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For circulation to Trainees only
Overview of Telecom
Network
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Outline of Lecture
What is Telecom?
Concepts and Definitions
Overview of Telecom Network
PSTN
Internet/Data Network
Cellular Telephone Networks
NGN
Transmission & Systems in Telecom
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What is Telecom ?
Telecommunication is the assisted
transmission of signals over a distance for the
purpose of communication.
It is the technology of transferring information
over a distance.
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Information
1. Information can be of several type:
Audio Telephone
Text - Telegraph , email, SMS
Pictures Picture attachments
Video Clipping over internet
Data ATM to bank.
2. The same telecom technology/service cannot
communicate all the types of information.
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Telecom scenario
Growing subscriber base.
New services and technologies.
More focus on wireless & internet.
Government wants more development in rural areas.
Decreasing Prices.
Increasing demand for bandwidth.
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OVERVIEW OF TELECOM NETWORK
There are three networking approaches for a telecom
network infrastructure.
Circuit-switched,
Internet / Data Network and
Cellular mobile,
Finally, all these architectures are migrating towards a
common IP network infrastructure called Next
Generation Network (NGN).
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CIRCUIT-SWITCHED NETWORKS &
DIGITAL SWITCHING SYSTEMS
Public Switched
Telephone Network(PSTN)
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Concepts & Definitions
Telecommunications is the transfer of information from a
transmitter to a receiver over a distance.
A telecommunication network is required to transmit
messages between any of its users (who are usually
called customers or subscribers), and the messages may
be conveyed by signals that are either digital or
analogue.
Telecommunication system - enable the transmission
of information over public or private networks (voice,
data, graphics, video)
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Concepts & Definitions
Definitions:
Transmitter: originates information transfer
Receiver: receives the transferred information
Circuit: a communications path between transmitter and
receiver over an established medium
Link: a two-point segment of an end-to-end circuit
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Concepts & Definitions
Definitions (contd)
Switch: a device that establishes, maintains, and
changes connections over circuits
Line: a single physical connection between a user
and a switch
Trunks: the physical connection between switches
Channel: a channel is a division in a transmission
medium so that it can be used to send multiple
streams of information, a circuit can contain
multiple channels
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Concepts & Definitions
Definitions (contd)
Bit : The binary digit or bit is a unit of information transfer.
Byte : a collection of 8 bits
Signal : It is electrical, electronic or optical representation of data, which can be sent over a communication medium. Stated in mathematical terms, a signal is merely a function of the data. Signals can be either analogue or digital.
Symbols : In communications, the analog signal shape, by pre-agreed convention, stands for a certain number of bits and is called a symbol.
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Concepts & Definitions
Definitions (contd)
Baud : Symbols transmitted per second is known as baud.
Modulation : The shaping of a signal to convey information is known as modulation.
Network : A network is a collection of transmitters, receivers and transceivers that communicate with each other.
Multiplexing : combining a defined integral number of input signals (called tributaries).
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Concepts & Definitions
Definitions (contd)
Modems (modulation/demodulation) : Changes signals from analog to digital and back to analog.
Spectrum -range of frequencies Bandwidth -width of the spectrum Bandwidth Alternatives : Bandwidth is the
frequency range of a telecommunications network. Determines the channels maximum transmission rate. Measured in bits per second (bps) or baud.
Narrow-band : Low-speed transmission. Broadband : High-speed transmission.
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ANALOG SIGNAL
Continuous Waveform
Analog signals are continuous-valued;
Voice Communications and video
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DIGITAL SIGNAL DISCRETE WAVEFORM i.e. depicted as discontinuous
TWO DISCRETE STATES:
1-BIT & 0-BIT
ON / OFF PULSE (Each pulse (on/off) is known as a
bit)USES MODEM TO TRANSLATE ANALOG TO
DIGITAL, DIGITAL TO ANALOG
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Advantages of Digital Transmission
The signal is exact
Signals can be checked for errors
Noise/interference are easily filtered out
A variety of services can be offered over one line
Higher bandwidth is possible with data
compression
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Network Elements of PSTN
A telecommunication network may therefore be
considered as a system consisting of four basic network
elements:
Station apparatus
Transmission
Switching
Signaling
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Network Elements
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Station apparatus
Station Apparatus are the transmitters and receivers:
Telephones
Answering Machines
Facsimile Machines
Most are combined transmitters and receivers
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TRANSMISSION
Transmission is the conveyance of signals from one
place to another.
