiple Access Technique. This Is Known As GOS (Grade Of Service).
Generally There Are Three Different Types Of Multiple Access Technologies. They Are
Frequency Division Multiple Access (FDMA)
Time Division Multiple Access (TDMA)
Code Division Multiple Access (CDMA)
Frequency Division Multiple Access (FDMA):
FDMA Is A Familiar Method Of Allocating Bandwidth, Where A Base Station Is Allowed
To Transmit On One Or More Number Of Preassigned Carrier Frequencies And A Mobile
Unit Transmits On Corresponding Reverse Channels. Both The Base And The Mobile
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Usually Transmit Continuously During A Conversation, And Fully Occupy Their Assigned
Forward And Reverse Channels. No Other Conversation Can Take Place On These Channels
Until The First Conversation Is Completed.
FDMA Analogy:s
It May Be Easier To Visualize FDMA By Imagining A Cocktail Party Where Two People
Wish To Converse With Each Other. Then Everyone In The Room Must Be Silent Except
For The Speaker. The Speaker May Talk As Long As They Wish, And When They Finish
Someone Else May Start Speaking, But Again Only One At A Time. New Speakers Must
Wait (Or Find Another Party) For The Current Speaker To Finish Before Starting. Everyone
In The Room Can Hear And Understand The Speaker, Unless They Are Too Far Away Or
The Speaker's Voice Is Too Soft.
Features Of Frequency Division Multiple Access (FDMA):
No Precise Coordination In Time Domain Is Necessary In FDMA System.
It Is Well Suited For Narrow Band Analog Systems.
Guard Spacing Between Channels Causes Wastage Of Frequency Resource.
Otherwise Good Modulation Techniques Are To Be Employed To Avoid Such
Guard Spacing.
The Transmission Is Simultaneous And Continuous And Hence Duplexers Are
Needed. Continuous Transmission Leads To Shortening Of Battery Life.
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f
c
t
Time Division Multiple Access (TDMA):
TDMA Is A More Efficient, But More Complicated Way Of Using FDMA Channels.
In A TDMA System Each Channel Is Split Up Into Time Segments, And A Transmitter Is
Given Exclusive Use Of One Or More Channels Only During A Particular Time Period. A
Conversation, Then, Takes Place During The Time Slots To Which Each Transmitter (Base
And Mobile) Is Assigned. TDMA Requires A Master Time Reference To Synchronize All
Transmitters And Receivers.
TDMA Analogy
In TDMA, Everyone In The Room Agrees To Watch A Clock On The Wall, And
Speak Only During A Particular Time. Each Person Wishing To Talk Is Given A Set Period
Of Time, And Each Person Listening Must Know What That Time Period Will Be
Features Of TDMA
There Can Be Only One Carrier In The Medium At Any Time, If A Simple TDMA
Scheme Is Followed.
Transmission Is In Bursts And Hence Is Well Suited For Digital Communication.
Since The Transmission Is In Bursts, Battery Life Is Extended.
Transmission Rate Is Very High Compared To Analog FDMA Systems.
Precise Synchronization Is Necessary.
Guard Time Between Slots Is Also Necessary
Time And Frequency Division Multiple Access
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Both Methods Of FDMA And TDMA Are Combined To Achieve Higher Capacity In
Practical Systems. A Channel Gets A Certain Frequency Band For A Certain Amount Of
Time. The Best Example For Such System Is GSM.
Code Division Multiple Access (CDMA)
CDMA Is Fundamentally Different Than TDMA And FDMA. Where FDMA And
TDMA Transmit A Strong Signal In A Narrow Frequency Band, CDMA Transmits A
Relatively Weak Signal Across A Wide Frequency Band. Using A Technique Called Direct
Sequence Spread Spectrum, The Data To Be Transmitted Are Combined With A Pseudo-
Noise Code (A Pre-Determined Binary Sequence That Appears Random) And Transmitted
Broadband. CDMA Under Interim Standard 95 Uses A Bandwidth Of 1.25 Mhz.
