introduction to communication systems and networks
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Introduction to Communication Systems and Networks. Communication Systems. Communications Components. Basic components of a communication system Communication technologies Communication devices Communication channels Communication software. A Communications Model. - PowerPoint PPT PresentationTRANSCRIPT
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Introduction to Communication Systems and Networks
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Communication Systems
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Communications Components• Basic components of a
communication system– Communication technologies– Communication devices – Communication channels– Communication software
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A Communications Model
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Data Communications Model
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Communication Technology Applications
voice mail Twitter
e-mailinstant messaging
chat rooms
newsgroups telephony videoconferencing
collaboration groupware global positioning system (GPS)
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Communication Technologies - Applications
• Different technologies allowing us to communicate – Examples: Voice mail, fax, email, instant message, chat rooms, news groups, telephony,
GPS, and more• Voice mail: Similar to answering machine but digitized• Fax: Sending hardcopy of text or photographs between computers using fax modem• Email: electronic mail – sending text, files, images between different computer
networks - must have email software – More than 1.3 billion people send 244 billion messages monthly!
• Chat rooms: Allows communications in real time when connected to the Internet • Telephony: Talking to other people over the Internet (also called VoIP)
– Sends digitized audio signals over the Internet – Requires Internet telephone software
• Groupware: Software application allowing a group of people to communicate with each other (exchange data) – Address book, appointment book, schedules, etc.
• GPS: consists of receivers connected to satellite systems – Determining the geographical location of the receiver– Used for cars, advertising, hiking, tracking, etc.
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Communication Devices• Any type of hardware capable of transmitting data, instructions, and information
between devices – Functioning as receiver, transmitter, adaptor, converter– Basic characteristics: How fast, how far, how much data!
• Examples: Dial-up modems, ISDN, DSL modems, network interface cards– Dial-up modem: uses standard phone lines
• Converts digital information into analog • Consists of a modulator and a demodulator • Can be external, internal, wireless
– ISDN and DSL Modem: Allows digital communication between networks and computers • Requires a digital modem• Digital is better than analog – why?
– Cable modem: a modem that transmits and receives data over the cable television (CATV) network• Also called broadband modem (carrying multiple signals) • The incoming signal is split • Requires a cable modem
– Network interface cards: Adaptor cards residing in the computer to transmit and receiver data over the network (NIC)• Operate with different network technologies (e.g., Ethernet)
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Communication Channels• A channel is a path between two communication devices• Channel capacity: How much data can be passed through
the channel (bit/sec) – Also called channel bandwidth– The smaller the pipe the slower data transfer!
• Consists of one or more transmission media– Materials carrying the signal– Two types:
• Physical: wire cable • Wireless: Air
destination network server
T1 lines
T1 lines
T1 lines
T3 lines
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Wireless Transmission Media• Broadcast Radio – Distribute signals through the air over
long distance – Uses an antenna – Typically for stationary locations – Can be short range
• Cellular Radio– A form of broadcast radio used for
mobile communication – High frequency radio waves to transmit
voice or data – Utilizes frequency-reuse
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Wireless Transmission Media• Microwaves
– Radio waves providing high speed transmission
– They are point-to-point (can’t be obstructed) – Used for satellite communication
• Infrared (IR) – Wireless transmission media that sends
signals using infrared light- waves - Such as?
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Physical Transmission Media
100 Mbps is how many bits per sec?
Which is bigger: 10,000 Mbps, 0.01Tbps or 10Gbps?
Wireless channel capacity:
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Networks
• Collection of computers and devices connected together • Used to transfer information or files, share resources, etc. • What is the largest network? • Characterized based on their geographical coverage, speed, capacities • Networks are categorized based on the following characteristics:
– Network coverage: LAN, MAN, WAN– Network topologies: how the computers are connected together – Network technologies– Network architecture
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Network coverage• Local Area Networks:
– Used for small networks (school, home, office)– Examples and configurations:
• Wireless LAN or Switched LAN• ATM LAN, Frame Ethernet LAN• Peer-2-PEER: connecting several computers together (<10)• Client/Server: The serves shares its resources between different
clients • Metropolitan Area Network
– Backbone network connecting all LANs– Can cover a city or the entire country
• Wide Area Network– Typically between cities and countries – Technology:
• Circuit Switch, Packet Switch, Frame Relay, ATM– Examples:
• Internet P2P: Networks with the same network software can be connected together (Napster)
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LAN v.s WANLAN - Local Area Network a group of
computers connected within a building or a campus (Example of LAN may consist of computers located on a single floor or a
building or it might link all the computers in a small company.
WAN - A network consisting of computers of LAN's connected across a distance WAN can cover small to large distances, using different topologies such as telephone lines, fiber optic cabling, satellite transmissions and microwave transmissions.