Signals may be audio, video, or data
Transmission systems include:
Open Wire
Copper wire cable (Twisted Wires)
Co-axial Cable
Microwave radio (terrestrial and satellite)
Fiber optic cable
Other wireless
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TRANSMISSION
Open wire
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TRANSMISSION (contd) The network is composed of transmission media linked at physical locations (central offices, carrier units, etc.)
Originally each line ran all the way back to the C.O.
Called a home run architecture
Circuit cards linked the transmission media
Access Lines Circuit
Ports
Toll Trunk
IXC Switch
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TRANSMISSION (contd)
Modern networks use multiplexing, the sharing of a transmission medium by multiple signals
Frequency (analog) & Time-division (digital) muxing
Multiple channels on a single circuit
Node architecture has replaced the home run
Circuit Digital Line DLC Ports
Carrier Units
Toll Trunk Splice point
Access Lines DLC IXC Switch
DLC
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Transmission Modes
Performance can be measured by the mode of the
connection.
Simplex transmission, messages can be
carried in only one direction.
Half-duplex, messages can be carried in
both directions just not simultaneously.
Full-duplex, messages can be carried in
both directions simultaneously.
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SWITCHING
Telephones introduced in late-1800s. Initially each telephone was directly
connected to another site. This led to an explosion of direct connections
(n*(n-1)/2) This lead to the need to switch the connections.
Switch
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SWITCHING
Switches establish, maintain, and change connectivity
between circuits
The earliest telephone exchanges used switchboards
worked by operators. The manual exchange was unique
among switching systems, since a single switch (i.e., the
operator) could make a connection to any of several
thousand lines by inserting a plug in a jack within arms
reach.
A modern electronic exchange performs basic actions
very rapidly, so it can be controlled by a single central
digital processor.
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SWITCHING
Switches used to be electro-mechanical in nature; most
are now digital
Digital switches are simply computers that make logical
routing decisions to connect circuits to complete calls
When a call is dialed, the end-office switch decides
whether it can handle the call or if it needs to pass it up
the hierarchy
Each switch in succession makes the decision to pass it
up or down the hierarchy until it reaches the end-office
that can complete the call
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SIGNALING
In order for the network to function properly, the various
components and elements must have the ability to signal
each other to indicate status and condition.
Signaling can be either:
In-band: takes place over the same physical path as
the conversation and occupy the same channel
Out-of-band: takes place over a separate channel or
physical path as the conversation
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SIGNALING
Signaling performs several functions:
Supervising: monitoring the status of a line
or circuit to see if it is busy, idle or requesting
service; and performing diagnostics
Alerting: indicates a specific condition such
as the arrival of an incoming call (ringing),
off-hook status (alert tone), busy signal, etc.
Addressing: transmitting routing, billing and
destination information
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SIGNALING MODELS
Point-to-Point Signaling Point-to-Point signaling model is used to establish
and release connections between two end-points. The is the most common model of signaling. Not only is this model popular, it is also very
simple to implement. Point-to-MultiPoint (PMP) Signaling
Point-to-MultiPoint signaling model is used to establish and release connections between a root and multiple end-points.
This form of signaling is mainly used for multicasting or broadcasting applications (e.g., distant learning).
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SIGNALING
Basic Phases of a Call
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Basic Phases of a Call
Phase 1- When a customer trying to make call he will lift
the receiver. This intern will activate the telephone exchange
and immediately dial tone will be fed from the exchange to
indicate that exchange is waiting for the dialing digits.
Phase 2- Customer starts dialing. Normally this dialing
period is variable and usually around 10 seconds.
Phase 3- When customer dials the complete B number (call
number) the originating exchange will decide the route that
has to be activated and send the B number details in an
agreed protocol to the terminating exchange. The time taken
for this phase too is variable but maybe limited to the
maximum of one or two seconds.