A Spread Spectrum Receiver With A Different PN Code Will Not Be Able To
Recover That Signal, And If The PN Codes Were Chosen Incorrectly, Will Hear Nothing But
Noise. This Relative Immunity To Interference, Whether From Outside Sources Or Other
Spread Spectrum Transmitters, Gives CDMA Systems The Ability To Pack Many Users Into
The Same Frequency Space At The Same Time. It Also Gives A Measure Of Security To
Each Signal, Since Each User Will Have A Different PN Code. CDMA Also Does Not
Require Different Base Station Radios For Each User - The Same Radio May Serve Multiple
Users With Just A Change In PN Code.
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Comparison Of Multiple Access Techniques:
Coverage Offered By CDMA System Is More Compared To TDMA And FDMA Systems.
Capacity Of CDMA System Is More Compared To TDMA And FDMA Systems.
2.3-Cellular Concepts:
Even Though Multiple Access Techniques Allowed Multiple Users To Share The Medium
Simultaneously, Due To Constraints In Providing Resources, An Amount Of Blocking Will
Exist.
2.4-Why Cellular?
Hence The Solution Is Dividing The Service Area Into Small Units, Called Cell, With Base
Stations Radiating With Low Power, And Limited Number Of Carriers Required As Per
Traffic. The Same Carriers Are Again Reused At A Different Cell, Which Is Geographically
Separated. (Frequency Reuse)
In Case Of CDMA It Appears That There Is No Limitation For Simultaneous Calls But
Practically There Is A Limit To CDMA Capacity. And It Is Essentially The Amount Of
Interference A CDMA Receiver Can Tolerate. As More And More Units Transmit, The
Amount Of Noise A Receiver Sees Goes Up, Since All Signals Not Using The Receiver's
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Specific PN Code Appear As Noise. At Some Point There Is So Much Noise That The
Receiver Can No Longer Hear The Transmitter. Boosting The Transmitter Power Won't Help
Overall, Since It Increases The Noise For All The Other Receivers, Who Would In Turn Tell
Their Transmitters To Boost Power, And The Situation Remains. In A Nutshell, If A Unit
Near A Base Station Is Transmitting With Too Much Power, Signals From Units Far From
The Base Station Will Be Lost In The Noise.
Hence Cellular Concept Is Applicable Even In The Case Of CDMA Where Code
Used For Identification Of Cell/Sector Is Reused.
Advantages Of Cellular Principle
Base Stations Can Transmit At Low Power Compared To A Single High Power Transmitter.
It Requires Less RF Bandwidth To Cover A Given Area. Frequency Reuse Gives Good
Spectrum Efficiency. (FDMA-TDMA)
Disadvantage Of Cellular Principle
Reuse Introduces Interference.
Established Calls Should Be Handed Over To Next Cell To Avoid Dropping Of Calls When
The Customer Is In Mobility.
2.5-Mobile Environment:
BTS Is Connected To Mobile Or Fixed Wireless Terminal By Air Interface. This
Connectivity Differs From Our Earlier UHF/Microwave Which Is Purely Line Of Sight
(LOS) System. In Mobilecommunication Due To The Mobility Of The User From The BTS
LOS To BTS May Exist Or May Not Exist.
Types Of Signal Strength Variations
The Signal Strength Variation For Mobile Is Due To Different Types Of Signal
Strength Fading. There Are Two Types Of Signal Strength Variations
Macroscopic Variations Due To The Terrain Contour Between BTS And MS The
Fading Effect Is Caused By Shadowing And Diffraction (Bending) Of Radio Waves.
Microscopic Variations. Due To Multipath, Short-Term Or Rayleigh Fading. As The
MS Moves, Radio Waves From Many Different Paths Will Be Received.
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2.6-Macroscopic Variations
Macroscopic Variations Can Be Modeled As The Addition Of Two Components That
Make Up The Path Loss Between Mobile And Base Station. The First Component Is The
Deterministic Component (L) That Adds Loss To The Signal Strength As The Distance(R)
Increases Between Base And Mobile. This Component Can Be Written As
L=1/Rn
Where N = Typically 4.
The Other Macroscopic Component Is A Log Normal Random Variable Which Takes Into
Account The Effects Of Shadow Fading Caused By Variations In Terrain And Other
Obstructions In The Radio Path.
