Telecommunication Network Competition: An Equilibrium Analysis
Telecommunication Network to Computer Network
Transcript of Telecommunication Network to Computer Network
Telecommunication Network
to
Computer Network
What is Telecommunication?
Telecommunication networks carry information signals among entities which are geographically far apart. An entity may be computer, human being, a facsimile machine, a teleprinter, a data terminal, and so on.
Historical Backdrop
The field of telecommunications has evolved from a stage when signs, drum beats and semaphores were used for long distance communication to a stage when electrical , radio and electro-optical signals are used.
Let’s a Look Back
Contd...
• 1837 Telegraphy introduced in GB & 1845 n France
• 1876: Alexander Graham Bell invents the telephone 1881: First telephone Yellow Pages directory 1891: First dial phone 1887: First coin-operated telephone installed in the Hartford Bank by the payphone's inventor, William Gray. 1915: The first "official" coast-to-coast call is made from Alexander Graham Bell in New York City to Thomas Watson in San Francisco.
Alexander Graham Bell
Point-to-Point Telephone Connection
In telephonic conversation, the one who initiates the call is known as calling subscriber and the one for whom the call is destined is known as called subscriber.
Fully Connected Network
10 point-to-point links for connecting 5 entities
In general, for connecting n entities we need to have n (n-1)/2 links
Problem in Point to Point Connection
• Networks with point to point links among all the entities are known as fully connected networks.
• The number of links required in a fully connected network becomes very large.
Contd... • Practical use of Bell’s invention on a large scale
even on a moderate scale was not possible and it demanded the application of switching system or switching office or the exchange. With the introduction of switching system, the subscribers are not connected directly to one another, instead via the switching system. The functions performed by a switching system in establishing and releasing connections are known as Control functions. Functionally, the communication channels between switching system are referred to as trunks.
Birth of Switching System
Basic Components of Telecommunication System
Telecommunication system consists of four main components. They are:
End system or Instruments
Switching system
Signalling
Transmission media
End System
Rotary Dial Telephone
• Pulse Dialling (1895)
• The number of pulses in a train is equal to the digit value it represents
• Dialling 1 means 1 pulse and subsequently
• Only 0 creates 10 pulses
• Takes 12 seconds for dialling 7 digits
Touch Tone Telephone
Multifrequency Dialling (1950)
Or Dual-tone Multifrequency (DTMF) Diallng
Touching a button generates
a tone which is combination
of 2 frequencies –one from
lower band and the other
from upper band
DTMF Tone Decoding
Switching System
4 types of connections in Switching System
Local call connection between 2 subscribers in the system
Outgoing call connection between a subscriber and an outgoing trunk
Incoming call connection between an incoming trunk and a local subscriber
Transit call connection between an incoming trunk and outgoing trunk
Classification of Switching System
Manual Switching System
Energy Requirement in Exchanges
Local Battery (LB) Exchange Microphone needs to be energised in order to produce electrical signals corresponding to the speech waveform
• 1917 wall telephone, open to show magneto and local battery
• The use of magneto generator alternatively called as magneto exchange
Central Battery (CB) Exchange
Today's all exchanges
are CB Exchanges
Automatic Switching System
• It was the first automatic switching system developed by Almond B. Strowger in 1889
Advantages of Automatic Switching System
Language independent
A greater degree of privacy
Control function is faster
Load on the system = total time required to establish & release a call
Disadvantages of Strowger Switching System
• Regular maintenance
• Skilled manpower
• Strowger switching system has been the basis of telephone switching system for almost 70 years after ts inception in 1889
• Crossbar switching system was designed on the Principle of Common Control Concept
Contd...
• Principle of Common Control Concept was originated for mainly for 2 reasons:
• Identification no. of a subscriber is route dependent
• User must have the knowledge of topology of the network
• Overcoming this problem:
• Routing is done by the exchange
• A uniform numbering scheme is presented
• A Subscriber number has 2 parts
• Exchange Identifier + Subscriber line identifier within the exchange
Crossbar Switching System
• A crossbar switching system is a collection of switches arranged in a matrix configuration formed of relays & latches
Disadvantages of Crossbar Switching System
• Electromechanical component’s operational speed is slow
• lifetime is limited
• This subsystem have limited capability
• Impossible to provide additional functionalities
Electronic Switching System • Control function of the
exchange s performed by a computer or a processor
• Carrying out the exchange control function through programs stored in the memory of a computer led to nomenclature Stored Program Control (SPC)
• New facilities can be added to SPC system by changing the control program
Categorization of Electronic Switching System
• Space Division Switching
Here a dedicated path is established between the calling as well as called subscriber.
Crossbar system + SPC = electronic switching system
It was originally designed for analog network but now it is used both in analog and digital network.