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Basic Phases of a Call
Phase 4- When the terminating exchange finds the B
customer is free it will send ringing current to the B
customer and send Ring Back Tone to the A customer (A
is the originating customer). This period is a variable and
can go up even to two minutes until the B customer
answers. If B customer does not answer within two
minutes (can be programmed) A customer will be
disconnected.
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Basic Phases of a Call
Phase 5- When the B customer answers the terminating
exchange will remove Ring Back Tone and ringing current
and inform the answer condition to the originating
exchange. Normally this will take around 100-200ms and
generally is variable within millisecond periods.
Phase 6- A and B customers speaking. Without their
knowledge they will follow the following phases
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Public Circuit Switched Network
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INTERNET AND DATA NETWORK (PSPDN)
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What Is the Internet?
Internet is the network of networks i.e. a global network which make WWW (world wide web).
An Internet: A network of networks of computer hosts able to seamlessly communicate - usually through the Internet Protocol (IP) and services
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Birth of the Net
The Internet grew out of an experiment in the
1960s by the U.S. Department of Defense. The
DoD wanted to create a computer network that
would continue to function in the event of a
disaster, such as a nuclear war. If part of the
network was damaged or destroyed, the rest of
the system still had to work. That network was
ARPANET, (Advanced Research Projects
Agency Network) which linked U.S. scientific
and academic researchers. It was the
forerunner of today's Internet.
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Internet Milestones
Originally called ARPANET, the Internet began as a military-academic network
1969
Worldwide: Over
1 billion Internet
users
2007 1990
Commercial
access to the
Internet begins
ARPANET splits:
Milnet - for military Internet - academic, education
and research purposes only
1983
NSF Net
created as US
Internet
backbone
1986
Government
funding of the
backbone ends
1994
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The Internet
Client
Connection Using TCP/IP Protocol
Internet
Server
Text, Audio, Video,
and Graphics Data
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Internet Services
Internet
Electronic Mail (e-mail)
World Wide Web (WWW)
Chat
Internet News
File Transfer Protocol (FTP)
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CELLULAR TELEPHONE NETWORKS (PLMN)
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CELLULAR TELEPHONE NETWORKS
The public land mobile networks (PLMN) use a landline component that employs many of the basic principles of landline telephony, either based on circuit or packet techniques.
However, they require additional functionality to enable radio connections to be made to mobile phones and to keep track of where the network users are located.
Just as major change is reshaping fixed, or landline, telephone networks, so, too, is massive change being seen in mobile networks with third-generation networks now being widely introduced.
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Evolution of Wireless Technology
1st Generation
2nd Generation
Generation 2+
4th Generation
1990
1995
2010
Analog
AMPS, TACS, JTACS
Digital (Speech)
GSM, IS-95, PDC
3rd Generation 2000
Digital, Multimedia-
Capable
IMT-2000
Broadband Wireless
Digital (Speech + data)
EDGE, GPRS, IS-95 B,C
1980
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GENERATIONS OF CELLULAR SYSTEMS
FIRST-GENERATION SYSTEMS
SECOND-GENERATION SYSTEMS
SECOND-AND-A-HALF GENERATION SYSTEMS
THIRD-GENERATION SYSTEMS
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GENERATIONS OF CELLULAR SYSTEMS
1979-80 Came the first Cellular Mobile
system such as:
AMPS ( Advance Mobile Phone Service),USA
:800 MHz Band
NMT ( Nordic Mobile Telephony ), Sweden,
Denmark 450 Mhz, & 900 MHz
TACS ( Total Access Communication System),
UK 900 MHz
These were analog in Nature and known as First
Generation System
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THE MOBILE SYSTEMS WORKING DURING EARLY 1980s
WERE INCOMPATIBLE & RESULTED IN MOBILE PHONES
DESIGNED FOR ONE SYSTEM COULD NOT BE USED WITH
OTHER SYSTEM.
IN 1982 CEPT (CONFEDERATION OF EUROPEAN POSTS &
TELECOMMUNICATION ) SET UP A COMMITTEE.
THIS COMMITTEE WAS KNOWN AS GROUP SPECIAL
MOBILE (GSM) & LATER KNOWN AS GLOBAL
SYSTEM FOR MOBILE COMMUNICATIONS.