Local Mean Value Of Path Loss=Deterministic Component +Log Normal Random Variable.
2.7-Special Features Of Mobile Technologies
All Mobile Techniques Incorporate Some Special Features To Overcome The Hazards
Created By Mobile Environment. The Following Are A Few To Name:
1. Coding.
2. Diversity Techniques.
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3. Adaptive Equalization( In Case Of GSM)
4. Rake Receiver (In Case Of CDMA)
1.Coding:
Coding Includes
Speech Coding,
Convolutional Coding Or Forward Error Correction Coding
Interleaving
Speech Coding:
Human Speech Is Band Limited Between 300Hz To 3400Hz And Undergoes Frequency
Modulation In Analog Systems. In Digital Fixed PSTN Systems Band Limited Speech Is
Sampled At The Rate Of 8 Khz And Each Sampled Is Encoded Into 8 Bits Leading To
64Kbps (PCM A-Law Of Encoding).Digital Cellular Radio Cannot Handle The High Bit
Rate Used For PSTN Systems. Smart Techniques For Signal Analysis And Processing Have
Been Developed For Reduction Of The Bit Rate
Different Mobile Communication Systems Use Different Bit Rates For Voice Encoding. The
Following Table Gives A Glimpse.
No. Technology Bit Rate Per Voice
Chl
Voice Coding
Technique
1 GSM 13Kbps RPE-LTP
2 CDMA IS95A 9.6Kbps/14.4 Kbps QCELP/EVRC
3 Cor-DECT 32Kbps ADPCM
RPE-LTP: Regular Pulse Excited Long Term Prediction
QCELP: Qualcomm Code Excited Linear Prediction
EVRC: Enhanced Variable Rate Coding
ADPCM: Adaptive Differential Pulse Code Modulation.
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Interleaving:
Interleaving Is A Simple, But Powerful, Method Of Reducing The Effects Of Burst Errors
And Recovering Bits When Burst Errors Occur. The Symbols (Output Of Forward Error
Correction Coder) From Each Group Are Interleaved In A Pattern That The Receiver Knows.
The Interleaver Is Located At The BTS And In The Phone.
An Illustrative Example Is Shown Below.
2. Diversity Techniques:
To Cope Up With The Mobile Environment Diversity Techniques Are
Employed .This Can Be Space Diversity, Polarisation Diversity, Frequency Diversity And
Time Diversity.
Space And Polarisation Diversity:
Frequency Diversity:
Signal Degradation Can Be Averted By Changing The Present Frequency To Another
In Case Of Narrow Band Systems. This Avoids Frequency Selective Fading. In A Narrow
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Band System Like GSM This Is Achieved By Slowly Hopping The Frequency Of
Transmission Of BTS In A Predetermined Manner.
In Case Of A Wide Band System Like CDMA Signal Occupies A Large Bandwidth
And Frequency Diversity Is Inherently Achieved.
Time Diversity:In All The Mobile Communication Systems By Employing Interleaving Time
Diversity Is Automatically Achieved.
3. Rake Receiver:
The Rake Receiver Is Multiple Receivers In One. There Is A Rake Receiver At Both The
Mobile And BTS. It Turns What Is A Problem In Other Technologies Into An Advantage For
CDMA. Signals Sent Over The Air Can Take Multi-Paths Resulting In Degradation Of
Signal. The Rake Receiver Identifies The Three Strongest Multi-Path Signals And Combines
Them To Produce One Very Strong Signal. The Rake Receiver Therefore Uses Multipath To
Reduce The Power The Transmitter Must Send.
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Conclusion:
Wireless Means Convenience. However To Achieve This Certain Precautionary
Measures Are Taken To Overcome The Bandwidth Scarcity, Multipath Problems, Etc., There
Are Multiple Access Techniques To Share The Bandwidth Amongst Several Users.
EWSD - System Description
3.0 Introduction :
The Department Of Telecommunications Had Announced Ambitious Plans
For The Addition Of 7.5 Million Lines To The Existing 5.8 Million By The End Of
The 8th Plan (1992-97) As Compared To Only 3.2 Million In 1982-92.