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Network Topologies • Configuration or physical arrangement in which devices are connected
together • BUS networks: Single central cable connected a number of devices
– Easy and cheap– Popular for LANs
• RING networks: a number of computers are connected on a closed loop – Covers large distances– Primarily used for LANs and WANs
• STAR networks: connecting all devices to a central unit – All computers are connected to a central device called hub– All data must pass through the hub – What is the problem with this? – Susceptible to failure
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Network Topologiespersonal
computerpersonal
computerpersonal
computer
personal computer
personal computer
host computer
printerfile server
personal computer
personal computer
personal computer
personal computer
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Network Architecture• Refers to how the computer or devices are designed in a network • Basic types:
– Centralized – using mainframes – Peer-2-Peer:
• Each computer (peer) has equal responsibilities, capacities, sharing hardware, data, with the other computers on the peer-to-peer network
• Good for small businesses and home networks • Simple and inexpensive
– Client/Server:• All clients must request service from the server• The server is also called a host• Different servers perform different tasks: File server, network server, etc.
client
client
client
server
laser printer
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P2P vs Client-Server
Peer-to-Peer Examples
Peers make a portion of their resources, such as processing power, disk storage or network bandwidth, directly available to other network participants, without the need for central coordination by servers or stable hosts
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Any Q?
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Introduction: “Everything is Connected to Everything”
• Computer Networking– Internet: A world-wide network connecting millions of
computer networks for the purpose of exchanging data and communications using special rules of communication.
– internet: (lower case i) Any network connecting two or more computer networks.
– The human need to communicate has motivated mankind’s creativity:• Cave dwellers drew pictures on walls.• Smoke signals, drum rhythms passed messages.• American pioneers: Pony express, Wells Fargo.• Alexander Graham Bell: invented the telephone.
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Communication Basics of Networks
• Types of connections of computers into networks: Physical versus Wireless connections
– The first type: The Physical Connection. • Physically connect computers together.
– Use of wires or optical cables.– The connections are called network links.
• Three most common physical links:– Twisted pair– Coaxial cable– Fiber-optic cable
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Communication Basics of Networks
• Twisted pair
– Two wires twisted together.• Makes them less susceptible to acting like an
antenna and picking up radio frequency information or appliance noise.
– Telephone company uses twisted-pair copper wires to link telephones.
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Communication Basics of Networks
• Coaxial cable
– Also two wires: • One of the wires is woven of fine strands of
copper forming a tube. • The wire mesh surrounds a solid copper wire
that runs down the center. • Space between has a non-conducting material.• Makes them more impervious to outside noise.
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Communication Basics of Networks
• Fiber-optic cable
– Light is electromagnetic.– Can transmit more
information down a single strand. • It can send a wider set of
frequencies.– Each cable can send
several thousand phone conversations or computer communications.
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Communication Basics of Networks
1. Type of signal communicated (analog or digital).– Analog: Those signals that vary with smooth
continuous changes.• A continuously changing signal similar to that found on
the speaker wires of a high-fidelity stereo system.– Digital: Those signals that vary in steps or jumps
from value to value. They are usually in the form of pulses of electrical energy (represent 0s or 1s).
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Communication Basics of Networks
2. The speed at which the signal is transmitted (how fast the data travels).– In digital systems: Speed is measured in... • Bits per second (bps).
– The number of bits (0’s and 1’s) that travel down the channel per second.
• Baud rate– The number of bits that travel down the channel in a given
interval.– The number is given in signal changes per second, not
necessarily bits per second.
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Communication Basics of Networks
• MODEM - MOdulator DEModulator
– Outgoing: Converts binary data from computer (digital) into telephone compatible signals (analog).
– Incoming: Converts telephone signal (analog) into binary data for the computer (digital).
– Can be an external or internal device (usually a “card”).
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Communication Basics of Networks
• Speed of Signal: Sample bps and baud rate speeds.
300 bps (=300 baud) Painfully slow to the college-level reader1200 bps (=1200 baud) Good reader can keep up2400 bps (=2400 baud) A speed reader would get the general idea9600 bps (=9600 baud) Impossible to read14.4 K bps (not measured in baud) 14,400 bps - 10 to 20 sec. wait for graphics28.8 K bps Minimum desired for WWW
(5 to 10 sec. wait for graphics)56 K bps Efficient speed for WWW.
These speeds are restricted to the maximum speed of the modem at theother end of the connection.
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Communication Basics of Networks
3. The type of data movement allowed on the channel. – Simplex transmission - One way transmission.– Half-duplex transmission - Flows only one way at a time.– Full-duplex transmission - Two-way transmission at the
same time.
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Communication Basics of Networks
4. The method used to transport the data.– Two types of data transmission, each requiring a
different modem.– Asynchronous transmission -
• Information is sent byte by byte.• Cheaper and more commonly used.
– Synchronous transmission - • Data is sent in large blocks rather than in small pieces.• Preceded by special information, concerning error detection
and block size.• These modems are expensive but very fast.
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Communication Basics of Networks
5. Single channel versus multichannel transmission– Channel - A path of a signal.– Single channel - Capable of only sending/receiving
one signal at a time.• Phone line: Single line = single phone call at a time.
– Multichannel - Capable of more than one channel at a time.• Fiber-optic cable, microwaves, Satellite transmissions.
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Communication Basics of Networks
• How is it possible to measure the capacity of communications links? – Bandwidth: Digital
• Number of bits per second (bps) that can be sent over a link.• The wider the bandwidth, the more diverse kinds of information can be sent.• Simplest is voice, most sophisticated is moving videos.
– Bandwidth: Analog• The difference between the highest and lowest frequencies that can be sent
over an analog link (like phone lines).• Measurement is given in hertz (Hz).
– For both: The wider the bandwidth, the more information can flow over the channel.
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Thank you