Contd... • Time Division Switching
• Here, sampled values of speech signals are transferred at fixed intervals
Time Division Switching is again 2 types-
1. Analog 2. Digital
In analog switching system, the sampled voltage
level are transmitted whereas , in digital
Switching system , they are binary coded &
transmitted
Signalling
A switching system provides for 3 different forms of signalling:
Subscriber loop signalling
Interexchange signalling
Intraexchange signalling
Five Signaling Functions By Operator
1. Respond to the calling subscriber to obtain the identification of the called party.
2. Inform the calling subscriber that the call is being established.
3. Ring the bell of the called party.
4. Inform the calling subscriber, if the called party is busy.
5. Inform the calling subscriber, if the called party line is not obtainable for some reason.
Dial Tone
1.Indicates that the exchange is ready to accept dialed digits from the subscriber.
2.The subscriber should start dialing only after hearing the dial tone.
3.Else, initial dial pulses may be missed by the exchange which may result in the call landing on a wrong number or exchange timing out
Transmission Media
• There are 2 basic categories of
Transmission Media: • Guided Transmission Media -
uses a "cabling" system that guides or bounds the data signals along a specific path. The data signals are bound by the "cabling" system. Guided Media is also known as Bound Media. Guided media is basically 3 types:
• Twisted Pair • Coaxial Cable • Optical Fibre
Twisted Pair
Coaxial Cable
Optical Fibre
Contd...
• Unguided Transmission Media - consists of a means for the data signals to travel but nothing to guide them along a specific path. The data signals are not bound to a cabling media and as such are often called Unbound Media.
• Radio transmission is the example of unguided transmission media
Radio Transmission
Radio is the wireless transmission of signals through free space by electromagnetic radiation in the frequency range of 3 KHz to 300 GHz. These waves are called the Radio Waves
Radio Wave Uses
• TV broadcasting, radio broadcasting, mobile communication, etc. • Navigation of the ships and aircrafts.
• Global Positioning Satellite to precisely pin point the location of the targets.
• The radio telescopes are used to study the radio waves emitted by the far flung
galaxies and the star to understand their origins and characteristics.
• The radio waves (20 Hz to 2000 Hz) are used by us to communicate with each other.
• Remote control of toys.
• Echolocation by bats
• To detect the sea objects and also used to detection of flaws in the manufactured products.
• Ultrasound, which lies in the radio wave range, is used in medical science to detect several diseases.
Few Features of Radio Waves
• The radio waves are used to carry information from one place to another by the use of air as a medium.
• The speed of radio waves is equal to the speed of the light.
• The radio wave can travels larger distance with very less attenuation and hence can be used for communication without the need of the wired medium.
Dangers of Radio Waves
• The constant exposure to radio waves may cause cancer. The other dangers are 1. Headaches, 2. Eye Discomfort, 3. Facial redness, 4. Fatigue, 5. Dizziness, 6. Sleep Disturbances, 7. High Blood-pressure, 8. Pain in the joints and muscles, 9. Immune system abnormalities 10. Allegies.
Categories of Radio Communication
Ionospheric communication
Microwave communication
Tropospheric scatter communication
Satellite communication
Mechanism of Radio Transmission
Microwave Transmission
Microwave transmission is considered a Line of Site technology. This is because
the proper functioning of microwave transmission requires that the airspace between two microwave towers in clear of mountains, buildings, and other objects that could possibly block signals from being intercepted by the towers. Microwave transmission is limited by this need for a clear line of sight, in addition to being susceptible to attenuation by the atmosphere.
Contd...
Satellite Communication
Contd...
Contd...
Contd...
Contd... • Basic Components of a Satellite Solar Panel Antenna
Transponder Satellites are Geostationary at 36000 Km above the
equator Every Satellites is provided with Attitude & Orbit Control System (AOCS) 3 frequency bands are allocated for commercial satellite
communication • C, Ku & Ka Band Of them C is widely used because it has least
atmospheric effect.
Technological Evolution • Voice Transmission Data Transmission
• PSTN ISDN
PSTN normally carries voice or analog signal
But they can however be used for data
Transmission using suitable interfaces like MODEM (modulator/demodulator)
Modem as Interface
Computer (D)
Modem (D to A)
Telephone Network (A)
Modem (A to D)
Computer (D)
Differences between voice and data transmission
Voice Traffic
1. Continuous
2. Low bandwidth for long duration
3. Typical line utilization is 85%-95%
4. Half Duplex
5. Real time
6. Loss acceptable
7. Error tolerable
Data Traffic
1. Bursty
2. High bandwidth for short duration
3. Typical line utilization is 5-15%
4. Half or full duplex
5. Non-real time
6. Loss unacceptable
7. Error unacceptable
Switching Technique for data transmission-
1. Circuit Switching
2. Store & forward switching
-Message Switching
-Packet Switching
To recognize the diverse characteristics of voice & data traffic, switching technique for data transmission was developed
A typical Packet Format
Header
User Data
Destination id Source id Message id Packet id Control