IN 1989 THE RESPONSIBILITY FOR FRAMING SPECS FOR
GSM WAS PASSED FROM CEPT TO ETSI (EUROPEAN
TELECOMMUNICATION STANDARD INSTITUTE) .
GENERATIONS OF CELLULAR SYSTEMS
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During 1990 many digital mobile standards were
introduced in different regions/ countries
DAMPS ( Digital Advance Mobile Phone
Service), USA: 800 Mhz.
GSM ( Global System for Mobile
Communications), EUROPE: 900/1800 MHz.
CDMA ( Code Division Multiple Access )
These are known as 2nd Generation System (voice & Data SMS)
GENERATIONS OF CELLULAR SYSTEMS
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For introduction of data transfer capability on
the Mobile ,additional Hardware was
introduced in GSM systems, known as GPRS (
General Packet Radio Service ) . These are
being referred as 2.5 Generation System
Data rate supported 64 kbps-144 kbps
ENHANCED DATA RATE FOR GSM EVOLUTION
EDGE-384 KBPS
GENERATIONS OF CELLULAR SYSTEMS
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Now a Global Standard IMT-2000
(International Mobile Telecom.-2000) is
proposed which encapsulate all the existing
networks and different access technologies to
provide any time and any where type of
communication in very near future and known
as 3rd Generation standard.
Supports 2Mbps
GENERATIONS OF CELLULAR SYSTEMS
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EVOLUTION TO IMT-2000/3G
GSM GPRS EDGE
PDC
CdmaOne
TDMA
IS-136
TDMA/
GPRS
TDMA/
EDGE
Cdma 2000 WCDMA
IMT-2000
CAPABLE SYSTEMS
2000 EVOLVED 2G
64-115 Kbps
TODAY 2G
9.6/14.4Kbps
3G
115-384 Kbps &384-2 Mbps
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Communication - Mobile
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Uplink and Downlink frequencies
Cell To Mobile Down Link
Mobile to Cell Up Link
935-960 Mhz
1805-1880 Mhz
890-915 Mhz
1710-1785 Mhz
BTS
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Multiple Access Techniques
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GSM Network Architecture
l
MS
BTS
BTS
BTS
BTS BTS
BTS
BTS
BTS
BSC
BSC
PSTN
VLR
TRAU HLR
EIR
OMC
SMSC
BC
AUC
VMSC
MSC
A
SMSC : Short Message Service Center
VMSC : Voice Mail Service Center
BC : Billing Center
OMC : Operations and Maintenance Center
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GSM Network Architecture
BTS : Base Transceiver Station
BSC : Base Station Controller
MS : Mobile Station
TRAU : Trans-coder Rate Adaptation Unit
MSC : Mobile Switching Center
HLR : Home Location Register
VLR : Visiting Location Register
AUC : Authentication Centre
EIR : Equipment Identity Register
SMSC : Short Message Service Center
VMSC : Voice Mail Service Center
BC : Billing Center
OMC : Operations and Maintenance Center
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One network for everything
Today Tomorrow
Telephone
network
Mobile radio
network
IP-Network
Multimedia Access - Advantages:
Easy to handle Reliable Mobile
Internet
Transition to NGN: Third wave
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Wireless
Gateways
Internet
POTS
Integrated
Services
Over IP
Evolving towards All IP Communications
Next Generation Networks (NGN) Present Day Networks
Next Generation Networks Technology
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NEXT GENERATION NETWORKS
It is a packet-based network that can use
multiple transport network technologies.
The transport network has QoS capabilities.
Service-related functions are separated from the
transport technologies.
The access and core networks are clearly
separated so that users can have a choice about
who delivers the services.
Generalized mobility is supported so that users
can have ubiquitous access to services.
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Transmission &
Systems
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ROLE OF TRANSMISSION SYSTEM
Transmission is the process of transporting
information between end points of a system or
network. The end-to-end communication distance
is often very long and there are many electrical
systems on the line.
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Elements of a Transmission System
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Transport Network by Geography
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Conclusion
There are unprecedented developments
happening in
Access
Core
Transport
Client Devices
Convergence at every level
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16-Feb-12