Consequent Upon Delicensing Of The Telecom. Equipment And Throwing It
Open To Foreign Investments, Six New Technologies Were Planned To Be Valida-
ted. These Foreign Suppliers Set Up Their Validation Exchanges, Each Of 10,000
Lines Capacity (Including Two Rsus Of 2K Each), At Different Places, E.G. EWSD
Of Siemens (Germany) At Calcutta, AXE-10 Of Ericsson (Sweden) At Madras,
Fetex-150 Of Fujitsu (Japan) At Bombay, OCB-283 Of Alcatel (France) At Delhi
Etc.
EWSD Is One Of The Technologies Selected For TAX And Is Also The
Technology For Intelligent Network And Mobile Communication. This Article Gives
A General Introduction To The EWSD System, Its Features, Architecture And
Facilities.
3.1 System Features :
EWSD Digital Switching System Has Been Designed And Manufactured By
M/S Siemens, Germany. The Name Is The Abbreviated Form Of German Equivalent
Of Electronic Switching System Digital (Electronische Wheler Systeme Digitale).
EWSD Switch Can Support Maximum 2,50,000 Subscribers Or 60,000 Incoming,
Outgoing Or Both Way Trunks, When Working As A Pure Tandem Exchange. It Can
Carry 25,200 Erlang Traffic. It Is Claimed That The System Can Withstand A
BHCA Of Four Million With CP-113C In Case Of EWSD Powernode (Two Million
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PDC3 without ccsPDC2 with ccs
PDC1 without ccs
PDC0 with ccs
Subscriber lines and PBX lines for small and med- ium-sized PBXs
Remote application
Local application
4Mbps
SNLTG
LTG
CP
4 MbpsDLU
DLU
Subscriber lines and PBX lines for small and medium-sized PBXs
CCITT standard interface G.703Remote application :
in same directory number area,in another directory number area,as extension to conventional exchange.
Applications and connection of Digital Line Unit
In Case Of EWSD Classic). However, The Effective Dynamic Call Set Up
Performance Depends On The Available Features And The Actual Call-Mix. It Can
Work As Local Cum Transit Exchange And Supports CCS No.7, ISDN And IN And
V5.X Features.
3.2 Digital Line Unit (DLU)
Analog Or Digital (ISDN) Subscribers, PBX Lines Or V5.1 Interface Are Terminated
On DLU . Dlus Can Be Used Locally Within The Exchange Or Remotely As Remote
Switch Unit , In The Vicinity Of The Groups Of Subscribers.
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Within The DLU, The Analog Subscribers Are Terminated On SLMA (Subscriber
Line Module Analog) Cards (Module). Similarly Digital (ISDN) Subscribers Are
Terminated On The SLMD Modules. Each Module Can Support 16 Subscribers,
Hence Has 16 SLCA/Slcds (Subscribers Line Circuit Analog/Digital) And One
Processor SLMCP.
DLUG :
The Latest Type Of DLU Is DLUG Which Can Accommodates Upto 1984 Analogue
Subscribers With 32 Ports Per SLMA But The SLMD Still Accommodates 16
Subscribers. It Can Be Connected To Four Ltgs With 16 Pdcs With A Provision Of
One Signalling Channel (CCS) Per LTG. It Can Handle Up To 390 Erlangs Of
Traffic.
Broadband
Introduction:-
Broadband Services Are Used By Telecom Companies Worldwide To L Everage Their
Existing Investment In Copper In The Local Loop. Copper As A Last-Mile Delivery
Medium Has The Advantage Of Near-Universal Penetration, And Local Telecom Companies
Are Increasingly Eyeing Broadband Services On It As A Means Of ‘Hitting Back’ At Cable
Operators Who Have Begun Infringing On Their Turf By Their Bundled Internet Offerings.
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This Article Attempts To Demystify The Basic Technologies Involved In Broadband
Delivery, The GOI’s Attempts To Promote Broadband Usage In The Country, And BSNL’s
Broadband Plans As Part Of Its Ambitious NIB-II Project.
4.1- What Is Broadband?
To State The Obvious, ‘Broadband’ Indicates A Means Of
Connectivity At A High Or ‘Broad’ Bandwidth. In India, TRAI Has Defined Broadband As
Any Connectivity Delivered To The End User At A Bandwidth Greater That 256 Kbps. (So
That Immediately Excludes The Popular DIAS Services Offered By BSNL At Many Places).
Why Is Bandwidth So Important And How To Estimate How Much Bandwidth Is Required
For A Particular Application? A Small Example Below Will Help Illustrate The Concept.
Assuming You Wish To Receive A VCD Quality Transmission ( Incidentally, This Is Also
The Quality Offered By Low Cost Desktop Videoconferencing Applications ) Over Your
Broadband Connection, The Maths Is:
Pixel Count Per Frame – 200 X 300 = 60000
Frame Rate -- 30 Per Sec (Minimum)
Bandwidth Required : 200 X 300 X 30 = 1800000 = 1.8 Mbps
Of Course, The Above Is Raw Transmission Rate – Modern Technologies Use Advance
Compression Algorithms To Reduce The Data Rate To A Great Extent.
4.2- Broadband Delivery Technologies
The Problem Of The ‘Last Mile’
While Telecom Companies Have Adequate High Speed OFC Infrastructure To
Connect Their Exchanges And Switches, The Same Does Not Hold Good With The Legacy
Fixed Line Customers Who Are Connected, However Adequately For Voice Communication,
By Good Old Copper. How To Deliver The Broadband Content Over This Seemingly Low
Bandwidth Medium Was The Question Till Recently, When Advanced Line Coding And
Compression Technologies ‘Solved’ The Problem.
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The Misunderstood Copper
It Has Been The General Perception That Copper Is ‘No
Good’ For Anything Other Than Speech Communications Of The Analog Variety. However,
The Blame For The Low Bandwidth Rests With The Telephone System Rather Than With
The Medium. The Telephone System Filters The Voice To A Range Of 400 Hz To 3.4 Khz,
Thereby Rendering The Local Lead Useless For Even Good Quality Sound Transmission.
And People Blame The Poor Copper !
DSL Stands For Digital Subscriber Loop. The Diagram Below Shows How DSL Modulates
The Line Spectrum. Data Signal Is Sent At A Frequency Higher That The Voice (3.4 Khz)
Frequency.
DSL ‘Modulation’
There Are Various Technologies Spawned Off From DSL Which Perform To Different
Expectations:
DSL: Digital Subscriber Line
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SDSL: Single Line Digital Subscriber Line
ADSL: Asymmetric Digital Subscriber Line
HDSL: High Data Rate Digital Subscriber Line
VDSL : Very High Data Rate Digital Subscriber Line
IDSL: ISDN Digital Subscriber Line
These Technologies Offer Differing Bandwidths Over Different Distances. The Table Below
Shows A Comparison Of Their Capabilities:
3. ADSl
Of All The Mechanisms Outlined Above, Asymmetric Digital Subscriber Loop (ADSL) Has
Found Favour As A Broadband Delivery Mechanism, In View Of Its High ‘Downstream’
Bandwidth. “Downstream’ Refers To Data Flowing From The Service Provider To The
User. Most Of The Popular
Applications, Like Web
Browsing, Video Streaming, FTP
Downloads, Etc., Require Much
Higher Downstream Bandwidth
Than Upstream Bandwidth.
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Bandwidth
(Downstream)
Range In Feet
1.544 (T1) 18000
2.048 (E1) 16000
6.312 (DS2) 12000
8.448 9000
ADSL Manages To Extract High Data Rates In This Direction. The Distance Limitations For
ADSL Are Shown Below:
With All The Local Telecom Companies Edging Closer To The Customer With Their
Distributed Access Mechanisms Like Dlcs And Rsus, The Above Distances Lie Well Within
The Range Of Most Customer Premises, And Thus Broadband Delivery Can Be Quite
Effective, With A Richer User Experience.
Multiplexing Voice And Data: DSLAM
The DSL Access Multiplexer, Popularly Known As DSLAM, Is Employed By The Telecom
Companies To Code The Subscriber Line With The Broadband Data Content. Once The
ADSL Copper Line Reaches The Customer, Some Customer Premises Equipment (CPE) Has
To Be Employed To Separate The Voice And Data Signals.
In Many Cases The Splitter Function Is Combined Within The DSL Modem CPE Equipment,
Which Is Also Known Sometimes As A ‘Set-Top Box’.
4. Broadband Services
Several Interesting Services Can Be Provided In An ‘Integrated’ Manner By The Broadband
Service Provider. Some Of These Are:
High Speed Internet Services
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Video On Demand
Multicast Video Streaming
Interactive ‘E’- Learning
Interactive Gaming
High Speed Internet Services Refer To Always-On Fast Internet Access.
5. The Indian Scenario
Broadband Services In India Have Not Yet Really Taken Off Because None Of The Major
Telcos Has Been Able To Rollout Such Services In A Really Big Way So Far. Broadband
Penetration Is, Of Course, Dependent Upon PC Penetration As A Major Factor. India Lags
Behind Other Major Countries Of The Region By A Substantial Margin, As The Following
Table Will Show.
OVERVIEW OF BROAD BAND
Definition Of Broad Band
Broadband Is Often Called High-Speed Internet, Because It Usually Has A High Rate Of
Data Transmission. In General, Any Connection To The Customer Of 256 Kbit/S Or More Is
Considered Broadband.
HOW IS BROADBAND DIFFERENT FROM DIAL-UP SERVICE?
Broadband Service Provides Higher Speed Of Data Transmission—Allows More Content To
Be Carried Through The Transmission “Pipeline.”
Broadband Provides Access To The Highest Quality Internet Services—Streaming Media,
Voip (Internet Phone), Gaming And Interactive Services. Many Of These Current And Newly
Developing Services Require The Transfer Of Large Amounts Of Data Which May Not Be
Technically Feasible With Dial-Up Service. Therefore, Broadband Service May Be
Increasingly Necessary To Access The Full Range Of Services And Opportunities That The
Internet Can Offer.
WHY IS BROADBAND IMPORTANT?
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Broadband Can Provide You With The Technical Capability To Access A Wide Range Of
Resources, Services And Products That Can Enhance Your Life In A Variety Of Ways. These
Resources, Services And Products Include,
Education, Culture, & Entertainment
Broadband Can Overcome Geographical And Financial Barriers To Provide Access To A
Wide Range Of Educational, Cultural And Recreational Opportunities And Resources.
Tele-Health & Telemedicine
Broadband Can Facilitate Provision Of Medical Care To Unserved And Underserved
Populations Through Remote Diagnosis, Treatment, Monitoring And Consultations With
Specialists.
Economic Development/E-Commerce
Broadband Can Promote Economic Development And Revitalization Through Electronic
Commerce (E-Commerce) By:
Creating New Jobs And Attracting New Industries.
Providing Access To Regional, National And Worldwide Markets.
Electronic Government (E-Government)
Electronic Government Can Help Streamline People’s Interaction With Government
Agencies And Provide Information About Government Policies, Procedures, Benefits And
Programs. .
Broadband Communications Services
Broadband Provides Access To New Telecommunications Technologies Such As Voice Over
Internet Protocol (Voip) Allowing Voice Communication Using The Internet.
Communications Services For People With Disabilities
Broadband Permits Users Of Telecommunications Relay Services (TRS) To Use Video Relay
Services (VRS) To Communicate More Easily, Quickly And Expressively With Voice
Telephone Users.
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TYPES OF BROADBAND CONNECTIONS
Broadband Includes Several High-Speed Transmission Technologies Such As:
Digital Subscriber Line (DSL)
Cable Modem
Fiber
Wireless
Satellite
Broadband Over Power Lines (BPL)
The Broadband Technology You Choose Will Depend On A Number Of Factors. These May
Include Whether You Are Located In An Urban Or Rural Area, How Broadband Internet
Access Is Packaged With Other Services (Like Voice Telephone And Home Entertainment),
Price And Availability.
What Is ADSL?
ADSL Stands For Asymmetric Digital Subscriber Line. It Is A Technology That Allows
Copper Telephone Pairs To Be Used To Provide A Broadband Connection. It Provides
Always-On Internet Connection That Is Automatically Established Once The PC And ADSL
Modem Are Switched On.
Modem Connections
The Following Shows The Switch And Various Connectors That Are Equipped On The Rear
Panel Of The ADSL Modem
1. Power Port This Is Where You Will Connect The Power Adapter.
2. Console Port Reserved For Future Development.
3. LAN Port This LAN (Local Area Network) Port Connects To Your PC With Network
Cable Included In Your Kit. You Can Also Connect Network Devices, Such As Hubs And
Switches With A Straight- Through RJ-45 Cable Or Use A Cross-Over RJ-45 Cable To
Connect A Router (Cross-Over Cable Not Supplied).
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4. Line Port Connects Your Modem To Your Telephone Line.
INSTALLATION
ADSL Installation Kit Contents
1 -ADSL Modem
1 - Ethernet Cable
1 - Telephone Cable
1 - ADSL Filter
1 - Phone Jack Splitter
1 - DC Power Adapter
Step 1
ADSL Modem Connection To Internet
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Plug The Telephone Cable Into The Slot Labeled “Line” On The Back Of Your Modem. Plug
The Other End Of The Telephone Cable Into The Telephone Jack, ADSL Was Provisioned
To (See Figure 3 & 4).
Figure 3
Figure 4
ADSL Can Provide Connectivity To More Than One Computer System In Your Home. For
This Reason We Have Two Different Patterns To Follow:
- If You Only Have One Computer To Supply Connectivity, Please Go To Step 2.
- If You Have More Than One Computer Please Jump To Step 3.
Step 2
ADSL Modem Connection To One Computer
Plug One End Of The Ethernet Cable (Only Use The Cable Supplied) Into The Slot Labeled
“LAN” On The Back Of Your ADSL Modem (See Figure 5). Then Plug The Other End Of
The Network Cable Into Your Ethernet Card On Your Computer System (See Figure 6).
Please Jump To Step 4.
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Figure 5
Figure 6
Step 3
ADSL Modem Connection To Multiple Computers
If You Have More Than One Computer To Connect You Will Need To Connect Each Of The
Computers And The ADSL Modem To A Hub Or Data Switch. You Will Also Need
Additional Network Cables.
Plug The Cross-Over Ethernet Cable Into The Back Of The ADSL Modem (See Figure 5).
Then Plug The Other End Of The Ethernet Cable Into Your Hub/Data Switch. This Cable
Must Be Connected To The Uplink Port On The Hub/Data Switch. If Your Hub/Data Switch
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Does Not Have An Uplink Port You Must Use A Regular Straight Through Ethernet Cable
Instead Of The Crossover Cable Included Within Your Kit.
ADSL Modem Power Connections
Plug The Black Power Cord Into Your ADSL Modem (See Figure 7) And Then Plug The
Opposite End Into An Electrical Outlet Or UPS. Turn On Your ADSL Modem. All Of The
Lights On Your ADSL Modem Should Flash For A Short Period Of Time (Up To 3
Minutes).
Figure 7
Step 5
Figure 8
Status Light Indication
If The Power, ADSL Link And LAN Link Lights On Your ADSL Modem Are Green Or
Flashing Green – Your ADSL Modem Is Connected Correctly. If They Are Not Green, See
The Explanations Below. The Lights Indicate The Following: (See Figure 8).
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Power: Amber. The Power LED Lights Up When The ADSL Modem Is Powered On.
ADSL Link: Green. The ADSL Link Is Continuously Lit Up When The ADSL Modem Is
Successfully Connected To An ADSL Line. If The Link LED Is Blinking, The Unit Is
Attempting A Connection To An ADSL Line.
PC Link: Green. The LAN Link Lights Up When A Successful Ethernet Connection Is Made
Through The Corresponding Port. If This LED Is Not Lighting Up, An Ethernet Connection
Has Not Been Established.
ADSLRX: Green. The ADSL RX LED Blinks When The Router Is Actively Sending Or
Receiving Data Over That Port.
ADSL TX: Green. The ADSL TX LED Blinks When The Router Is Actively Sending Or
Receiving Data Over That Port.s
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